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© International Telecommunication UnionINTERNATIONAL RADIO CONSULTATIVE COMMITTEE

C.C.I.R.
DOCUMENTS OF THE

Xlth PLENARY ASSEMBLY
OSLO, 1966

VOLUME III
FIXED AND MOBILE SERVICESSTANDARD-FREQUENCIES AND TIME-SIGNALSMONITORING OF EMISSIONS

Published by the

INTERNATIONAL TELECOMMUNICATION UNIONGENEVA, 1967

March, 1969

ADDENDUM No. 1
toVOLUME III OF THE DOCUMENTS
OF THE Xlth PLENARY ASSEMBLY OF THE C.C.I.R.
Oslo, 1966

Note by the Director, C.C.LR.
1.

During the Special Meeting of Study Group XIII (Mobile services), Geneva, 1967, the Interim
Meetings’of Study Groups VII (Standard-frequencies and time-signals) and VIII (International
monitoring), Boulder, Colorado, 1968 and the Interim Meeting of Study Group XIII, Geneva,
1968, it was decided that, in view of the urgency of commencing work on the problems involved,
certain Draft Questions and Study Programmes should be circulated to Administrations forapproval by correspondence, in accordance with Article 14, § 2(1) of the International Tele­
communication Convention, Montreux, 1965.
Each of the texts submitted has received more than the twenty approvals necessary for theiradoption from the Members and Associate Members of the I.T.U. and they have, in conse­
quence, now become official Questions and Study Programmes of the C.C.I.R. (see Adminis­
trative Circulars A.C./124 of 7 November, 1968 and A.C./126 of 25 November, 1968 (Study
Groups VII and VIII) and A.C./106 of 4 August, 1967 and A.C./128 of 18 December, 1968
(Study Group XIII)).
These texts are:
— Question 5/VII, which is reproduced on a separate sheet numbered 318;
— Question 2-1 /VIII, which is reproduced on a separate sheet numbered 426a;— Questions 9/XIII, 10/XIII, 11/X III and 12/XIII, which are reproduced on separate sheets
numbered 270a to 270c;— Study Programmes 2-1A/XIII and 6A/XIII, which are reproduced on separate sheets
numbered 426a, 426b and 265a.

2. The text of Question 2-1/VIII is intended to replace the existing text of Question 2/VIII, which
will be recommended for deletion to the X llth Plenary Assembly.
3. One Administration, while approving the text of Question 12/XIII, recommends that thewords “ without speech ” should be deleted from the text in the footnote. This proposition
will be discussed at the next meeting of Study Group XIII.
4. Advantage has been taken of the issue of this Addendum to notify the following corrections
to Volume III:
Page 10. In the list, replace “ Recommendation 429 ” by “ Recommendation 429-1 ”.
Page 146. Replace equation (2) by:
U P ' = P 0 t'o<Po/K’\

Page 147. Replace equation (3) b y :“ G' = qPo/P' = qK/()'o9o ”•
In paragraph 6, replace “ asuumed ” by “ assumed

— 2 —

Page 148. The paragraph “ For distances less ............ over the route ” should follow theexpression 4m = v e rtic a l(degrees) ”.
Page 149. In Fig. 1, on the axis of ordinates, replace “ 110 ” by “200 ”.
Page 291. Concerns the French text only.
Page 326. In the figure the words “ Resolving power ” should be
removed fromtheaxisof
ordinates and replaced above the “ -<• >- ” at the top.
Page 327. Concerns the French text only.
Page 381. In the 7th line of § 4.1.3, replace “ Report 275-1 ” by “Report 279-1
Page 414. In Fig./3, insert “ E-plane ” over the left-hand figuresand “ H-plane”oright-hand figures.

INTERNATIONAL RADIO CONSULTATIVE COMMITTEE

C.CI.R.
DOCUMENTS OF THE

Xlth PLENARY ASSEMBLY
OSLO, 1966

VOLUME III
FIXED AND MOBILE SERVICESSTANDARD-FREQUENCIES AND TIME-SIGNALSMONITORING OF EMISSIONS

Published by the

INTERNATIONAL TELECOMMUNICATION UNIONGENEVA, 1967

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENT

Recommendations of Section C (Fixed services)FIXED
SERVICES

Reports of Section C (Fixed services)

Questions and Study Programmes assigned to Study
Group III (Fixed service systems) - Opinions and Resolu­
tions of interest to this Study Group - Lists of documents

Recommendations of Section D (Mobile services)

MOBILESERVICES

Reports of Section D (Mobile services)

Questions and Study Programmes assigned to Study
Group XIII (Mobile services) - Opinions and Resolutionsof interest to this Study Group - Lists of documents

Recommendations of Section H (Standard-frequencies andtime-signals)
STANDARDFREQUENCIESAND
TIME-SIGNALS

Reports of Section H (Standard-frequencies and time-signals)

Questions and Study Programmes assigned to Study
Group VII (Standard-frequencies and time-signals) - Opinions
and Resolutions of interest to this Study Group - Lists of
documents

Recommendations of Section J (Monitoring of emissions)

MONITORING
OF EMISSIONS

Reports of Section J (Monitoring of emissions)

Questions and Study Programmes assigned to Study
Group VIII (Monitoring of emissions) - Opinions and Reso­lutions of interest to this Study Group - Lists of documents

— 4 —

DISTRIBUTION OF THE TEXTS OF THE Xlth PLENARY ASSEMBLY
OF THE C.C.I.R. AMONG VOLUMES I-Vl
- Volumes I to VI of the documents of the Xlth Plenary Assembly contain all the C.C.I.R. texts at present
in force.
- For Questions and Study Programmes, the final (Roman) numeral indicates the Study Group to which
the text has been assigned. The plan on page 5 shows the Volume in which the various texts of that
Study Group can be found.
- Recommendations, Reports, Opinions and Resolutions which have been amended by the Xlth Plenary
Assembly, have retained their original number, followed by the indication 1 (e.g.: Recommendation 326-1).
which is not shown in the Table below. Further details on the numbering system appear in Volume VI.
1.

2.

Recommendations
NumberVolumeN um berVolumeNumberVolume45
48, 49
75-77
80
100
106
136
139, 140
162
166
168
182
205
212
214-216
218,219
224

III
V
III
V
III
III
V
V
III
III
II
III
V
V
V
III
III

237
239
240
246
258
261, 262
264-266
268
270
275, 276
279
281-283
289, 290297-300302
304-306
310,311

I
I
III
III
III
V
V
IV
IV
IV
IV
IV
IV
IV
IV
IV
II

313
314
325-334
335-349352-367368-373374-379
380-406
407-421422, 423
425
427-429430-433
434, 435
436-443444-446447-451

II
IV
I
III
IV
II
III
IV
V
III
III
III
I
II
III
IV
V

NumberVolumeNumberVolumeNumberVolume

19
32
42
79
93
106, 107
109
111,112
122
130
134
137

III
V
III
V
III
III
III
III
V
IV
IV
IV

175-194
195-198
200-203204-219222-224226
227-239241-266267
269-273275-282283-290

I
III
III
IV
IV
IV
II
II
III
III
III
IV

292-295
297-316318-320321322
323-335
336-339340
341-344345-373374-397398-412413-415

V
V
III
I
(!)
I
II
(!)
II
III
IV
V
(!)

Reports(!) Published separately.

3.

4.

Opinions
N um berVolumeN um berVolumeN um berVolume

1,2
3
11

I
IV
III

12-14
15-17
19

IV
V
V

21
22, 23
24-30
31

III
II
III
V

N um berVolumeNumberVolumeNumberVolume

1
2-4
7, 8
10

III
II
II
II

12, 13
14-16
19-20
21-23
24

II
III
III
I
VI

26, 2730, 31
32
33-36

VI
II
V
VI

Resolutions

— 6 —ARRANGEMENT OF VOLUMES I TO VI OF THE DOCUMENTS
OF THE Xlth PLENARY ASSEMBLY OF THE C.C.I.R.
(Oslo, 1966)

V olum e

I

Volume II

Emission. Reception.
and XIV).

Vocabulary (Sections A, B, K and Study Groups I, II

Propagation (Section G and Study Groups V and VI).

V olumeIII

Fixed and mobile services. Standard-frequencies and time-signals. International
monitoring (Sections C, D, H and J and Study Groups III, XIII, VII and VIII).

V olum eIVRadio-relay systems. Space systems and Radioastronomy (Sections F and L andStudy Groups IX and IV).

V olum e

VSound broadcasting and Television (Section E, Study Groups X, XI and XII and
the CMTT).

Volume VI

List of participants.
Minutes of the Plenary Meetings.
Resolutions of a general nature.
Reports to the Plenary Assembly.
Lists of documents in numerical order.

Note 1. - To facilitate references, the pagination in the English and French texts is the same.
Note 2. - At the beginning of Volume VI will be found information concerning the X lth Plenary
Assembly of the C.C.I.R. and the participation at this meeting, on the presentation of texts(Definitions, origins, numbering, complete lists, etc.), together with general information on
the organization of the C.C.I.R.

— 7 —TABLE OF CONTENTS OF VOLUME III

Page

Distribution of the texts of the XlthPlenary Assembly of theC.C.I.R.among Volumes I to VI

4

Arrangement of Volumes I to VI of theXlth PlenaryAssembly of the C.C.I.R........................

6

Table of contents of Volume III

7...................................................................................................

RECOMMENDATIONS OF SECTION C (FIXED SERVICES)
Rec.
Rec.
Rec.
Rec.
Rec.
Rec.
Rec.
Rec.
Rec.

75
100
106
162-1
166-1
240
246-1
335-1
336-1

Classification and essential characteristics of feed-back suppressors . . .
Reduction of occupied bandwidth and transmitter power in radio telephony
Voice-frequency telegraphy on radio c ir c u its ............................................
Use of directional antennae in the bands 4 to 28 M H z ..........................
Unit of quantity of information..................................................................
Signal-to-interference protection r a tio s .......................... .............................
Frequency-shift k e y in g .................................................................................
Use of radio links in international telephone circuits.................................
Principles of the devices used to achieve privacy in radiotelephone
conversations...................................................................................................
Channel separation ...................................................
Bandwidth required at the output of a telegraph or telephone receiver .
Bandwidths and signal-to-noise ratios in complete systems . . . . . . .
Fading allowances for the various classes of em ission..............................
The concept of transmission loss in studies of radio systems ...............
Automatic error-correcting system for telegraph signals transmitted overradio c ir c u its .............................

15
15
16
17
20
20
22
23

Rec.
Rec.
Rec.
Rec.
Rec.
Rec.

337
338-1
339-1
340
341
342-1

Rec. 343-1

Facsimile transmission of meteorological charts over radio circuits . . .

46

Rec. 344-1

Standardization of phototelegraph systems for use on combined radio
and metallic c irc u its ....................................................................................

47

Rec. 345

Telegraph d is to rtio n .....................................................................................

49

Rec. 346
Rec. 347

Four-frequency diplex systems ...................................................................
Classification of multi-channel radiotelegraph systems for long-range cir­
cuits operating at frequencies below about 30 MHz and the designation of
the channels in these systems ; ..................................................................

52

53

Rec. 348-1

Arrangement of channels in multi-channel single-sideband and independentsideband transmitters for long-range circuits operating at frequencies below
about 30 MHz ............................................................................................

56

Rec. 349-1

Frequency stability required for single-sideband, independent-sideband
and telegraph systems to make the use of automatic frequency control
superflu o u s....................................

58

Arrangement of voice-frequency telegraph channels working at a modula­tion rate of about 100 bauds over HF radio c irc u its .............................

60

Rec. 436

25
26
27
28
31
34
37

— 8 —Page

REPORTS OF SECTION C (FIXED SERVICES)
Report 19-1
Report 42-1

63

Report 106

Voice-frequency telegraphy over HF radio circuits..............................
Use of radio circuits in association with 50-baud, 5-unit start-stop telegraphsystems...........................................................................................
Improvement obtainable from the use of directional a n te n n a e ...............

Report 107-1

Directivity of antennae at great distances................................................

69

Report 109-1

Radio systems employing ionospheric-scatter p ro p a g a tio n .......................

71

Report 111

Influence on long-distance HF communications using frequency-shift key­ing of frequency deviations associated with passage through the ionosphere

75

Report 112

Transmission loss in studies of radio systems.........................................

80

Report 195

Bandwidths and signal-to-noise ratios in complete systems -Prediction of
the performance of telegraph systems in terms of bandwidth and signal-tonoise ratio .................. i ............................................................................

86

Report 196-1

Some aspects of the application of communication th e o ry .......................

94

Report 197-1 .

Factors affecting the quality of performance of complete systemsof the
fixed services ...............................................................................................

97

Report 198

Voice-frequency (carrier) telegraphy over radio c ir c u its ..........................

99

Report 200-1

Telegraph distortion, e r r o r-ra te ...................................................................

99

Report 201-1

Remote control signals for facsimile transmissions..................................

100

Report 202

Identification of the carrier frequency relative to the assigned frequencyof an emission ...........................................................................................

101

64
65

Report 203

Multipath propagation over HF radio circuits - Measurements of path-timedelay differences and their incidence on typical radio l i n k s ......................

102

Report 345

Performance of telegraph systems over HF radio c ir c u its .......................

105

Report 346

Performance of systems using phase-shift keying over HF radio circuits

118

Report 347

Voice-frequency telegraphy over radio circuits........................................

122

Report 348

Single-channel simplex ARQ telegraph system........................................

123

Report 349

Single-channel radiotelegraph systems employing forward error-correction.127

Report 350

Single-channel duplex ARQ telegraph system .............................................

131

Report 351

Efficiency f a c t o r ......................................................................... ..................

132

Report 352

Use of pre-emphasis and de-emphasis for phototelegraph transmission
over HF radio c irc u its................................................................................

133

Report 353

Use of common-frequency systems on international radiotelephonec ir c u its ..........................................................................................................

133

Report 354

An improved transmission system for use over HF radiotelephone circuits

138

Report 355

Use of diversity on international HF radiotelephone circuits....................

143

Report 356
Report 357
Report 413 *Report 414 *Report 415 *Use of directional antennae in the bands 4 to 28 M H z ..........................
Operational ionospheric sounding at oblique incidence.............................
Operating noise-threshold of a radio receiving sy stem .............................
Efficient use of the radio-frequency spectrum ............................................
Models of phase-interference fading for use in connection with studies ofthe efficient use of the radio-frequency sp e c tru m .....................................

146
150
151
151

* Published separately.

151

9 —
Page

QUESTIONS AND STUDY PROGRAMMES ASSIGNED TO STUDY GROUPIII (FIXEDSERVICES) - OPINIONS AND RESOLUTIONS OF INTEREST TO THIS STUDY GROUP
Introduction by the Chairman, Study Group I I I ..................................... * ...............................
Resolution 1-1
Question l/III

Improved efficiency in the use of the radio-frequency spectrum.....
155
Factors affecting the quality of performance of complete systems of the
fixed service........................................................................................
155

Study Programme 1A/III

Question 2/III
Question 3/III

153

Factors affecting the quality of performance of complete
systems of the fixed services - Signal-to-noise and signal-tointerference protection ratios for fading signals, bandwidth andadjacent channel spacing ...................................................

156

Arrangement of channels in multi-channel telegraph systems for long-range
radio circuits operating at frequencies below about 30 MHz ...............

160................................................

160

Study Programme 3A/III

Directivity of antennae at great distances

Improvement obtainable from the use of directional antennae

161

Study Programme 3B/III

Directivity of antennae for fixed services using ionosphericscatter propagation..............................................................

162

Question 4/III

Radio-relay systems employing ionospheric-scatter propagation.....

163

Question 5/III

Communication th e o r y ......................................................................

163

Study Programme 5A/III
Question 6/III^ Q u e stio n 7/III
Question 8/III

Communication th e o r y ..............................................

164

Use of intermittent communication in radiotelegraphy...................

165

Influence of frequency deviations associated with passage through theionosphere on radiocommunications................................................
165
Frequency-shift k e y in g ......................................................................

Study Programme 8A/III

166

Four-frequency diplex systems...................................

167

Question 9/III

Use of common-frequency systems on radiotelephone circuits.........

167

Question 10/111

Use of directional antennae in the bands 4 to 27-5 MHz -Limitation ofradiation outside the direction necessary for the service..................
168

Question 11/III

Automatic control of the output power of HF tran sm itters........

Question 12/111

Distortion characteristics required for single-sideband and independentsideband systems used for high-speed data transmission over HF radioc irc u its ..............................................................................................
170

Question 13/111

Improvements in the performance of HF radiotelephone circuits. . . .

170

Question 14/111

Automatically controlled radio systems in the HF fixed service. . . .

171

Question 15/111

The operational use of efficiency f a c t o r .........................................

169

171

Question 16/111
Transmission characteristics of HF radiotelephone c irc u its............
172
Study Programme 17A/III
Voice-frequency (carrier) telegraphy over radio circuits . . .
Study Programme 18A/III
Efficiency f a c t o r ...........................................................................
Study Programme 19A/III
Identification of the carrier frequency relative to the assigned
frequency of an em ission...........................................................

173
174

Study Programme 20A/III

176

Operational ionospheric sounding at oblique incidence

. . .

175

List of documents concerning Study Group III (Period 1963-1966) ................................................

177

List of documents of the Xlth Plenary Assembly established by Study Group III

184

— 10 —
Page

RECOMMENDATIONS OF SECTION D (MOBILE SERVICES)
D. 1 : General
Rec. 258-1
Rec. 422
Rec. 423-1
Rec. 437

Single-sideband aeronautical and maritime mobile radiotelephony systems
Pulse transmission for radio direction-finding.............................................
Use of 8364 kHz for radio direction-finding.............................................
Publication of the “ Codes and abbreviations for the International Tele­
communication Services ” by the International Telecommunication Union

187
189
190
192

D. 2: Maritime mobile service
Rec. 45
Rec. 76
Rec. 77-1
Rec. 218
Rec. 219-1
Rec. 224
Rec. 257
Rec. 425
Rec. 427
Rec. 428-1
Rec. 429
Rec. 438
Rec. 439
Rec. 440

Avoidance of interference from ships’ radar to other radiocommunication
apparatus on b o a r d ....................................................................................
Voice-operated devices for ship stations and carrier-operated devices forshore s ta tio n s ...............................................................................................
Conditions necessary for interconnection of mobile radiotelephone stations(for instance, automobiles, aircraft and ships) and international telephonel i n e s ..............................................................................................................
Prevention of interference to radio reception on board ships ...............
Alarm signal for use on the maritime radiotelephone distress frequencyof 2182 kHz ...............................................................................................
Testing of 500 kHz radiotelegraph auto-alarm receiving equipment onboard s h i p s ...................................................................................................
Selective calling devices for use in the international VHF (metric) maritime
mobile radiotelephone serv ice.....................................................................
Technical characteristics of frequency-modulation VHF (metric) maritime
mobile e q u ip m e n t........................................................................................
Interference due to intermodulation products in the VHF (metric) maritime
mobile radiotelephone serv ice.....................................................................
Direction-finding in the 2 MHz band on board s h ip s ..............................
Interference level on the radiotelegraph distress frequency.......................
Use of classes of emission A2H and A3H on the distress frequencies 500 kHz
and 2182 kHz respectively.........................................................................
Emergency position-indicating radio beacons operating at the frequency
2182 k H z ......................................................................................................
The introduction of direct-printing telegraph equipment in the maritime
mobile service...............................................................................................

193
194
195
196
197
199
200
201
203
204
207
208
209
211

D. 3: Land mobile service
No Recommendations in this sub-section
D. 4: Aeronautical mobile service
Rec. 441

Signal-to-interference ratios and minimum field strengths required in themobile service - Aeronautical mobile services above 30 M H z ..................

213

REPORTS OF SECTION D (MOBILE SERVICES)
D. 1: General
Report 93
Report 358

HF (decametric) and VHF (metric) direction-finding ..............................
Signal-to-interference protection ratios and minimum field strengths
required in the mobile service ..................................................................

215
219

— 11 —Page

D. 2 : Maritime mobile service
Report 318
Report 320-1
Report 359
Report 360
Report 361

Marine identification d e v ic e s ......................................................................
221
Selective-calling systems for the international maritime mobile service 225
Use of a control-tone for automatic gain control of receivers in single­
sideband radiotelephone systems operating in the HF maritime mobileb a n d s..............................................................................................................
226
Operational procedures for single-sideband (SSB) radiotelephone systems
in the HF maritime mobile b a n d s..............................................................
227
The introduction of direct-printing telegraph equipment in the maritime mobile service...............................................................................................
228

D. 3 : Land mobile service
Report 319-1

Characteristics of equipment and principles governing the allocation of
frequency channels between 25 and 500 MHz for the land mobile service

231

D. 4 : Aeronautical mobile service
No Reports in this sub-section
QUESTIONS AND STUDY PROGRAMMES ASSIGNED TO STUDY GROUP XIII (MOBILESERVICES); OPINIONS AND RESOLUTIONS OF INTEREST TO THIS STUDY GROUP
Introduction by the Chairman, Study Group X I I I ......................................................................
Opinion 24
Facsimile transmission of meteorological charts forreception on boards h i p s ..............................................................................................................
Opinion 25
Emergency position-indicating radio b e a c o n s .............................................
Question 1/XIII
Signal-to-interference protection ratios and minimum field-strengths requiredin the mobile service .................................................................................
Question 2/XIII
Direction-finding and homing in the 2 MHz band on board ships . . .
Resolution 19-1
Selective-calling systems for use in the international maritime mobiles e r v ic e ..........................................................................................................
Question 3/XIII
Selective-calling systems for use in the international maritime mobiles e r v ic e ................................................................................
Study Programme 3A/XIII
Selective-calling systems for use in the international maritime
mobile service..................................................................
Question 4/XIII
Operational procedures for single-sideband radiotelephone systems inthe HF maritime mobile bands..............................................................
Question 5/XIII
The introduction of direct-printing telegraph equipment in the maritime
mobile service...............................................................................................
Question 6/XIII
Self-supporting antennae for use on board s h i p s ......................................
. Resolution 20-1
Characteristics of equipment and principles governing the allocation of
frequency channels in the land mobile service between 25 and 500 MHz
Question 7/XIII
Characteristics of equipment and principles governing the allocationof frequency channels in the land mobile service between 25 and 500 MHz
Study Programme 7A/XIII
Technical characteristics of land mobile equipment
between 25 and 500 M H z ................................................
Study Programme 7B/XIII
Minimum channel-separation and optimum systems ofmodulation for land mobile systems between 25 and
500 MHz...........................................
Study Programme 7C/XIIIInterference due to intermodulation products in the land
mobile service between 25 and 500 MHz ......................
Question 8/XIII
MF and HF land mobile services - Preferred technical characteristics of
single-sideband equipm ent.............................................................................

251
257
258
259
259
260
261
262
262
263
264
265
266
267
268
268
269

List of documents concerning Study Group XIII (Period 1963-1966) . , .....................................

271

List of documents of the Xlth Plenary Assembly established by Study GroupXIII

279....................

12
Page

RECOMMENDATIONS OF SECTION H (STANDARD-FREQUENCIES AND TIME-SIGNALS)
Rec. 374-1

Standard-frequency and time-signal emissions.............................................

281

Rec. 375-1

Standard-frequency and time-signal emissions in additional frequency bands

282

Rec. 376-1

Avoidance of external interference with emissions of the standard-frequency
service in the bands allocated to that service............................................

283

REPORTS OF SECTION H (STANDARD-FREQUENCIES AND TIME-SIGNALS)
Report 267-1

Standard-frequencies and time-signals........................................................

285

Report 269-1

Reduction of mutual interference between standard-frequency and timesignal em issio n s...........................................................................................

295

Report 270-1

Frequency-spectrum conservation for high precision time-signals . . . .

296

Report 271-1

Stability and accuracy of standard-frequency and time-signals as received

297

Report 362

Single-sideband operation for the standard-frequency and time-signals e r v ic e ..........................................................................................................

299

Report 363

Intercomparisons of time scales by various methods.........................

300

Report 364

Instability of standard-frequency generators............................................

300

Report 365

Comparative statistics concerning the properties of UT and AT radio
em issio n s......................................................................................................

301

Report 366

A method for classifying systems which yield time and frequency informa­tion from the same radio emission ................................

302

QUESTIONS AND STUDY PROGRAMMES ASSIGNED TO STUDY GROUP VII (STANDARDFREQUENCIES AND TIME-SIGNALS); OPINIONS AND RESOLUTIONS OF INTEREST TO THISSTUDY GROUP
Introduction by the Chairman, Study Group V I I .........................................................................
Resolution 14-1

Standard-frequency and time-signal emissions................................

Opinion 26

Studies and experiments concerned with time-signal e m issio n s................

Question 1/VII

Standard-frequency and time-signal emissions................................

309
309

310

Study Programme 1A/VII

Standard-frequency and time-signal em issions...................

Study Programme 1B/VII

Single-sideband operation for the standard-frequency andtime-signal s e rv ic e .................................................
311

Study Programme 1C/VII

Time-signal emissions

Opinion 27

307

310

........................................................

311

Standard-frequency and time-signal emissions in additional frequency
bands ..........................................................................................................

312

Question 2/VII

Standard-frequency and time-signal emissions in additional frequency
bands ..........................................................................................................
Study Programme 2A/VII
Standard-frequency and time-signal emissions from artificial
earth satellites........................................................
313

Question 3/VII

Stability of standard-frequency and time-signal emissions as received . .

Study Programme 3A/VII

Frequency-spectrum conservation for high precision timesignals .................................................................................

312

313
314

13 —
Page

Study Programme 3B/VII
Study Programme 3C/VII

Instability of standard-frequency generators.......................
314
International comparison of standard-frequency and timesignal em issio n s............................................................
315
Question 4/VII
Dissemination of standard-frequencies and tim e-signals.....................
315
Study Programme 4A/VII
Dissemination of standard-frequencies by carrier-frequency
stabilization of broadcasting em issions.......................
316
Opinion 28
Special monitoring campaigns by the I.F.R.B. with a view to clearing thebands allocated exclusively to the standard-frequency service............
316
List of documents concerning Study Group VII (Period 1963-1966)

319

List of documents of the Xlth Plenary Assembly established by Study Group V I I ......................

324

RECOMMENDATIONS OF SECTION J (MONITORING OF EMISSIONS)
Rec. 182-1
Rec. 377-1
Rec. 378-1

Automatic monitoring of occupancy of the radio-frequency spectrum . . 325
Accuracy of frequency-measurements at monitoring s ta tio n s ..............
326
Accuracy of field-strength measurements at monitoring stations . . . .
328

Rec. 379-1
Rec. 442
Rec. 443

Identification of radio stations ...................................................................
Expeditious method of measuring field strength atmonitoringstations.
Bandwidth measurements at monitoring stations.................................

330
331
331

REPORTS OF SECTION J (MONITORING OF EMISSIONS)
Report 272-1
Report 273-1
Report 275-1
Report 276-1
Report 277-1
Report 278-1
Report 279
Report 280-1
Report 281-1
Report 282-1
Report 367
Report 368
Report 369
Report 370
Report 371
Report 372
Report 373.

Frequency measurements at monitoring stations ......................................
333
Field-strength measurements at monitoring s ta tio n s .............................
336
Bandwidth measurement at monitoring stations ......................................
341
Monitoring of radio emissions from spacecraft at fixed monitoringsta tio n s....................................................................................................
344
Measurements at mobile monitoring s ta tio n s ........................................
349
Automatic monitoring of occupancy of the radio-frequency spectrum . . 354
Visual monitoring of the radio-frequency sp e c tru m .............................
361
Identification of radio stations ...................................................................
364
Identification of sources of interference to radio reception..................
365
International monitoring facilities - Reply to Recommendation No. 5 of the
Administrative Radio Conference, Geneva, 1959
367
Monitoring of sweeping-type pulse em issions........................................
369
Expeditious method of determining field strength at monitoring stations
371
Measurement of frequencies of single-sideband, independent-sideband andother complex em issio n s.......................................................................
374
Types and methods of assistance by monitoring stations to the operationof various radio services - Exchange o f technical information between
receiving and measuring stations by means o f exchange o f s t a f f .........
375
Monitoring services in the new and developing c o u n tr ie s ......................
376
Direction-finding at monitoring s t a tio n s ...............................................
384
Antennae for monitoring s ta tio n s .......................................................
399

- 14
Page

QUESTIONS AND STUDY PROGRAMMES ASSIGNED TO STUDY GROUP VIII (MONITORING
OF EMISSIONS); OPINIONS AND RESOLUTIONS OF INTEREST TO THIS STUDY GROUP
Introduction by the Chairman, Study Group VIII ......................................................................
Resolution 15
Extension of the international monitoring system to aworld-wide scale
Resolution 16-1
Handbook for monitoring stations ............................................................
Opinion 11
List of stations using special means of identification.............................
Question 1/VIII
Frequency measurements at monitoring stations ......................................
Study Programme 1A/VIII
Method of determining the average accuracy of frequency
measurements at monitoring stations...................
425
Question 2/VIII
Measurement of frequencies of single-sideband, independent-sideband
and other complex em issions........................................................
426
Question 3/VIII
Field-strength measurements at monitoring s ta tio n s .....................
426
Question 4/VIII
Expeditious method of determining the field strength at monitoring stations
Question 5/VIII
Bandwidth measurements at monitoring stations ......................................
Question 6/VIII
Monitoring at fixed monitoring stations of emissions from spacecraft
Question 7/VIII
Monitoring of sweeping-pulse type em issions................................
429
Question 8/VIII
Direction-finding at monitoring s ta tio n s .......................................
430
Question 9/VIII
Automatic monitoring of occupancy of the radio-frequency spectrum . .
Question 10/VIII
Visual monitoring of the radio-frequency s p e c tru m .....................
431
Question 11/VIII
Antennae for monitoring s ta tio n s ..................................................
432
Question 12/VIII
Monitoring services in the new and developing c o u n tr ie s ..........
432
Opinion 29
Types and methods of assistance by monitoring stations to theoperationof various radio se rv ic e s...............................................................
433
Question 13/VIII
Types and methods of assistance by monitoring stations to the opera­tion of various radio services
433
Study Programme 13A/VIII
Types and methods of assistance by monitoring stations to
the operation of various radio services ..........................
Opinion 30
Identification of radio stations ...................................................................
Question 14/VIII
Identification of radio stations ...................................................................
Question 15/VIII
Identification of sources of interference to radio reception..........
436

417
420
421
424
424

List of documents concerning Study Group VIII (Period 1 963-1966).........................................

437

List of documents of the Xlth Plenary Assembly established by Study Group VIH

442

427
428
428

430

434
435
435

— 15 —

Rec. 75, 100

RECOMMENDATIONS OF SECTION C (FIXED SERVICES)RECOM M ENDATION 75
CLASSIFICATION AND ESSENTIAL CHARACTERISTICS
OF FEED-BACK SUPPRESSORSThe C.C.I.R.,(1951)CONSIDERING

that the feedback suppressors now generally used are of a type, the operation of which is
sufficiently independent of the characteristics of those at the opposite end of the circuit;
UNANIMOUSLY RECOMMENDS

that no classification of types nor terminology should be adopted.
Essential characteristics
The essential characteristics of the feedback suppressors, used on radiotelephone circuitsin the United Kingdom and in the United States of America for fixed services, are described
respectively in Docs. 49 and 51, Geneva, 1951. These are in substantial accord with thecharacteristics described in C.C.I.F., 1950-1951, 5th Study Group, Doc. 7, Question 2.

RECOM M ENDATIO N 100
REDUCTION OF OCCUPIED BANDWIDTHAND TRANSMITTER POWER IN RADIOTELEPHONY(Question 1/III)The C.C.I.R.,(1953)CONSIDERING(a) the urgent need for improved use of the radio-frequency spectrum, particularly in the range
below 30 MHz;(b) that a very great improvement in the use of the spectrum will arise from the replacementof double-sideband by single-sideband technique (see Recommendation 335-1, §§ 2.1 and 2.2);

— 16 —

Rec. 100, 106(c) that improvements can be obtained by the use of noise reducers and devices enabling the
average percentage of modulation to be maintained at a high level, e.g. peak-clipping devices(see Recommendation 339-1);
RECOMMENDS

1.

that Administrations should, whenever possible, make use of single-sideband systems in
preference to double-sideband systems *;2.

that noise reducers should be employed at the receiving terminal of all circuits, where an
improvement in signal-to-noise ratio can be obtained **;3. that devices should be employed at the transmitting terminal of all circuits, to enable theaverage percentage of modulation to be maintained at a high level (for example, peak-clipping
devices). With the use of these devices, adequate precautions must be taken to prevent
radiation outside the necessary bandwith (for example, by the use of an adequate low-passfilter after the device) ***.

RECOMMENDATION 106
YOICE-FREQUENCY TELEGRAPHY ON RADIO CIRCUITSThe C.C.I.R.,(1953)CONSIDERING(a) that diversity reception is not a common practice on radiotelegraph circuits;(b) that, when voice-frequency equipment is used on radio circuits at frequencies lower than about
30 MHz, the quality of these circuits will, in general, be insufficient if no means of diversity
reception is provided;(c) that, in the presence of fading, space- or frequency-diversity gives comparable improve­ments in the quality of reception of telegraph signals transmitted over radio channels;(d) that, for adequate frequency diversity, it appears necessary that the frequencies which areused in combination to obtain this diversity should differ by at least 400 Hz;(e) that space diversity needs only half the bandwidth and less power for each telegraph channel,
as compared with frequency diversity, but usually requires more equipment;
UNANIMOUSLY RECOMMENDS

1.

that, when voice-frequency telegraph systems are used on radio circuits at frequencies lower
than about 30 MHz, diversity reception should be used on the individual voice-frequency
channels;* A n improvement o f signal-to-noise ratio, or a reduction in power o f at least 9 dB, is obtained by the useo f single-sideband systems instead o f double-sideband systems.
** The improvement, which may be obtained in practice, by the use o f a noise reducer is dependent upon
the signal-to-noise ratio at the input to the noise reducer (for example, an improvement o f the order o f
10 dB m ay be obtained on radiotelephone circuits o f good commercial quality).
*** The improvement, which may be obtained in practice, is dependent upon the original average percentage
m odulation o f the transmitter. Improvement up to 6 dB may be obtained in practice.

2.

that, whenever practicable, space diversity should be used in preference to frequency diversity;

3.

that, for frequency diversity, the channel frequencies used in combination should have aseparation of at least 400 Hz so that adequate diversity effects may be obtained.

RECOMMENDATION 162-1
USE OF DIRECTIONAL ANTENNAE IN THE BANDS 4 TO 28 M Hz
(Question 10/111)
The C.C.I.R.,(1953 - 1956 - 1966)CONSIDERING(a) that there is serious congestion in the fixed-service bands between 4 and 28 MHz;(b) that occupancy of the radio-frequency spectrum is represented, not only by occupancy inbandwidth and time, but also by the spatial distribution of the radiated power;(c) that radiation outside the directions necessary for the service can be effectively reduced by
the use of directional antennae;(d) that Articles 12 and 14 of the Radio Regulations, Geneva, 1959, would seem to justify explicit
requirements for the use of directional antennae in these bands;(e) that the Panel of Experts, in Recommendation No. 13 of its Final Report, Geneva, 1963,
advocates the use of directional antennae for transmission and reception in the fixed service;(f) that the request by the Panel of Experts in Recommendation No. 38 of its Final Report, andthe urgent question of the I.F.R.B., Question 10/111, ask for specification of reasonable stan­dards of directivity for antennae in the various types of radio services in the bands between
4 and 28 MHz, with due regard to economy of cost;(g) that the adoption of minimum standards for directional antennae would contribute to thesolution of frequency sharing problems;(h) that antenna performance materially better than these minimum standards are attainable ateconomic cost using modern technique;
UNANIMOUSLY RECOMMENDS

1Definitions

that the following definitions should be used in specifying the performance of directional
antennae;
1.1 Directive gain (G)The ratio of the power radiated from a reference antenna to the power radiated fromthe antenna being considered, both antennae producing in the wanted direction, the same

Rec. 162-1— 18 —

field at the same distance. It is convenient for present purposes that the reference antennashould be an isotropic radiator in free space.
1.2 Service sector (S )The horizontal sector containing the main beam of the antenna radiation and including
the direction required for service. It is very close to twice the angular width of the main
beam measured to the half-power (- 3 dB) points.
1.3 Interference sector (I)The horizontal sector outside the main beamp = 360° 1.4 Minimum standard antenna
The antenna having the specified minimum characteristics as regards directive gain andservice sector at its operating frequency or frequencies.
1.5 Economic standard antenna
The antenna having specified characteristics as regards directive gain and service sector
at its operating frequency or frequencies which are justifiable on economic grounds (i.e. bysavings in the cost of providing a given transmitter output power).
1.6 Antenna directivity factor (M ) *The ratio of the power flux density in the wanted direction to the average value of power
flux density at crests in the antenna directivity pattern in the interference sector. This isequivalent to the average improvement in signal-to-interference ratio achieved by using theactual antenna in place of an isotropic radiator in free space;2.

that the minimum standard antenna should have a directivity factor given by
M = 0 1 /2
/b e in g the operating frequency in MHz;

3.

that the economic standard antenna should have a directivity factor given by
M = 0-25/2;

4.

that, for a radiated power of 5 kW or greater, the performance of the antenna used should
not be worse than that of the minimum standard antenna;

5.

that, for a radiated power of 10 kW or greater, antennae having performances not worse thanthat of the economic standard antenna should be used to the extent practicable;

6.

that, for transmitter powers below 5 kW, the power flux density in the interference sector should
not exceed that radiated in this sector from the minimum standard antenna with a total
radiated power of 5 kW;

7.

that, in the interests of reducing the effects of interference, the performance of the receiving
antenna should not be worse than that of the minimum standard antenna and should, as far
as practicable, attain that of the economic standard antenna.
* The derivation o f the value o f the directivity factor for any given antenna is explained in Report 356.

Explanatory notes
The values of directive gain and service sector appropriate to the specified M values forthe minimum standard antenna and the economic standard antenna respectively are given in
the following table:

M inimum standard antenna

Economic standard antenna

Operatingfrequency/(M H z)

M

G(dB)

s°

M

G(dB)

s°

5

2-5

13-8

54

6-25

17-5

35

10

10

16-6

39

25

20-4

25

15

22-5

18-3

32

57

22-1

21

20

40

19-4

28

100

23-3

18

The antenna gain relative to a half-wave dipole above earth may be obtained by sub­tracting 8 dB from the value of G. It should be noted that the S value is the minimum boundat the directive gain specified and has been derived on the assumption that at least 40% of
the total power is radiated in the main beam (a value appropriate to many rhombic antennae).
Where (as is commonly the case) the (power) gain of the antenna (No. 99 of the Radio Regu­
lations) is known, a suitable adjustment should be made to account for the efficiency of
the antenna in deriving the directive gain.
No preferred polarization or type of antenna is established. Horizontal polarization
offers better round reflection characteristics and, for receiving, some reduction of interference
due to man-made noise. Where reflection over sea water or over earth of very high conduct­
ivity takes place, the use of vertical polarization can enhance the low-angle performanceneeded for long paths. This important consideration is reflected in the computation of M,
which includes a weighting factor 10/A, where A is the vertical angle of optimum radia­
tion. There is no requirement for the transmitting and receiving antennae to have the samepolarization characteristics because of the randomisation of the polarization in the iono­
spheric transmission process.
The M-factors chosen are largely based upon the measured performance of typicalrhombic antennae and typical antenna-arrays. The radiation characteristics of single rhombic
antennae in the interference zone, are in general, somewhat inferior to other types of antenna(e.g. halfwave antenna arrays), a fact which is reflected in the M -factor. Provided the para­
meters are correctly chosen, the performance of antennae of differing types possessing thesame M-factor are comparable.

Rec. 166-1, 240— 20 —♦

RECOM M ENDATION 166-1
UNIT OF QUANTITY OF INFORM ATIONThe C.C.I.R.,(1956 - 1966)

UNANIMOUSLY RECOMMENDS

the following definition of the unit of quantity of information:“ the unit of quantity of information corresponds to a message unit consisting of arandom choice between two equally probable signals.” (Xth General Assembly of
U.R.S.I., Sydney, 1952). This unit may be designated by the word bit.

R ECOM M ENDATION 240 *SIGNAL-TO-INTERFERENCE PRO TECTION RATIOS(Question 1/III — Study Programme 1A/III)The C.C.I.R.,(1953 - 1956 - 1959)CONSIDERING

that knowledge of the signal-to-interference protection ratios for various types of serviceis needed;
RECOMMENDS

1.

that the values of signal-to-interference ratios for stable conditions, below which harmfulinterference occurs, can be used in conjunction with the fading allowances in the Annex toRecommendation 340;

2.

that the values shown in the Table are appropriate to emissions indicated.

* This Recom m endation replaces Recommendation 163. The R.P. o f Bulgaria, the Ukrainian S.S.R.,
the Czechoslovak S.R. and the U .S.S.R . reserved their opinion on this Recommendation.

T ableMinimum protection ratios and frequency separations required under stable conditions
Interfering signal

W anted signal
Al
100 bauds

A1
50 baudsC1)
Type o f service

1

2

3

4

1

2

3

(dB)

(kHz)

(dB)

(kHz)

Al-50 baud teleprinterB = 500 Hz

11

0-36 0-44 114

( 2)
12

0-25 0-35

FI-50 baud teleprinter
2D = 280 Hz, B = 500 Hz

1

0-2

(2)

( 2)

0-28 0-6

F I 100 bauds
2D = 400 Hz

F I 50 bauds
2D = 280 H z(!)
4

1

2

3

4

(dB)

(kHz)

13

0-46 0-54 1-24

7

0-32 0-39 0-67

1

2

(dB)

( 2)

3

3
(kHz)

( 2)

4

1
(dB)

(3)

( 2)

F I—171 baud ARQ system
2D = 400 Hz, B = 500 Hz

(4)

3

(2)

( 2)

( 2)

(4)

0-35 0-50

2

3

4

(kHz)

( 2)

18

Fl-50 baud teleprinter
2D = 400 Hz, B = 500 Hz

2

0-40 0-55

Fl-50 baud teleprinter
2D = 280 Hz, B = 3000 Hz

F4-phototelegraphy, 60 r.p.m.
B =1000 Hz

B roadcast^)

( 2)

( 2)

(3)

3

(3)

4-5

(3)

7-5

0-45 0-60( 4)0-40 0-55

(4)

4

(4)

( 4)

4

0-50 0-70

15

100 1-20

15

M0

1-20

f1) Bandwidth o f interfering signals limited to 500 H z;
(2) For a character error rate o f 1/10000;(3) F o r a character error rate o f 1/1000;(4) F o r a traffic efficiency o f 90 %;(5) Average m odulation degree o f 4 0 % ; for this test the sideband components extended to ± 9 kHz.

Rec. 240

In the column “ Type o f service ”, B represents the receiver bandwidth and 2D represents the total frequency shift. Columns numbered 1 give the limiting values o f signal-tointerference ratio (dB) when the occupied band o f the interfering emission either falls entirely within the pass-band o f the receiver, or covers it completely. Columns numbered 2, 3 and4 indicate the frequency separation necessary between a wanted and an interfering signal, when the level o f the latter is 0, 6 or 30 dB higher than the wanted signal.

— 22 —

Rec. 246-1

RECOM M ENDATION 246-1
FREQUENCY-SHIFT KEYING(Question 8/III)The C.C.I.R.,(1951 - 1953 - 1956 - 1959 - 1966)CONSIDERING(a) that frequency-shift keying is employed in radiotelegraphy in the fixed service and that its
use has also been extended to the mobile service;(b) that it is desirable to adapt the frequency-shift used to the modulation rate;(c) that traffic interruptions should be reduced to a minimum by avoiding frequent changesof the shift employed;(d) that it is often necessary to employ the same radio transmitter to work with more than one
receiving station;(e) that it is desirable to standardize the main operating characteristics of systems em­
ploying frequency-shift keying;(f) that various technical factors influence the choice of operating characteristics in such systems,
in particular:- economy of bandwidth and the consequent need to control the shape of the transmitted
signals,- signal distortion due to propagation conditions,- instability of the characteristics of certain transmitter and receiver elements (such as oscilla­
tors, filters or discriminators); this instability being one of the reasons for the relatively
large shift employed in many existing types of equipment;(g) that difficulties can arise from the use of terms “ mark ” and “ space ” on teletype circuits
and also that the C.C.I.T., at its V llth Plenary Assembly, issued Recommendation 1.4
introducing new terms; these terms have been published by the I.T.U. in the “ List of
Definitions of Essential Telecommunication Terms ”, Part I, General Terms, Telephony,
Telegraphy, June 1957;
UNANIMOUSLY RECOMMENDS

1.

that it is too early to standardize actual values of frequency-shift, but that every effort should
be made to achieve this as quickly as possible for emissions using only two frequencies; andto assist in this, the characteristics shown below should be used as far as possible;

2. that the value of the frequency-shift employed should be the lowest compatible with the maxi­
mum modulation rate regularly used, the propagation conditions and the equipment stability;
3. that for frequency-shift systems working on two conditions only (i.e. single-channel or timedivision multiplex systems) and operating between about 3 MHz and 30 MHz, the preferredvalues of frequency-shift are 200 Hz, 400 Hz and, for modulation rates above 250 bauds,
500 Hz;4. that the values 140 Hz, 280 Hz and 560 Hz may be used provisionally, but 560 Hz should
not be adopted for new systems;
5. that the value of the frequency-shift should, if possible, be maintained within ± 3 % of its
nominal value and, in any case, within ± 10%;

— 23 —
6.

Rec. 246-1, 335-1

that for circuits using the Morse code, the higher frequency should correspond to the marksignal, and the lower frequency should correspond to the space signal;

7.* that for circuits using the International Alphabet No. 2 code with start-stop apparatus, thehigher frequency should correspond to the start signal (position A) and the lower frequency
to the stop signal (position Z );8.* that, for telex circuits using the International Alphabet No. 2 code directly on the radio
circuit, the higher frequency should correspond to the C.C.I.T.T. “ free circuit condition ”(position A) and the lower frequency to the C.C.I.T.T. “ idle-circuit condition ” (position Z);
9.* that for channels of a 7-unit automatic repetition system, which are referred to in the Annex
to Recommendation 342-1 as directly keyed channels (e.g. channel A of a two-channel system),the higher frequency should correspond to the code elements shown as letter A and the lower
frequency to the code elements shown as letter Z. For the channels which are tohave reversed keying (e.g. channel B of a two-channel system), the higher frequency should
correspond to the code elements shown as letter Z and the lower frequency to the code ele­ments shown as letter A.

RECOMMENDATION 335-1
USE OF RADIO LINKS IN INTERNATIONAL TELEPHONE CIRCUITSThe C.C.I.R.,(1951 - 1963 - 1966)CONSIDERING(a) that, at the present time, radiotelephone systems connecting the various countries usuallyemploy carrier-frequencies below about 30 M H z**;(b) that the use of such a radio link, in a long-distance telephone circuit, implies certain special
conditions, which introduce particular difficulties not encountered when purely metallic
connections are used;(c) that such a radiotelephone circuit differs from a metallic circuit in the following ways;
c.a such a radiotelephone circuit is subject to attenuation variation with the special difficultyof fading;c.b such a radiotelephone circuit suffers from noise caused by atmospherics, the intensity of which
may reach, or even exceed, a value comparable with that of the signal which it is desired toreceive;c.c special precautions are necessary in the setting up and maintenance of such a radiotelephone
circuit, to avoid disturbance of the radio receiver by any radio transmitter and especiallyby its own radio transmitter;
c.d to maintain the radiotelephone link in the best condition from a point of view of transmis­
sion performance, it is necessary to take special measures to ensure that the radio transmitter* When modification o f equipment is necessary, it is recognized that it may take som e time before
the recommendations o f these paragraphs can be implemented on circuits between different Administrations.
** Further reference to 30 M H z in this Recom m endation means “ about 30 M H z ”.

Rec. 335-1— 24 —

always operates, as far as possible, under conditions of full loading, whatever may be thenature and the attenuation of the telephone system connected to the radiotelephone circuit;c.e it is necessary to take measures to avoid or correct conditions of abnormal oscillation or
crosstalk;c .f although the recommended frequency band, to be effectively transmitted by international
landline circuits, has been determined by a study of the requirements of the human ear, thisband (for a radiotelephone circuit operating at a frequency below 30 MHz), may be limitedby the necessity of obtaining the maximum number of telephone channels in this part of theradio-frequency spectrum and so that each telephone channel does not occupy a radiofrequency band larger than necessary;c.g in general, such a radiotelephone circuit is a long distance international circuit giving telephoneservice between two extended networks, and this fact is of great importance from two pointsof view:
c.g.a on the one hand, international conversations, in general, are of great importance tothe subscribers and, on the other hand, they are made in languages which are not always
their mother tongue, so that high quality reception is particularly important;c.g.b the public should not be deprived of a very useful service under the pretext that it does
not always satisfy the degree of excellence desirable for long distance communication;

UNANIMOUSLY RECOMMENDS

1. Circuits above 30 MHz
that between fixed points, telephone communications should be effected wherever possible
by means of metallic conductors, or radio links using frequencies above 30 MHz to makethe allocation of radio frequencies less difficult; where this can be realized, the objective
should be to attain the transmission performance recommended by the C.C.I.T.T. for inter­national telephone circuits on metallic conductors;

2. Circuits below 30 MHz
2.1 that, since it becomes necessary to economize in the use of the frequency spectrum, when
considering international circuits which consist mainly of single long-distance radio links
operating on frequencies less* than 30 MHz, it is desirable to use single-sideband transmission
to the maximum extent possible, to employ a transmitted band less than the 300 to 3400 Hz
recommended by the C.C.I.T.T. for landline circuits and, preferably, to reduce the upper
frequency to 3000 Hz or less, but not below 2600 Hz, except in special circumstances;
2.2 that, although it will be necessary to tolerate large variations in noise level on such a radio­
telephone circuit, every possible effort should be made to obtain minimum disturbance tothe circuit from noise and fading by the use of such techniques as full transmitter modulation,
directional antennae and single-sideband operation;
2.3 that, during the time that such a radiotelephone circuit is connected to an extension circuit
equipped with echo suppressors, the intensity of disturbing currents should not be sufficientto operate the echo suppressor frequently;
2.4 that such a radiotelephone circuit should be provided with a reaction suppressor (voiceoperated switching device), to avoid singing or echo disturbance on the complete circuit;
2.5 that such a radiotelephone circuit should be equipped with automatic gain control to com­pensate automatically, as far as possible, for the phenomenon of fading;
2.6 that the terminal equipment of such a radiotelephone circuit should be such that it may beconnected, in the same way as any other circuit, with any other type of circuit;

— 25 —

Rec. 335-1, 336-1

2.7 that, where privacy equipment is used, this equipment should not appreciably affect thequality of telephone transmission;
2.8 that, when suitable automatic devices are not provided, the circuit controls should be adjusted,
as often as necessary, by an operator to ensure optimum adjustment of transmitter loading,received volume and the operating conditions of the reaction suppressor.
Note. - Although the requirements contained in § 2 of this Recommendation are much less severe
than those imposed on international landline circuits, the objective remains to attain thesame standards of telephone transmission in all cases. In view of this, it is desirable thatthe telephone systems connected to a radiotelephone circuit should conform to C.C.I.T.T.
Recommendations covering the general conditions to be met by international circuits used
for landline telephony, especially in respect of equivalent, distortion, noise, echoes andtransient phenomena.
Bearing in mind the recommendations contained in §§ 1 and 2, it is desirable that ineach particular case, Administrations and private operating agencies concerned should firstreach agreement on how far the standards usually employed for international landline circuits
may be attained in the case considered. If the technique of § 1 of the Recommendation canbe used, the objective should be to obtain, as far as possible, the characteristics recommended
by the C.C.I.T.T. for international landline circuits. Otherwise the Administrations andprivate operating agencies concerned should study the best solution from the point of viewof both technique and economy.

RECOMMENDATION 336-1
PRINCIPLES OF THE DEVICES USED TO ACHIEVEPRIVACY IN RADIOTELEPHONE CONVERSATIONSThe C.C.I.R.,(1951 - 1963 - 1966)CONSIDERING(a) that the devices referred to are intended to achieve privacy rather than secrecy in radiotele­phone conversations;(b) that, in the interest of maximum privacy, the details of the systems employed and of theirperformance, should be agreed upon between the Administrations and private operating
agencies concerned;
UNANIMOUSLY RECOMMENDS

1.

that the following statement of principles and characteristics of the devices concludes thestudy of Question 30, for radio circuits operating at frequencies less than about 30 Hz;

1.1 Principles o f the devices
Two general types of system are used to achieve privacy in radiotelephone circuits operating
at frequencies less than about 30 MHz;1.1.1 For double-sideband systems
inverter systems, with or without wobbling of the carrier (i.e. rapid cyclic variation of
the carrier frequency over a few hundred hertz), the speech band being inverted abouta fixed frequency;

Rec. 336-1, 337— 26 —

1.1.2 For single-sideband and independent-sideband systems
band-splitting systems, in which the speech band is subdivided into equal frequency
bands, the speech components in the sub-bands being interchanged, with or without
frequency inversion, and, according to a prearranged sequence, to give “ scrambled ”
speech. The process is reversed at the receiving terminal to reform the speech signals.
Accurate synchronization of the switching processes at the two terminals is required;
1.2 Characteristics o f the devices
1.2.1 the band-splitting system provides privacy superior to that obtained with the inverter
system, but for satisfactory operation it can tolerate less distortion;
1.2.2 the apparatus is designed to reduce attenuation distortion and the levels of unwanted
products of modulation and of carrier signals to a minimum. The extent of
the permissible distortion due to the presence of the privacy devices is, in general,
dependent on the type of privacy and is usually agreed between the Administrations
or private operating agencies concerned;
1.3 Location o f the devices
to facilitate control and maintenance and on the grounds of economy, the privacy apparatus
is normally located at the point where the transmitting and receiving channels of a radio­
telephone circuit are combined;
2.

that, for frequencies above about 30 MHz, the details of the systems to be employed and of
their performance should be agreed upon between the Administrations or private operating
agencies concerned.

RECOMMENDATION 337 *CHANNEL SEPARATIONThe C.C.I.R.,(1948 - 1951 - 1953 - 1963)CONSIDERING(a) that, in the more usual cases, the primary factors which determine frequency separation
between channels include:- the signal power required by the receiver;- the interference power intercepted by the receiver, including that from interfering signals
and from noise;(b) that transmitters, in general, emit radiations outside the frequency bandwidth necessarily
occupied by the emission;(c) that many factors are involved, among which are the properties of the transmission medium(which are variable in character and difficult to determine), the characteristics of the receiver
and, for aural reception, the discriminating properties of the human ear;
* This Recommendation replaces Recommendation 97.

Rec. 337, 338-1— 27 —UNANIMOUSLY RECOMMENDS

1.

that the required separation between channels should be calculated by the following method:- determine the signal power intercepted by the receiver;- determine the interfering power intercepted, including both noise and interfering signal;- determine, from these data, the degree of frequency separation that produces acceptableratios of signal power to interfering power, for an acceptable percentage of the time.
Account should be taken of the fluctuating nature both of the signal and of the interference,
and, whenever appropriate, the discriminating properties of the human ear;2.

that, at every stage of the calculation, comparison should be made, as far as possible, withdata obtained under controlled representative operating conditions, especially in connection
with the final figure arrived at for the channel separation.

RECOMMENDATION 338-1
BANDWIDTH REQUIRED AT THE OUTPUT OF A TELEGRAPH
OR TELEPHONE RECEIVER(Question 1/III)The C.C.I.R.,(1953 - 1963 - 1966)CONSIDERING(a) the urgent need to determine the minimum separation between frequency assignments ofstations operating on adjacent channels, in the range 10 kHz to 30 MHz;(b) that the width of the frequency band, which is necessary at the output of the receiver, is oneof the factors which determine the band of frequencies required for the overall system;(c) that, for telegraphy, the permissible degree of distortion is not yet defined;(d) that, for telephony, the bandwidth may depend, among other factors, upon the type of privacy
equipment in use;
UNANIMOUSLY RECOMMENDS

1.

that, for telegraphy, a provisional value for the bandwidth necessary at the output of thereceiver, under average practical conditions, should be as follows:

1.1 for A1 emissions, the bandwidth in hertz, after the final detector stage, should be equal
to 2-5 times the modulation rate in bauds;
1.2 for F I emissions, the bandwidth in hertz after the discriminator, should be equal to 1-4 times
the modulation rate in bauds.
The extent to which these values can be applied, to permit closer spacing of adjacentchannels, depends upon the degree and speed of amplitude variations due to fading and upon
the differential fading of the frequencies corresponding to the two significant conditionsof modulation;

Rec. 338-1, 339-1
2.

— 28 —

that, for telephony, as a compromise between intelligibility and economy of bandwidth, thebandwidth necessary, for each speech channel at the output of the receiver, should be as
follows:

2.1 in accordance with Recommendation 335-1, the upper limit frequency should be reduced to3000 Hz or less but not lower than 2600 Hz;
2.2 the lower frequency limit of speech channels should be 250 Hz, and that of programme trans­mission channels should be 100 Hz;
2.3 for systems employing commercial privacy equipment, the necessary bandwidth for satisfac­
tory service may require the use of an upper limit frequency greater than 2600 Hz (e.g.
in five-band privacy equipment the necessary bandwidth is 2750 Hz, the upper limit
being 3000 Hz).

RECOM M ENDATION 339-1
BAND WIDTHS AND SIGNAL-TO-NOISE RATIOSIN COMPLETE SYSTEMS(Question I /III)The C.C.I.R.,(1951 - 1953 - 1956 - 1963 - 1966)CONSIDERING

that it is not yet possible to give a full and accurate answer to Question 1/III, but to assist
in giving such an answer, it is desirable to classify the important points with which future
study will have to deal;
UNANIMOUSLY RECOMMENDS

1.

that meanwhile, the values given in Table I should be adopted as provisional values for thesignal-to-noise ratio required for the class of emission concerned;

2.

that, in further study relating to the minimum separation between frequencies of stations
operating on adjacent channels, the factors detailed in the Annex should be taken into consi­
deration.

— 29 —

Rec. 339-1

TABLE I .
Signal to-noise ratios required(Stable conditions (Note 6))
Audio
bandwidtho f receiver
(kHz)

Audio
signal-to-noise
ratio
(dB)

Bandwidtho f receiver(kHz)

R atio o f peakradio-frequency
signal-noise ina 6 kH z band(dB)
(Note 1)A1 telegraphy
8 baud, low grade .................................
24 baud ...................................................
120 baud, recorder .................................
50 baud, printer ....................................

1-5
1-5
0-6
0-25

- 4
11
10
16

3
3
0-6
0-25

- 7
8
0
2

A2 telegraphy
8 baud, low grade.................................

1-5

- 4

3

...................................................

1-5

11

3

- 3
(Note 2)
12(Note 2)

FI frequency-shift telegraphy
120 baud, recorder .................................
50 baud, printer ....................................

0-25
010

4
10

1-5
1-5

2
- 2

Class o f emission

24 baud

F3 telephony
D is the frequency deviation (kHz) . . .
M is the audio bandwidth (kHz) . . . .
K is normally 1, but sometimes a higher
value is necessary(The ratio of peak radio-frequency signal-tonoise in a 6 kHz band, is lower by (4*77 -h
20 log D/M) dB than that required for A3
double-sideband telephony)

2M+2DK

3

F4 Phototelegraphy
Sub-carrier frequency-modulation single­
sideband em ission....................................

3

15

3

12

Hellschreiber
Frequency-shift........................................

1-5

6

3

3

Telephony
Double-sideband, just usable quality, ope­
rator to operator (Note 4 ) ......................
Double-sideband, marginally commercial(Note 5 ) ...............................................
Double-sideband, good commercial quality(Note 5 ) ...............................................
Single-sideband and independent-sideband,
Just usable quality, operator to operator(1 ch a n n e l)............................................
Marginally commercial (Note 5)
1 channel .....................................
4 c h a n n e ls .....................................
Good commercial quality (Note 5) . . .
1 channel .....................................
4 c h a n n e ls ....................................

(Note 3)
3

6

6

18

3

15

6

27

3

33

6

350

3

6

3

9

3
3

15
15

3
3 (2)

3
3

33
33

3
30

180
20
0, 0
260
28
0, 0

t 1) Assuming 10 dB improvement due to the use o f noise reducers.
(2) per channel.
(3) N o. 466 o f the R adio Regulations, Geneva, 1959, prohibits F3 emissions for the fixed services in the bands below 30 MHz.
(4) Assuming a nom inal allowance for 4-channel loading. If amplifier load control is used, the margin will vary dependent
upon the num ber o f talkers.

Rec. 339-1— 30 —

Note 1. - Measured as the ratio of the r.m.s. signal corresponding to peak output of the trans­mitter and the r.m.s. noise in a 6 kHz band, assuming stable conditions.
Note 2. - Carrier keyed. Beat-frequency oscillator used.
Note 3. - For telephony, the figures in this column represent the ratio of the audio signal, as

measured on a standard VU-meter, to the r.m.s. noise, for a bandwidth of 3 kHz. (Thecorresponding peak signal power, i.e., when the transmitter is 100% tone-modulated, isassumed to be 6 dB higher).
Note 4. - For 90% intelligibility of unrelated words.
Note 5. - When connected to the public service network.
Note 6. - These values are based on Doc. 138, Washington, 1950, Doc. 112, Geneva, 1951,
and Doc. 11, The Hague, 1952.
ANNEX
FACTORS TO BE TAKEN INTO ACCOUNT FOR VARIOUS SERVICES
IN DETERMINING THE MINIMUM SEPARATION BETWEEN THE
FREQUENCIES OF STATIONS OPERATING ON ADJACENT CHANNELS

1.

Required signal-to-interference ratios.

2.

Necessary bandwidth for required intelligence.

3.

Transmitters:- out-of-band radiation,- frequency instability.

4.

Propagation:- allowances for fluctuations due to absorption and fading.

5.

Receivers:- necessary bandwidth,- attenuation slope,- frequency instability.

6.

Effect of:- inequalities of received field-strength on wanted and adjacent channels,- antenna directivity at transmitter and receiver.

Rec. 340

— 31 —

RECOMMENDATION 340 *FADING ALLOWANCES FOR THE VARIOUS CLASSESOF EMISSION(Question 1/III, Study Programme 1A/III)The C.C.I.R.,(1951 - 1953 - 1956 - 1963CONSIDERING(a) that Table I to Recommendation 339-1 is a provisional and partial reply to Question 1/III,

applying to stable conditions;(b) that there is a need for figures which take into account fading and fluctuations in field intensity;(c) that it is not yet possible to give a full answer to Study Programme 1A/III;(d) that, however, the information contained in Reports 248-1 and 266-1 give some results fromwhich provisional data on fading allowances can be derived;
UNANIMOUSLY RECOMMENDS

1.

that the studies in connection with Recommendation 339-1 and Study Programme 1A/III
should be continued, in conjunction with those of Study Programme 16A/VI for the purposeof determining whether the provisional values given in the Annex may be accepted or should
be modified;

2.

that meanwhile, the values given in the Annex may be regarded as provisional total fading
allowances (combined fading safety-factors and intensity fluctuation-factors);

3.

that meanwhile, these values may be used as a guide, in conjunction with the values
for signal-to-noise ratios required for stable conditions given in Recommendation 339-1,
Table I to estimate monthly-median values of hourly-median field intensity, necessary forthe various types and grade of service: similarly, the fading allowances may be used as a
guide, in conjunction with the values for signal-to-interference ratios (for stable conditions),
appropriate to the various services.

* This Recommendation replaces Recommendation 164.

Rec. 340

— 32 —

ANNEX
Provisional total fading allowances0
F or the protection o f a fading signal against :atmospheric noise
subject to day-to-day
intensity fluctuation(subtract 4 dB forprotection against
steady noise or steadyinterfering signal)(see N ote 1)

Class o f emission(2)interfering signal
subject to fading
and day-to-day
intensity fluctuation(see N ote 2)dB relative to ratios o f monthly medianvalues of- hourly-median field-strength

A1 telegraphy
8 baud, low grade .................. . . (Note 3)
24 baud ........................................ . . (Note 4)
120 baud recorder ......................
(Note 6)50 baud p r i n t e r ..........................

21
25
25
32

17
20
20
27

A2 telegraphy
8 baud, low g r a d e ...................... . . (Notes 3, 7)
24 baud ........................................ . . (Notes 4, 7)

17
20

13
17

FI telegraphy
120 baud recorder ......................
50 baud p r i n t e r ..........................
automatic repetition printer (ARQ)

25
32
17

20
27
12

23

20

23

20

17
19
21

11
14
17

21

17

(Note 6)(Notes 5, 6). (Notes 6, 8)

F4 phototelegraphy
sub-carrier
frequency-modulation
emission .....................................

single-sideband

Hellschreiber frequency-shift . . . .

.

(Note 9)A3 telephony
DSB just usable quality, operator too p e ra to r.....................................
(Note 10)(Note 11)
DSB marginally commercial . . .
DSB good commercial quality . .
. (Note 12)( 1 channel . . . .
• | (Note 12)
SSB and ISB j \V4 channels . . . .
(!) Combined fading safety factor and intensity fluctuation allowances.
(2) From Recommendation 339-1, Table I.

— 33 —

Rec. 340

Note 1. - The allowance for day-to-day fluctuation (intensity fluctuation factor) for the signal,
against steady noise, is 10 dB, estimated to give protection for 90% of the days. The fluctua­
tions in intensity of atmospheric noise are also taken to be 10 dB for 90% of the days. Assum­
ing that there is no correlation between the fluctuations in intensity of the noise and thoseof the signal (the worst condition likely to exist), a good estimate of the combined signal andnoise factor is:]/ 102 + 102 = 14 dB
The combined fading allowance in Column 1 is obtained by adding 14 dB to the fading
safety factor applied to each type of service. Subtraction of 4 dB reduces the intensity
fluctuation allowance to 10 dB, which is the value for the signal alone; the net allowance
would then be appropriate for the protection of a fading signal against steady (non-fluctuating)noise or a steady (non-fading or fluctuating) interfering signal.
Note 2. - The probability distribution of the ratio of two signals fading independently has been
applied in accordance with Doc. 443 (U.S.A.), London, 1953. The combined intensity
fluctuation allowance for two signals has been taken as 7 dB, which represents a compromise
between the 0 dB allowance, appropriate to perfectly correlated intensity fluctuations of thetwo signals, and the 14 dB allowance, appropriate to uncorrelated intensity fluctuations of
the two signals (see Note 1).
General Note. - Use of the recommended values only permits an estimate to be obtained, which
may have to be adjusted for radio circuits of different lengths, depending on the quality oftransmission required. In calculating the fading safety factor for rapid or short-periodfading, a log-normal amplitude distribution of the received fading signal has been used (using
7 dB for the ratio o f median level to level exceeded for 10 % or 90% of the time) except for
high-speed automatic telegraphy services, where the protection has been calculated on theassumption of a Rayleigh distribution. The following notes refer to protection against rapid
or short-period fading.
Note 3. - For protection 90% of the time.
Note 4. - For protection 98 % of the time.
Note 5. - For protection 99-99% of the time.
Note 6. - Minimum of 2-element diversity assumed.
Note 7. - Total sideband power, combined with keyed carrier, is assumed to give partial (twoelement) diversity effect. An allowance of 4 dB is made for 90 % protection (8 baud),
and 6 dB for 98 % protection.
Note 8. - Based on 90% traffic efficiency.
Note 9. - Based on 95 % protection.
Note 10. - Based on 70% protection.
Note 11. - Based on 80% protection.
Note 12. - Based on 90% protection.

3

Rec. 341

— 34 —

RECOMMENDATION 341 *THE CONCEPT OF TRANSM ISSION LOSS
IN STUDIES OF RADIO SYSTEMS(Question 1/III, Study Programme 1A/III)The C.C.I.R.,(1959)CONSIDERING(a) that the radio-frequency signal power, pa, available ** at the terminals of a receiving antenna
for a given power input, pt, to the terminals of a transmitting antenna, provides a measure
which is useful in determining, at the terminals of the receiving antenna, the service from, or
the interference produced by, a radio system involving a transmitting antenna, a receiving
antenna, and the intervening propagation medium;(b) that the ratio, pt/p&, which will be called the system loss, is a convenient dimensionless form
for expressing this measure of the combined radio propagation and circuit loss characteristics
of such a system;(c) that the available power, at the terminals of the receiving antenna, is sometimes a simpler
and more directly useful concept than that of the effective field-strength, especially where theeffective field is the resultant of a large number of received field components, corresponding
to several modes of propagation, arriving at the receiving antenna at different angles andpossibly with different polarizations;(d) that the relationship between the system loss and the conditions in the neighbourhood of thereceiving antenna, does not depend solely on the received field-strength, because the impedanceof the antenna depends itself upon the conditions in its neighbourhood;(e) that the power, P t, radiated from the transmitting antenna, required for satisfactory reception
in the presence of noise, is precisely determined for a system with transmission loss, L, by thesimple relation: Pt = L +P; P is the minimum signal power that is required to provide
satisfactory reception (as defined in Report 322), available from an equivalent lossless receiving
antenna;(f) that it is desirable to standardize terminology and notation for describing system loss andits various components;
UNANIMOUSLY RECOMMENDS

that the terminology and notation given in the Annex should be adopted for use by the
C.C.I.R., in accordance with the further discussion of the use of these terms given in
Report 112.

ANNEX
1.

System loss (Ls) .
The system loss of a radio circuit, consisting of a transmitting antenna, a receiving antenna
and the intervening propagation medium, is defined as the ratio, pt/pa, where pt is the radiofrequency power input to the terminals of the transmitting antenna and p a is the resultant radio­* This Recommendation replaces Recommendation 241.
** The available power, p a, is the power which would go to the load if it
antenna impedance.

werematchedtothe— 35 —

Rec. 341

frequency signal-power available at the terminals of the receiving antenna. Both pt and p a
are expressed in watts. The system loss is usually expressed in decibels: *Ls — 10 lOglO {ptjpa) — Pt — Pa
Note that the system loss, as defined above, excludes any transmitting or receiving antennatransmission line losses, since it is considered that such losses are readily measurable. On
the other hand, the system loss includes all of the losses in the transmitting and receiving
antenna circuits, including, not only the transmission loss due to radiation from the trans­mitting antenna and re-radiation from the receiving antenna, but also any ground losses,
dielectric losses, antenna loading coil losses, terminating resistor losses in rhombic antennae,
etc. The inclusion of all of the antenna circuit losses in the definition of system loss provides
a quantity which can always be accurately measured and which is directly applicable to thesolution of radio system problems.

2.

Transmission loss (L) .
The transmission loss of a radio circuit, consisting of a transmitting antenna, a receiving
antenna, and the intervening propagation medium, is defined as the dimensionless ratio,
Pt IPa } where pt is the radio-frequency power radiated from the transmitting antenna, andp a' is the resultant radio-frequency signal power which would be available from the receiving
antenna, if there were no circuit losses other than those associated with its radiation resistance.
The transmission loss is usually expressed in decibels:
L = 10 logio (pt IP a ) — Ls — Ltc — Lrc
where Ltc and Lrc are the losses, expressed in decibels, in the transmitting and receiving
antennae circuits respectively, excluding the losses associated with the antennae radiation
resistances; i.e., the definitions of Ltc and L rc are 10 logio (r'/r), where r' is the resistive compo­
nent of the antenna circuit and r is the radiation resistance.

3.

Basic transmission loss (Lb)»
The basic transmission loss (sometimes called path loss), of a radio circuit, is the trans­mission loss expected between ideal, loss-free, isotropic, transmitting and receiving antennae
at the same locations as the actual transmitting and receiving antennae.

4.

Path antenna gain (Gp)
The path antenna gain is equal to the change in the transmission loss when lossless,isotropic antennae are used at the same locations as the actual antennae:
Gp — Lt> — L

5.

Path antenna power gain (Gpp)
The path antenna power gain is equal to the increase in the system loss when lossless,isotropic, antennae are used at the same locations as the actual antennae:
Gpp = Lb — Ls — Gp — Ltc — Lrc* Throughout this Recommendation, capital letters are used to denote the ratios, expressed in decibels,
o f the corresponding quantities designated with lower-case type; e.g. .P«=10 logio Pi. Pt is the input
power to the transmitting antenna, expressed in decibels above 1 W.

Rec. 341

— 36 —

Note that Gpp will be negative when the antenna circuit losses exceed the path antenna gain.
In some idealized situations, the path antenna power gain, GPP, is simply the sum(GtP + Grp) of the free space power gains, Gtp and Grp, of the transmitting and receiving
antennae relative to lossless, isotropic antennae. However, in most practical situations, Gpp
is less than (GtP + Grp), because o f the complex nature of the received field. The pathantenna power gain may be measured, by determining the increase in the system loss whenboth the transmitting and receiving antennae are replaced simultaneously, by simple standard
antennae such as short electric or magnetic dipoles, and then adding the calculated pathantenna power gain corresponding to the use of the standard antennae. For ionospheric or
tropospheric scatter propagation, the path antenna power gain is sometimes substantiallysmaller than the sum of the free space power gain (GtP + Grp); in such cases, the path antenna
power gain cannot be defined by the sum of the effective power gains of the transmitting andreceiving antennae (as determined by replacing first one antenna and then the other successively
by a standard antenna), since such effective power gains depend upon the gain of the antennaused at the other terminal.
For ionospheric or tropospheric propagation, the transmission loss L, the basic trans­mission loss L d, and the path antenna gain Gp, are all random variables with respect to time,
and tend to be normally distributed about their expected values. Typically, L and Gp are
negatively correlated with each other, and thus the variance of Lb is usually substantially lessthan the sum of the variances of L and of Gp; for this reason it will often be more practical
simply to measure the system loss with the particular antennae intended for use, rather thanattempt to calculate the expected system loss and its variance with time, in terms of the measured
or calculated values of the basic transmission loss, the path antenna gain, and the losses Ltc
and Lrc.
Note also that the path antenna gain may actually be negative. For example, the pathantenna gain will usually be negative for ground wave or tropospheric wave propagation
between a vertically polarized and a horizontally polarized antenna, and the concept of pathantenna gain should prove to be useful for expressing the results of such cross-polarization
measurements.

6. Propagation loss (Lp)
The propagation loss is the system loss expected if the antennae gains and circuit
resistances were the same as if the antennae were located in free space:
L p — Ls — Lt — Lr
Lt and L r are defined by 10 logio (r'fr/) where r' is the actual antenna resistance and r/ is theresistance the antenna would have if it were in free space and there were no losses other thanradiation losses.

— 37 —

Rec. 342-1

RECOMMENDATION 342-1
AUTOMATIC ERROR CORRECTING SYSTEM FOR TELEGRAPH
SIGNALS TRANSMITTED OVER RADIO CIRCUITS(Study Programme 5A/III)The C.C.I.R.,(1951 - 1953 - 1956 - 1959 - 1963 - 1966)CONSIDERING(a) that it is essential to be able to interconnect terminal start-stop apparatus employing theInternational Telegraph Alphabet No. 2 by means of radiotelegraph circuits;(b) that radiotelegraph circuits are required to operate under varying conditions of radio pro­pagation, atmospheric noise and interference, which introduce varying degrees of distortion
which may at times exceed the margin of the receiving apparatus;(c) that, in consequence, the transmission of 5-unit code signals over radio circuits is liable toerrors and that such errors are not automatically detectable by the receiving apparatus;(d) that an effective means of reducing the number of wrongly printed characters is the use ofcodes, permitting the correction of errors by detecting the errors and automatically causing
repetition;(e) that the method using synchronous transmission and automatic repetition (ARQ), is now
well proven;(f) that it is desirable to permit the correct phase to be established automatically on setting
up a circuit;(g) that certain circumstances can occur which may result in a loss of the correct phase relationshipbetween a received signal and the receiving apparatus;(h) that it is desirable to permit the correct phase relationship to be re-established automaticallyafter such a loss, without causing errors;(i) that, to avoid mis-routing traffic, it is essential to prevent phasing to a signal which has been
unintentionally inverted;(j) that there is sometimes a need to subdivide one or more channels, to provide a number of
sub-channels at a proportionately reduced character rate;(k ) that the method of automatically achieving the correct phase relationship between the received
signal and the sub-channelling apparatus should be an integral part of the phasing process;(I) that compatibility with existing equipment, designed in accordance with Recommendation 242;
Los Angeles, 1959, is a requirement;
UNANIMOUSLY RECOMMENDS

1.

that, when the direct use of a 5-unit code on a radio circuit gives an intolerable error rate andthere is a return circuit, a 7-unit ARQ system be employed;2.

when automatic phasing of such a system is required, the 7-unit system, described in
Annex I, should be adopted as a preferred system;

3.

that equipment, designed in accordance with § 2, should be provided with switching, to permit
operation with equipment designed in accordance with Recommendation 242, Los Angeles,
1959.

Note. - Methods in accordance with this Recommendation are described in Doc. I ll/17, Geneva,
1962.

— 38 —

Rec. 342-1

ANNEX I.

1.

Table of conversion
T able I
Table of code conversion

A
B
C
D
E
F

G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
w

X
Y
z

Carriage return
Line feed
Figures
LettersSpace
Unperforated tape
Signal repetition
Signal a
Signal p

2.

International code N o. 2

7-unit code

ZZAAA
ZAAZZ
AZZZA
ZAAZA
ZAAAA
ZAZZA
AZAZZ
AAZAZ
AZZAA
ZZAZA
ZZZZA
AZAAZ
AAZZZ
AAZZA
AAAZZ
AZZAZ
ZZZAZ
AZAZA
ZAZAA
AAAAZ
ZZZAA
AZZZZ
ZZAAZ
ZAZZZ
ZAZAZ
ZAAAZ
AAAZA
AZAAA
ZZAZZ
ZZZZZ
AAZAA
AAAAA

AAZZAZAAAZZAAZZAAZZAA
AAZZZAAAZZZAAAAAZAAZZZZAAAAZZAZAAZAZZZAAAAAZAAAZZAAAZAZZZZAAAZAZAZAAAZZAZAZAAZAAAZZAZAAZAZAAAAZZAZZZAAZAAAZAZAZAZAAAZAZAZZAAZAZAAZAAZAZAAZAZ
AAZAZZAAAZAZAZAZZAAAZZAAAAZZZAZZAAAAZAAZZAAAAZZZAZZAZAAA
AAAAZZZAZZAZAAAZAZAAZAZAZZAA

Repetition cycles

2.1 Four characters for normal circuits, which are not subject to excessive propagation time.
The cycle should comprise one “ signal repetition ” and three stored characters.
2.2 Eight characters on circuits for whichthe four-character repetition cycle isinadequate. The
cycle should comprise one “signalrepetition ”, three signals p and four stored characters, or
one “ signal repetition ” and seven stored characters.

3.

Channel arrangement

3.1

Channel A
3.1.1 For equipment employing a 4-character repetition cycle: one character inverted followedby three characters erect. (See Fig. 1a).
3.1.2 For equipment employing an 8-character repetition cycle: one character inverted
followed by seven characters erect. (See Fig. 2d).

— 39 —

Rec. 342-1

3.2 Channel B
3.2.1 For equipment employing a 4-character repetition cycle: one character erect followedby three characters inverted. (See Fig. 1b).
3.2.2 For equipment employing an 8-character repetition cycle: one character erect followed
by seven characters inverted. (See Fig. 2b).
3.3 Channel C
As for Channel B (See Figs. lc and 2c),
3.4 Channel D
As for Channel A (See Figs. Id and 2d).
3.5 Order o f transmission
3.5.1 Characters of Channels A and B are transmitted consecutively. (See Figs. le and 2e)
3.5.2 Elements of Channel C are interleaved with those of Channel A. (See Figs. 1g and 2g).
3.5.3 Elements of Channel D are interleaved with those of Channel B. (See Figs. 1g and 2g).
3.5.4 In the aggregate signal, A elements precede those of C, and B elements precede those ofD. (See Figs. Ig and 2g).
3.5.5 The first erect character on A, transmitted after the inverted character on A, is followedby the erect character on B. (See Figs. le and 2e).
3.5.6 The erect character on C is followed by the inverted character on D. (See Figs. I f
and 2/).
3.5.7 The inverted character on A is element-interleaved with the erect character on C.
(See Figs. 1g and 2g).

4.

Sub-channel arrangement

4.1 The character transmission rate of the fundamental sub-channel should be a quarter of thestandard character rate.
4.2 Sub-channels should be numbered 1, 2, 3 and 4 consecutively.
4.3 Where a 4-character repetition cycle is used, sub-channel 1 should be that sub-channel which
has opposite keying polarity to the other three sub-channels of the same main channel.
(See Fig. 3a-d).
Where an 8-character repetition cycle is used, sub-channel 1 should be that sub-channel
which has alternately erect and inverted keying polarity. (See Fig. 3e-li).
4.4 When sub-channels of half-character rate, or three-quarter-character rate are required,combinations of the fundamental sub-channels should be arranged as shown in Table II.
T able I I
Proportiono f full-channel character rate

Combinationof fundamental sub-channels(1) quarter(2) quarter(3) half

No: 1
No. 3
Nos. 2 and 4(!) half(2) half

Nos. 1 and 3
Nos. 2 and 4(1) quarter(2) three-quarters

No. 1
Nos. 2, 3 and 4

Rec. 342-1

5.

— 40 —

Diagrams
As a result of the characteristics specified in §§ 2, 3 and 4 of this Annex, the transmissionof characters will be as shown in Figs. 1, 2 and 3.

6.

Automatic phasing

6.1 Automatic phasing should normally be used.

It should be initiated either:

6.1.1 after a waiting period during which cycling due to the receipt of errors has occurred
continuously on both channels of a 2-channel system, or on at least two main channels
of a 4-channel system;
6.1.2 after equal counts of A and Z elements have been made over at least two consecutive
system cycles whilst continuous cycling due to the receipt of errors is occurring on
all main channels;
6.2 when the slave station is phasing, it should transmit in each channel, in place of the “ signal
repetition ”, a 7-element signal in which all 7 elements are of the same polarity, all othercharacters in the repetition cycle being transmitted unchanged; *7.

C.C.I.T.T. Recommendation S. 12 recommends, that the interval between the beginning of
successive start elements of the signals transmitted into the landline network be 145 5/6 ms.
Therefore, the duration of the transmission cycle on the radio circuit and also the modulation
rate must be chosen correspondingly, if connection to the network is required.
Practical values for the modulation rate in bauds and the duration of the transmission
cycle, which enable synchronization to be effected by using a single oscillator for three cases,
are shown in Table III.
T able III

Transmission
cycle
(ms)

145 5/6

M odulation rate (bauds)
2-channel
operation

96

4-channel
operation

192

This is the preferred standard. See C.C.I.T.T. Recommenda­
tions S. 12 and S. 13
163 1/3
140

85 5/7100 -171 3/7
200

The transmission cycle of 145 5/6 ms is the preferred standard for connection to 50-baud
networks.
The transmission cycle of 163 1/3 ms is suitable for connecting to 45-bauds networks.
The transmission cycle of 140 ms is suitable for radio circuits without direct connection
to a landline network.
The tolerance on the frequency of the master oscillator, controlling the timing of eachterminal equipment, should be ± 1 x 10-6.
8.

C.C.I.T.T. Recommendation U.20 gives the signalling conditions to be used when telexcommunication is to be established by means of such radio circuits.
* Existing systems without this facility need not be modified because compatibility is assured.

— 41 —

Rec. 342-1

8.1 for circuits on switched telegraph networks, the conditions of C.C.I.T.T. Recommendation
U.20 should apply;
8.2 for point-to-point circuits, Administrations may adopt, at the terminal equipment under
their jurisdiction, their own method of stopping and starting the motors of the receiving
machines, based on C.C.I.T.T. Recommendation S.7;
8.3 signal 3 should normally be transmitted to indicate the idle circuit condition. However, forsignalling purposes, the signals a and 3 may be employed.

Characters

Ref in Annex I

1------(a)3.1.1

Channel A

(b)

3.2.1

Channel B

(c)

3.3

Channel C

(d)

3.4

Channel D

l_L.
2

3

4

3

4

____ i____

T
i T

j

_______ J________

1
2

!~T

1-------34

L I.

Four-character repetition cycle

(e)

3.5.1
3.5.5

Combination of charactersof channels A and B(B1 follows A2)

(f)

3.5.6

Combination of charactersof channels C and D(D1 follows Cl) •

(g)

3.5.2
3.5.3
3.5.4
3.5.7

Ai

B4

A 2 1 Bi ' As

B2

A4

B3

At

D4

C1

T TTTTCl

Expanded view of
4 channels A, B, C and D^Di

C2 D2 Cs D3 C4-----CM , CO . CO

. lO . LO . CD . CD .

The characters of channels A and C Channels
are element-interleaved
B and DF igure 1

Channel arrangement for a four-character repetition cycle

Rec. 342-1— 42 —

Ref. in Annex I

Characters-—i --- :—i--- —i

(a)

3.1.2

Channel A

L_lT

(b)

3.2.2

Channel B

n

2

(c)

3.3

Channel C

n

2

(d)

3.4

Channel D

2

3

4

5

3

4

5

J — ----- 1—___ I

1

3

I

4

I

r

n----- -i— —-\

6 - 7

6

L.

5

I

5

|

1

8

|

1

I___

1-------- 1_____ I

6,

7~T~ r r

7

8

I

7

,

6

I

8

|

8

i

,

7

1

I
,

1

I__

Eight-character repetition cycle

( e)

3.5.1
3.5.5

(f)

3.5.6

Combination of charactersof channels A and B(B1 follows A2)

Ai E>8 A2 B1A3|B2{^B3[^B4{A6{B5|A7|B6[A8|B7 Al_

Combination of charactersof channels C and D(D1 follows Cl)

C1 Pi C2|d^C3Hc4|d^ 5 H c6H c7|dt|c8|d8Ci]

L
(g)

3.5.2
3.5.3
3.5.4
3.5.7

Expanded view of
4 channels A, B, C and D

CM. CM . CO . CO| ^ ■ r f ■ i n . l O . CD. cd T ' 1—

The characters of channels A and C Channels
are element-interleaved
B and DF igure 2

Channel arrangement for an eight-character repetition cycle

— 43 —

Ref. in Annex I

(a)

3.1.1
4.2
4.3

(b)

3.2.1
4.2
4.3

(c)

3.3
4.2
4.3

( d)

Rec. 342-1

Four-character repetition cycle

Channelcharacters

Sub-channel
No.

3.4
4.2
4.3

Eight-character repetition cycle

(e)

3.1.2
4.2
4.3

(/)

3.2.2
4.2
4.3

( 8)

3.3
4.2
4.3

(h)

3.4
4.2
4.3

4

3

1

5

r

I__

1

2

5

6

I__7

4

1---3

4

3

4

F igure 3

Sub-channelling arrangements for a four and an eight-character repetition cycle.

Rec. 342-1— 44 —

ANNEX IIT erm s r e l a t e d t o A R Q -S y ste m s *Part 1

1. Signal repetition
RQ-signal
Signal Roman one- the seven unit combination (AZZAZAA) which is used torequest a repetition (RQ-signal) or to precede a re-transmission(BQ-signal);

2. Repetition cycle- the sequence of characters, the number of which is deter­
mined by the loop time-delay o f the system, to provide auto­
matic repetition of information;

3. RQ-cycle
Request cycle- the repetition cycle transmitted by ARQ-apparatus at thedetection of a mutilation;

4. BQ-cycle
Response cycle- the repetition cycle transmitted by ARQ-apparatus at a request
for repetition;

5. Non-print cycle- the interval at the ARQ-receiver, initiated by the detection ofa mutilation or a signal repetition, that has the same duration
as a repetition. cycle and during which all signals received
are prevented from being printed;

6. Gated RQ- a procedure in which a check is made for the presence of asignal repetition during a non-print cycle;

7. Tested RQ- a procedure in which a check is made for the presence of asignal repetition and a check is made for the ratio A/Z on all
characters received after the signal repetition within the non­print cycle;

8. Tested repetition cycle- a non-print cycle in which a check is made for the presence ofa signal repetition and for the correct ratio A/Z of all thecharacters received;

9. Cycling- the condition that a repetition procedure is in progress;

10. Marking pattern- a specific pattern of polarity inversions applied to characters inan aggregate signal;

11. Marked cycle
System cycle- a cycle consisting of a specific character marking pattern,that is continuously repeated and has the duration of arepetition cycle',

12. System phase
Marked cycle phase- the condition in which the marking pattern of the local timing
coincides with the marked cycle of the received signal;

13. Phasing
Phase hunting- the condition in which a station is hunting for character phaseor system phase',

14. Manual phasing- phasing by manual action only;* The twenty-three terms and definitions in Part 1 o f this list have been studied by a joint Working Partyo f Study Groups III and XIV during the Xth Plenary Assem bly o f the C.C.I.R. Geneva, 1963, as a pro­visional contribution (see § 2 o f the Annex to Resolution 21-1) to the “ List o f Definitions o f Essential
Telecommunication Terms ” (Volume II to be published later).
The other terms and definitions contained in Part 2 o f this list, which are o f more general application,
are given as information pending examination by the C.C.I.T.T.

— 45 —

Rec. 342-1

15. Semi-automatic phasing- phasing completed automatically after manual initiation;

16. Automatic phasing- phasing, initiated and completed automatically after automaticI
detection of “ out-of-phase
17. Master station- the station, the transmitting equipment of which is directly
driven by a master oscillator but the receiver timing of which
is normally synchronized to the incoming signal;

18. Slave station- the station, the receiver and transmitter timing of which areboth synchronized to the received signal;

19. End-to-end time delay- the delay between the output terminals of an ARQ-transmitterand the input terminals of the ARQ-receiver at the other end(this is the sum of radio and line circuit delays in one directionof a route);

20. Loop time-delay of a route - the sum of the end-to-end time delays in the send and return
directions of a route;
21. Master station delay

the period between the beginning of reception of a signal
repetition at the ARQ-input terminals at the master station andthe beginning of transmission of the replying signal repetitionat that station.
Note. - This comprises the “ scanning ” and equipment
delays and a further delay which, when added to the loop
time delay o f the system, produces an integral multiple of thecharacter cycle duration;

22. Slave station delay

the period between the beginning of reception of a signal
repetition at the ARQ-input terminals at the slave station andthe beginning of transmission of the replying signal repetitionat that station.
Note. - This comprises “ scanning ” and equipment delays
and a “ pre-set ” delay between the receiver and the trans­mitter;23. Loop time-delay of a sys­tem (as seen from the mas­
ter station)

the sum of the loop time-delay o f the route and the slave station
delay, measured under working conditions.

Part 2(a) Aggregate signal- the synchronous signal produced by combining the channel
signals;(b) Balanced aggregate signal- an aggregate signal containing equal numbers of elementsof each polarity;(c) Character cycle- the period in which each channel of a time-division multiplex
transmission has completed one character in the synchronouspath;(d) Element synchronism- in synchronous systems:
the condition in which an element of the local timing coincides
completely with an element of the received signal;

Rec. 342-1, 343-1— 46 —(e) Synchronizing

the action of adjustment of element synchronism;■(f) Phase relationshipin synchronous systems:
the relative phase of receiving apparatus and incoming signals,
or receiving and sending apparatus;(g) Character phasethe condition in which a character cycle of the local timing
coincides completely with a character cycle of the received
signal.
Note .- Under these conditions, a character of the aggregate
signal transmitted on a particular channel is received on thecorrect channel.

(h) Sub-channel

a teleprinter channel which is allocated a quarter rate of anormal channel, or multiples thereof;(j) Sub-channel phasethe condition in which a character transmitted on a particular
sub-channel is received on the correct sub-channel;(k ) Transposition

Add to definition 33.25 of the I.T.U. “ List of definitions . . ”(Part I):
“ Transpositions may be regarded as of first or higher orderaccording to the number of interchanges occurring withina character.”

RECOMMENDATION 343-1
FACSIMILE TRANSMISSION OF METEOROLOGICAL CHARTSOVER RADIO CIRCUITS(Question 232)
The C.C.I.R.,(1956 - 1959 - 1963 - 1966)CONSIDERING(a) that increasing use is being made of facsimile telegraphy for the transmission of meteoro­
logical charts for reception on direct-recording apparatus;(b) that it is desirable to standardize certain characteristics of the radio circuits for this purpose;
UNANIMOUSLY RECOMMENDS

1.

that, when frequency modulation of the sub-carrier is employed for the facsimile transmissionof meteorological charts over radio circuits, the following characteristics should be used:
centre frequency
frequency corresponding tofrequency corresponding to

black
white

1900 Hz
1500 Hz2300 Hz;Rec. 343-1, 344-1— 47 —
2.

that, when direct frequency modulation is employed on radio circuits, the following charac­
teristics should be used:

2.1 H F (decametric) circuits.

.

centre frequency(corresponding to the assigned frequency) - fo,
frequency corresponding to black
fo — 400 Hz,
frequency corresponding to white
fo + 400 Hz;
2.2 LF (kilometric) circuits
centre frequency(corresponding to the assigned frequency)
frequency corresponding to black
frequency corresponding to white

3.

f 0,
fo —150 Hz,
fo + 150 Hz;

that this Recommendation should be considered as an answer to Question 232, the studyof which is hereby terminated.

RECOM M ENDATION 344-1
STANDARDIZATION OF PHOTOTELEGRAPH SYSTEMS FORUSE ON COMBINED RADIO AND METALLIC CIRCUITSThe C.C.I.R.,(1948 - 1953 - 1956 - 1959 - 1963 - 1966)CONSIDERING(a) that to facilitate interworking, it is desirable to standardize the characteristics of systems
employed for phototelegraph transmission over long-distance H F (decametric) circuits;(b) that it is desirable to standardize certain characteristics of these systems in such a way as
to make them equally suitable for transmission over metallic circuits;(c) that the transmission system using direct amplitude-modulation is generally unsatisfactory
over H F (decametric) radio circuits, because o f the intolerable fading ratio usually encountered;(d) that the system of sub-carrier frequency-modulation has proved satisfactory, but requires
standardization in respect of the centre frequency and shift frequencies, taking into accountthe values of the picture-modulation frequencies to be transmitted;(e) that, when a direct frequency-modulation system is employed, the terminal equipment normallyused for a sub-carrier modulation system should be usable without serious modifications;(f) that, taking into account the degree of distortion that is tolerable, the effect of multipath
echoes on long-distance H F (decametric) radio circuits normally limits the maximum admis­
sible picture-modulation frequency to approximately 600 Hz;(g) that Recommendations M. 88 , T .l, T.10, T .ll, T.12, T.15 and T.20 of the C.C.I.T.T.' givestandards for phototelegraph systems;

Rec. 344-1— 48 —UNANIMOUSLY RECOMMENDS

1.

that over the radio path,

1.1

the preferred method of transmission of half-tone pictures is by sub-carrier frequency-modula­tion, of a single-sideband or independent-sideband emission with reduced carrier. The
following characteristics should therefore be used:
centre frequency
1900 Hz,frequency corresponding to white
1500 Hz,frequency corresponding to black
2300 Hz;(The 1500 Hz frequency is also used for the phase-synchronizing frequency)

1.2

when a direct frequency-modulation system is employed, the following characteristics should
be used:centre frequency(corresponding to the assigned frequency)
frequency corresponding to whitefrequency corresponding to black

f 0,
f 0 — 400 Hz,
f 0 + 400 Hz;

1.3 that the frequency tolerances on each of the various sections of a combined radio and metallic
circuit should be no greater than those proposed by the C.C.I.T.T. (see Annex V to Doc. III/3,
1963-1966) as shown in Fig. 1, which gives the composition of a very long ..circuit of thistype.

Sending
statio n

R eceiving
stationt
F req u en cy to le ra n c e s (Hz) fo r sh o rt-te rm (I s)

8

2

2

8

F req u eu cy to le ra n c e s (Hz) fo r lo n g -te rm (15 min)
16

2

2

16

16

16

F ig u r e 1

If it is assumed that these deviations are allocated at random and if we take the standard
deviations, we obtain 15 and 28 Hz respectively;
2.

that, for the present, the following alternative characteristics should be used:aindex of cooperation
speed of rotation of drum in r.p.m.

b

352 264
60 90/45(The speed of 45 r.p.m. isfor use when the radio
propagation
conditions
demand it);
In due course, characteristic b will become obsolete.

3.

that frequency-modulation or amplitude-modulation may be used in the metallic portions of
the combined circuit. When conversion from amplitude-modulation to frequency-modulation

— 49 —

Rec. 344-1, 345(or vice versa) is required, the conversion should be such that the deviation of the fre­quency-modulated carrier varies linearly with the amplitude of the amplitude-modulated
carrier.
The standards for both amplitude-modulated and frequency-modulated transmissions
will be found in C.C.I.T.T. Recommendations T .l, T .ll and T.15.
Each Administration will decide, when the question arises, on the location of modula­tion converters. They may be placed either at the terminal phototelegraph station or at
the control station associated with the radio station, to facilitate speech on the circuit used
for phototelegraphy, if the radio channel will carry speech.
Note. - The provisions of § 2 do not imply the imposition of such standards on private users
who use their own equipment for the transmission of pictures over private circuits.

RECOMMENDATION 345 *TELEGRAPH DISTORTION
The C.C.I.R.,
CONSIDERING(1953 - 1956 - 1959 - 1963)‘

that the definitions applying to telegraph distortion and to the mutilation of telegraphic
signals, which appear in Section 33, Part I, of the List of Definitions of Essential Telecom­
munication Terms, published by the International Telecommunication Union, give an answer
to Question 18, which required a general definition of telegraph distortion capable of being
usefully applied to the cause of radio telegraphy;
UNANIMOUSLY RECOMMENDS

that the following definitions, contained in Section 33 of the above-mentioned List of Defi­
nitions of Essential Telecommunication Terms, should beapplied to radiotelegraphy:
Perfect modulation (or restitution) (Definition 33.01 of the List)■,
Modulation (or restitution) such, that all the significant intervals are associated with. correct significant conditions and conform accurately to their theoretical durations.
Incorrect modulation (or restitution), ,,\Defective modulation (or restitution)

} ^
.
„„
„ „
.
Y (Definition 33.03 of the List)

Modulation (or restitution) containing one or more elements, the significant conditionof which differs from that corresponding to the kind prescribed by the code.
Telegraph distortion (o f a modulation or a restitution) (Definition 33.04 of the List)(a) A modulation (or restitution) suffers from telegraph distortion, when the significant inter­vals have not all exactly their theoretical durations.
(b) A modulation (or restitution) is affected by telegraph distortion, when significant instants
do not coincide with the corresponding theoretical instants.
* This Recommendation replaces Recommendation 245.
4

Rec. 345

— 50 —

Transmitter distortion (Definition 33.059 of the 1st Supplement to the List)
A signal transmitted by an apparatus (or a signal at the output of a local line with its
termination), is affected by telegraph distortion, when the significant intervals of this signal
have not exactly their theoretical durations.
Degree o f individual distortion o f a particular significant instant (o f a modulation or o f a restitu­tion) (Definition 33.06 of the List)
Ratio to the unit interval of the displacement, expressed algebraically, of this significant
instant from an ideal instant.
This displacement is considered positive when the significant instant occurs after the ideal
instant.
The degree of individual distortion is usually expressed as a percentage.
Degree o f isochronous distortion (Definition 33.07 of the 1st Supplement to the List)(a) Ratio to the unit interval of the maximum measured difference, irrespective of sign,
between the actual and the theoretical intervals separating any two significant instantsof modulation (or of restitution), these instants being not necessarily consecutive.
(b) Algebraical difference between the highest and lowest value of individual distortion
affecting the significant instants of an isochronous modulation. (The difference isindependent of the choice of the reference ideal instant.)
The degree of distortion (of an isochronous modulation or restitution), is usually expressed
as a percentage.
Note. - The result of the measurement should be completed by an indication of the period,
usually limited, of the observation.
For a prolonged modulation (or restitution), it will be appropriate to consider the pro­bability that an assigned value of the degree of distortion will be exceeded.
Degree o f start-stop distortion (Definition 33.08 of the 1st Supplement to the List)(a) Ratio to the unit interval of the maximum measured difference, irrespective of sign,
between the actual and theoretical intervals separating any significant instant of modula­tion (or of restitution) from the significant instant of the start element immediately pre­ceding it.
(b) The highest absolute value of individual distortion affecting the significant instants of astart-stop modulation.
The degree of distortion of a start-stop modulation (or restitution) is usually expressed
as a percentage.
Note 1. - See Note to Definition 33.07.
Note 2. - Distinction can be made between the degree of late (or positive distortion andthe degree of early (or negative) distortion.
Degree o f gross start-stop distortion (Definition 33.09 of the List)
Degree of distortion determined when the unit interval and the theoretical intervals
assumed are exactly those appropriate to the standardized modulation rate.
Note. - See Note to Definition 33.07.
Degree o f synchronous start-strop distortion (i.e. at the actual mean modulation rate) (Definition
33.10 of the List)
Degree of distortion determined when the unit interval and the theoretical intervals
assumed are those appropriate to the actual mean rate of modulation (or of restitution).
Note 1. - See Note to Definition 33.07.
Note 2. - For the determination of the actual mean modulation rate, account is only takenof those significant instants of modulation (or restitution), which correspond to a change ofcondition in the same sense as that occurring at the beginning of the start element.

Characteristic distortion (Definition 33.15 of the List)
Distortion caused by transients which, as a result of the modulation, are present in thetransmission channel and depend on its transmission qualities.
Fortuitous distortion (Definition 33.16 of the List)
Distortion resulting from causes generally subject to random laws (accidental irregu­
larities in the operation of the apparatus and of the moving parts, disturbances affecting thetransmission channel, etc.).
Bias distortion, Asymmetrical distortion (Definition 33.17 of the List)
Distortion affecting a two-condition (or binary) modulation (or restitution), in which
all the significant intervals corresponding to one of the two significant conditions have longer
or shorter durations than the corresponding theoretical durations.
Character error rate o f a telegraph communication (Definition 33.19 of the 1st Supplement to
the List)
Ratio of the number of alphabetic signals of a message incorrectly received (after auto­
matic translation, where applicable), to the number of alphabetic signals of the message, thekeying being correct.
Note 1. - A telegraph communication may have a different error rate for the two directions oftransmission.
Note 2. - The notion of character error rate could be applied to any operation taking place
in a telegraph communication (e.g. keying, translation, etc).
Note 3. - The statement of the error rate will be accompanied by that of the time interval,
generally limited, during which the observation was made. For a communication established
for a sufficiently long time, the probability of exceeding an assigned value of error rate could
be considered.
Note 4. - Faulty translation, resulting from a previous error in functional control (such as
shift, line feed, synchronism, etc.), is not counted in calculating a character error rate; in sucha case, the error in the functional control signal is alone counted and is counted only once.
Element error rate (Doc. 203, Geneva, 1963)
The ratio of the number of unit elements incorrectly received to the total number of unit
elements sent.
Efficiency factor in time (of a telegraph communication with automatic repetition for thecorrection of errors) (Definition 33.23 of the List)
Ratio of the time necessary to transmit a text automatically without repetition, at a
specified modulation rate, to the time actually taken to receive the same text with a given
error rate.
Note 1. - The whole of the apparatus comprising the communication is assumed to be in
the normal conditions of adjustment and operation.
Note 2. - A telegraph communication may have a different efficiency factor in time for thetwo directions of transmission.
Note 3. - The actual conditions in which the measurement is made should be specified, inparticular the duration of the measurement.
Mutilation (Definition 33.24 of the List)
A transmission defect in which a signal element becomes changed from one significant
condition to another.
Transposition (Definition 33.25 of the List) (See also Annex II, Part 2, definition k of Recom­
mendation 342-1)
A transmission defect in which, during one character period, one or more signal elements
are changed from one significant condition to the other, and an equal number of elements
are changed in the opposite sense.

— 52 —

Rec. 346

RECOMMENDATION 346 *FOUR-FREQUENCY DIPLEX SYSTEMS(Question 8/III)The C.C.I.R.,(1956- 1959- 1963)CONSIDERING(a) that there are in use, in the fixed radiotelegraph services operating between 2 MHz and 2 7 MHz,four-frequency diplex (or twinplex) systems, in which each of four frequencies is used to trans­
mit one of the four possible combinations of signals corresponding to two telegraph channels;
it being understood that either one, or both of the two telegraph channels may be sub-channelled
by time-division methods and that the use of such systems may be extended;(b) that it is desirable to standardize the main characteristics of four-frequency diplex systems;(c) that it may sometimes be necessary to employ the same radio transmitter to work with morethan one receiving station;(d) that circuit interruptions should be reduced to a minimum, by avoiding frequent changes ofthe spacing between adjacent frequencies and of the correspondence between the frequencies
and the significant conditions of the channels;(e) that various technical factors influence the choice of operating characteristics in such systems,
in particular:- the economy of bandwidth and the consequent need to control the shape of the transmitted
signals;- that a relatively wide spacing between adjacent frequencies may be necessary for hightelegraph speeds;- the signal distortion due to propagation conditions;- the instability of the characteristics of certain receiver and transmitter elements such as
oscillators, filters or discriminators;(f) that many existing four-frequency diplex systems each use one of four values of spacing
between adjacent frequencies with corresponding telegraph speeds;(g) that it is desirable to use only one coding system, the simpler the better;
UNANIMOUSLY RECOMMENDS

1.

that the following preferred values should be adopted for the spacing between adjacentfrequencies:
Spacing
between adjacent frequencies
(Hz)

1000

5000
4000
2000

Nominal telegraph speedof each channel(bauds)over 300
200 to 300
100 to 200
200 (2)(x) Lower telegraph speeds may be used with these spacings at present.
(2) Synchronous operation with phase-locked channels.

* This Recommendation replaces Recommendation 247.

Rec. 346, 347— 53 —
2.

that the following coding system should be adopted: *Channel 1

Channel 2

Frequency o f emission

f i (highest frequency)hhf i (lowest frequency)

TeleprinterMorse

Teleprinter

Morse

A
A
Z
Z

Mark
Mark
Space
Space

A
Z
A
Z

Mark
Space
Mark
Space

where /i, fz, fa, f \ designate the frequencies of the emissions; the spacings between adjacentfrequencies ( / 4 —fz) (fz —ft) (fz — fi), being equal,
A represents the start signal of the teleprinter,Z represents the stop signal of the teleprinter;
3.

that the value of the frequency separation between adjacent frequencies employed should be
the lowest of the preferred values compatible with the maximum telegraph speeds regularly
used, the propagation conditions and the equipment stability;

4.

that, when the two channels are not synchronized, it is desirable to limit the maximum rateof change of frequency to minimize the bandwidth of the emission.

R ECOM M ENDATION 347 **CLASSIFICATION OF MULTI-CHANNEL RADIOTELEGRAPH SYSTEMSFOR LONG-RANGE CIRCUITS OPERATING AT FREQUENCIESBELOW ABOUT 30 MHz AND THE DESIGNATION OF THE CHANNELS
IN THESE SYSTEMSThe C.C.I.R.,(1956- 1959- 1963)CONSIDERING(a) that there exists a large number of long-range multi-channel radiotelegraph systems using
frequencies below about 30 MHz and that it is desirable to classify them in categories;(b) that the lack of uniformity in the arrangement and designation of the channels in these systems,
may give rise to certain difficulties when one transmitting station has to work with several
receiving stations;(c) that the increasing use of multi-channel telegraph systems makes it desirable to adopt a uni­
form designation of channels in such systems;* Where modification of equipment is required, it is recognized that it may take some time before the cod­ing systems indicated in this paragraph can be implemented on circuits between different Administrations.
** This Recommendation replaces Recommendation 248.

Rec. 347

— 54 —UNANIMOUSLY RECOMMENDS

1.

that the systems should be classified and the different categories designated by letters, as
follows:

1.1 Time-divisiort multiplex systems: capital letter T (for example, synchronous systems, such as
Baudot, RCA and TOR multiplex and double-current cable code);
1.2 Frequency-division multiplex systems
1.2.1 Systems with constant frequency arrangements of significant conditions: capital letter U(for example: voice-frequency multiplex with frequency shift);1.2.2 Systems with variable frequency arrangements of significant conditions: capital letter V(for example: four-frequency diplex);
1.3 Multi-channel systems using a combination o f these processes
1.3.1 Frequency-division systems, with constantfrequency arrangement, combined with atime-division multiplex;
1.3.2 Four-frequency diplex system, combinedwith a time-division multiplex system.
2.

combination of the above-mentioned
letters (always beginning with thefrequency-division letters U or V)

when a multi-channel telegraph signal is applied to a multi-channel telephone transmitter, the' designation of the telephone channel should come first in the sequence and should be inaccordance with Recommendation 348-1;

3. when a multi-channel telegraph signal is applied to an independent-sideband transmitter usedsolely for telegraphy, the designation of the sideband should come first in the sequence.
letter H should denote the upper sideband, and the letter L the lower sideband;The

4. that in time-division systems, the telegraph channels should be designated by capital letters
A, B, C, D, etc.; for sub-division, the sub-channels should be designated by A l, A2, A3, A4,
B l, B2, B3, B4, etc.;

5. that in'frequency-division systems, the telegraph channels should be designated by figures;
6.

that in a combination of multi-channel processes, the telegraph channels should be designatedby a letter and figure sequence.
For example:
when using a frequency-division system with constant frequency arrangement of significant
conditions (letter U), and modulating the 3rd channel of this latter system with a time-divisionmultiplex (letter T), channel B of this latter system would be indicated by U3TB;
where channel B of the time-division system is sub-divided and sub-channel 2 is in use, thedesignation would be U3TB2;
if the above-mentioned system is applied to channel B of an independent-sideband telephonetransmitter, the corresponding designation would be BU3TB or BU3TB2;
if the above-mentioned system is applied to the upper sideband of an independent-sideband
multi-channel transmitter used solely for telegraphy, the corresponding designation would
be HU3TB or HU3TB2;
where additional information is required, the multiplex system may be identified by a number
inserted between the letters T and B, and where two sub-channels (quarter-channels) arelinked together to form a half-speed sub-channel (half-channel), each quarter-speed sub­channel component may be designated by the use of numbers separated by an oblique stroke.

_

55 —

Rec. 347

The full designation HU3T4B2/4 would be applicable to the arrangement shown diagrammatically by the arrows on the right of the figure below
in established communication networks, where the sub-carrier, multiplex system, channels
and sub-channels arrangements are mutually known to the station management at each endof the circuit, it shall be permissible to shorten the full designation HU3T4B2/4 above,
beginning at the first letter or number which is of major significance for identification purposes.
For example, in the given instance 4B2/4 will identify the specific area illustrated by thearrows to the right of the figure below.
Lower
sideband ( L )Carrier F

Upper
sideband ( H )Sub-carriers

Multiplex systems

Time-division channels

1 2

3

V

4

Time-divisionsub-channels

J

Multi-channel independent-sideband radiotelegraph transmitter
Note. —Sub-carriers are numbered sequentially in both upper and lower sidebands, starting with thenumber 1, adjacent to the carrier (radiated or suppressed).

Rec. 348-1— 56 —

RECOMMENDATION 348-1
ARRANGEMENT OF CHANNELS IN MULTI-CHANNEL SINGLE-SIDEBAND
AND INDEPENDENT-SIDEBAND TRANSMITTERS FOR LONG-RANGECIRCUITS OPERATING AT FREQUENCIES BELOW ABOUT 30 MHz(Question 2/III)The C.C.I.R.,(1953 - 1956 - 1959 - 1963 - 1966)CONSIDERING(a) that the lack of uniformity, in the arrangement and designation of the channels in multi­
channel transmitters for long-range circuits operating on frequencies below about 30 MHz,may give rise to certain difficulties when one transmitting station has to work with several
receiving stations;(b) that, since it is necessary to economize in the use of the radio-frequency spectrum, when
considering international circuits consisting mainly of single long-distance radio links, operat­ing on frequencies below 30 MHz, it is desirable:- to use independent-sideband transmissions to the maximum extent possible;- to transmit a band less than the 300 to 3400 Hz recommended by the C.C.I.T.T. for landline circuits;- to reduce the upper frequency to 3000 Hz, or less in special circumstances, but never below
2600 Hz;(c) that there are already in operation international multi-channel radiotelephone circuits, inwhich the bandwidth allocated to each channel is 3000 Hz, but are actually transmitting aspeech band of 250 to 3000 Hz;(d) that, in general, the outer channels are liable to cause and receive more interference to andfrom stations operating on adjacent assigned frequencies, the outer channels being thoselocated furthest from the assigned frequency;(e) that there are numerous transmitters in service which, when operated on a twin-channel
basis, give rise to excessive cross-talk unless one of the channels is placed away from thecarrier;(f) that there are advantages in adopting channel arrangements which are the same in all partsof the H F (decametric) range;
UNANIMOUSLY RECOMMENDS

1.

that standard channel arrangements should be adopted for multi-channel radiotelephonesystems;2.

that the effective speech channel allocation should be 3000 Hz;

3.

that the transmitted band in each speech channel should be from 250 Hz with an upper fre­quency of 3000 Hz, or lower in special circumstances, but never below 2600 Hz;

4. that in four-channel systems the channel arrangement should be as shown in Fig. 1a\5.

that, when less than four channels are used, the channels nearest to the carrier should beselected according to the arrangements shown in Figs. lb, c, d, e, or / ;Rec. 348-1

Audio

frequency(H z)— 57 —

R ad io frequency (kH z)

F igure 1

Relationship between audio-frequencies and radio-frequencies for the various channel arrangements

Rec. 348-1, 349-1
6.

— 58 —

that with some transmitters in service, which do not give satisfactory operation with thearrangement shown in Fig. Id, a channelling arrangement such as that shown in Fig. 2 may
be used to minimize cross-talk;

F igure 2

7.

that the effective date of these arrangements be fixed by the next Administrative
Radio Conference.

RECOMMENDATION 349-1
FREQUENCY STABILITY REQUIRED FOR SINGLE-SIDEBAND,
INDEPENDENT-SIDEBAND AND TELEGRAPH SYSTEMS TO MAKE THE USE
OF AUTOMATIC FREQUENCY CONTROL SUPERFLUOUS(Question 182)
The C.C.I.R.,(1963 - 1966)CONSIDERING(a) that it is the practice with certain single-sideband (SSB) and independent-sideband (ISB)
telephone systems, and with many telegraph systems, to employ automatic frequency control(a.f.c.) to adjust the receiver oscillator frequency in sympathy with variations in the frequencyof the transmitted signal;(b) that such automatic frequency control systems may give rise to difficulty under unfavourable
conditions of propagation, at frequencies below 30 MHz;(c) that the frequency stability, which can now be achieved, is much higher than that laid downin Appendix 3 to the Radio Regulations, Geneva, 1959, and is approaching a value which
could provide sufficient inherent stability to enable automatic frequency control to be dis­pensed with;(d) that, with systems dispensing with automatic frequency control, the frequency error of themodulating and demodulating stages and of the radio-frequency translating stages at thetransmitting and the receiving ends, together with the frequency error due to the propagation
path, contribute to an overall frequency error;(e) that the overall frequency error of the complete system is decisive and that as far as feasible
this error should be shared equally by both the transmitting and the receiving ends;

Rec. 349-1— 59 —(f)that, however, in certain cases when narrow-shift telegraph systems are employed, reasons
other than frequency stability of the equipment may still require the use of automatic fre­quency control;
UNANIMOUSLY RECOMMENDS

1. that the values of permissible frequency errors given in Table I, should be considered
as suitable for use on systems giving access to the public service network and dispensing
with automatic frequency control;
2. that the figures in column (a) of Table I are decisive for the system, and that those givenin the columns (b), (c) and (d) should be considered as an example as to how the overallfrequency error could be split up into errors permissible in the parts constituting a complete
system;3.

that, however, for multi-channel voice-frequency telegraph systems, the use of automatic
frequency control may be retained (see Annex).
T a b leI

Maximum
permissible
overall f
error
(Hz)

SystemFrequency error due to: Frequency error due tothe radio-frequency
stages at both
Dem odu­ translatingends and to the
M odulator
lator
propagation pathstagesstages(Hz)(3)
(Hz)
(Hz)

0)

(2)

(3)

(4)

20

5

5

10

2.1 Two-tone multi-channel telegraphy
with 340 Hz tone spacing and
MCVF frequency-shift telegraphy
with 30 Hz channel spacing

12(D

3

3

6

2.2 Frequency-shift telegraphy (FI)(e.g. 50 baud, 200 Hz shift) and
four-frequency diplex telegraphy(F6) using narrow-band filters at
the receiving end

12

3

3

6

2.3 FI and F 6 systems using a limiter/
discriminator at the receiving end,
modulation index ZZ 2; (e.g. 196
baud 400 Hz shift)

20 (4)

3

3

14

2.4 Phototelegraphy(2)

16

4

4

8

1. Single-sideband andsideband telephony

independent-

2. Radiotelegraphy:

I1) See D oc.III/27, Geneva, 1962.
(2) For short-term frequency stability, see Recommendation 344-1. The figures under line 2.4 o f this Table should beconsidered as provisional pending a reply by the C.C.I.T.T. to the questions put to it by the C.C.I.R. (see D oc.III/66(Rev.), Geneva, 1962).
(3) This is the maximum error at the demodulator in the frequency o f the carrier, if transmitted.
(4) For radiotelegraph systems, which use a device at the receiving end to correct for possible bias distortion due to fre­quency error, values larger than those indicated in the Table may be permitted.

Rec. 349-1, 436— 60 —ANNEX
FACTORS OTHER TH A N FREQUENCY STABILITY W H IC H MAY MAKE
THE USE OF AUTOMATIC FREQUENCY CONTROL DESIRABLE

1.

Introduction
The above Recommendation, which is a reply to Question 182 tabulates the permissible
overall frequency errors for various systems. It excludes however, narrow-shift telegraphy.

2.

Relationship between distortion and frequency error
A number of H F radiotelegraph circuits operating at modulation rates of about 100
bauds with a channel spacing of 170 Hz, use sub-carriers on independent-sideband trans­missions.
Measurements made on various well-designed frequency-shift telegraphy receivers haveindicated an increase in element distortion of approximately 1-25% for each 1 Hz frequency
error. Poorer band-pass filter designs or narrower channelling will raise this distortion
considerably.
It has been observed that frequency changes due to ionospheric propagation of up to
7 Hz may occur during periods of up to 15 min [1,2]. This can, therefore, result in an addi­
tional distortion of up to 9 %, which could be reduced by the application of automatic fre­quency control. Further information about the statistical distribution of these phenomena
would be desirable to permit fuller evaluation of their effect on circuit efficiency.
BIBLIOGRAPHY

1. R ishbeth, H. and G arriott,' O. K. Relationship between simultaneous geomagnetic and ionosphericoscillations. Radio Science, Vol. 68D, 3, 339-343 (March, 1964).
2. D avies, K. Doppler studies of the ionospheric effects of solar flares. Proceedings of the International
Conference on the Ionosphere, 76-83 (1963).

RECOM M ENDATION 436
ARRANGEMENT OF VOICE-FREQUENCY TELEGRAPH CHANNELSWORKING AT A MODULATION RATE OF ABOUT 100 BAUDS OVERHF RADIO CIRCUITS(Study Programme 17A/III)The C.C.I.R.,(1966)CONSIDERING(a) that lack of standardization in the arrangement of channels for voice-frequency
multi-channel telegraph systems working over H F radio circuits can give rise to difficulties
when setting up such systems;

Rec. 436

— 61 —(b) that it is necessary to use the radio-frequency spectrum to the best advantage in the interestsof both spectrum economy and circuit efficiency;(c) that frequency-shift systems are in use on many routes;(d) that the frequency-exchange method of operation is in use on long routes suffering fromsevere multipath distortion;(e) that on such systems, radiotelegraph channels which operate synchronously at a modula­tion rate of 96 bauds and employ automatic error correction are being increasingly used;
UNANIMOUSLY RECOMMENDS

1.

that the channel arrangement shown in Table I be preferred for voice-frequency multi­
channel frequency-shift systems operating at a modulation rate of approximately 100 bauds
over H F radio circuits;

2.

that for frequency-exchange systems, the central frequencies of Table I should be used,and should be paired in the manner found to be best suited to the propagation conditionsof the route. (A typical arrangement would take alternate pairs giving 340 Hz between
tones.)
Note. - Theoretical work in Japan indicates an optimum frequency-shift of 0-8 B(Hz); where B
is the modulation rate in bauds. This would lead to a required minimum bandwidth (atthe — 3 dB points) of B (Hz). Laboratory experiments and measurements on the syn­chronous ARQ circuit Frankfurt — Osaka, support these conclusions.
T able I

Central frequencies o f voice-frequency frequency-shift telegraphchannels with a channel separation of 170 Hz and a modulation index of about 0-8(Frequency deviation: ±42-5 Hz or ± 4 0 Hz)
ChannelnumberCentral frequency
(Hz)

1
2

425
595
765
935
1105
1275
1445

3
4
5
6

7

ChannelnumberCentral frequency
(Hz)

8

1615
1785
1955
2125
2295
2465
2635
2805

9
10
11
12

13
14
15

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENT

— 63 —

Rep. 19-1

REPORTS OF SECTION C (FIXED SERVICES)REPORT 19-1
VOICE-FREQUENCY TELEGRAPHY OVER HF RADIO CIRCUITS(Study Programme 17A/III)(1953-1966)
In principle, the voice-frequency telegraph systems describedin C.C.I.T.T.
Recommendations R.35, R.35 bis, R.36, R.37, R.38A and R.38B are capable of being usedover H F radio circuits, but the following considerations need to be borne in mind:
1. Specifications of performance in C.C.I.R. Recommendations do not normally follow thepractice adopted by the C.C.I.T.T.
2. The ratio between the frequency spacing and the nominal modulation rate of the channels
is greater in the C.C.I.T.T. Recommendations than that which is currently used for FDM FSK systems in operation over H F radio circuits. The systems fisted by the C.C.I.T.T. would
consequently be slightly less resistent to noise, but slightly more resistent to the effects ofmultipath propagation than the narrower channels proposed by the C.C.I.R. Furthermore,
the number of channels that can be used in a given bandwidth will be less.
3. Since the C.C.I.T.T. systems do not normally have to contend with fading, there may beinsufficient protection by the receiving filters against inter-channel interference when thefading is frequency-selective. Also the range of levels over which the channel receiver should
operate would need to be increased by at least 10 dB.
4. Systems for use over H F radio circuits should incorporate features which permit diversity
reception.
Although it might appear convenient to have unified standards for fine and radio sys­tems, the divergent requirements referred to above will make this uneconomic. The cha­racteristics of radio transmission lead to the operation of point-to-point channels withsynchronous operation, and, ideally, regeneration at the radio receiving station. This is
in contrast to the requirement, in landline systems, to be able to connect channels in tandem
without regeneration and to transmit start-stop signals with acceptable quality.

* This Report was adopted unanimously.

Rep. 42-1

— 64 —REPO RT 42-1
USE OF RADIO CIRCUITS IN ASSOCIATION WITH 50-BAUD
5-UNIT START-STOP TELEGRAPH SYSTEMS(Study Programme 17A/III)(1953 - 1956 - 1963 - 1966)
The principal factors determining the error rate in radiotelegraphy transmission arise
from the fact that:- radio propagation is essentially variable,- unwanted signals caused by noise or interference appear at the receiving end.
1.

As a result of variations in propagation, a complex signal is supplied to the receiver, consising of superimposed signals from several transmission paths with differential delays of up
to several milliseconds (see Report 203). As a result, the telegraph signal appearing at theoutput of the demodulator suffers random distortion, the limiting value of which is prac­
tically independent of the signal-to-noise ratio.
Start-stop systems are particularly vulnerable to this form of distortion, because- ofthe risk of a loss of synchronization produced by mutilation of a start or stop element (seeReport 195, Fig. 4).

2.

Various Administrations have, for several years, had in service, on certain H F circuits, equip­
ment with a channel spacing of 120 Hz, the central frequencies and frequency deviationsof which are given in Table I.
T a b leI

Central frequencies o f voice-frequency frequency- shift telegraph channels witha channel separation o f 120 Hz and a modulation index o f about 1-4(Frequency deviation: ±35 Hz or ±30 Hz)
Channel No.

Central frequency(Hz)

Channel No.

Central frequency
(Hz)

1
2

11
12

3
4
5

420
540
660
780
900

1620
1740
1860
1980

6

1020

7

1140
1260
1380
1500

8

9
10

13
14
15
16
17
18
19
20

* This Report, which cancels Report 199, was adopted unanimously.

2100
2220

2340
2460
2580
2700

— 65 —

Rep. 106REPORT 106 *IMPROVEMENT OBTAINABLE FROM THE USE
OF DIRECTIONAL ANTENNAE(Question 3/III)(1953- 1956- 1959)

1.

Introduction
Contributions by Administrations to the VIIIth Plenary Assembly, Warsaw, 1956,
and to the interim meeting of Study Group III, Geneva, 1958, provide a basis for a preli­minary report on the question of signal power gain, and signal-to-interference discrimina­
tion, afforded in practice by rhombic antennae. The experimental observations given by
Docs. III/4 and 111/31, Geneva, 1958, are summarized, as well as the pertinent Docs. 19,
139, 265, 320 and 532, Warsaw, 1956. The relation of these preliminary results to the mediangain, given by Recommendation 162-1, is indicated.
In the text below:
I = length of leg (m),(p = half the obtuse angle (deg),h = height above ground (m).

2.

Summary and discussion of reported results
Doc. III/4 (Federal Republic of Germany), Geneva, 1958, contains a summary (Table I
below) of median values of measurements made, using a rhombic of a type in general service
in the Post Administration, having / = 115 m, h = 20 m, (p = 75°. This first set of measure­ments was made relative to a vertical antenna', the results are otherwise expressed in
Recommendation 162-1;
T able 1

M edian value o f gain relative to main lobe
(direction o f optim um gain) (dB)Fre­
quency(M H z)10
15
20

A zim uthal ranges(degrees)

In Arc Bm ain lobe

In Arc A

0
0
0

-8
- 6
-8

U nidirectional
antenna

R eversible
antenna

-2 1

-1 2
-1 7
-1 5

-2 3

H alf
o f m ain arc

A\ = A2Arc

H a lfo f arc B

23
18
13

22
29
24

135
133
14 3

In Doc. 111/31, Geneva, 1958, there are also reported the results of observations of
the gain of the rhombic antenna in the main lobe, relative to a half-wave horizontal antenna.
These observations were, in the main, made at 15 MHz receiving WWV which transmits
with an omni-directional antenna, but there is also one set of observations made at 18 MHz
receiving PPZ which transmits with a directional antenna. The data show the realized gain
* This Report was adopted by correspondence without reservations.
5Rep. 106

— 66 —

to be less than the plain-wave gain in direction of maximum response, and to have a striking
variability with time of day and/or signal strength. The data are not adequate to establish
a systematic diurnal variation, but the 15 MHz data suggest that the greatest values of gain
are realized at times o f high signal intensity. This result is contradicted by the observations
at 18 MHz of transmissions from a distant directional antenna, which emphasizes the needfor additional observations and draws attention to the virtually certain dependence of all
such observations on the directivity o f antennae at both ends o f the path. Table II below gives
the decile and median values of the gain realized in these tests.

T a b leII

PeriodG ain 10 %(dB)

Gain 15 %(dB)

Gain 90 %(dB)

Receiving WWV 15 MHz
11-22 June 1956
130 >28 July - 6 August 1956 117
29 Sep.-11 Oct. 1956 217 I observations
28 Feb.-23 Mar. 1957 405
15-25 January 1958
162 ,

12-9
15-2
12-9

6-7
7-7

10 8
111

91
11*7
10-7
7-1
8-5

130

7-8

Receiving PPZ 18 MHz
29 Sep.-lO Oct. 1956

6-8
00

3-2

4-4

Doc. 139 (United Kingdom), Warsaw, 1956, gives results of the power gain and dis­
crimination of rhombic receiving antennae, that is, off-azimuth response relative to maximum
response. The measurements were made receiving distant transmissions 13 and 20 MHz,
using a ring of 30 antennae having I = 81 m, A = 23 m, <p = 70°. The results are given in
Table III for the main lobe and the forward arc (180°) excluding the main lobe, and forthe backward arc.

T a b leIII

G ain relative to half-wave horizontal dipole(1) (dB)Frequency

Main lobe
gain
(dB)

Forw ard arc (180°)
excluding main lobe

Backward arc (180°)

G ain 10 %Gain 50%

Gain 90 %

Gain

10 %

Gain 50 %Gain 90 %13-4 MHz (New York)

11

-2 .5

-1 1

—19-5

-8-3

-12-7

-1 7

20-4 MHz (Pretoria)

15

3-5

- 50

—13-5

-4-3

- 8-7

-1 3

20-4 MHz (Pretoria)

15

2-5

- 60

—14-5

-9-2

—13 6

-1 8

(!) Median and decile values are relative to the arc, except for the main lobe.

More detailed data are given in the same document; an examination of the data for
all observed azimuths has been made, and median values of gain obtained for the arcs speci­
fied in Recommendation 162-1, as follows:'

— 67 —

T a b leRep. 106Ilia

M edian value (x) o f gain relative
to half-wave dipole (dB)

Azimuthal range (degrees)(Rec. 162-1)

Frequency
A rc A

Arc B

H alf
o f main arc

13-4 MHz (New York)

11

-5

-1 3

12

20-4 (Pretoria)

15

2

-1 0

8*

Arc
A i = A2

H alf
o f arc B

21

147

OO

M ain
azimuth153(!) Median values are relative to the arc, except for the main azimuth.

It is worth noting that values given in Table Ilia, with respect to discrimination against
off-azimuth signals, are somewhat better than the values shown in Recommendation 162-1;
it seems unlikely that values as favourable as those given in Tables III and Ilia are generally
realized in practice. The value for arc A at 13 MHz is in fact better than might, at first sight,
be expected; but, especially in arc A, the available data were not adequate to establish a
median value with much confidence.
Doc. 265 (Netherlands), Warsaw, 1956, summarized experimental observations of
the power gain in the main azimuth, and for certain discrete directions off the main azimuthare given. The values of gain are for receiving rhombic antennae, expressed relative to ahorizontal half-wave antenna at the same height. Directional antennae were also used at
the transmitters for the measurements. The design data for the receiving antennae used at
Amsterdam, for which observations are summarized in this document, are as follows:IfAntennaA

B

Length I ( m ) ...............
Height h ( m ) ..................
Angle tp ( d e g ) ...............
Design frequency (MHz)

120

174-5
29-5
70
7-5

33
71
14-5

The gain measurements for the main lobe were made on a long propagation path
(7500 km), whereas some of the observations of gain off-azimuth were for a medium range
path (3000 km). The results gave values of realized gain which are less than expected theo­
retically. The data showed marked variability of gain and/or discrimination with time of
day and somewhat with season, though the data did not establish a systematic seasonal
dependence, there was an apparent tendency for the highest values of gain in the main azimuth
to be observed during periods corresponding to maximum daylight on the path; a depressionof gain appeared systematically in the morning hours on the path. These data were reported
for 13 MHz which was not worked throughout the night hours. Values of gain in directions
off the main azimuth also showed marked variability with time of day and season, but thedata were not conclusive as to any systematic pattern. Table IV summarizes theobservations.
Doc. 320 (Japan), Warsaw, 1956, concludes that discrimination of greater than 15 to
20 dB cannot be relied upon; a number of observations are cited for values of discrimina­tion (response outside the main lobe, relative to response in the main lobe), for a rhombic
antenna having values of / — 120 m and (p = 70° (height unspecified). These are shownin Table V; there were not enough data available to permit statistical analysis in terms of
the arcs of Recommendation 162-1.

— 68 —

Rep. 106

T a b l e IV

Gain relative to half-wave horizontal antenna (dB)
AntennaA

B

M ain lobeFre­
quency(MHz)
H ourso f obs.

Gain
10%

Gain
50 %

Gain
90%

7-7
13-7
13-7
13-7
13-7
17-6

83
158

9-4
13-4

8-3
11-4

6-7
8-8

46

14-2

13-3

12-1

7-7
13-7
17-6

30
50
34

15-0
13-7
9-9

11-4

7-6
9-2
60

1 1 .0

7.8

Off-azimuth

Dis­
tance
(km)

Azimuthrelative
to mainlobe(degrees)

H oursof obs.

Gain
10%

Gain
50%

Gain
90%

2000
3200
9300
2000
5800

317
236
143
14
37

17
49
56
14
42

8-5
-7 -3
-2 -9
1-8
6T

5-6
- 8-7
-1 0 -7
0-5
4-5

2-4
-1 0 -3-1 3 -5- 1-4
0-2

T able V

Median values of discrimination in decibels(Off-azimuth response relative to main lobe)
Frequency ranges (MHz)13-3 to 14-5

10-3 to 12-2
Differencein azimuth(degrees)

14-5 to 15-6

MedianMedianstandard
deviationMedianM edianstandard
deviation

12-5

20

6
121/a
IB/a
21
7-5

22
25/a

M edianMedianstandard
deviation

3-8

21

8-9

2-5

80

3-2

'O
oo

D iscrimination (dB)

1-4

2-9

1-4

9-3

27

13 5

1-7

39/a

12-5

21

46/a

14-5

1-4

52/a

17-6

20

79/a

19 8

2-8

93

12-5

3-6

20-3

3-8

11-8

3-4

-

109 i/ 2
117
168/a

15-5

21

— 69 —

Rep. 106, 107-1

Doc. 19, Warsaw, 1956, draws attention to azimuthal variations of signals propagatedover great distances via the ionosphere, in relation to realized directivity of antennae atgreat distances. Measured azimuths show only slight differences among the values of devia­
tion for propagation paths of various lengths. 80 % of the measurements showed less than ± 2 °average deviation; 98% showed average deviation less than ± 4°. The shortest link observed(2000 km), showed the greatest deviation and the longest path the least deviation.
3.

Conclusions

The present data do not offer an adequate basis for revision of Recommendation 162-1.
The results show striking variability of gain and/or discrimination with time, especiallytime of day and, to some extent, season of the year. There are undoubtedly important effects
near times o f sunrise and sunset, at times of signal failure on operating frequencies near
the MUF, and at times of ionospheric disturbance when great azimuth deviations can beobserved. Statistical correlation of values of gain with values of transmission loss would
be of interest and the data expected from Study Programme 3A/III may be expected to showwhether, and under which circumstances, such a correlation exists. The data given above
suggest the extent of azimuth deviation encountered during normal propagation conditions.
It must be noted that, because of the influence of irregularities in the ionosphere, such asgive rise to azimuth-deviations, the directivity gain realized at the receiving terminal depends
in a fundamental way on the directivity of the transmitting antenna — and vice versa. It
is, therefore, important in carrying out observations (such as those outlined in Study Pro­
gramme 3A/III), to specify the directivity of antennae at both terminals.

REPORT 107-1 *DIRECTIVITY OF ANTENNAE AT GREAT DISTANCES(Q uestion 3/III)(1959 - 1966)
1.

Introduction

Methods of testing the directivity of antennae at great distances have been:- the “ Statistical method” , a comparison of numerous observations of the same signal
on different fixed antennae at the same location but at different orientations [1,2 ];- mechanical rotation of antenna structures with various approaches to data statistics[3, 4];- the “ back-scatter ” method, a comparison of back-scatter signals in a method similar
to that of the statistical method [5].
Most of the studies have been made at high frequencies, although at least one was per­formed in the standard MF broadcast band [6 ].
References [3] and [4] indicate that, at moderately long distances the main lobes areon the average preserved, even under conditions of severe ionospheric disturbance. A more
serious matter, which merits further study, is the question of preservation of nulls and frontto-back ratios. Reference [6 ] indicates that these are not preserved at medium frequencies.
* This Report was adopted unanimously.

Rep. 107-1— 70 —

Measurements of these effects are very difficult because of noise and interference. Besides,
electrical balance, at both polarizations in antennae, feeders, and equipment antenna cir­
cuits, is a very critical matter in the realization of nulls and minima with rhombic antennae
in ionospheric propagation [7].
References [8] and [9] deal with non great-circle effects. These effects were noted in
the 1930’s [10].
The effect of the propagation medium on transmission loss at different antenna orien­
tations is dealt with in [11].
The directivity of antennae is dealt with in the following documents:- Question 3/III - Directivity of antennae at great distances,- Study Programme 3A/III - Improvement obtainable from the use of directional antennae,- Recommendation 162-1 - The use of directional antennae.
N o te .- It is noteworthy that in the IR E Standards on transmitters, modulation systems
and antennae, 1948, the definition of directivity is: “ the value of the directive gain in
the direction of the maximum value ”, thus differing from the usage in these documents.

2.

Directivity in the vertical plane *The results of measurements of the vertical angles of wave-arrival on a number of long
distance H F routes received in the United Kingdom are reported (Doc. 111/25, 1963 - 1966).
Some of the experiments and the method of measurement used are more fully described
elsewhere [12].
T a b leI

Statistical summary o f measurements of vertical angles
o f wave-arrival in the United Kingdom

Transmitter

Distance(km)

A ppro­ximatefrequency(MHz)

M onths ofmeasurements

Total
numberofmeasure­ments

D om inant vertical angle of wave-arrival
not exceeded for the indicatedpercentages o f all measurements
10%

50%

90%

New York(])(U.S.A.)

5500

13-4

May, June &July, 1961

4900

2°

9°

13-5°

Poona O
(India)

7300

14 5

April, June &July, 1961

4434

3°

9°

13°

Sydney^)(Australia)

17 00014-7

June & July
1961

3780

4°

9°

13°

Barbados

6800

7-5

Aug. 1963
Nov. 1963
Jan. 1964

2954
798
437

2°

4°
6°
7°

3°
3°

.

7°
8°
10°

C1) These measurements were performed on antennae which were not particularly favourable to the reception o f waves at
low angles o f arrival.

* Directivity in the vertical plane refers to the characteristics o f an antenna measured from the ground ina vertical plane containing the transmitter and receiver.

— 71 —

Rep. 107-1, 109-1

The results are summarized in Table I and may be regarded as typical of circuits withpropagation paths in latitudes of 50° or below.
Conclusions are drawn that signals over long-distance H F circuits are propagated via
modes with angles of wave-arrival below 10° for a high percentage of time. The lowest pathattenuation and the highest effective antenna gain will therefore be achieved with antennae
having directivity characteristics in the vertical plane which favour these propagation modes
at both transmitting and receiving stations.
B ibliography

1. C.C.I.R. Doc. 23, Geneva, 1951.
2. C.C.I.R. Doc. 206, London, 1953.
3. P ession, Admiral G. Papers appearing in Rassegna delle P.T.T., September, 1935 and Alta Frequenza,
August, 1936. Work abstracted in C.C.I.R. Stockholm, 1948 book: (Proposals submitted to the
C.C.I.R.), Study Group II (Radio Propagation), 288.
4. S ilberstein, R. The long-distance horizontalradiation pattern of a high-frequency antenna. Nation­
al Bureau of Standards Report 3538. Abstract given in Transactions of the Instituteof Radio Engi­
neers, Vol. AP-5 (Antennas and Propagation), 4, 397 (October, 1957).
5. B eckmann, B. and V ogt, K„ Beobachtung der Riickstreuung im Kurzwellengebiet an kommerziellen
Telegraphiesignalen (Observations on back-scattering of commercial telegraph signals in the HFband), Fernmeldtechnische Zeitschrift, Vol. VIII, 473-481 (1955). Doc. VI/45, Geneva, 1958, con­tains some of this material.
6 . F ine , H. and D amelin, J. Suppressional performance of directional antenna systems in the standard
broadcast band. Federal Communications Commission Report TRR, 1.2.7.
7. B rueckmann , H. Suppression of undesired radiation of directional HF antennas and associatedfeed lines. Proc. IRE, 46, 1510-1516 (August, 1958).
8. M iya , K. I shikawa , M., and K anaya , S. On the bearing of ionospheric radio waves. Rep. Iono­
sphere Res. Japan, 9. 3, 130-144 (1957).
9. M iya , K. and K awai, M. On the propagation of long-distance HF signals above the classical MUF —Pulse and dot transmission tests between England and Japan. Electronic and Radio Engineer (United
Kingdom).
10. K een, R. Wireless direction finding, 4th ed., Iliffe and Co., London (1947).
11. N orton, K. A. System loss in radio wave propagation (See Sec. 9 of Report). National Bureauof Standards Journal o f Research, 63 D, 1, 53-74 (July-August, 1959).
12. Low, A. T. and H arris, B. V. Vertical wave-arrival angle measurements of HF transmission during
the period December 1960 to July 1961. Proc. I.E.E. Convention on HF Communication, 52 (2527 March, 1963).

R E P O R T 109-1 *RADIO SYSTEMS EMPLOYING IONOSPHERIC-SCATTER PROPAGATION(Q uestion 4/III)(1959 - 1966)
A contribution, relating to Question 4/III, has been received from the U.S.A.
(Doc. 111/29, Geneva, 1958); references are cited in which information on ionospheric-scatter
propagation relevant to exploitation of systems has been published [1,6]. Basic propagation
characteristics are given in Report 260-1.
* This Report was adopted unanimously.

Rep. 109-1

1.

— 11 —

Variation with frequency of propagation characteristics relevant to the use of systems
For estimation of the performance of fixed systems, it is important to know the variation
with frequency, of the mean signal intensity, the fading characteristics, such as short-term
amplitude distribution and fading rate, and the background galactic noise level. For prac­
tical purposes, received power may be considered inversely proportional to approximately the
7th power of the frequency, using scaled antennae. The background galactic noise is inversely
proportional to the 7/3 power of the frequency. The resulting signal-to-noise ratio, using
scaled antennae, is proportional approximately to f~h. Studies have shown that the frequency
dependence during hours of weakest signal intensity is not significantly different from thatobserved for the mean signal intensity. The short-term amplitude distribution of signal
intensity approximates a Rayleigh distribution at frequencies observed in the range of 30
to 74 MHz. The typical measured fading rate (median crossings), at 50 MHz, is approxi­
mately 1 Hz: the fading rate is proportional to operating frequency raised to a power of
0-7 to 1-2, depending on conditions.
Another important propagation characteristic which varies with frequency is the occur­
rence of long-distance F2 propagation giving rise to mutual interference and back-scatter,
which represents a source of self-interference to a scatter system used for high-speed tele­graph services. The occurrence of this type of propagation is dealt with in the following
paragraphs, along with consideration of mutual interference.

2.

The extent to which systems employing this mode of propagation and operating on the sameor neighbouring frequencies are liable to interfere with each other and with other services
The propagation modes, most significant in long distance interference between scatter
services and other services, are sporadic-E and F2. Adequate world-wide measurementsof sporadic-E are not yet available to permit a complete evaluation of the percentage oftime that interference is likely to occur. A comprehensive study of world-wide occurrenceof Es observed at H F by ionosphere recorders has been published [7,8]. For practical pur­poses, ionospheric-scatter circuits, to avoid sporadic-E interference, should have their trans­mitting and receiving terminals geographically separated from other circuits or services by atleast 2500 km. Figs. 1 to 3 of Report 260-1 represent contours of the F2-4000 km MUF
exceeded for 1 % of the hours for the December solstice, the June solstice and the Equinox,
at sun-spot maximum. These are derived from standard C.R.P.L. F2-prediction data,using measured distributions of day-to-day values of F2 M UF about the median. A circleof 2 000 km radius centred on the station gives the locus of frequencies at which propagation
over 4000 km paths occurs 1 % or 10% of the time during the season indicated. The percen­
tage of the time is less for paths longer or shorter than 4000 km.

3.

Radio-frequency and baseband characteristics of ionospheric scatter systems
Ionospheric-scatter systems of high reliability are currently in operation and the numberof such systems may be expected to increase. These systems employ highly directional
antennae and transmitter output powers of the order of 40 kW.

— 73 —

Rep. 109-1

In view of rapid technical advances, standardization is not practical at this time. There­
fore, the modulation characteristics of typical systems in use or under consideration arepresented for illustration:- a single voice channel of response from 300 to 3100 Hz using SSB, or narrow-band frequency
modulation with a peak deviation of 3 kHz;- four to sixteen channel, time-division multiplex, at a rate of 150 to 600 bauds with fre­quency-shift keying; a separation of 6 kHz is commonly used between mark and spacefrequencies, to minimize errors due to Doppler components;- combinations of the above, using linear transmitters, such as a voice channel and a fre­quency-shift keying system or two independent frequency-shift keying systems; as analternative, two transmitters may be used, one carrying voice intelligence and the otherteleprinter;- a system has been proposed with a single voice channel and four teleprinter channels,
using error correction and detection techniques at 177 bauds. A typical channel arrange­
ment for 20 kHz spectrum occupancy is shown in Fig. 1;- a frequency-shift radioteleprinter system using heterodyne frequency-changing, the oscillator
frequency being chosen between the frequencies representing the two significant condi­
tions of modulation (See Doc. I ll/112 (U.S.S.R.), 1963-1966) in such a manner that theupper beat frequency corresponding to one condition and the lower beat frequency corres­
ponding to the other condition are both within a narrow band; among the advantages
found for this method may be cited an increase in the signal-to-noise ratio and low cost.

Modulation characteristics of the propagation medium must be considered in systemapplication. Some pertinent characteristics are:- diversity reception is beneficial for voice or teleprinter operation.
is commonly used;

Dual or triple diversity- the coherence bandwidth, as determined by multipath considerations of the transmission
medium, is limited to approximately 3 kHz;- meteoric multipath will, in general, limit the maximum modulation rate;- during periods where the M UF may be above the operating frequency, F2, propagation
may be expected. The above conditions are frequently accompanied by long-delay multipath echoes, ranging up to 50 ms or more. The echo pulses may have amplitudes com­parable to or even greater than the desired signal, thus resulting in a very high error rate.
Long-delay multipath problems may find solution by the use of antennae having moredesirable directivity characteristics, the use of a frequency above the MUF, or by the useof special modulation techniques;- ionospheric-scatter systems characteristically employ high power and highly directional
antennae; during periods of sporadic-E or high MUF, they must be considered as potential
sources of interference to other services sharing the same frequency band;- current four-channel teleprinter systems, using dual-space diversity, typically require asignal-to-noise ratio of 24 dB (noise measured in a 250 Hz band), for a binary error rateof 1 x 10-4;- voice systems currently in use will provide usable operator-to-operator quality over a single
link with a radio-frequency signal-to-noise ratio of approximately 14 dB, as measured in a
3 kHz noise bandwidth.

Rep. 109-1— 74 —

The frequencies used for this mode of propagation are generally between 30 and 40 MHz.
A few circuits currently being installed will use dual-frequency operation. Higher frequencies,
perhaps as high as 60 MHz, will be useful as a means to avoid distance propagation during
periods of high F2 M U F’s at time of maximum solar activity.
The distance over which these circuits operate generally range from 1000 to 2000 km,
and several of these circuits are now in operation.
B (Speed in bauds)

SSB V oice

B (Speed in bauds)

N a rro w -b a n d voice

F igure 1

Typical 20 kHz channel arrangements for ionospheric-scatter transmission(B is the frequency in hertz corresponding to the telegraph speed in bauds)

B ibliography

1. B ailey, D. K., B ateman, R. and Kirby , R. C. Radio transmission at VHF by scattering and otherprocesses in the lower ionosphere. Proc. IRE, 43, 1181-1230 (1955).
2. A bel, W. G., D e B ettencourt, J. T., C hisholm, J. H. and R oche, J. F. Investigations of scatter­ing and multipath properties of ionospheric propagation at radio frefluencies exceeding the MUF.
Proc. IRE, 43, 1255-1268 (1955).
3.

B ray , W. J., Saxton , J. A., W hite, R. W. and L uscombe , G. W. VHF propagation by ionosphericscattering and its application to long-distance communication. Proc. I.E.E., 103, Part B, 236-260(1956).
In addition to the above, attention is drawn to entire issues of journals as follows:

4.

Proc. IRE, 43, 10 (October, 1955).

5. IRE Transactions on Communications Systems. Vol. CS-4, 1 (March, 1956).
6.

I.E.E. Symposium on long-distance propagation above 30 Mc/s. Journal of the I.E.E., 105, Part B.
London (28 January, 1958).

7. S mith, E. K. Worldwide occurrence of sporadic-E. National Bureau o f Standards Circular 582.
(15 March, 1957). . . . . . .
8.

S mith, E. K. and D avis, Jr., R. M.

The effect of sporadic-E on VHF transmission in the U.S.

9. J.T.A.C. Joint Technical Advisory Committee EIA-IRE. Radio transmission by ionospheric andtropospheric scatter. Supplement to Radio Spectrum Conservation (1952). Proc. IRE, 48, 3-46
(January, 1960).
10. R ose, J. et al. Pacific scatter communication system. Fifth National Symposium on Global Commu­
nications (Convention Record), Chicago, U.S.A., 110-113 (May, 1961).
11. R ose, J. et al. Improved ionoscatter receiving techniques used on the Pacific scatter communica­tion system. Fifth National Symposium on Global Communications (Convention Record), Chicago,
U.S.A.,. 114-117 (May, 1961),

— 75 —

Rep. I l l

REPORT 111 *INFLUENCE ON LONG-DISTANCE HF COMMUNICATIONSUSING FREQUENCY-SHIFT KEYING OF FREQUENCY DEVIATIONSASSOCIATED WITH PASSAGE THROUGH THE IONOSPHERE, (Question 7/III)(1959)
1.

Introduction

This Report, based mainly on Doc. III/34 (U.S.A.), Geneva, 1958, deals with three
aspects of the question. Firstly, the magnitude and time duration of the frequency changes
to be expected are considered. Secondly, upper bounds of error rates for frequency-shiftsystems are calculated. Thirdly, experimental element-to-element phase changes are shown,
relevant to phase-modulation techniques.
The present Report gives only partial information on the subject and a more complete
study may be expected, to provide definitive information on the minimum frequency shift
which is feasible in practical systems.
2.

Characteristics of frequency changes over HF circuits

It is well known that the rapid fading observed on H F circuits is the result of interference
between a number of different waves that have been reflected from different portions of theionosphere. The ionosphere may be thought of as an irregular reflecting surface that isdrifting across the sky. Because of this drift, waves that arrive at the receiving site are beingreflected from elemental surfaces that are in motion; consequently, each reflected wave will
have a small Doppler frequency change. The interference of these frequency-shifted waves
gives rise to rapid fading. (This Report will be concerned only with rapid fading and not slow
variations resulting from changes in absorption). This being the case, a reasonable model
describing the fading signal is to assume it has the character of very narrow-band Gaussian
noise. This approach was probably first described by J. A. Ratcliffe [1].
When the narrow-band noise representation is used, it is then possible to use the exten­
sive work done by S. O. Rice [2], in determining the nature of a fading H F signal.
Now the relationship between the fading rate N g (defined as the mean number of times
per second the signal envelope passes through the median signal level with positive slope),
and the corresponding “ equivalent noise bandwidth ” of the fading signal is
N g = l-4 8 a
where a is the standard deviation of ah assumed Gaussian shaped band-pass filter. (Thisequivalent noise bandwidth refers to the received signal only and not the noise that may
accompany it.) It is equivalent to the 2-17 dB half-bandwidth of the filter. If a rectangularfilter is assumed then the fading rate N r is
N r

= Bl2-32

where B is the bandwidth of the filter. The Gaussian shaped filter seems to be a close approxi­
mation to the true fading bandwidth of an H F signal [3]; however, for convenience, only arectangular filter will be considered. Once we have a measure of the bandwidth of the fading* This Report was adopted by correspondence without reservation.

Rep. I l l— 76 —

signal, we may proceed to find the probability distribution of the instantaneous frequency
along with several other statistics.
Fig. 1 shows the cumulative probability distribution of the instantaneous frequency.
This curve has been normalized to the fading rate. For a fading rate of 1 Hz, the instanta­
neous frequency will be within about 20 Hz of the carrier frequency 99-96% of the time.
Taking into account the fading rate indicated in Report 266, the values of excursion of
instantaneous frequency are not inconsistent with the deviations of 3 parts in 106 for a few
milliseconds duration reported in Doc. III/3 (United Kingdom), Geneva, 1958.
The mean duration of the instantaneous frequency deviation may also be found with theaid of results worked out by Rice. He derives the expression for the mean number of times
per second that the instantaneous frequency exceeds or crosses a given instantaneous fre­quency, when the bandwidth of the filter is known. Taking the reciprocal of these crossingsper-second gives the mean time interval between them. And since we also know the per­centage of the time the instantaneous frequency spends beyond the given crossings, we may
compute the mean time duration it spends there. This is simply the product of the probabil­
ity that it will be beyond the crossing and the mean time interval between the crossing. This
mean time interval, A t, versus frequency change from the centre frequency, is shown in Fig. 2.
Fading rate is the parameter. If the fading rate is known, the mean duration of exceeding agiven frequency change may be found. It is interesting to note that A t is practically inde­
pendent of the fading rate.
It should be noted that a more complete study is required to provide the cumulative
distribution of the time durations for various specified frequency changes. This is beyond
the scope of the present Report.

3.

The effects on frequency-shift keying of frequency changes due to passage through the iono­
sphereTo determine the effect of frequency changes associated with passage through theionosphere, we shall assume that no noise is present and that our detector is a frequency
discriminator. Our system will make an error, if the transmitted frequency is changed far
enough to cross over into the wrong side of the discriminator and remains there for a period
comparable to half the element length. We shall choose 20 ms as the element length.
If we assume a fading rate of one per second and a frequency shift of 40 Hz, we find,referring to Fig. 1, that the frequency of either the mark or space channel will change by 20 Hz
and cross over into the wrong side of the discriminator for only 0 04% of the time. The
0-04 % represents the upper limit of the binary error rate to be expected in the no noise case.
If reference is made to Fig. 2, we find that A t is only 6-2 ms; consequently, even when the
instantaneous frequency does lie on the wrong side of the discriminator, its duration is so shortthat only rarely will an error be made.
Fig. 3 shows the maximum binary error rate to be expected versus the frequency shift ofthe system with the fading rate as a parameter. It is assumed that errors occur with theprobability that the instantaneous frequency has been displaced to the wrong side of thediscriminator. This over-estimates the true error rate due to frequency changes, when themean length of time of the change is small compared with the signal pulse length, since thediscriminator (or post detection filter) time constant has been ignored. As an aid in estimating
the region where this time constant becomes effective, points on the curves, corresponding to
At of 10 ms, have been located from the curves of Fig. 2.

4.

Experimental data relevant to phase modulation
Several experimental studies have been conducted, to determine the performance ofthe frequency-shift keying systems and a phase-shift (synchronous) system over sky-wave
transmission in the H F band. The phase-shift modulation system requires reasonable phase— 77 —

Rep. I l lstability over an approximate period of 44 ms. Results of these studies are pertinent to thisstudy of Doppler frequency changes.
A short study has been made of the phase stability of signals from WWV as received
in Burbank, California [4]. Measurements were made at frequencies of 5, 10 and 15 MHz.
A sequence of discrete phase comparisons were made at a rate of 50 Hz. Each measurementcompared the phase of the incoming signals during a 20 ms period with that during the fol­lowing such period.
Stability of receiving equipment for such measurements is of primary importance. For
this test, all receiving gear was frequency controlled by a single high stability local standard
oscillator (1 part in 10 s), thus ensuring that apparent phase shifts due to frequency error
were insignificant compared to phase changes due to the propagation.
In general terms, the measuring technique consists of driving an extremely high Q
resonator circuit with the received signal for 20 ms. The resonator was then allowed to ring,
while the second resonator was driven by the signal for another 20 ms. The relative phasebetween the two resonators was then measured in a phase detector. This resultant measure­ment was the phase difference between two integration-phase samples taken 20 ms apart.
By a suitable connection between two quadrature phase detectors, a polar display of relative
phase and amplitude was presented on an oscilloscope. The oscilloscope intensity level was
blanked except at the end of each 20 ms integration period. The resulting display is a seriesof dots representing the tips of vectors, whose lengths from the origin are proportional tothe amplitude of the applied signal, and having angles equal to the signal phase changes
between samples. Photographs of these dot displays were made with exposure times of from15 s to 5 min. The major results of the study were polar displays of signal phase shift andamplitude. Fig. 4 shows approximate probability contours drawn from these displays. These
indicate a decrease in phase stability at higher frequencies, as expected, and give an indi­
cation of the degree of phase uncertainty, which cannot be attributed to additive noise.

5.

Conclusions
To the degree that the theoretical model describes the behaviour of an HF fading signal*
it appears that frequency changes imposed by the propagation are small for typical fading
rates. This conclusion is supported by some experimental evidence on phase uncertainty
obtained over H F paths. Further studies, especially of the distribution of the duration of
frequency changes are needed to improve the estimates of errors imposed in frequencyshift keying systems.
B ibliography

1. R atcliffe, J. A. Diffraction from the ionosphere and the fading of radio waves. Nature, 162, 9(1948).
2. R ice, S. O. Properties of a sine wave plus random noise. Bell System Technical Journal, 27, 109157 (1948).
3. P rice, R. The autocorrelogram of a complete carrier-wave received over the ionosphere at oblique
incidence, Proc. IRE, 45, 879 (1957).
4.

D oelz , M. L., H eald, E. T. and M artin , D . L. Binary data transmission techniques for linear
systems. Proc. IRE, 45, 656-662 (May, 1957).

Rep. I l l

—

78 —

x>
o

F' = Instantaneous departure from centre frequency (Hz)N r = Fading rate (fades per second)
F igure 1

Cumulative probability distribution of instantaneous frequency-changeHz

Departure from centre frequency (Hz)Curve A: 0-2 fades/second

Curve B: 1 fade/second

Curve C: 5 fades/second

F igure 2
Average duration that instantaneous frequency change due to the ionosphere exceeds F', with fading rates
o f 0 2, 10, and 5 0 fades per second (assuming a model o f narrow-band Gaussian noise)Rep. I l l— 79 —%I

Frequency shift of the system (Hz)F igure 3

Relation between binary error-rate and frequency-shift of the system for fading rates,
N, o f 0 2, 1 and 5 fades per second.
Element length = 20 ms (50 bauds)
A) 5 M H z

B) 10 MHzC) 15 M Hz

F igure 4

Polar probability contours of phase change and amplitude of WWV
The numbers shown represent the probability that a measurement will fall outside the contours.

Rep. 112

— 80 —REPORT 112 *TRANSMISSION LOSS IN STUDIES OF RADIO SYSTEMS(Question 1/III)(1959)

1.

Definitions of system loss, transmission loss, basic transmission loss, path antenna directivity
gain and path antenna power gain
Definitions and standard notations ** have been given in Recommendation 341 forthe system loss L s, the transmission loss L , the propagation loss L p, the basic transmission
loss Lb, the path antenna directivity gain GP and the path antenna power gain G pp. It is
the purpose of this Report to illustrate the use of these terms and the concepts involved,
and to show their relationship to other parameters.

2.

Transmission loss in free space
As an example of the simplicity of transmission loss calculations in some cases, we
may consider the transmission loss between two isotropic antennae in free space. At a dis­
tance, d, very much greater than the wavelength, X, the power flux density (field intensity),
expressed in watts per square metre, is simply p 2/4nd2, since the power is radiated uni­
formly in all directions. Since the effective absorbing area of the receiving antenna is X2/4n,
the available power at the terminals of the loss-free isotropic receiving antenna is given by:' ■ " ( £ ) (r o r )Consequently, the basic transmission loss in free space may be expressed by:
Lbf = 10 logio (4 n djX)2(d p X)(2)

Since the free-space gain of a short lossless electric dipole is g t = gr — 1-5, the path antenna
gain for two optimally oriented short electric lossless dipoles in free space is:
Gp =

Gt +

Gr =

3-52 dB(3)

Consequently, the transmission loss between two optimally oriented short lossless electric
dipoles in free space is :L =3.

10 logio (4 n d/X) 2 - 3-52 dB(4)

The concept of propagation loss and the influence of the environment of the antenna
To illustrate the influence of changes in the impedances of the antennae, caused byenvironmental factors which are independent of the antennae circuit losses, we will consider* This Report was adopted by correspondence without reservation.
** Throughout this Report, capital letters are used to denote the ratios, expressed in decibels, of the corres­
ponding quantities designated with lower-case type; e.g. P< = 10 logiopt. Pt is the input power to thetransmitting antenna expressed in decibels relative to 1 watt.

— 81 —

Rep. 112

the transmission loss between two short vertical lossless electric dipoles at heights ht and hr,
respectively, above a plane perfectly conducting surface and separated by a distance, d,large with respect to the wavelength, along the surface. In free space, the field strengthe (V/m), at a distance d (m) in the equatorial plane of a short lossless electric dipole radiat­ing p r (W), is given by:
e 2/r|o = 1-5p rl(4 n d 2)(5)where r|o = 4 nc X 10-7 is the impedance of free space (Q), and c = 2-997925 x 108 (m/s),
is the velocity of light in free space. The factor (1-5) can be identified as the free space gainof the transmitting dipole antenna. The radiation resistance of a short vertical electric dipoleof effective length / at a height hi, above a perfectly conducting plane, is given b y :

r=

At =

+ A0 = r / ( 1 + A f )(2k ht)2

s in (2kht)' ... . .
— cos (2k ht)
2k ht

(6)

(7)

In the above, k = 2njX — 2nf/c, i. e., X is the wavelength in free space. Note that At appro­aches zero at large heights above the surface and r approaches its free-space value, r/. On
the other hand, At = 1 for ht = 0, and the radiation resistance is then just twice its freespace value. The field intensity expressed in W /m 2 at a height h, for a short vertical lossless
electric dipole at a height, ht over a perfectly conducting plane surface, may be expressed by:e2
1 • 5 p r [2 cos2 v • cos (kht sin'v )]2— ~rio
4 71d 2 (1 + At)(8) *In the above expression, tan vj/ = hrjd and the distance, d, along the surface must be large
with respect to both'A, and ht; in this case, the distance between the antennae is approximately
d/cos \\i- Since At = 1 for ht = 0, the field intensity is 3 dB greater, when y = 0 and thedipole is on the surface of a perfectly conducting plane (i. e., e 2/r|o = 3p2/4nd2)), than when
it is in free space; note that in free space we must use (5) and not (8), since the ground relec­tion influences the radiation for all values of ht. In more familiar units, when ht = hr = 0, (8 )may be expressed by:
e = 2-998962 x 105 (j/pjd)(9)

where e is in \iV/m; p r is in kW; and d is in km
The effective absorbing area of a short vertical lossless electric dipole receiving antenna,at a height h, above a perfectly conducting plane, may be expressed by:
1-5 X2 cos 2 viz
ae = 4, n (1 +. Ar)
. -v

(10)

where Ar is defined by (7), with ht replaced by hr. Since p a = e2aelr\o, we find by combining(8) and ( 10) that the transmission loss between two short vertical lossless electric dipoles, atheights ht and hr above a plane perfectly conducting surface, may be expressed by:
T

ln l
~

f[4 7i d/(X cos \j/)]2 (1 + At) (1 + Ar))
0gl° 1 (1-5) 2 [2 cos 2 \|/ • cos (kht sin y )]2 J* These relations are derived by S. A. Schelkunoff in Chapters VI and IX of the book Electromagnetic
Waves, D. Van Nostrand Co., 1943.
6

Rep. 112

— 82 —or L = Lbf + A + Lt + L r — G p — 6-02 = L P + L t + L r (dB)

(12)

where
L t = 10 logio [1 + L t], L r = 10 logio [1 + Ar] Gv
20 logio [(3/2) cos2 \|/] andA z z — 20 logio [cos (k ht sin v|/)]. It is of interest to note that the transmission loss between the
dipoles on the plane perfectly conducting surface, ht = hr — 0 , is the same as if the dipoles

were separated by the same distance in free space, although the field intensity is 3 dB
greater for the same power radiated. On the other hand, when the dipoles are several
wavelengths above the perfectly reflecting surface {ht = hr > X), and are separated by a large
distance (y ^ 0), the transmission loss is 6-02 dB less than for dipoles separated by thesame distance in free space.
The above is not the only logically consistent method of describing the gains and losses
in the presence of a perfectly conducting ground. Thus, Schelkunoff, in the reference cited,considered the perfectly reflecting surface to be an integral part of the transmitting andreceiving antennae, and set Gts = 10 logio [3/(1 + At)] and G rs = 10 logio [3/(1 + Ar)].
In other words, he referred his maximum gains to those expected for isotropic antennae withthe earth removed; this leads to a path antenna gain, referred to that expected between iso­tropic antennae with the earth removed, given by G ps = G P + 6 02 — L t — L r — A , andthis transmission loss is simply L = Lbf — G ps. However, this method of approach is notrecommended since:- it is impracticable to remove the Earth to measure Gp s;- it would lead to antenna gains 3 dB larger than their free-space values, even when they
are many wavelengths above a perfectly reflecting plane surface, and this is inconsistent
with the present usage of the concept of antenna gain in the higher frequency ranges.
Although it appears to be desirable to separate the effects of earth reflections from thegains of the antennae, by means of the propagation loss concept described earlier, there will
be other situations in which such a separation of environmental effects is undesirable. For
example, the power gain of an antenna, mounted on an aircraft, satellite, or spacecraft
should be considered as the gain which would be determined by integrating the cymomotive
force over all directions as the vehicle is rotated in free space. Equation (12) illustrates thedefinition of L p, the propagation loss, i. e., the transmission loss expected if the antennae
had the same impedances they would have had if they were in free space. L t and L r are defined
above for antennae over a perfectly conducting ground plane; more generally, L t and L r are
defined as 10 logio (r'/rf), where r' is the actual resistance of the antenna and r/ is the radia­
tion resistance it would have if it were in free space. We note that L t and L r contain the loss
components Ltc and L rc and may also vary substantially from one antenna site to the next,
depending upon polarization and ground conditions. They are also a function of the sizeof the ground screen used, and depend on other environmental factors, such as the presenceof trees or over-head wires. It is thus clear why it is desirable to separate these components
from the system loss and to have a propagation loss, L p, independent of these antenna envi­
ronmental conditions.

4.

Simplification possible at higher frequencies
At higher frequencies, the antennae are usually located several wavelengths away fromthe ground and other environmental disturbing elements and, in such cases, L t, L r, Ltc and
Lrc will all be sufficiently small so that the propagation loss, the transmission loss, and thesystem loss will all have essentially the same magnitude, and it will then be unnecessary to
distinguish between L p, L and L s.

5.

Relation to current C.C.I.R. terminology
It is desirable to relate the above transmission loss terminology to the terminology
used in other C.C.I.R. documentation. We may express the free-space cymomotive force

— 83 —

Rep. 112

C = 20 logio(e.d) in dB rel. 1 V (e. g., relative to 1 V/m at a distance of 1 m) as in Recom­
mendation 168-1 In free space, we find by (5), when we note that P t = P t — Ltc and L t = L td
C =10 logio (prC.gt x 1(H) = P t - L t + Gt + 14-77 (dB)(13)

The relation between the available power, p a, from the receiving antenna and the field strength,e, may be expressed in decibels as follows:
E =10 logio [4 TCTloPa{r'lrf ) X 1012/(Hgr)] = Pa + 20 logio/ - Gr + L r + 107'22 dB (14)where / is in MHz.
If (13) is solved for P t and (14) for Pa and we combine the results, the following expression
for L s is obtained:
Ls = P t -Pa = C -

Ec -

GP +

20 lo g io /+ 92-45+ Lt + L r(15)

where / i s in MHz.
In Recommendation, 370-1, the curves of tropospheric field strength E , expressed in decibels
relative to 1 |4V/m, were referred to a free-space cymomotive force C = P t — L t + Gt + 14-77= 46-92 dB relative to 1 Y (i. e., 222 V), since they correspond to 1 kW radiated{P t — L t = 30) from a half-wave dipole {Gt = 2-15); thus, the propagation loss corres­
ponding to the values of E in those documents is given b y :L p = L$ — L t — L r = 139-37 -Gp +20 logio/ - E{C =46-92)(16)

where / is in MHz.
The inverse distance field I (expressed in dB relative to 1 V/m at 1 m), may be determinedover a perfectly conducting ground plane from (8):/ = P t' - L t + Gt + 20-79 (dB)(17)

Noting that P t — P t over a perfectly conducting ground plane and then solving (17) for P t
and (14) for P a and combining the results, the following expression for L s is obtained:
Ls = P t -Pa =I - E i - G P + 20 lo g ic/+ 86-43 + L t + L r(18)

where / is in MHz
In Recommendation 368, the curves of E = f {d) were referred to a value of / = 20 logio 300 =
49-54 dB relative to 1 V, i. e., by (17) the inverse distance field corresponding to 1 kW radiated(P r = 30) from a short vertical electric dipole {Gt = 1-76) over a perfectly conducting
ground {Lt = 3-01) and thus the propagation loss corresponding to the values of E in Recom­
mendation 368 is given by:
Lp = L s — L t — L r =135-97 - G P + 2 0 l o g ic /- E(/ = 49-54)(19)

where / is in MHz.
It is seen from the above discussion that the propagation loss, L p, may be calculatedby (16), from the values of E given in Recommendation 370-1, or by (19) from the valuesof E in Recommendation 368. The fact that there are different relations between L p andthe values of E in these documents, illustrates the complexity of the conventions used inpast studies of radio wave propagation. There may be some advantage to the C.C.I.R. in
adopting the propagation loss, L p, between short electric dipoles, as a standard methodof presenting the results of radio propagation studies such as those in the above documents.
This would make possible the use of a single convention throughout the spectrum and would
result in a presentation which is directly useful to those engaged in studies of radio systems.
Short electric dipoles are suggested as reference standards for the uniform presentationof propagation data throughout the spectrum, in preference to either isotropic antennaeor half-wave dipoles, for the following reasons:- short electric dipoles are physically realizable throughout the spectrum;84 -Rep. 112- short electric dipoles have polarization characteristics, as do all real antennae;- short vertical electric dipoles have some directivity in the vertical plane
and thussimulate
typical real antennae somewhat better, as regards ionospheric wave propagation in thelower frequency ranges.
It is recognized, that it will often be more convenient, at the higher frequencies, to makepropagation measurements using half-wave dipoles, but such measurements can readily be
adjusted to the results expected with a short electric dipole, since the maximum gain of ahalf-wave dipole is just 0-39 dB larger than that of a short electric dipole.
If the propagation loss, L p, between short electric dipoles were used as a standard by
the C.C.I.R., then Gp = 3-52 dB and the field E (C = 46-92) of Recommendation 370-1
could, by (16), be determined from:E (C=46-92) = 135-85 + 20 lo g ic /- L P(20)and the field E (/ = 49-54) of Recommendation 368 could, by (19), be determined from:E ( I = 49-54) = 132-45 + 20 logic/ - L P(21)

where / is in MHz in both cases.

6.

Comparison between the measurement of field strength and the measurement of the available
power from the receiving antenna
The essential advantage of measuring or calculating propagation characteristics, interms of system loss rather than in terms of field strength, is the fact that the former requires
the determination of the available power from the receiving antenna for a given input power
to the transmitting antenna, and thus automatically allows for both the directivity and thecircuit losses of the transmitting and receiving antennae. The available power pa = c2/4r',
where r' is the resistive component of the receiving antenna output impedance, including
both its radiation resistance, r, and loss resistance component, rc, while v is the open circuit
voltage When the antenna is loaded by the complex conjugate of its output impedance,
the voltage appearing across its terminals is v/2 ; thus the available power is simply the power
delivered by the receiving antenna to a matched load. The accurate determination of theavailable power requires the measurements of both r' and, v, whereas the field strength
is independent of r' and, to this extent, does not provide a direct measure of the expected
performance of a radio system, at least in those cases where receiver noise is comparable
to, or larger than, the noise picked up by the receiving antenna.

7.

Simplicity of system problems solved in terms of system losses
Finally, it should be noted that the concept of system loss provides a simple solution to
the problem of allowing for the effects of interfering transmissions. Consider, as one example,
the determination of the interference to the reception at a particular receiving location ofa wanted transmission caused by an unwanted transmission on the same channel. The ratioof the wanted-to-unwanted signal .power, available at the terminals of the receiving antenna
may be expressed by:
R = Ptd — Ptu — Lsd 4“ Lsu(22)

where Ptd and Ptu denote the antenna input powers to the wanted and unwanted transmissions,while Lsd and L su denote the system loses for the wanted and unwanted transmission paths.
When it is noted that the component L rc is the same in Lsd and Lsu j (22 ) becomes:
R — P td — Ptu — L d + L u(23)

where P U and P tu are the radiated powers from wanted and unwanted transmitters, whileand L u are the transmission losses for the wanted and unwanted transmission paths.

Ld

— 85 —

Rep. 112

Both Ld and Lu will vary with time, and these variations will, over long periods of time,
be positively correlated, so that the variance of R with time will be somewhat less than thesum of the variances of L a and L u. If R exceeds a prescribed minimum acceptable level, R m,
for a sufficiently large percentage of time, then this particular receiving location may beconsidered to be free of interference. Note that the effect of the directivity of the receiving
antenna is appropriately allowed for in determining R , since L d will be measured (or calcu­
lated), with the antenna directed towards the desired station, while L u is the transmission
loss corresponding to the effective receiving antenna gain in the direction of the unwanted
transmitter. For a broadcasting service, one may choose a large number of receiving loca­
tions within the service area of the wanted station in some systematic way * and at eachof these locations determine, in the manner described above, whether it is satisfactorily freeof interference. This constitutes a useful solution of the problem of assessing the impor­tance of the interference between stations on the same channel; the same method can also
be used for interference between stations on adjacent channels, simply by changing the valueof R m. It is important to notice that the transmission losses, La and Lu, will be very muchinfluenced by the irregularities in the terrain profiles to the wanted and unwanted stations res­pectively. Furthermore, there will be a tendency for Ld and L u to be correlated as one moves
from one receiving location to the next, since unfavourable locations for the reception of
the wanted station will also tend to be unfavourable for the reception of the unwanted station.
The above discussion represents one of a number of possible examples of the utility of
the concept of transmission loss in systems studies. There are many circumstances, however,as, for example, in assessing the interference potential of Industrial Scientific and Medical
equipment, where it is more convenient to specify the interference in terms of field strengths,
rather than attempt to specify the parameters involved in system loss calculations, and it
is not the intention of this Report to suggest that the concept of system loss should necessa­
rily replace that of field strength. Rather it has been the intention in this Report merely
to discuss the possible advantages of this concept and to show its relation to other terms
in use by the C.C.I.R.

8.

Relationship to other C.C.I.R. Questions and Study Programmes
Note that this method of presenting the results of propagation studies has a direct
bearing on the following work of the C.C.I.R.
Questions: 3/HI, 4/III, and 4/V;
Study Programmes: 4A/I, 1A/III, 3A/III, 6 A/V, 11A/VI, 13A/VI and 17A/VI* It is convenient to choose these VHF receiving locations at the intersections of a regular lattice with separa­tions of, say, 2 km, since it is known that there is very little correlation between the transmission losses
at VHF for receiving points separated by such distances, and this will permit a maximum of information
to be derived with a relatively small sample.

86 —Rep. 195

REPORT 195 *BANDWIDTH AND SIGNAL-TO-NOISE RATIOS IN COMPLETE SYSTEMS
Prediction of the performance of telegraph systems in termsof bandwidth and signal-to-noise ratio(Study Programme 1A/III)(1959- 1963)
1.

Study Programme 1A/III sets out some questions, the answer to which would form a basis
for the evaluation of the performance of complete systems. The questions include terms
like “ excellent service ”, the interpretation of which depends greatly on the type of traffic
the system is intended to carry and the grade of service. This Report will not discuss suchquestions in detail, but rather attempt to give a basis for a more objective method of per­formance specification in the light of recent work on communication systems.
Theoretical studies of the mechanisms of detection of telegraph signals in the presenceof noise, having a Gaussian distribution [1, 2], have made it possible to define the perfor­
mance of a system, in terms of element error-rate, as a function of the signal-to-noise ratio
just prior to the detector. The word “ detector ” is used here in a very general sense andthe detector might be a limiter-discriminator. It is convenient to use a quantity called
the “ normalized signal-to-noise ratio ”, R, which is defined as the quotient of the averageof the specific energies of the mark and the space signals, and the noise power per unit band­
width. For systems which use two equally probable signals of equal energy, this ratio is
equal to the signal-to-noise power ratio per baud per unit bandwidth, or the ratio of thesignal power to the noise power per unit bandwidth, divided by the number of bauds. Directcomparison between receivers, even when working at different speeds is, therefore, possible.
In these studies, it was also found possible to specify the performance of a telegraphreceiver by a single parameter. This parameter has been called the “ demodulation factor ”
and it is the amount (in dB), by which the signal-to-noise ratio (normalized), applied to thereceiver under test, exceeds that applied to an idealized receiver of the same type for thesame element error-rate. For the purpose of this work, we have to distinguish between
coherent and non-coherent receivers. The coherent receiver has a priori knowledge ofthe phase of the elementary waveform. The mark- and space-elements are assumed tobe equally probable.

1.1 Coherent reception.

No fading

Assume that xi (t) and xz (t) are the two signal waveforms, that x is the unit interval(duration of one element), and that N is the noise power per Hz. Then if:

the element error-rate Pe is given by:* This Report, which replaces Report 105, was adopted unanimously.

Rep. 195

— 87 —In terms of the “ normalized signal-to-noise ratio ” , R, this error-rate can be expressed in
the form:Pe =ie r f c (aR )i/2;- for phase-reversal modulation ai = 1 ;- for frequency-shift keying with two orthogonal signals ct2 = 1/2;
- for amplitude keying (on-off signals) too, 013 = i.
For large values of R, the complementary error function can be well approximatedby an exponential curve:Pe «1.2 Non-coherent reception.

“ 77=
exp ( — a R )
lynaR
\
’

No fading

For non-coherent reception of a steady signal, the error-rate is of the form:
P e = i exp

a Rj

Again:- for differentially coherent reception [3] of phase-reversal modulation ai = 1;
- for matched filter reception and envelope detection [4] of frequency shift keying a 2 = i(for narrow-band FSK with shifts of the order (0-8/x), the effect of correlation leads tobetter results);- for amplitude keying, we get approximately [4] a 3 = \.
1.3 Coherent diversity reception.

Flat fading

It is assumed that the fading is of Rayleigh type, that the fadings in different branches
are uncorrelated (but that they are the same for mark and space signals), that the mean
signal-on energies of all branches are equal, and that the fading is so slow, relative to the
speed of signalling, that the signal power may be regarded as constant during any one signal
element. The outputs of the diversity branches are assumed to be weighted, according
to the signal energy and combined (maximal ratio combination).
For Rayleigh fading and one receiver, we get the following error-rate:
1 1-----------------

2 ~ 2 V a R^a R + 1 )For dual diversity:- P e 2 = - — ~ | / a i ? ( a R + - ) 2 / ( a R + l )3
For triple diversity:Rep. 195

— 88 —For quadruple diversity:

=

+

+

+

l(*R+WFor large values of P, these results are closely approximated by:
Pei = l/4 a P ;P e2 = 3Pei 2 = 3/(4aP)2; P e3 = 10 P ie 3 - 10/(4aP)2; P e4 = 35 P ei4 = 35/(4aP ) 4
respectively.
In the definition of the normalized signal-to-noise ratio R, the average signal energy
and signal power per branch should now be substituted for signal energy and signal power
respectively.
The basic curves, for idealized coherent reception of frequency-shift signals in fading(a = £), are given in Fig. 1 for single, double, triple and quadruple diversity systems.
1.4 Non-coherent reception.

Flat fading

The equations for the error-rate for non-coherent reception, under the circumstances
otherwise specified in § 1.3. (maximum ratio combining), are:P ei =V2 (1+ ctP),

P e2 =V2 (1+ a P )2, dual diversity;

Rayleigh fading,one receiver;

P ei =V2 (1+ aP )3,

Pe4 =

V2 (1

+ a P ) 4, quadruple diversity.

triple diversity;

The basic curves for this case are given in Fig. 2, again for the reception of frequency
shift signals in fading (a = f).

1.5 Coherent reception.

Independent fading

1.6 Non-coherent reception.

Independent fading

If it may be assumed that the frequencies corresponding to the two significant condi­
tions of modulation are sufficiently widely separated for the fading in the two branches tobe independent, then independent reception in the two branches is possible.
If, furthermore, the same assumptions are made as in §§ 1.3 and 1.4, the resulting error
rates may be derived directly from the above. Then, going from flat fading to independent
fading is equivalent to doubling the order of diversity, while having the power in each diver­sity branch [6].

2.

Demodulation factor
If the performance curve of an actual receiver for coherent reception is of the comple­
mentary error function type, then a constant factor indicates the extent by which a practicalreceiver falls short of the ideal, and it is the same for all types of diversity.
Also, if the performance curve of an actual receiver for non-coherent reception is of
the exponential type, the demodulation factor will be a constant.

— 89 —

Rep. 195

Equipment for measuring the demodulation factor of a receiver in the laboratory, undersimulated fading conditions, has been described elsewhere [5]. Alternatively, a measureof the demodulation factor may be obtained by calculation from the performance of thereceiver under non-fading conditions, as in the Annex.
In this Report we have only discussed maximum-ratio combining. In the literature [7],one can find a comparison of this type o f diversity with equal-gain and selection diversity.
The loss for equal-gain combining is apparently of the order of 1 dB.
The performance of a circuit is usually expressed in terms of character error-rates.
Calculations from the probability functions involved give a simple conversion from an ele­ment error-rate to a character error-rate for various types of telegraph code, thus providing
a simple relationship between the signal-to-noise ratio and the number of errors on the prin­ted copy. The particular case for random arrival of element errors represents a useful limit­
ing condition which is approached closely when the error-rate is low.
Relationships between element and character error-rates are shown in Fig. 3 and 4.
In Fig. 3, curve (1) represents the upper limit of the character error-rate for a synchro­nous seven-unit code, when the element errors are mutually independent. It should be
noted here, that the character error-rate is defined as being the number of characters subject
to error at the output of the detector and thus an error in “ letter shift ” or “ figure shift ”
is counted only once and similarly for other errors, such asthose occurring in “ carriage
return ” or “ line feed ”. However, if the fading characteristicsgive rise to groups of errors,then the curve showing the relationship between element and character error-rates becomes
asymptotic to curve (2 ) which was calculated on the assumption that the signal level remains
constant during a character. For element error-rates lower than 1 X 10-3, the curve (1)is appropriate.
In Fig. 4, the upper limits are shown as follows:- Curve 1: for a five-unit synchronous code: Pc eE 5Pe;
- Curve 2 : for a seven-unit code: Pc x lP e\-

Curve3: for a five-unit start-stop system with tape printing and allowing for errors due
to loss of synchronism, in addition to the simple character-errors Pc ^ 17Pe’,-

Curve4: for a five-unit start-stop system with page printing, i.e., including an additional
allowance for multiple errors due to carriage return and line-feed failures.
Again, as for the previous curves, errors in “ letter shift ” or “ figure shift ” areonly counted once Pc = 34Pe.

An example is given below to demonstrate the way in which the curves may be used.
It is stressed that this example shows the method employed in making one of the steps inthe calculations necessary to plan circuits for a specified grade of service, but that the demo­
dulation factor of the receiver must be known as a result of measurement.
First, we take the general case for reception of a steady signal.
Let Ro = the pre-detection signal-to-noise ratio (dB);
R n = the normalized signal-to-noise ratio, corresponding to R (dB);
Rn = 10 logio R',
S = the modulation rate in bauds (elements/s);
B — the pre-detection bandwidth (Hz) of the receiver in question;
D = the demodulation factor of the receiver for the modulation rate specified, in decibels;thenRo = R n + 10 logio (S/B) + D(1)

ExampleA coherent receiver, having a pre-detection bandwidth of 1000 Hz, is used for 50 bauds,
5-unit synchronous working, using triple diversity. The measured demodulation factor

Rep. 195

— 90 —of the receiver, for this signalling speed and bandwidth, is 10 dB. A character error-rateof l x l O -4 is permissible; what must be the pre-detector signal-to-noise ratio ?
From Fig. 4, the corresponding element error-rate is 2 x 10~5. From Fig. 1, an ideal
receiver using triple diversity produces an element error-rate of 2 x 10~5 for R n = 16 dB.
Using equation (1), we find:
Ro = Rn +10 logio (S /B ) + D

and inserting the known values we haveRo =16 — 13 + 10 = 13 dB.

This is the required signal-to-noise ratio per branch.
combining will be 3 R 0 or 18 dB.

3.

The signal-to-noise ratio after

Conclusion
Extension of this work, to cover noise other than thermal noise, may result in the needfor more parameters to describe fully system performance, but it seems clear that:- the performance of telegraph circuits should be related to stated character error-rates,
and for the engineering planning of circuits and design of equipment it is preferable tohave these expressed in corresponding element error-rates;- the approach indicated in this Report forms a useful starting point in the developmentof an objective method determining the performance of telegraph systems.

B ibliography

1. K otelnikov, V. A. Theory of optimum noise-immunity. Thesis, Moscow, U.S.S.R. (January,1947).
2. L aw , H. B. The detectability of fading radiotelegraph signals in noise. Proc. I.E.E., 104B, 130140 (March, 1957).
3. L awton , J. G. Theoretical error-rates of “ differentially coherent ” binary and “ Kineplex ” datatransmission systems. Proc. IRE, 47, 333-334 (February, 1959).
4. R eiger, S. Error probabilities of binary data transmission systems in the presence of random noise.
Convention Record of the IRE, Point 9, 72-79 (1953).
5. L aw , H. B., L ee, F. J., L ooser, R. C. and L evett, F. A. W. An improved fading machine. Proc.
I.E.E., 104B, 117-123 (March, 1957).
6. B arrow , B. B. Error probabilities for data transmission over fading radio paths. Thesis Delft,
Netherlands (March, 1962).
7. B rennan , D. G. Linear diversity combining techniques. Proc. IRE, 47, 1075-1102 (June, 1959)

ANNEX
In the absence of a fading simulator, it is possible to derive an approximate value ofthe element error-rate under fading conditions from the results of tests under steady condi­
tions.
These steady-state tests will give the error-rate as a distribution function g (R),of the normalized signal-to-noise ratio R .
If, for coherent reception, g(R) can be expressed in the following form:g(R) = i erfc (bR/2)ithen the demodulation factor is constant, 10 logio b, independent of the order of diversity
employed.

— 91 —

Rep. 195

In practice, this will not generally be the case and then the demodulation factor will
be a function of both R, and q (the order of diversity). However, by an extension of thework in [2 ], it can be shown that, in general, the element error-rate with q diversity branches
will be:For large signal-to-noise ratios, or small error-rates, the following approximation forthe demodulation factor Dq, with q diversity branches, and flat fading, can be found:cDaY = [2q . ql/(2q - 1)1]

- g(y)dy.

2 1

Measured distribution functions under steady-state conditions can be expressed in thefollowing form:

Then for large values of R:(Da)* = [2<.q\(q - \)\j(2q - 1)!] I («*/£*«)For other forms of the function g (R), similar calculations can be performed.
For non-coherent reception, the reasoning is completely analogous. Again, the answer
is simple, if the error-rate under steady conditions can be expressed as a single exponential
form.
For the more complicated error performance given by a sum of exponentials, as above,the demodulation factor is given in this case by:(Dq)* = 2 (a*l2) (2bjc)aElement error-rate

Rep. 195

-5

0

10

20

30

40

i

Normalized signal-to-noise ratio per diversity branch (dB)
Rn = 10 log R (n = number of diversity branches)

Normalized signal-to-noise ratio per diversity branch (dB)
Rn = 10 log R (n = number of diversity branches)

F igure 1

F igure 2

Coherent-reception

Non-coherent reception

Character error-rate,

Character error-rate

F igure 3

F igure 4

Curve 1: 5-unit synchronous code,
2:* 7-unit synchronous code,
3: 5-unit start-stop, tape printing,
4: 5-unit start-stop, page printing.

Rep. 196-1— 94 —REPORT 196-1 *SOME ASPECTS OF THE APPLICATION OF COMMUNICATION THEORY(Question 5/III)(1959- 1963 - 1966)

1.

Introduction
Question 5/III has as its subject the relationships between permissible delay, residual
uncertainty and bandwidth utilization. The residual uncertainty at the output can be cal­culated if the a posteriori probabilities that certain signals were transmitted are given at
the received output. Instead, usually a decision is made, and the probability of error is
calculated. We shall characteristize the channel by this error probability.

2.

Block codes
The permissible delay is related to the length of the code. Assume first, that a blockcode [1] (each code word consisting of n elements) is used for error correction. The delay(from coding and decoding) is then at least 2n elements. If feedback is used and retrans­mission (as is done in ARQ systems [2]), for good signals, the delay will not change much.
When the signal deteriorates the delay is likely to grow much larger.
If R is the rate at which digital information is transmitted (bits/second), and W is the
bandwidth of a channel, S the signal power of the transmitted signal, and N the noise power(the noise is supposed to be white noise), then we have Shannon’s relation:
R / W = log (1 + S/N)
This relation gives the minimum signal-to-noise ratio required to provide a certain infor­
mation rate per unit bandwidth, with a probability of error Pe, that can be made arbitrarily
small by using a sufficiently large value of n (the length of the code). This is an asymptotical
relation, and the question of how the probability of error goes down as n increases, hasbeen studied by many writers. An early study was given by Rice [3]. For any noisy chan­nel without memory having only a finite number of received signals, the error in transmitting
information at a rate H < C (C is the channel capacity) is bounded by an expression

where F and B are constants depending upon the channel parameters but not upon H or n.
This result was given in 1955 by Feinstein [4]. More accurate error bounds have since
been derived by Shannon [5, 6 ], Fano [7], Zetterberg [8] and Gallager [9].
Using Shannon’s results, Slepian [10] calculated the relation between the signal-tonoise ratio {SIN) and the information rate per unit bandwidth (R / W ) for a number of given
code length values n, and a given permissible error rate Pe (e.g. 1 x 10 ~4). Upper andlower bounds for S / N are given. The upper bound gives the value of S / N for which codeswith the required probability of error have been shown to exist, and the lower bound givesthat value of S / N below which a code with the required probability of error cannot exist.
*

This Report was adopted unanimously.

— 95 —

Rep. 196-1

For n = 25 the distance between upper and lower bound is about 1 dB, and for n — 101
the distance is only 0-15 dB. (Slepian uses decimal digits). For a code length of 25 deci­
mal digits, one needs 4 to 5 dB more than the asymptotical result of Shannon; and for acode length of 101 decimal digits about 2 dB, when the probability of error is 1 x 10~4.
We do not yet know how to construct such good codes. However, block codes thatcan be decoded in a simple way, e.g. Bose-Chaudhuri codes have been used in practice.
The decoding scheme guarantees correction of up to some fixed number of errors per
block, and corrects nothing beyond. For algebraic block codes it is not yet known, how
to use the a posteriori probabilities of error, this in contrast with the probabilistic decoding
techniques of convolutional codes. For block codes it is not yet clear which combina­
tion of error detection or correction, use of null-zone thresholds, and automatic error
correction, will give the best results.

3.

Convolutional codes

Wozencraft [11, 12, 13] found that in his convolutional technique the complexity ofthe decoding operation goes up slower than the square of the length of the code, insteadof growing exponentially with it. The decoding is simpler because the block structure is
replaced by a tree structure, and the maximum likelihood decoder by a threshold decoder.
The amount of computation required per digit is a random variable. This creates a waiting
fine problem at the decoder. ARQ is necessary when the buffer capacity is exceeded. Wozen­
craft showed also that the error bounds obtainable through the use of sequential decoding
were essentially the same as those obtained for probabilistic block codes having the same
constraint-length.
By combining signal design with sequential coding, an information rate of 7500 bits/swith an error propability of 1 X 10-9 was obtained as far as can be estimated from opera­tion over a long distance telephone channel during 40 hours. The system is now [14] imple­
mented for communication via active or passive satellite (e.g. the moon), with as its primary
purpose, the communication of vocoded speech in a hostile environment.
Convolutional codes with orthogonal parity checks can be decoded very simply byMassey’s threshold decoding [15]. It is most effective at relatively short constraint lengths.
Low density parity check-codes have been studied by Gallager [16].

4.

Burst-correcting codes

The effect of bursts on the 7/5 code automatic error correction system is discussed else- ,where (Report 197-1).
The use of longer block codes for detection only may lead to a
too high retransmission rate, see § 2. By interleaving n short block codes, which are capableof correcting one or two errors, bursts of length n or 2n can be corrected. This requires
rather long guard spaces. (Burst error correcting codes are characterized by the maximum
burst length, b, they can correct, provided the separation between bursts, the guard space,
has a minimum length g.) Long cyclic codes are also suitable for burst error correction [17].
Their guard space to burst ratio is near the theoretical minimum.
A new development in convolutional codes is the adaptive convolutional code (Galla­ger). In this technique, mostly used in combination with sequential decoding, the guard
space adapts to the actual length of the burst rather than remaining at the maximum value.
In addition the guard space to burst ratio is significantly reduced by allowing a very small
probability that a burst of less than the maximum length will not be corrected.
As already mentioned in §§ 2 and 3, even advanced codes will require automatic error
correction when the channel is very poor.

Rep. 196-1— 96 —A (15, 10) Abramson block code interleaved to give two-second burst error protection,
tested at teletype speeds over an H F channel gave one order of magnitude improvement
at a bit error rate of 1 x 10 -2, and two orders of magnitude at a bit error rate of 1 x 10 ~3.
An adaptive coding system with maximum-burst error-correction of 6 s and a guard
space a few bits longer than the actually occurring bursts, operated at telegraph speeds,
led to 90% of error-free blocks, whereas diversity without coding only gave 15% errorfree (50-line) blocks [18].
A short burst error correcting code for H F telegraphy transmission was found to allow
for an 18 dB decrease in power for equal performance as a non-coded system.

5.

Other advanced systems
Most communication channels are physically continuous even though they are used
to transmit discrete codes. In the more obvious systems, discrete symbols are transmitted
individually as time functions, and are reconstructed individually from continuous received
signals. Lower error rates can be obtained by reconstructing code words as a whole, fromreceived signals, rather than symbol by symbol. Application of matched filter techniques
to detection of redundant code words is one illustration of this principle [19, 20].

6.

Return channels (Question 5/III, § 2)
The channel capacity cannot be increased by the presence of a return channel, if thechannels are totally independent. A return channel can be used very effectively to dimi­nish the probability of error, even if the disturbances in the two channels are uncorrelated;
however, the same result can, in principle, always be obtained by more complex coding
procedures. New results on the use of feedback channels have appeared in the literature[21, 22]. Systems in which effective use is made of the correlation between noise in thego and return channel are, e.g., the Janet System, and a tropospheric-propagation systemused in France [23].

7.

Time-varying channels
Time-varying channels with delay spread have been studied by Price and Green [24],Siforov [25], Kailath [26] and Bello [27]. The Rake System, adapted to small values of the
product of multipath duration and fading rate, has been described in detail.

B ibliography

1. P eterson, W. W. Error-correcting codes, M.I.T. Press, John Wiley and Sons, New York (1961).
2.

van D uuren , H. C. A. Error probability and transmission speed on circuits using error detec­tion and automatic repetition of signals, IRE Trans. Comm. System, Vol. CS-9, 38-50 (1961).

3. R ice, S. O. Communication in the presence of noise. B. S. T. J. 29, 60-93 (1950).
4. F einstein, A. Error bounds in noisy channels without memory. IRE Trans. Inform. Theory (Sep­tember, 1955).
5. Shannon , C. E. Certain results in coding theory for noisy channels. Information and Control 1,
6-25 (1957).
6. Shannon , C. E. Probability of error for optimal codes in a Gaussian channel. B.S.T.J. 38, dl l 657 (1959).
7. F ano , R. M.

Transmission of information. , M.I.T. Press, John Wiley and Sons, New York (1961).

— 97 —

Rep. 196-1, 197-1

8. Z etterberg, L. H. Data transmission over a noisy Gaussian channel. Trans-Royal Inst. Techn.,
Stockholm, 184 (1961).
9. G allager, R. G. A simple derivation o f the coding theorem and some applications. IEEE Trans.
Inform. Theory, I.T. 11 (January, 1965).
10. Slepian, D. Bounds on communication. B.S.T.J. 42, 681-707 (1963).
11. W ozencraft, J. M. Sequential decoding for reliable communications. IRE Nat. Com. Rec. 5part 2 (1957).
12. W ozencraft, J. M. and R eiffen, B. Sequential decoding. M.I.T. Press, John Wiley and Sons,
New York (1961).
13. W ozencraft, J. M. and K ennedy , R. S. Coding and communication. Progress in radio science(1960-63), Vol. VI, Elsevier (1965).
14. Lebow, J. L. Sequential decoding for efficient channel utilization. IEEE Annual Comm. Syst.
Conference (1965).
15. M assey, J. L. Threshold decoding, M.I.T. Press (1963).
16. G allager, R. G. Low-density parity-check codes. M.I.T. Press (1963).
17. W yner , A. D. and A sh, R. B. Analysis of recurrent codes. IEEE Trans. Inform. Theory. Vol. 9,
143-156 (3 July, 1963).
18. K ohlenberg, A. and B erner, A. S. An experimental comparison of coding as frequency diversity
for HF telegraphy transmission. IEEE Trans. Comm. Tech. (July, 1966).
19. A rthurs , E. and D ym, H. On the optimum detection of digital signals in the presence of white
Gaussian noise. IRE Trans. Comm. Syst, Vol. CS-10, 336-372 (1962).
20. K adota , T. T. Optimum reception of binary Gaussian signals. B.S.T.J. (November 1964).
21. W eldon , E. J. Jr. Asymptotic error coding bounds for binary symmetric channel with feedback.
U.S. Air Force Cambridge Research Lab. Report 63-122 (April, 1963).
22. B erlekamp, E. R. Block coding with noiseless feedback. M.I.T. Ph. D. Diss. (E.E.) (August, 1964).
23. Simon, J. C. Prodiffusion tropospherique a frequence optimale. Ann. Telecomm. (1964).
24. P rice, R. and G reen, P. E. A communication technique for multipath channels. Proc. IRE,
Vol. 46, 555-570 (1958).
25. Siforov, V. I. U.R.S.I. Monograph of Commission VI, 1957-1960 Elsevier (1962).
26. K ailath, T. Sampling models for linear time-variant filters. M.I.T. Res. Lab. Electronics, Rep. 352(May 25, 1959).
27. B ello, P. A. Characterization of randomly time-variant linear channels. IEEE Trans. Comm.
Syst. Vol. CS-11, 360-393 (1963).

REPORT 197-1 *FACTORS AFFECTING THE QUALITY OF PERFORMANCE
OF COMPLETE SYSTEMS ON THE FIXED SERVICES(Study Programme 1A/III)(1963 - 1966)

1.

Urgent need for information

The attention of Administrations is drawn to the urgent need for the information reques­
ted in Study Programme 1A/III, for several classes of emission. As requested in the Annex
to Study Programme 1A/III, the establishment of minimum protection ratios for additionalclasses of emission under stable conditions should be given priority. It is realized that no
Administration will be able to give all the answers, but partial answers are very welcome.
This information will permit an improvement in the calculation of the probability of harmfulinterference between assignments and the consideration of the possibility of sharing.
* This Report was adopted unanimously.
7

Rep. 197-1— 98 —The Study Group also needs the information to complete Recommendations 240, 339-1
and 340 and to bring them up to date *.
The documents received allow only a very partial answer to some of the questions pro­
posed.

2.

Number of transposition errors in automatic error-correction (ARQ) systems

In a study of the efficiency factor of a TOR circuit under varying signal-to-noise condi­
tions, a relation was derived between the probability, v, of a correct character being printed
and the attendant probability, p, of a transposition being printed [1]. One gets different
theoretical limits for flat fading, uncorrelated fading and selective fading.
It has now been shown experimentally, that, under normal traffic conditions the results
are nearly those expected for flat fading, or between those expected for flat fading and uncor­
related fading. Under unfavourable conditions, the results are more characteristic of those
expected for uncorreiated fading.
For telegraph channels on which the errors occur in bursts a two state Markov process
gives a suitable model for calculations [2]. In one state the probability of error is 0-5, inthe other state the channel is error free. Moreover a third decision can be taken into account,when it is not sufficiently sure, whether a mark or a space was received. This suggests thatthe use of such a third decision may materially reduce the appearance of undetected errors
at the output of an ARQ channel.
Calculations were made for selective and non-selective fading, and compared withresults from several experimental circuits. The results with the model for selective fading
fit closely the experimental curve. The values of error probability for non-selective fading
are a factor of 50 - 100 higher in the region of practical interest.

3.

Tables for the computation of distorted amplitude-modulation envelopes

When a signal consisting of a single frequency carrier modulated in amplitude by asinusoidal signal passes through a dispersive medium (or filter) the envelope will be distorted.
This distortion can be seen to depend on three parameters. For 6270 such triplets, the enve­
lope contour has been calculated in 24 points, and also the harmonics up to the eleventh [3].

4.

Error rates on long distance HF communications

Experimental results on long distance radiocommunications (2500 - 6000 km) in theWest-East direction in the U.S.S.R. have shown that the erorr-rate depends not only on
the signal-to-noise ratio but also on the distance. Diversity reception with an integrating
regenerator was used. The reasons for the distance dependence need further study (timeand frequency spread). In [4, 5, 6 ], statistical results are given for different operating speeds(282 and 141 baud), and different permissible error-rates (1 x 10~4, 5 x 10~3, 1 x 10~3).

B ibliography

1.

van D uuren , H. C. A. Error probability and transmission speed on circuits using error detection
and automatic repetition of signals. IRE Transactions on Communication Systems, Vol. CS9, 1, 4448 (1961).

* The I.F.R.B. has given a list of the classes of emission in which it is most directly interested in Doc.III/63,
Geneva, 1962.

— 99 —
2.
3.
4.

5.
6.

Rep. 197-1,198, 200-1

van D uuren , H. C. A.

Error control on high frequency radio channels. Het P. T. T. Bedryf, pt. XIV,
65-72 (1966).
E gidi , C. and O berto, P. Amplitude-modulation with the three spectral lines having anyamplitude
and phase. Letter to the Editor-Alta Frequenza, 2, 152-160 (February, 1965).
K onopleva, E. N. Field intensity distribution curves o f short wave signals anderror-rate depen­
dence on the ratio Ua+n/Un. Electrosviaz, 9 (1959).
K o n o p l e v a , E. N. Communication reliability and required signal-to-noise ratios on short wave radio
channels. Elektrosvjaz, 5 (1964).
K orol, V. Integral m ethod o f radiotelegraph reception. Vestnik Svjazi, 5 (1953).

R EPORT 198 *VOICE-FREQUENCY (CARRIER) TELEGRAPHY ON RADIO CIRCUITS(Study Programme 17A/III)(1963)
Theoretical work in Japan (Doc. 111/23, Geneva, 1962), indicates an optimum frequencyshift of 0-8 B (Hz), where B is the number of bauds. This would lead to a required mini­
mum bandwidth (at — 3 dB points) of B Hz. Laboratory experiments and measurementson the synchronous ARQ circuit Frankfurt-Osaka, support these conclusions.
It is to be noted, that this shift is preferably to be used on circuits near M UF and that
otherwise a larger shift may be beneficial. For asynchronous circuits, some theoreticalresults indicate B to 2 B as best shift [Akima, Voss]. Further experiments, on circuitsof different lengths, in different directions and in different seasons, are desirable before adefinite conclusion can be reached.

REPORT 200-1 *TELEGRAPH DISTORTION, ERROR-RATE(1963 - 1966)
1.

Distribution of telegraph distortion

The study of the relationship between telegraph distortion and error-rate has received
further consideration. The statistical distribution of distortion can be of value for assessing
the quality of a radiotelegraph circuit (see Report 351).
2.

Isochronous telegraph distortion

2.1 The measurement of isochronous telegraph distortion can be applied meaningfully at several
points in a radiotelegraph system.
* This Report was adopted unanimously.

Rep. 200-1, 201-1— 100 —

2.2 In making measurements of isochronous distortion of the separate components of the system
the following C.C.I.T.T. Recommendations should be taken into consideration:
Recommendation R.4 - Methods for the separate measurements of the degrees ofvarious types of telegraph distortion.
Recommendation R.5 - Observation conditions recommended for routine measure­ments of distortion on international circuits.
Recommendation R.74 - Choice of type of distortion measuring apparatus.
2.3 The measurement of the variation in restitution delay is important in determining the for­tuitous distortion contributed by the transmission medium.
2.4 Bias distortion is one component of the distortion produced by equipment and its measure­ment is useful in determining equipment performance.
: 3.

Statistical measurements of error-rate, on the Warsaw-New York circuit did not indicate
any direct relationship between error rate and the level of the received signal.

REPORT 201-1 *REMOTE CONTROL SIGNALS FOR FACSIMILE TRANSMISSIONS(Question 232)
(1963 - 1966)
1.

Introduction

With the rapidly increasing use of facsimile transmissions for various purposes, using
continuous web (chart type) recorders, it has become desirable for the C.C.I.T.T. to set up
standards for the remote control signals to be employed for the connection, starting, phasing,
speed control, stopping, etc. of a facsimile transmission.
2.

Remote control signals for the meteorological facsimile service

The World Meteorological Organization, in collaboration with the C.C.I.T.T. has estab­lished a set of standards, including control signals for use over the leased weather network(see C.C.I.T.T. Recommendation 343).
3.

Remote control signals for the subscribers’ facsimile service

The C.C.I.T.T. proposals for the remote control of subscribers’ apparatus for the trans­mission of business documents are given in Vol. VII of the Blue Book, p. 255.
4.

Conclusions

These documents make known to the C.C.I.R. proposals for the standardization of
remote control signals. The C.C.I.R. will study them to determine whether these signals
are acceptable and applicable on radio circuits.

* This Report was adopted unanimously.

Rep. 202

— 101 —REPORT 202 *IDENTIFICATION OF THE CARRIER-FREQUENCY RELATIVE
TO THE ASSIGNED FREQUENCY OF AN EMISSION(Study Programme 19A/III)(1963)
1.

Introduction

The following method of carrier-frequency identification formed the subject of Doc. III/60(U.S.A.), Geneva, 1962, and appears to provide a simple and precise method of identifying
the carrier frequency of those classes of emission in which the carrier frequency and thecentre of the assigned frequency band do not coincide. Examples of the application of thismethod are given in the Annex to this Report.
2.

Description of method

2.1 Represent the assigned frequency o f the emission by A. Let the carrier frequency o f the emissionb e / c;2.2 determine the value of the difference (f c — X ) , let this value be n Hz;
2.3 divide the value of n by 100 to obtain the code number;
2.4 if the value of n is negative (i.e. the carrier frequency lies below the assigned frequency),
follow the value n/1 0 0 by the indicator X ;2.5 if the value of n is positive (i.e. the carrier frequency lies above the assigned frequency),
precede the value n/1 0 0 by the indicator A;I

2.6

the results obtained I

H

\ 100

A or Aft \1 give the location of the carrier frequency relative to

100 /the assigned frequency.
ANNEX
E x a m ples o f t h e a p p l ic a t io n o f t h e m e t h o dExisting station
designation

Assignedfrequency(kHz)

Carrierfrequency(kHz)

Frequency
difference(Hz)

WEO86 A3 6840-5 kHz
WEO86 A 6844-1 kHz
WEO86 B 6845-9 kHz
WEP26
6851-8 kHz
WER33 A 13448 kHz
WES38 B 18942 kHz
WMF27 B2 7717-7 kHz
WMH30 A2 10387-3 kHz

6845
6845
6845
6852-5
13450
18940
771.5
10390

6840-56844-16845-96851-813448
18942
7717-710387-3

-4500
- 900
+ 900
- 700
-2000
+2000
+2700
-2700

Value
n

.100
-4 5
- 9
+ 9
- 7
-2 0
+20
+27
-2 7

Coded
indicator

Coded station
designation^)

45A
9A
A9

WEG86 45A
WEO86 9A
WEO86 A9
WEP26 I X
WER33 20A
WES 38 A20.WMF27 A27
WMH30 27A

IX

20A
A20
A27
27A

t 1) 'F o r use in the exchange o f operating information between the terminals o f a radio circuit.

* This Report was adopted unanimously.

Rep. 202, 203— 102 —
Assigned frequency band

/

X

fo'

Assigned frequency
f c is a carrier frequency designatednf c is a carrier frequency designated X n'

REPORT 203 *MULTIPATH PROPAGATION ON HF RADIO CIRCUITS
Measurements of path-time delay differences and their incidence on
typical radio links(Study Programme 1A/III)(1963)

1.

Measurements on HF radio circuits of the fixed service

1.1 Summary
Some 4000 facsimile pictures, received over a number of important radiotelegraph circuits
terminating in London, during the period from sunspot minimum to sunspot maximum(1953 to 1957), have been examined, to ascertain the incidence of multipath propagation andto measure the dispersion of path-time delays. Multipath conditions were found to obtainfor a considerable proportion of the time throughout the whole period and path-time dif­ferences were observed up to 2-5 ms. The measurements were made on pictures received fromNew York (1420 pictures), Melbourne (1600 pictures) and Moscow (350 pictures), together
with a few-less frequently used circuits. The technique of measurement is outlined below
and is similar to that given by Japan in a contribution to the VHth Plenary Assembly.

1.2 Method o f measurement
The facsimile transmissions use frequency-modulation so that, in general, the received
picture will be derived from the predominating path. If, due to fading, signals from different
paths of unequal length predominate at different times, a sharp, straight line in the transmitted
picture, at right angles to the line of scan, will appear as a jagged line in the received picture.
By measuring the width of the ripple of the received line, it is thus possible to determine the* This Report was adopted unanimously.

— 103 —Rep. 203

difference in propagation time over the shortest and longest paths that predominate from time
to time during the transmission of the picture.
The spread in path-time delay, as seen on the facsimile pictures, was obtained by measuring
the ripple on a line, at right angles to the direction of scan, which could be safely assumed to
be sharp and straight when transmitted. A low-power microscope, having a graticule divided
into squares, was used to measure the ripple. The magnification was adjusted so that one
square represented a time difference of 2 ms for the machines most generally used. Displace­ments were estimated to the nearest 0-5 ms and, when a number of different delays were observ­
ed, only the maximum delay difference was recorded. In some cases, this maximum delay
was not typical of the distortion throughout the picture as a whole.
A check was made under controlled conditions, using a fading machine which was adjusted
to produce random fading with known differences in path-time delay and with various mediansignal levels on the two paths. The incidence of multipath observed in these tests was almost
identical with that obtained by mathematical analysis.

1.3 Measurement on facsimile pictures
Each picture was examined to determine the maximum path-time delay difference.
Since the values of delay were approximated to the nearest 0-5 ms, the probable distributionof differences in path-time delay between 0 and 2-5 ms was obtained by the usual method ofapportioning the number of pictures at each value of delay, other than zero, equally between
the adjacent delay ranges.
The incidence of multipath distortion on each picture was assessed according to four
categories, viz: none, rate, frequent, continuous.
For each month, the percentages of pictures received for each range of delay difference
and for each category of incidence were obtained. For simplicity, these monthly percentages
have been averaged over a complete year, and the results are shown in Fig. 1.

1.4 Discussion o f results
The results show that, for each of the four years 1953 to 1957, frequent or continuous
multipath was in evidence on between 40 and 50% of the pictures analyzed. Approximately
half the pictures affected by multipath showed path-time delay difference of 1 ms or more, andnearly 30% had delay differences of 1-5 ms or more.
Multipath effects such as these are not particularly troublesome in facsimile transmission.
Facsimile pictures have been used merely as a convenient means of obtaining data on incidence
and delay difference over a long petiod on typical high-frequency fixed-service radio links.
The effect of such multipath propagation could be more serious on telegraphy and data
circuits, particularly where the path-time delay difference is appreciable in relation to theduration of the telegraph element. For example, a path-time delay difference of 2 ms would
have an adverse effect on the performance of a telegraph circuit working at 200 bauds, since
the delay difference is equal to 40% of the duration of the signalling element. Circuits
working at lower modulation rates would be less affected by multipath propagation, since
the path-time delay difference would be smaller in relation to the duration of the telegraphelement. For example, a 2 ms delay difference would equal only 20 % of the element duration
at 100 bauds.

2.

Measurement on meteorological broadcast services
Section 1 of this Report shows the incidence of multipath propagation and path-timedelay differences observed on typical point-to-point high-frequency radio circuits. MoreRep. 203

— 104 —

severe multipath effects may, however, be experienced when frequencies below optimum haveto be used. Such circumstances often arise, for example, in high-frequency meteorologicalbroadcast services, and an analysis has been made of meteorological charts received in the
United Kingdom by facsimile transmissions from Washintgon, D.C., and from Japan.
Some 1600 charts received during the period June to September, 1961, have been analyzed.
Of these, 1000 were received from Washington and 600 from Japan. The method of measuring
the path-time delay differences was similar to that described in § 1 of this Report. The results
are tabulated below and are shown graphically in Fig. 2.
Percentage o f charts for each circuit
M ultipath time-delay difference
(ms)

0.

-

W ashington, D .C . to U nited Kingdom(6000 km)Japan to U nited K ingdom(9600 km)

10
20
28
21
10
6
2
2
1

0
5
9
10
30
26
11
6
2

1/2

V2-1
1 -1V2
1 /2 -2
2-2 /2
2 /2 -3
3 - 3 /2
3 /2 -4
4
-4 /2

<Dw
is
O

*3 4>
oM
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REPORT 345 *PERFORMANCE OF TELEGRAPH SYSTEMS ON HF RADIO CIRCUITS(Study Programme 17A/III)(1966)

1.

Introduction
This Report summarizes the results of an extensive series of tests in which different
systems of voice-frequency radiotelegraphy are compared, both in the laboratory and ona real circuit. The systems treated in the laboratory are two-tone and narrow-band frequency
shift modulation; results have already been published [1], but a summary of the major con­clusions is given in § 2. Tests were also carried out on a differential phase-modulation system,
but the results are excluded from this Report.
The results of a practical comparison, on a real circuit, of two-tone and narrow-band
frequency shift is given in § 3.
* This Report was adopted unanimously.

Rep. 345

2.

/ — 106 —Laboratory measurements

2.1 Description o f systems
It will be convenient to refer to the various systems by means of code designations
defined as follows:
2.1.1 System A is a frequency-exchange or two-tone system using the method of detection
described by Allnatt, Jones and Law [2], Each channel can be regarded as comprisinga pair of amplitude-modulation channels with complementary keying, separate detec­tion and additive combination of the detected signals to produce a frequency-diversity
improvement. For modulation at 100 bauds the modular spacing of the frequencies
is 170 Hz. The two frequencies used for a channel may be separated by a multipleof this, being interleaved with the frequencies of other channels. The separation ischosen according to the most likely multipath propagation time difference, the optimum
in herz being equal to half the inverse of this time difference in seconds.
2.1.2 System B1 is a frequency-shift system with a channel spacing of 170 Hz [3]. The normal
modulation rate of each channel is 100 bauds and the frequency-shift is 80 Hz. The
channel receiver comprises the conventional limiter and discriminator arrangement.
When diversity reception is used, the demodulated signals produced by each branchchannel receiver are weighted according to the amplitude of the input signal to eachbranch.
2.1.3 System B2 is a frequency-shift system of the same basic form but with a channel spacingof 340 Hz and frequency-shift of 170 Hz. The channels can accept a modulation rateof up to 200 bauds.
2.1.4 Reference system
To facilitate comparison between the systems, there is included with each set of
performance curves one representing the hypothetical system mentioned in C.C.I.R.
Report 195, which is based on the use of coherent detection of a non-fading signal.
2.2 Method o f testing
The performance of each system has been measured in terms of mean element error
rate versus normalized signal-to-noise ratio under various conditions of fading signal withadded uniform-spectrum random noise. The transmission path was provided by a fading
simulator [4] with facilities for simulating equal-activity two-path propagation (with selec­
ted path-time difference) and dual-space diversity reception.
2.3 Test results
Since the application of dual space-diversity reception is quite usual for telegraphy,
the performance curves for that mode only are given here in Figs. 1 to 3.
In considering these curves, it should be borne in mind that, in system A (two-tone)
the spacing of the significant frequencies was 510 Hz (i.e. three times the modular spacing);
hence its optimum performance occurs when two-path propagation is present, with equal
activity in both paths and a propagation time difference about 1 ms.
2.4 Discussion o f results
The results will be discussed in the light of possible working requirements, first in termsof the normalised signal-to-noise ratio required for a given error-rate in the case of

— 107 —Rep. 345

unprotected transmission, and then in terms of a given time-efficiency factor when anerror-correction (ARQ) system is used.

2.4.1 Unprotected transmission
Different classes of user will tolerate various limits for accuracy, but it will beassumed in these comparisons that an acceptable mean error-rate is 1 in 104 elements
corresponding to 1 in 2000 characters for synchronous 5-unit code transmission.
In the absence of multi-path propagation it would not, of course, be necessary
to limit the modulation rate to one or two hundred bauds, but it will be of interest
to compare the systems in this condition. However, on long-distance circuits, multipath propagation with effective path-time differences in the range 1 to 2 ms is often
encountered and must be taken into account. Under these test conditions systems B
could not produce the required performance. System A would require a normalized
signal-to-noise ratio ranging from 17 to 24 dB according to the actual path-time diffe­
rence and relative activity of the paths.

2.4.2 Protected transmission
When automatic error-detecting and correcting systems are used on radio chan­nels, the radio signal element error-rate may be permitted to rise considerably above
1 in 104 before the undetected error-rate approaches 1 in 2000 characters printed;
no data is available on the exact relationship between detected and un-detected errors
for each transmission system under fading conditions, but it is estimated that theincrease could be by a factor approaching 102. Thus an element error-rate of 1 in 102
can be taken to define the upper limit of consideration. With similar conditions
in each direction of transmission and assuming that errors occur randomly and without
correlation between the two directions, this corresponds to a time-efficiency factorof 60-70%, i.e. about one-third of the circuit time is taken up by automaticr etransmission for correction of errors. An element error-rate of 1 in 103 will still produce
an efficiency factor of approximately 97% with a negligible undetected character errorrate. Hence the range of practical interest in element error-rate of transmission
systems can be confined between the limits 1 in 102 to 1 in 103. This leads to theconclusion that, a system having a residual error-liability which would make it un­
desirable for unprotected use can still be used with an ARQ system if it possesses otherdesirable features.
To illustrate the comparative performance of the systems in ARQ operation,
curves of time-efficiency factor versus normalized signal-to-noise ratio, with spacediversity reception, have been derived from the element error-rate curves and areshown in Fig. 4. It has been assumed that the fading rate may be up to 20 per minute.
With flat fading there are slight differences between systems A and B \ but for thesake of clarity only a single curve is shown; system B2 has been omitted since its per­formance at 100 bauds is not better overall than that of B \ and its performance at
200 bauds with a path-time difference of 2 ms would produce, an inferior efficiency.
From these curves it is concluded that the order of merit would be A, B l and B2 and,if fading conditions ranging between the extremes considered are assumed, that B lneeds approximately 3 dB better normalized signal-to-noise ratio than A to maintain
90% efficiency.

2.4.3 Bandwidth utilization
It is, however, unusual to encounter radio circuits engineered to such close limits
that a difference in performance of 3 dB would be easily discernible in practice;Rep. 345

— 108 —
furthermore, frequency-band requirements of the systems have not so far been consi­
dered. For a given number of channels, System A will require almost exactly twice
the bandwidth of System B.
Assuming that the best use is to be made of a conventional 3 kHz bandwidth,
Table 1 shows the number of 100 baud channels which may reasonably be provided
by each system and the aggregate signal-to-noise power required to produce various
values of time-efficiency factor.

T able 1

Performance of a pratical fully-occupied
nominal 3 kHz telephony channel

Type o f system

N um ber o f
100-baud channels

A
Bl

8

16

Aggregate signal-to-noise power ratio in a 3 kH z bandwith,to give stated efficiency
(dB)
50%

70%

90%

2 to 36 to 7

3* to 5i
8i to 10

6\ to 912 to 14

It is likely that the application of frequency diversity in addition to space diver­sity to System B l would produce a performance comparable to System A as regards
both channel capacity and signal-to-noise power ratio, at least over the range of errorrates of practical significance when used on protected circuits.

3.

Comparison of systems A and Bl operating over a real circuit
A series of directly comparative tests was carried out over periods aggregating to fourweeks on a 7200 km route between Singapore and Nairobi.

3.1 Test arrangements
The telegraph system between Singapore and Nairobi normally uses a six-channel twotone equipment carrying a number of 96-baud ARQ aggregate signals of the Singapore
to London circuit which are relayed at Nairobi. At Singapore the two lowest frequency
channels of the two-tone system utilising frequencies of 765, 935, 1105 and 1275 Hz were
suppressed and four frequency-modulation channels (shift 80 Hz) were injected into thecomposite signal on these frequencies.
One of the Singapore/London circuits, which is usually busy throughout the twentyfour hours, was selected for the tests and arranged to key both a two-tone (the component
frequencies being spaced at 340 Hz) and a frequency-modulation channel so that the same
information was radiated within a 3 KHz bandwidth on the two systems.
Adjacent channels on both the two-tone and FM-VFT systems were activated withdifferent live traffic or reversal signals to simulate normal working conditions. Tone levels
were adjusted so that equal peak powers were radiated by all tones as observed on a spec­
trum analyser.
At the Nairobi receiving station, the composite group of signals was received on a dual­
path SSB receiver and fed to both the double-diversity two-tone and FM-VFT channel
equipment.

— 109 —Rep. 345

Synchronous electronic regenerators were used to eliminate the distortion from channels
on boths systems. Outputs from the regenerators which correct all distortion up to 48%
were connected to electromechanical ARQ equipment modified to detect all incorrect 3: 4
ratios of the 7-unit ARQ signals. Counters were employed to register the mumber of
errors detected, and hourly readings were recorded. The regenerators and ARQ equipmentused for the two channels being tested were interchanged every twenty-four hours so that,should any hidden fault have developed in the equipment which could not be detected bynormal means, it would have affected both channels equally. The output from the regene­rator connected to the normal channel was also used to key the onward circuit to London.
In this manner, every effort to ensure a valid comparison of the two systems was made,and, in conjunction with reports from receiving stations logs, radio conditions reports, anddistortion recorder charts, doubtful information which could have been caused by interfe­
rence (QRM) was eliminated.

3.2 Test results
Each test run was taken over either seven or eight consecutive days and nights andthe “ errors detected ” figures were examined. As the scatter of these hourly average figures
would have given the graphs a saw-tooth shape, a running three-hour average figure wasused for the error graphs.
The most useful criterion for the communicator is the percentage efficiency of the cir­
cuit, and as these error figures refer to only one direction of a normal ARQ circuit it is notpossible to give an accurate assessment from the test results. However, by the use of acurve [5] reproduced here as Fig. 7, it is possible to estimate the effect the detected errors
would have had on the percentage efficiency of the circuit if the return path had been errorfree. Any detected errors on the return path, i.e. Nairobi to Singapore would have lowered
the efficiency graphs, but the effect would apply equally to either system. (See Fig. 6). On
this figure the efficiency expected from the receiving station logs is shown in shadow-graphform; the actual efficiency of the whole Singapore-Nairobi-London ARQ circuit for theperiod covered is also given.

3.3 Discussion o f results
It will be seen from Fig. 5 that, in general, the two-tone system results were always
better than the FM system results, even though the channels were of equal radiated power *.
During the hours of “ good propagation conditions ” the errors per hour on either systemwere very few. However, as conditions deteriorated errors increased on both systems,
but were more frequent on the FM system than on the two-tone system.
It is of interest to note that as the efficiency of the circuits decreases, the difference bet­
ween the two systems generally increases.

4.

Conclusions
These tests demonstrate that under difficult radio propagation conditions the twotone system provides channels which have a higher efficiency factor than individual channelsof an FM-VFT system when equal power per channel is used.
* If the maximum number o f channels were to be used in each case, a frequency-modulation channel would be
3 dB lower than a two-tone channel for the same aggregate peak envelope power.

Rep. 345

— 110 —

However, if the major traffic load to be carried during the hours when radio propagation
conditions are not unusually difficult then the larger number of channels given by the FMVFT system, within a 3 KHz bandwidth is a great asset.
It should be noted that if the lower limit of Telex circuit-efficiency proposed by somemembers of Study Group X of the C.C.I.T.T. is recommended, i.e. Telex circuits are auto­
matically “ cleared ” if the efficiency falls below 80 %, then a situation could arise where
for appreciable periods no Telex operation would be possible if an FM-VFT system were
employed, whereas satisfactory operation would be obtained by the use of the two-tonesystem.
B ibliography

1. R idout , P. N. and W heeler, L. K. Choice of multi-channel telgraph systems for use on h.f. radio
links. Proc. I.E.E., Vol. 110, 1402 (1963).
2. A llnatt, J. W., Jones, E. D., and L a w , H. B. Frequency diversity in the reception of selectivity
fading binary frequency-modulated signals. Proc. I.E.E., Vol. 104B, 98, (1957).
3. L yons, W. Considerations in SSB and ISB system for long distance radio telegraph communica­
tions. Transactions A1EE. (Communication and Electronics) (18 January, 1960).
4. L a w , H. B., L ee, F. J., L ooser, R. C., and Levett, F. A. W. An improved fading machine. Proc.
I.E.E., Vol. 104B, 117 (1957).
5. C roisdale, A. C. Teleprinting over long-distance radio links. Post Office Electrical Engineers'
Journal. Vol. 51, Part. 3, 219 (1958).

— I ll —Rep. 345

I

10

30

20

40

dB

Normalized signal-to-noise ratio per antenna (dB)
System A
Reference system

a: flat fading and also a path-time difference ofabout 2 ms
b: path-time difference 1 ms
c: path-time difference 4 ms

Modulation rate: 100 bauds; fading rate: 40 per min
F igure 1

System A.

Dual space-diversity receptionRep. 345

— 112 —

Normalized signal-to-noise ratio per antenna (dB)------------Reference system----------- System Bl
a: flat fadingb : path-time difference 0-5 ms
c: path-time difference 1 ms
d: path-time difference 2 ms
Modulation rate: 100 bauds; fading rate: 40/min
F igure 2

System Bl. Dual space-diversity reception

Element— 113 —dB

Normalized signal-to-noise ratio per antenna (dB)
— Reference system
System B2: modulation rate 100 bauds
System B2\ modulation rate 200 bauds
a: flat fadingb: path-time difference 0-5 ms
c: path-time difference 1 ms
d: path-time difference 2 ms
e: flat fading
f: path-time difference 0-5 ms?'• path-time difference 1 ms
h: path-time difference 2 ms
F igure 3

System B2. Dual space-diversity reception

Rep. 345

Rep. 345

— 114 —

Normalized signal-to-noise ratio (dB)r. System A.
b: System A.
System Bl.
:: System Bl.

Path-time difference 1 ms (optimum for frequency-spacing)
Flat fading and path-time difference 2 ms
Flat fading
Path-time difference 2 ms (in this case no frequency-diversity
improvement is realized with a spacing of 510 Hz)
Modulation rate: 100 bauds
F igure 4

Time efficiency-factor

Rep. 345

— 115 —

Number of incorrect 3/4 ratios per hourI

F igure 5

Typical performance curves
Average number of errors per day over three hours on the
Singapore-Nairobi telegraph system during the period 26 March-1 April 1963
A: System A (two-tone)

B: System Bl (FM)Rep. 345

— 116 —

■ 100%
QQ_7no/Efficiency expected from receiving
station logs, Signal classed as ZSO□<70%
F igure 6

Estimated performance of error-corrected (in one direction only) systems (based on Fig. 5)
Measurements of average daily efficiency factor of the overall Singapore-London circuit
for the period 26 March — 1 April, 1963 (Average daily efficiency of overall Singapore-London circuit forthis period 90%)
A: System A (Two-tone)

B: System B l (FM)Rep. 345

Efficiency - number of correctly printed
characters per 1000 transmitted

Number of undetected errors per1000 characters printed with ARQ working

117 —Number of mutilated characters per 1000 characters transmitted(ARQ working, using gated ARQ and an error-free return path)>: Efficiency of ARQ

B: ARQ undetected errors

Rep. 346

— 118 —REPORT 346 *PERFORMANCE OF SYSTEMS USING PHASE-SHIFTKEYING OVER HF RADIO CIRCUITS(Study Programme 17A/III)(1966)

1.

Introduction
This Report summarizes the results of a field test, in which the performance of two
types of telegraph system using phase-shift keying, both employing four-phase modulation,
are compared with a narrow-band system using frequency-shift modulation.* *2.

Description of systems
It will be convenient to refer to the various systems by means of code designations defined
as follows:

2.1 System B l is a frequency-shift system with a channel spacing of 170 Hz [2], The modulation
rate of each channel was 75 bauds and the frequency-shift is 85 Hz.
2.2 System C l is a time-differential phase-shift keyed system (TD-PSK) according to the prin­ciples described in [3, 4], in which two information bits are phase multiplexed on each oftwenty tones. All tones are keyed isochronously at a rate of 75 bauds, thus providing an
aggregate data capacity of 3000 bits/s. Each receiving channel comprises two gated, very
high-Q, mechanical resonators. These are connected alternately to the signal path during
successive element periods, so that the incoming signal is integrated during one period andstored for reference use during the next. Phase comparison between the oscillations in
the two resonators near the end of each element period effectively demodulates the signal.
Each resonator is quenched at the end of its storage period, immediately prior to being
reconnected to the signal input. The gating period of the signal (before integration) is
somewhat less than the duration of the signal element length so as to reduce the effects ofdistortion occurring at the signal transition due to multipath propagation. Synchronization
is obtained by means of a transmitted pilot tone.
2.3 System C2 is a frequency-differential phase-shift keyed system (FD-PSK) according to theprinciples described in [5, 6], in which three information bits are phase coded on each of
forty tone pairs (channels). All channels are keyed isochronously at a rate of 25 bauds,
thus providing an aggregate data capacity of 3000 bits/s. In addition, twenty-two unmo­
dulated reference tones are transmitted, spaced at regular intervals throughout the base­band, so that there are two information channels between adjacent reference tones. At
the receiver, all tones are translated to a common processing frequency, the reference tones
are extracted by means of narrow-band filters and phase-demodulation is effected by cross* This Report was adopted unanimously.
** Results o f laboratory tests comparing one type o f system using phase-shift keying with a two-tone system
and a narrow-band system using frequency-shift m odulation are given in [1],

— 119 —Rep, 346

correlating each signal tone with a phase reference obtained by linear addition of appro­
priate fractions of the two references which bracket the signal tone. A delay line in theinformation tones path provides compensation for the delay in the narrow-band reference
extraction filters. By virtue of the long transmitted symbol compared to the prevailing
multipath delay, spread-inter-symbol interference is minimized. Synchronization is obtained
through the use of two unused channel positions and by comparison of the phase of thebeat frequencies between successive reference tones with the receiver time base.

3.

Comparison of systems B l, Cl and C2
The tests were conducted over an available commercial radio circuit from Pretoria,
South Africa to Riverhead, Long Island, U.S.A., a great circle distance of approximately
12 700 km. The emission of the transmitters was a reduced-carrier, independent single­
sideband (ISSB) signal, with a maximum of 12 kHz bandwidth consisting of four independent
3 kHz/s baseband slots. Both transmitter and receivers were frequency stabilized by meansof synthesizers, providing frequency stability of 1 part in 108 per day. At the receiving
terminal at Riverhead, the test signals were received in space diversity by two rhombic anten­
nae, feeding the stabilized receiving system consisting of two receivers and two converters.

3.1 Test arrangements
Whenever possible, two systems were run simultaneously in the two 3 kHz slots oneither side of the carrier (“ dual mode ”), with periodic sideband switching to average out
any systematic channel inequalities. However, conditions of unequal QRM in the twoslots often precluded this mode of operation. Under such conditions, the three systems
were tested on a sequential basis, each system having an “ on ” period of fifteen minutes,
with five-minute silent periods between successive test periods to evaluate channel noise
and QRM.
To evaluate the performance of each system on an equal energy per bit basis, the avai­lable transmitter power was maintained constant while the voice frequency output levelof each data system (drive) was set in accordance with the values computed to provide equal
energy per bit. In these computations, the total composite signal powers of the PSK systems(including pilot tone and reference tone powers) was used as the basis for determining theenergy per bit values.
Collateral data on the characteristics of the propagation medium were continuously
monitored visually by means of two spectrum analysers and audibly by means of a loud­speaker. In addition, pen recordings were made o f the a.g.c. voltages of the H F receivers.
By comparing the a.g.c. level during the test run with the levels during the preceding andfollowing five-minute off periods, a measure of received signal-plus-noise to noise ratio wasavailable.
Manually set-up word generators were used to supply the modems at the transmitting
terminal with a 52-bit binary sequence, and to detect errors at the receiving terminal. Sixteen
bits of this pattern were used for sequence synchronization purposes. Bit timing for theword generators was derived from the timing clocks of the modem(s) under test.
The test circuit was operated during two 30-day test periods, which included the monthof April, 1964, and the period from 15 June to 14 July 1964.
The accumulation of test data was hampered by all the usual difficulties of H F commu­
nications. In general, data runs could be attempted for only about 16 hours out of each24-hour period. During the hours of 0100 to 0900 GMT the circuit was not usable becauseof extreme QRM or lack of signal strength.
The amount of QRM experienced throughout the entire test period was a particulardifficulty. Some QRM was experienced at nearly all times of the day. At times, it waspossible to .sidestep this type of interference by moving the radio-frequency carrier by 500
to 1000 Hz in an attempt to move away from the interfering signal.

Rep. 346

— 120 —

Finally, test data time was limited by circuit outages experienced during frequency changeovers. This problem was minimized whenever possible by frequency dualing when extra
transmitters were available.
3.2 Test results
Fig. 1 presents the cumulative performance curves for the three systems, representing
some 100 hours of recorded data and including periods of significant QRM and severe atmo­
spheric noise.
Fig. 2 gives scatter-diagrams showing the comparative results of parallel runs between
TD-PSK/FSK and FD-PSK/FSK. These results exclude data known to contain significant
QRM or known to contain moderate to severe static (exceeding 100 static bursts per run).
The diagonal in a scatter diagram is the locus of points of equal performance and divides
the diagram in two fields. The result of each parallel run is plotted as a point in the
diagram, with ordinates corresponding to the measured bit error-rate of each system.
3.3 Discussion o f results
The FSK system was not operated at the optimum keying speed consistent with its
channel characteristics [7]. (Theoretical considerations and experimental results show that,
under conditions of constant energy per bit, this represents a penalty in the performanceof the FSK system of approximately 0-5 dB; that is, at optimum modulation index, the FSK
system would have required 0-5 dB less signal-to-noise ratio for a given error-rate. In addi­tion, the aggregate data capacity of the FSK system used should be considered to be1600 bits/s in a 3 kHz channel.)
The results presented in Figs. 1 and 2 show that both PSK systems performed about
as effectively as the particular FSK system tested. The “ goodness ” criterion for the typeof curves of Fig. 1 is quite evident as long as the curves do not cross over. A cross-over may
result from the type of time distribution of error-rates, and the inclusion of sequential runs,
where the amount of data, especially at the lower error-rates, may not be sufficient to ensure
averaging out of differences in channel conditions.
The apparent randomness of the scatter diagrams of Fig. 2 is typical of H F communica­
tions. Similar results can be obtained when comparing individual channels of a single multi­
channel system.
Observed values of multipath spread were in general between 1 and 2 ms, with occasional
values of up to 3 or 4 ms. The tests were conducted during a year of low sunspot activity,and larger values may therefore be expected for this circuit under conditions of higher sunspot
activity. The observed values, however, are not abnormally low for many circuits; although
values in excess of 4 ms may be encountered during 1 % to 2% of the time (Report 203).

4.

Use of bit-synchronous systems on protected circuits
Present day practice tends to identify a channel of a multi-channel voice-frequency tele­graph system with a given number of ARQ channels, for example, it is common practice
to send two-channel ARQ (96 bauds) over each channel of a narrow-band (170 Hz spacing)
FSK system. The fact that the channel rates of PSK systems are often not directly compat­
ible with the ARQ rate, and the need for isochronous keying of all channels in unison, havebeen cited as a disadvantage of these systems. However, PSK systems, as in the examples,
have capacities which are multiples of 300 bits/s, e.g. by using six-channel ARQ operation(288 baud) on channel blocks of 300 bits/s capacity, the loss in efficiency of the PSK sys­
tems would be not more than 4 %. Furthermore, the synchronous character of the PSK
systems, coupled with an intelligent use of the “ spare ” bits, may well prove to be of
considerable value inautomatic phasing of the ARQ systems in multi-channel point-topoint operation. For the introduction of PSK systems on ARQ circuits, operational
procedures have still to be developed.

— 121 —5.

Rep. 346

Conclusions

The limited duration of the tests preclude definite conclusions with respect to the relative
performance of PSK and FSK systems for ionospheric transmissions. However, the tests
demonstrated that, under conditions reasonably typical for systems of the fixed service,
the four-phase PSK systems compared to a conventional two-level FSK system were capableof providing increased bandwidth efficiency without penalty in error-rate, or total power,
for the same amount of information transmitted.

6.

General remarks
The tests discussed in this Report refer only to a limited number of systems. Other
techniques may be able to achieve equal or better results.
Members of the C.C.T.R. are urged to submit results of tests of any such systems.

B ibliography
1.

2.
3.
4.
5.
6.

7.

R id o ut , P. N . and W heeler , L. K. Choice of multi-channel telegraph systems for use on H F radio
links. Proc. I.E.E. Vol. 110, 1402 (1963).
L yons , W . Considerations in SSB and ISB system for long distance radio telegraph communica­
tions. Trans. AIEE (Communication and Electronics) (18 January 1960).
D oeltz , M . L. H e ald , E. T. and M a r tin , D . L. Binary data transmission techniques for linear
systems. Proc. IRE Vol. 45, 656 (1957).
M osier , R. R. and C la ba u g h , R. G. Kineplex, a bandwidth-efficiency binary transmission system.
AIEE (Communication and Electronics), Vol. 34, 723 (1955).
D e H aas , T. A frequency-differential PSK modem for H F data communications. IEEE 1st AnnualCommunications Convention (June 1965).
W alker , W . F . A qualitative theory of the frequency-differential modulation system. IEEE 1st AnnualCommunications Convention, (June 1965).
C.C.I.R. Recommendation 436.

o o
M+°->
C

8

J?
Cm

105

lO'"

1 0 '3Bit error-rate
F igure 1

Cumulative performance curves

10'2Rep. 346,347

TD-PSK— 122 —FSK

FSK
F igure 2

Scatter diagrams of error-rates for parallel runs

REPORT 347 *VOICE-FREQUENCY TELEGRAPHY OVER RADIO CIRCUITS;’ (Study Programme 17A/III)(1966)

On certain radio circuits with special characteristics (e.g. North-South links, such as
Paris-Abidjan), several Administrations have since 1965 used automatic 96 baud errorcorrection devices associated with voice-frequency, multi-channel, frequency-shift telegraphsystems with a channel spacing of 120 Hz and a frequency deviation of ± 35 Hz as in the
Table of Report 42-1. The systems used were arranged for radio circuits.
Circuits thus set up are used in particular for transmission of cyphered messages andthey have been working satisfactorily since they came into operation. Measurements con­ducted by the French Administration using error-correction over such a circuit during aperiod totalling more than 50 hours showed that values of efficiency factor were achievedin accordance with the attached curve.
This method of operation may suit quite a large number of links (e.g. Europe-West
Africa links) and bearing in mind the constant search for the most rational use of the radio
spectrum, it is concluded that as much information as possible should be obtained on theperformance of circuits of this type, in particular concerning the undetected error-rate.
* This Report was adopted unanimously.

— 123 —Rep. 347, 348

Percentage of the time during which thevalue of the efficiency factor is exceeded
F ig u r eDistribution of efficiency factor in a 100 baud ARQ system with a 120Hz central frequency-spacing

REPORT 348 *SINGLE-CHANNEL SIM PLEX ARQ TELEGRAPH SYSTEM(Study Programme 1A/III)(1966)
1. Introduction
1.1 Study Programme 1A/III points out that regard should be given to new techniques andsystems for application to the fixed services.
1.2 Large areas of the world do not yet have the facility of being connected to the international
telegraph network, although they have a potential need for the exchange of messages bytelegraph.
2.

In the Annex to this Report, a type of telegraph system is described that might be quite useful
in both the fixed and the mobile services for the realization of this facility.
2.1 It has been assumed that the amount of traffic to be dealt with will initially be small, andthat usually the distances to be bridged will be great. A radio system might therefore best
be suited to link an isolated station to one of the officesof the world-wide telegraph network.
A suitable radio system could be a synchronous telegraph system making use of the wellknown principle of automatic error-correction, by which the quality of the radio circuit isimproved to a grade comparable with that of landline connections.
* This Report was adopted unanimously.

Rep. 348

— 124 —

2.2 It has also been assumed that localities of such isolated stations, and particularly mobile
stations do not permit the simultaneous use of the radio transmitter and radio receiver.
2.3 Furthermore, it has been assumed that the power consumption of the equipment should be
kept to a minimum.
2.4 To participate in the telex network the direction of traffic flow should be reversible instantly.

ANNEX
1.

General

1.1 The system is a single channel ARQ system utilising the 7-unit error-detecting code laid downin the table of conversion.
1.2 Instead of duplex operation, alternate operation is used in the radio link (see § 2.2 of thisReport).
1.3 The line terminal output uses the 5-unit start-stop code of the International Telegraph
Alphabet No. 2 at a modulation rate of 50 bauds with a character cycle of 150 ms (see § 1.2of this Report).
1.4 The modulation rate on the radio link is 100 bauds.
1.5 To provide an uninterrupted flow of start-stop signals during periods of no repetition andto permit the “ information receiving station ” (IRS) to confirm the good reception or to ask
for repetition, the transmission is arranged in blocks o f three characters (of 21 signal elements)
spaced by an adequate transmitter pause.
1.6 Three “ control ” signals are employed on the return channel, two of which are used to informthe “ information sending station ” (ISS) whether the traffic flow is received correctly or not,the third control signal is needed to obtain the facility to change the direction of information
flow.
2.

Characteristics

2.1 Arrangement o f information in blocks with marked sequence
When a circuit is established, the ISS commences to mark the transmission intervalof successive blocks of information as interval 1 and interval 2. The third interval is marked
in a similar way to interval 1, the fourth like interval 2, the fifth like interval 1, etc. This
marking is continued as long as the station remains in the ISS position.
The sequence of reception at the IRS is marked in a similar way so long as unmutilated
blocks are received. The sequence marking at the IRS is initially synchronized to the sequencemarking at the ISS.
2.2 Control signals
These will be referred to as abl, abl, and ab3.
2.2.1 On the return channel the control signals abl and abl are alternately sent back to theISS by the IRS.
The following rules apply to the signals transmitted on the'return channel.
2.2.1.1 At reception of an information block the IRS transmits only one control signal
on the return channel.
2.2.1.2 At reception of a mutilated block the same control signal is transmitted on
the return channel as at the reception of the previous block. This means:
repeat transmission of the last block.
2.2.1.3 At reception of an unmutilated block the IRS transmits the alternative of thecontrol signal transmitted at the reception of the previous block. This means:continue by transmitting the next block. If the sequence numbering at the125 —

Rep. 348

IRS is 1, 2, 1, 2, etc., normally after interval 1, control signal abl is transmitted.
After interval 2 this will be control signal abl.
2.2.2 The control signal ab3 serves to reverse the direction of transmission of information
between the two stations.
2.3 Repetition procedure
2.3.1 The ISS starts to repeat the transmission of the block previously transmitted when
the control signal received does not fit to the interval of the local sequence that isjust ending. So at a sequence numbering 1,2, 1,2, etc., no repetition action is initiatedas long as control signal abl is received at the end of interval 1 and control signal abl
at the end of interval 2.
2.3.2 When the control signal is not received or is received multilated at the ISS, this station
will transmit three “ signals repetition ” in the next block instead of information.
2.3.3 The IRS will not print or pass a block when this contains a “ signal repetition ”, or
when its content is mutilated. Moreover, on the return channel it retransmits thecontrol signal transmitted last.
2.4 Modulation rate
On the radio circuit during the signal-on periods: 100 bauds. One block, consistingof three characters, is transmitted in 210 ms; an answer back signal in 70 ms.
At the start-stop terminals the interval between successive start elements will be 150 ms,
so that the interval between successive blocks is 450 ms.
2.5 Master and slave arrangement
The station that initiates the establishment of the circuit becomes the master stationand the station that has been called will be the slave station.
2.6 Change o f traffic flow direction
2.6.1 When transmitting the block “ signal 3 -sig n al a -s ig n a l P ”, ISS urges the IRS tochange to the information sending position.
2.6.2 To ensure that this is achieved both under favourable and unfavourable conditionsof radio propagation the procedure is as follows:
2.6.2.1 The ISS, after having transmitted all its traffic, transmits the characters“ figures-Z-B ” (this is the “ OVER ” -signal: “ figures - plus - interrogation ”).
The IRS confirms the reception of these characters by transmitting theappropriate one of the control signals abl and abl on the return channel.
2.6.2.2 At the reception of the control signals, the ISS transmits a meaningless block(i.e. three signals P). The IRS, after unmutilated reception of this block,
will transmit on the return channel the control signal ab3, indicating that since
the reception of the previous characters it has noted these to be “ figures-ZB”. In addition the line output will be switched to Z polarity.
2.6.2.3 At the reception of the control signal ab3, the ISS transmits the block “ signal P signal a - signal P ”.
After unmutilated reception of this block the IRS switches over to theISS-position and starts transmitting its first block, consisting of three “ signals
repetition ”.
2.6.2.4 At the reception of the first “ signal repetition ”, the ISS switches over to the
IRS-position and transmits the control signal “ abl “ during the interval thatcoincides with the position of the third character of a block, if this would havebeen transmitted.
2.6.2.5 Then the flow of information will start in the direction to which it has beenchanged over.

Rep. 348

— 126 —

2.7 (Selective) call signal
A block consisting of three chaiacters of which the first one is a “ signal repetition
The other two characters determine the station that is called.
2.8 Phasing and rephasing
2.8.1 Phasing
Stations in stand-by position are able to get into touch with each other. At theestablishment of a circuit, the station that calls another station is in the master posi­tion. A station in stand-by position, and tuned to the transmitter frequency of themaster station, will be alarmed by the reception of “ signal repetition ”. By meansof a one-shot phasing procedure, this station’s receiver is quickly phased to the mastertransmitter at the reception of the appropriate call signal. When phased, this station
is in the slave position and starts transmitting control signals. The master receiver,also by means of a one-shot phasing procedure, phases quickly to the slave transmitterat the reception of a control signal by which the phasing procedure is accomplished.
TABLE OF CONVERSIONInternational Code N o. 2

(not used)
E
Line feedSpace
Carriage return
T
A
I
N
'
O
Z
s
R
H
D
L
U
C
M
B
W
J
P
F
G
Y
K
V
X
FiguresQ
Letters
Signal repetition
Signal a
Signal 3
Control signals:
abl
abl
ab3

AAAAA
ZAAAA
AZAAA
AAZAA
AAAZA
AAAAZ
ZZAAA
AZZAA
AAZZA
AAAZZ
ZAAAZ
ZAZAA
AZAZA
AAZAZ
ZAAZA
AZAAZ
ZZZAA
AZZZA
AAZZZ
ZAAZZ
ZZAAZ .
ZZAZA
AZZAZ
ZAZZA
AZAZZ
ZAZAZ
ZZZZA
AZZZZ
ZAZZZ
ZZAZZ
ZZZAZ
ZZZZZ

AZAZAZZAZZAZAZAAZZAZZAAZZZAZAAAZZZZAAZAZZZZZZAAAZZAZZAAZZAAZZAZZAAAZZZZZAAAZZZZAZAAZZAZAZAZZAAZAZZZZAAZAZZAZAAZZAZZZAAZZAZZZAAZAAZZZAAZAAZZZZZZAAZAZZZAZAAZAZZAZAZZAZZAAZAZAZZAZZAZAZAAZZZZAA
AAZZZZAAZAZZZAAZZAZZAAZZZAZAAZAZZAZAZZAAZZZZZZAAAZZAAZZA(L)(not used)\ (N)

ZAZAAZZAZAZAZZZAAZZAZs:r

7-unit code

— 127 —Rep. 348, 349

2.8.2 Rephasing

If master station and slave station lose contact because of unfavourable reception
conditions, the slave station will change over to the stand-by position, when after eightcycles of 450 ms no “ signals repetition ” or control signals have been received. The
master station continues operation as ISS or IRS. As soon as reception conditions
improve, the slave receiver phases, by means of a one-shot phasing action, to the“ signals repetition “ or to the control signals of the master station, after which rephas­ing is accomplished.

R EPORT 349 *SINGLE-CHANNEL RADIOTELEGRAPH SYSTEMSEMPLOYING FORWARD ERROR CORRECTION(Study Programme 5A/III)(1966)

1.

Introduction
Contributions by Administrations to the X lth Plenary Assembly, Oslo, 1966, provide
a basis for a preliminary report on the question of protection of single-channel radiotelegraphchannels by means of methods of forward error-correcting. The experimental results repor­
ted in Docs. III/113 (XIII/82) and XIII/120, 1963-1966, are summarized, as well as thepertinent Docs. I ll /107 and III/117, 1963-1966.

2.

Summary and discussion of reported results
Docs. XIII/82 (United Kingdom) and XIII/120 (Norway) both report on trials con­ducted with a system described by Keller [1]. This system uses a ten-unit self-checking
code, a synchronous mode of transmission and is capable of correcting all single errors in
the text and of detecting all double errors as well as most multiple errors introduced by thetransmission path.
The ten-unit code consists of the 5 elements of the International Teleprinter Code No. 2
followed by 5 parity check elements. The 5 parity elements are either an erect or an inverse
repetition of the information elements, depending on whether the Z count in the information
elements is odd or even. Errors which are detected, but cannot be corrected, are indicatedby the printing of “ error ” symbols, usually combination 31 or 32.
Transmission over the radio circuit is at modulation rates of 62-3, 68-5 or 102 bauds
for teleprinter circuits operating at modulation rates of 45-45, 50 and 75 bauds respectively.
At the lower modulation rates the system is capable of extension over the inland telegraphnetwork using conventional 50-baud voice-frequency channels.
No special phasing signals are required, as the system is capable of fully automatic
phasing during periods of traffic as well as during periods of idling.
* This Report was adopted unanimously.

Rep. 349

— 128 —The system reported in Docs. XIII/82 and XIII/120 is currently in commercial ser­
Results obtained from field trials with this system are summarized in Table I.
In addition to these results, Doc. XIII/82 also reports that over the period of 7 August1965 to 27 November 1965 a total number of 1099 data tapes, each containing between 1500
and 1800 characters, were transmitted from ships at sea to an office in London. Of these,
889 were accepted without need for later re-transmission (i.e. contained no errors).
It is further reported that tests between ship and shore stations with plain language
messages, and ship-borne reception of Broadcast Services (e.g. press (transmissions) wereconsidered satisfactory, provided some measure of diversity in reception is used.
Doc. III/107 (Netherlands) proposes a single-channel error indicating system, operating
at a modulation rate of 100 bauds, having to some extent capability for error-correction.
The system uses a constant-ratio, seven-unit error detecting code, described in Doc. III/82,
1963-1966, but transmits each character twice with four other characters (equivalent to
280 ms) between the repetitions. If the reception of the first transmission of a character
passes the constant-ratio check, it is accepted and passed to the printer through a delay cir­cuit. If not accepted, the reception of the repeated transmission of the character is checked,
and if accepted is passed direcly to the printer. If neither reception is found acceptable,
a special “ space ” symbol is printed.
Transmission over the radio circuit is at a modulation rate of 100 bauds for teleprintercircuits operating at a modulation rate of 50 bauds.
Before starting the transmission of information, and in the idle time between successive
messages or message blocks, the transmitting station emits idle time signals which are also
used for phasing.
vice.

2.1 This system may be viewed in either of two ways:
2.1.1 As a time-diversity system with additional error detection capability. In this case,error performance (including detected but uncorrected errors) appears to be similar
to the performance obtained by straight time-diversity such as reported by Lyons [2],provided that the separation of error bursts is not less than 420 ms. The additional
four bits used in the system proposed in Doc. I ll/107 are used both for diversity selec­tion and for error-detection;
2.1.2 As a time-spread forward error-correcting system. As such, the system is capableof correcting all single errors and most multiple errors, including error bursts of up
to 280 ms, provided that the period between the occurrence of errors is at least 420 ms.
It is further capable of detecting most uncorrectable errors.

2.2 System measurements have been made in the laboratory. The measurements concern theperformance under varying signal-to-noise ratios for three cases, viz. a stable signal, a signal
under flat fading conditions and a signal subject to selective fading. The results of themeasurements are shown in Fig. 1 as curves for the probability for characters in error (pc)in relation to the normalized signal-to-noise ratio (R), in accordance with the principles
adopted in Report 195. The quasi fading-frequency was adjusted to approximately N = 0-5
per second for these measurements.

Note. - The curves of Fig. 1 do not take into account the 3 dB loss in normalized signalto-noise ratio due to the higher modulation rate for time-diversity operation.

T a b leI

S u m m a r y o f results
7

2

3

4

D ocum ent Ref.

Trial and circuit details

Characters passed

Errors detected
and corrected

XIII/82

Ship to shore,
double-sideband transmission,
single path reception

36 600

XIII/82

Ship to shore,
single-sideband transmission,
space diversity reception

XIII/120

Ship to shore,
double-side-band transmission,
space diversity reception C1), (2)28 7776

1-26 per 1000
characters

0-56 per 1000
characters

1-82 per 1000
characters

XIII/120

Ship to shore,
single-sideband transmission,
space diversity reception C1)

42 952

1-42 per 1000
characters

0.54 per 1000
characters

1.96 per 1000
characters

XIII/120

Shore to ship,
FSK transmission,
single path reception

297 464

0-88 per 1000
characters

0-3 per 1000
characters

118 per 1000
characters

XIII/120

Shore to ship,
FSK transmission,
single path reception

54 508

1-76 per 1000
characters

0-31 per 1000
characters

2 07 per 1000
characters

3-41 in 1000
characters

5

6

1

R esidual uncorrected
Detected but
error-rateuncorrected error-rate

2-27 in 1000
characters

0 055 in 1000
characters

Overall error-rate

2-33 in 1000
characters
0-84 in 1000
characters

Rep. 349(1) The distance between the two receiving antenna systems is rather small for space diversity operation.
(2) F o r these trials the ship transm itter was reduced to 1/4 o f nominal power for technical reasons.

Rep. 349

— 130 —

10

15

20

25

30

35

40

45

Normalized signal-to-noise ratio, R (dB)(These curves do not take account of the 3 dB loss in normalized signal-to-noise ratio dueto the higher modulation rate for the time-diversity case)•

Stable signal— . o . — Flat fading—— A

Selective fadingA:

Non-diversity reception

B:

Time-diversity reception
F ig u r e 1

Doc. III/117 (U.S.A.) refers to four general types of forward error-correcting codes
suitable for use on H F radio circuits. It further reports results from two field tests:
2.2.1 A system using a (15,10) block code (i.e. 10 information bits and 5 check bits per
block), interleaved to provide 2 second burst error correction capability. This system
was tested at teletype speeds over an H F link [3], and provided an improvement in
the bit error-rate of about one order of magnitude when the uncorrected channel
error-rate was 1 x 10~2, and two orders of magnitude when it was 1 x 10-3;
2.2.2 A system using an adaptive convolutional code (Gallager code) with maximum burst
error-correction capability of six seconds. A specific feature of this system is that— 131 —Rep. 349, 350

the error-free interval, required for burst correction (guard space), is equal to the actual
length of the burst plus about 20 bits, rather than equal to a fixed interval determinedby its maximum burst correction capability.
2.3 A test is reported whereby this system was compared with the use of frequency diversity.
Analysed in terms of blocks of about 3300 telegraph characters, it was found that, with thecoding, over 90% of the blocks were error free, as compared with about 15% of the blocks
when using diversity [4].
3.

Conclusions
The present data available do not offer an adequate basis for comparison of the various
systems described. Results from field trials are still limited and tests of different systems
have not been conducted on the same basis or under similar conditions. It will be desir­able to conduct further investigations, in particular trials which may provide a direct com­
parison between various systems.
B ib l io g r a p h y

1.
2.

L yons,3.

F r i t c h m a n , B . D. and L e o n a r d ,K e lle r,

P. R. Point-to-point telecommunications. Vol. I, 33, 14 (June, 1963).
W. Error protection via time diversity, IEEE Trans, on Comm. Tech.,Vol. 13, 2 (June,

1965).
J. F . Test results of a time-dispersed forward error-control sys­tem, IEEE Trans, on Comm. Tech., Vol. 13, 2, 233-234 (June, 1965).
4. K o h l e n b e r g , A. and B e r n e r , A. S. An experimental comparison of coding versusfrequency diver­sity for H F telegraphy transmission. IEEE Trans, on Comm. Tech. (July, 1966).

REPORT 350 *SINGLE-CHANNEL DUPLEX ARQ TELEGRAPH SYSTEM(1966)
1.

Nowadays, multiplex systems effecting error-correction by automatic repetition (ARQ),
are frequently used in the transmission of telegraph signals over radio circuits. The cha­racteristics of such ARQ systems are laid down in Recommendation 342-1.

2.

Where the volume of traffic does not justify the use of more than one channel, a single-channel
ARQ system seems appropriate. A possible solution is to follow the principles laid downin Recommendation 342-1, Annex I, §§ 1, 2, 4, 6**, 7*** and 8 where they apply to single­
channel operation.

* This Report was adopted unanimously.
** For the purpose o f this Report, Recommendation 342-1, §6.1.2, Annex I should be read as: “ After appro­
priate counts o f A and Z elements . . . ”*** For the purpose o f this Report m odulation rates o f 48, 72 and 96 bauds with transmission cycles o f 145 5/«
97 2/o and 72 11/iz ms apply respectively.

— 132 —Rep. 351

REPORT 351 *EFFICIENCY FACTOR(Study Programme 17A/III)(1966)
Docs. 111/23 (Federal Republic of Germany) and III/106 (Rev. 1), pp. 3-16 (Companhia
Portuguesa Radio Marconi), 1963-1966, report on tests which were carried out on shortas well as on long-range ARQ-radio circuits operated with a modulation rate 192 bauds,
to analyse whether a correlation can be shown to exist between the results of the efficiency
factor measurements and the assessment of the signal performance of the radio circuits.
Measurements of efficiency factor were made, using time intervals of 15 min (Doc.
III/23) and intervals of 10 min, 1 min, and 20 s (Doc. III/106). Moreover, the mean valueof the telegraph distortion and the relative field strength were recorded at the same timebases.
In addition, the following data were recorded in Doc. 111/23: the operating frequencies,
the variation of the geomagnetic field, the observed M UF and LUF values applicable tothe circuits, the weekly and daily forecasts of M UF and LUF, the assessment of the qualityof the circuits according to the SINPO code; and the following data were mentioned inDoc. I ll/106: the operating frequencies, the transmitting power, the class of emission, thetransmitting and the receiving antennae gains, and the type of reception.
Identifiable disturbance due to causes other than the propagation medium were exclu­
ded from the results.
A critical study of results of the tests made shows that a correlation exists between
the efficiency factor measured and telegraph distortion at the radio receiver output. On
several circuits, where the efficiency factor was measured over periods of 15 min, a corre­
lation coefficient of between 0-8 and 0-5 has been established [1].
In many, but not in all cases, a certain degree of correlation could be shown to exist
between the results of efficiency factor measurements and the signal strength. However,in moments where a strong signal is disturbed by interference this correlation does not exist.
From this, it may be concluded that the measurement of telegraph distortion is themost suitable measurement to permit a rapid and continuous assessment of transmission
quality, if reference cannot be made to efficiency factor measurements.
B i b l io g r a p h y
1.

F r o m m e r , E., K o b , H. and L e n h a r t , B. Untersuchungen um Funktelegrafieverbindungen zur
Ermittlung eines geeigneten Kriteriums fur die laufende Giitebeurteilung von Funklinien (Investiga­
tions on radiotelegraph circuits for the derivation of a single criterion for the operational efficiency
factor of radio circuits). Mitt. Funkamt, Frankfurt-am-Main (1965).

* This Report was adopted unanimously.

REPORT 352 *USE OF PRE-EMPHASIS AND DE-EMPHASIS FOR PHOTOTELEGRAPH
TRANSMISSION OVER HF RADIO CIRCUITS(Study Programme 1A/III)(1966)

Introduction
The relationship between the picture density and the degree of modulation at present
used concentrates the deterioration produced by noise at the darker end of the density range,
whereas a linear relationship over the whole graduation range of picture density would
distribute the effects of noise and so improve the picture quality. A further advantage
would be to make the effect of frequency errors in transmission less noticeable.
To keep this relationship, a technique was introduced in Doc. 111/31 (Japan), 19631966, which is described below.

Description of technique
The output of the photocell is proportional to the intensity of the reflected luminous
flux, while the density of a picture is inversely proportional to the logarithm of the reflectedflux.
The quality of the picture may be improved considerably when the signal is transmitted
through a pre-emphasis network with a logarithmic characteristic, and received througha de-emphasis network with the inverse characteristic.
B i b l io g r a p h y
M i c h i s h i t a , H., N a k a o , K., N a r i t a , F. and K a w a i , K. A method of improvement on the picture
quality in phototelegraph transmission. Journal o f Institute of Telecommunication Engineer of Japan.
Vol. 45, 6 (June, 1962).

REPORT 353 *USE OF COMMON-FREQUENCY SYSTEMS ON
INTERNATIONAL RADIOTELEPHONE CIRCUITS(Question 9/III)(1966)

Introduction
This Report deals with the technical characteristics required for common-frequency
operation of radiotelephone circuits using single-sideband and independent-sideband
emissions* This Report was adopted unanimously.

— 134 —Rep. 353

2.

The characteristics to be specified for radiotelephone systems using the principles of commonfrequency operation
It is preferable to use the channel configurations shown in Recommendation 348-1
and only to shift the radiated frequency spectra between the two directions of transmission
by about 150 Hz when using reduced carrier.

3.

Minimum difference in level, at the input of the receiver, between the received signal from the
distant station, and signals from the nearby transmitting station, to avoid interference between
the wanted signal and that from the nearby transmitter operating at the same frequency
In the fixed service, the signal level received from the nearby transmitting station isusually lower than that from the distant station. However, if the signal from the nearby
transmitting station exceeds the signal from the distant station by a considerable amount,the distortion products generated in the nearby transmitter will appear as crosstalk in theremaining channels of the distant multi-channel system. Tests have indicated that, where
the nearby transmitter has an intermodulation level (see Recommendation 326-1 (of 30 dB,
the signal from the nearby transmitter should not exceed that from the distant transmitterby more than 10 dB.

4.

The extent to which the use of transmitting and receiving antennae with different characteristics
reduce the possibilities of application of this technique
For point-to-point commercial communications, where the separation between trans­mitter and receiver of one terminal is approximately 30 km, it is not normally necessary
to take such a problem into account.

5.

The extent to which the possibilities of application of this technique are reduced by the presenceof different noise levels at the receiving location
The effectiveness of the common-frequency technique is independent of the noise levelat the receiving station.

6.

Other factors to be taken into account when planning systems

6.1 Characteristics o f the carrier filter
In several instances of the practical application of this type of operation the crystal
filter used in the carrier branch amplifier for isolating the reduced carrier had a nominal
bandwidth of 20 Hz. The actual characteristics of this filter are as follows:
Bandwidth (Hz)Loss (dB)

±10

0±2

±20

10

±50

38

±70

50

In an effort to determine the effect that the carrier frequency received from the nearby
transmitter might have on the receiver when it was receiving a signal from the distant trans­mitter, a test was made to determine the strength of signal required at various separations
to make the receiver lose control.

— 135 —Rep. 353

The following data indicate that, if the two frequencies can be kept separate by 50 Hz
or more, the near-end transmitter signal level can be considerably greater than that received
from the distant transmitter.

Received frequency(MHz)

Separation frequency(Hz)

Signal generator input simulating
distant transm itter(dV)

Signal generator input simulatingnear-end transmitter. Input varied
from 0-5 pV to 50 mV

5

50
100
200
50
100
200
50
100
200

0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5
0-5

The a.f.c. was notaffected up to alevel of 50 mV

50

0-5

The a.f.c. was dis­turbed at 5 mV

10
15

20

A review of the above data shows that, if the frequency stabilities of the two transmitters
are adequate to maintain a separation of greater than 50 Hz, there is no danger of the nearby
transmitter taking control of the receiver away from the desired distant end signal. Assum­
ing that the spacing is maintained between 50 and 250 Hz, the distortion products received
from the near-end transmitter would be excessive long before its signal strength would begreat enough to take control of the receiver.
6.2 Frequency stability o f the equipment
To prevent an audible beat note in the channel adjacent to the reduced carrier, thefrequencies of the two transmitters must not differ by more than 250 Hz, assuming thatthe pass band of the voice circuit is 250 to 3000 Hz. At the same time, because of the cha­racteristic of the carrier filter, the frequency separation must be 50 Hz or more. From this
we arrive at the most desirable separation of 150 Hz. This will allow a deviation of ± 100 Hz
without exceeding the permissible limits, and is well within the capabilities of modern equip­
ments, even at the highest frequencies.
7.

Practical results
A number of systems operating on this basis have been in service since 1951. The
experience from this operation has shown that radiotelephone systems using terminals havingv o d a s equipment will operate successfully on a common-frequency basis. Based on thisexperience, and the tests noted above, the Annex summarizes the several methods ofoperation with reduced and suppressed carrier. The left column lists the important cha­racteristics which need to be defined for use of common-frequency systems on radiotele­phone circuits, and the right column contains associated definitions and remarks which haveresulted from the above tests.

— 136 —Rep. 353

ANNEX

1.

Reduced carrier multi-channel operation
Criteria

1.1 Recommendation 335-1. The cha­racteristics of the radiotelephonesystem shall be as specified in
Recommendation 335-1.
1.2 Level o f signal received from local
transmitter. Important character­istics include physical separation
between local receiving and trans­mitting stations, frequency of oper­
ation, physical terrain (hills, etc.),
antenna patterns, antenna radiation
efficiency, transmitting power, etc.

1.3 Mode o f operation. Reversible
simplex operation.
1.4 Intermodulation distortion at thetransmitter.
1.5 Frequency stability o f the trans­mitter
1.6 Bandwidth o f a.f.c. carrier filter

2.

Remarks
The equipments used in the system described above
generally agree with the characteristics specified inthis Recommendation.
The physical separation between local receiving andtransmitting stations must be great enough that thecarrier signal level from the nearby transmitter will
normally be less than the signal received from the
distant transmitter and will rarely exceed it by asmuch as 10 dB. The use of transmitting and receiv­
ing antennae of differing characteristics will affect thistype of operation only to the extent that they influence
the strength of the signal received at the local receiverfrom the local transmitter.
vodas

e q u ip m e n t u s e d o n e a c h v o ic e c ir c u it.

The intermodulation level (Recommendation 326-1)
should be lower then — 30 dB.
Transmitter frequencies must be sufficiently stable tomaintain a space of 150 ± 100 Hz between trans­mitted carriers.
The carrier filter should have an attenuation of
approximately 40 dB at the ± 50 Hz points.

Suppressed carrier multi-channel operation
Criteria

2.1 Recommendation 335-1. The cha­racteristics of the radiotelephonesystem shall be as specified in
Recommendation 335-1.
2.2 Level o f signal received from local
transmitter. Important character­istics include physical separation
between local receiving and trans­mitting stations, frequency of oper­
ation, physical terrain (hills, etc.),
antenna patterns, antenna radiation
efficiency, transmitter power, etc.

2.3 Mode o f operation.
Reversible simplex operation.
2.4 Distortion at the transmitter.
2.5 Frequency stability o f receiver andtransmitter.

Remarks
See Recommendation 335-1.

The physical separation between local receiving andtransmitting stations must be sufficiently great, thatthe signal level from the nearby transmitter will nor­mally be less than the signal received from the distanttransmitter and will rarely exceed it by as much as
10 dB. The use of transmitting and receiving antennaeof differing characteristics will affect this type ofoperation only to the extent that they influence thestrength of the signal received at the local receiverfrom the local transmitter.
v o d a s equipment used on each voice circuit.
The intermodulation level (Recommendation 326-1)
should be lower than —30 dB.
Transmitter and receiver must be sufficiently stableto maintain an overall frequency difference not exceed­ing 20 Hz for speech.

— 137 —3.

Rep. 353

Suppressed carrier, single-channel operation
Remarks

Criteria
3.1 Recommendation 335-1. The cha­racteristics of the radiotelephonesystem shall be as specified in
Recommendation 335-1.
3.2 Level o f signal received from local
transmitter. Important character­istics include physical separation
between local receiving and trans­mitting stations, frequency of oper­
ation, physical terrain (hills, etc.),
antenna patterns, antenna radiation
efficiency, transmitter power, etc.

3.3 Mode o f operation.
Reversible simplex operation
3.4 Transmitter distortion.
3.5 Frequency stability o f receiver andtransmitter.
3.6 Residual noise level at the trans­mitter.
3.7 Blocking characteristics o f thereceiver.

See Recommendation 335-1.

For single-channel operation, the physical separation
between the local receiving and transmitting stations
must be great enough, that the level of residual noiseat the receiver in the desired sideband is not increasedby more than 1 dB when the transmitter power
amplifier is operating normally but with no modula­tion applied. (Under this condition, the transmitteris producing broadband noise from the exciter anddriver which can, if sufficiently high, interfere withthe signal received from the distant station. See§ 6 below).
vodas

e q u ip m e n t u s e d o n th e v o ic e c ir c u it.

The intermodulation level (Recommendation 326-1)of the transmitters should be lower than — 30 dB.
Transmitter and receiver must be sufficiently stableto maintain an overall frequency difference not exceed­ing 20 Hz.
The residual-sideband noise level should not exceed— 56 dB relative to the peak envelope power.
The receiver blocking characteristics must be suchthat the receiver will recover from a severe overload
in less than 01 s if the front end of the receiver is
not desensitized during the period of transmission
from the local transmitter. (In this case, the local
transmitter and receiver can be much closer together
because there is no a.f.c. problem, only problems ofinterference and blocking remain. In some cases,
the two may be co-located. The receiver can beleft operative, during the period of transmission by
the local transmitter, if it cap receive a signal fromthe distant transmitter immediately after the local
transmitter has ceased operation).

Rep. 354

— 138 —REPORT 354 *AN IMPROVED TRANSMISSION SYSTEMFOR USE OVER HF RADIOTELEPHONE CIRCUITS(Question 13/111)(1966)

1.

Introduction
Terminal apparatus currently employed on H F radiotelephone circuits includes constantvolume amplifiers (c.v.a.) and singing suppressors in each speech channel. The transmit
c.v.a. performs its design function of maintaining a sensibly constant mean speech level at
the transmitter input regardless of talker level but, because of the inherent high peak-to-mean
power ratio of speech, the transmitter inevitably works well below its maximum power rating
for a large percentage of time. The receive c.v.a. reduces the speech level variations caused
by fading, but cannot discriminate against atmospheric noise and interferences and will infact accentuate them if their level is permitted to exceed the c.v.a. input threshold. The
singing suppressors are susceptible to misoperation by high levels of received noise, andclipping or suppression of speech in the transmit channel can result. Even under good cir­
cuit conditions the use of singing suppressors operates against a smooth flow of conversation.
In line transmission the effects of noise can be reduced by the use of a compandor, butsuch a system will function correctly only if the loss remains constant between the compressor
output and the expandor input. This requirement has so far precluded the application ofcompandor techniques to H F radio circuits. If, however, the information concerning thedegree of compression introduced at the transmitting end can be accurately conveyed tothe expandor a t the receiving end (e.g. by the use of a separate information channel), thensuch a system could be made to operate satisfactorily. The use of a separate control signal
will, moreover, remove the usual restriction on the degree of compression; greater compres­sion can be employed, resulting in more effective use of the power-handling capability ofthe transmitter.**
The “ Lincompex ” (Linked Compressor and Expandor) system has been developed
from this concept. The speech is compressed to a sensibly constant amplitude and thecompressor control current is utilized to frequency-modulate an oscillator in a separate control
channel. The speech channel, which contains virtually only the frequency information of
the speech, and the control signal channel which contains the speech amplitude infor­
mation, are combined for transmission over a 3 kHz channel. As each speech syllable
is individually compressed the transmitter is more effectively loaded than in current practice.
On reception both the speech and the control signals are amplified to constant level, thedemodulated control signal being used to determine the expandor gain and thus restore theoriginal amplitude variations to the speech signal. Because the output level at the receiving
end depends solely on the frequency of the control signal, which is itself directly related to* This Report was adopted unanimously.
** The earliest known reference to the use o f a separate control channel in this manner is an article
by P. Dem an, “ Circuits telephoniques sur liaisons de faible qualite ”. L ’Onde Electrique, 49,
656 (July/August, 1961).

— 139 —Rep. 354

the input level at the transmitting end, the overall system loss or gain can be maintained at
a constant value. Operation with a slight loss (two-wire to two-wire) permits singing suppres­sors to be discarded, although echo suppressors will be needed, as on long-line circuits.

2.

Outline description of Lincompex system
A simplified block schematic of a terminal equipment is shown in Fig. 1.

2.1 Transmitting side
The speech signal, after passing through the echo-suppressor (of the type normally usedon line circuits) traverses two paths. One path leads to the amplitude assessor, the solefunction of which is to generate a d.c. control signal corresponding to the speech amplitude.
Over the other path, the speech signal passes through a delay unit (approximately 4 ms)
and thence to the compressors. Two compressors are used in tandem, the variable-loss
networks being energised by the d.c. control signal instead of by their individual outputs.
The separate derivation of the control signal, together with the delay unit, ensures that the
speech signal and the control signal are so synchronized that precursive peaks at thecompressor output, due to a suddenly applied signal, are minimized. This arrangement ofcompressors can produce, in the steady state of the signal, a substantially constant output
over an input signal level range of approximately 50 dB.
The d.c. control signal, in addition to determining the compressor gain, modulates thefrequency of an oscillator so as to produce a 2 Hz frequency change for each 1 dB change

F

G

F

K

F igure 1
B lo c k-sch em a tic o f L in c o m p e x sy ste m

A: Amplitude assessor
B: Frequency-modulated oscillator
C: Frequency discriminator
D: Limiter-amplifier
E: Constant-volume amplifier(fading regulator)
F: Delay network

G: Compressor
H: Expandor
J: Half echo-suppressor
K: Low-pass filter (2700 Hz)
L: Band-pass filter (3000-2800 Hz)
M: Hybrid transformer

I

Rep. 354— 140 —

in level at the input to the amplitude assessor. The approximate frequency limits are 2950 Hz
for no input and 2850 Hz for the maximum input to the amplitude assessor. The circuit
constants of the assessor and oscillator are such that, under dynamic conditions, the spectrumof the control signal may extend from 2810 to 2990 Hz.
The compressed signal in the speech path is subjected to a time delay (discussed later)
and then band-limited in a 2700 Hz low-pass filter. Finally, the compressed speech and thecontrol tone are combined to form a composite signal in the band 250-3000 Hz suitable forapplication to a radio transmitter.

2.2 Receiving side
The received signal is divided between two paths, the speech signal being selected in a
2700 Hz low-pass filter and the control signal in a 2810-2990 Hz band-pass filter. Levelvariations of the speech signal due to fading are removed by amplification to a constantlevel in a specially designed quick-acting c.v.a. (fading regulator). The control tone islimited and applied to a frequency discriminator to recover the d.c. control signal. After
suitable delay the speech signal is applied to the expandors which, under the influence ofthe control signal, perform a complementary function to that of the transmitting-end com­pressors to restore the amplitude variations in the speech.
#

2.3 Transmission time equalization
The necessity for the pre-compressor delay has already been explained. Additionally,
however, time equalization may be required in the speech path to compensate for the delay
inherent in the control path due to the narrow-band filtering. Laboratory tests have shownthat the omission of this equalization introduces some degradation of speech quality andcauses severe distortion of signalling impulses. Although the control path delay occurs
mainly at the receive terminal, the equalization is equally divided between the transmit andreceive paths of each terminal. By adopting this arrangement the delay may conveniently
be removed when it is not required, e.g. when 5-band privacy equipment, with its inherent
delay, is in use.

3.

Field trial
Experimental equipment, similar in principle to the Lincompex system described but
differing in detail, has been tested operationally at the terminal stations of the London-New
Delhi radio circuit. This circuit carries a three-channel telephone system and the perform­
ance of a Lincompex-equipped channel carrying public-service traffic has been comparedwith that of a conventionally-equipped channel. The Lincompex equipment and the conven­tional terminal were applied to the two inner channels of the radio system, the channels being
interchanged at weekly intervals throughout most, but not all, of the 17-week trial period(December 1964-April 1965).
The Lincompex equipment gave consistently longer commercial time than the conven­tional equipment, the average daily commercial periods being 6-6 and 5-8 hours (14% increase)respectively during a 12-week period when channels were systematically interchanged, but
taking the 17-week trial period as a whole, the corresponding figures were 6-2 and 5-2 hours(19% increase) per day.
Quite apart, however, from the extension of commercial circuit availability, a noteworthy
feature was the greater potential call-handling capacity of the Lincompex channel due tothe smoother flow of conversation, of operators and subscribers alike, which the omissionof singing suppressors made possible. This was clearly demonstrated during a special
4-week service observation period when particular attention was paid to the quality of calls.

Rep. 354

— 141 —Of the observed calls, 70 % were graded “ excellent ” or “ good ” on the Lincompex channel,
the corresponding figure for similar gradings on the conventional channel being 58 %. The
improvements were particularly noticeable on transit calls extended over long-distance cable
circuits.

ANNEX

1.

Introduction
The function of the transmit compressors in the Lincompex system is to provide a sensibly
constant output over a wide range of input levels. In an ideal circuit a constant level would
be directly applied to the expandors, so in a practical radio circuit, level variations caused
by fading have to be compensated by a constant volume amplifier (fading regulator) at thereceive end of the circuit. The fading regulator employed in the Lincompex system is un­
like conventional c.v.a.’s, which revert to zero gain for input levels below the threshold,in that its gain rises to a maximum in the absence of a signal and thus contributes
additional gain in the overall speech path. To ensure that the system always works in astable condition, in particular when there is no signal input, the controlled expandor loss
must at all times exceed, by a small margin, the sum of the gains in the speech compressor
and the fading regulator.
Practical design difficulties dictate a maximum control range of 60 dB and, since a fading
regulator gain of 15-20 dB is customary, it follows that the compressor gain must not exceed
40 dB. For input levels below the compression range the compressor must therefore be
arranged to operate as a linear amplifier, any level reductions being compensated by thefading regulator gain. The full improvement in signal-to-noise ratio will not, therefore, be
achieved for input levels which fall into the linear part of the compressor range; existing
systems also suffer degradation when the input signals fall below the range of the transmit
c.v.a.
The system parameters to which equipment is currently being produced for an extensive
field of the Lincompex system are set out below.

2.

Speech path

2.1 Compressor (Controlled by amplitude assessor)
Input levels between which the output is sensibly constantLinear range
Time constant— 4 to — 44 dBm (Note 1)
below — 44 dBm
18 to 20 ms

2.2 Pre-compressor delay

3.5 ms to 4.5 ms

2.3 Low-pass filter

Effectively limits
band to 2700 Hz

speech

2.4 Constant volume amplifier (Fading regulator)
Input range
Time constant— 3 to — 27 dBm (Note 2)
18 to 20 ms

2.5 Expandors (Controlled by the discriminator)
Effective range of less variation
Time constant

60 dB
8 to 10 ms

— 142 —Rep. 354
3.

Control path

3.1 Amplitude assessor (A self-controlled compressor)
Compression law
Input levels over which the 2:1 law is obtained
Time constant
3.2 F M oscillator (Frequency controlled by amplitude assessor)
Nominal centre frequency
Maximum frequency deviation
Change of frequency per dB, change of level at the inputof the amplitude assessor
Level at input of the amplitude assessor to produce
nominal centre frequency
Direction of frequency change for an increase of levelat the input to the amplitude assessor
Time constant
Output spectrum
3.3 Limiter
Input range
3.4 Discriminator
Change of frequency at input to produce a level changeof 1 dB at the output of the expandors

4.

2:1— 4 to — 64 dBm (Note 1)
18 to 20 ms
2900 Hz± 60 Hz
2 Hz- 34 dBm
Negative
Approx. 4 ms
Effectively
limited2800 to 3000 Hzto— 8 to — 45 dBm (Note 2)

2 HzTransmission time equalization
Allowable overall difference of transmission time between
the speech and the control paths± 4 ms

Note 1. - This assumes speech levels varying between — 6 and — 45 dB relative to RTP at thetwo-wire input.
Note 2. - These levels are based on the assumptions that the median level of the received signal
in the speech paths is — 10 dBm when a test tone within the compression range is appliedat the speech input of the Lincompex equipment and that the level of the signal in the control
channels is 5 dB lower.

— 143 —Rep. 355

REPORT 355 *USE OF DIVERSITY ON INTERNATIONAL HF RADIOTELEPHONE CIRCUITS(Question 13/111)(1966)

1.

Introduction
This Report describes tests of several diversity techniques for H F radiotelephone ser­vice, including wide spaced diversity, frequency diversity, and time diversity.

2.

Wide space-diversity for voice operation
Recently, H F wide space-diversity tests using an experimental comparator to selectthe better of two overseas circuits have been performed. Briefly, this comparator measures
the received noise and/or interference during outgoing speech (under control of the v o d a s ),and switches its output to the quieter of the two circuits. The tests were made to determine
the transmission improvement that can be obtained by using such a device to select the better
output from two widely spaced receivers.
These tests were made using similar radio receivers located about 135 km (85 miles)
apart. The receivers were adjusted to have as nearly as possible the same performanceand they were tuned to an idle channel on the same overseas transmitter. The output ofboth the accepted and rejected circuits were recorded on a dual pen recorder which was
equipped also with an event recording pen to give a continuous record of the switch posi­tion. At all times the receiver with noise peaks, occasioned by radio fading at the receiversites, was rejected by the diversity switch.
D ata from these tapes were selected on a time basis using samples of one second dura­tion as the basic units. Fig. 1 shows the received noise from both the accepted and therejected receivers plotted against the percentage of the total time that levels were equal
to or greater than the absolute values of the ordinate. These curves were plotted from
21 600 one-second samples when noise alone was controlling the switching. The median
improvement as read from the curve is greater than 3 dB and for 1 % of the total time, during
the deep fading periods, the improvement is about 7 dB. As expected no improvement
is indicated at noise levels below 35 dBrn where the noise is inaudible.
The diversity switch control circuit (comparator and switch) has two inputs with asingle output. The two input signals are compared and the quieter signal is automaticallyswitched to the output. Monitoring jacks are provided for both the accepted channel andthe rejected channel. Provision is made to monitor the incoming signals under two condi­
tions ; the first for monitoring only during the periods when the v o d a s relay action indicatesthat there is no incoming speech, the second, which was used in these tests, provides forcontinuously monitoring an idle channel, by simulating continuous v o d a s operation. The
dynamic range of the switch is from 30 dBrn (practically inaudible) to 85 dBrn (objectionable)
when measured at either of the comparator inputs with 3 kHz flat weighting. Attenuators
were inserted ahead of the switch inputs, so that cases of extreme noise levels could be brought* This Report was adopted unanimously.

Rep. 355

— 144 —

within the operating range of the switch. A built-in delay prevents the switch from operat­ing on occasional impulse noise peaks but discriminates against the characteristic noisecaused by electrical storms.
There is a lack of correlation in the fading rates of H F signals at receiving stations sepa­
rated by a number of miles. No effort has been made to determine the minimum distanceat which this lack of correlation is sufficient to permit diversity operation. The improvement
obtained through use of duplicate receiving and connecting wire-line facilities is sufficient
to justify its use on important radio systems.

3.

Time-diversity of voice operation
The new time-diversity system for radiotelephone transmissions described below issuitable for push-to-talk type operation, broadcast relay, and other similar services but,
since the system introduces a time delay of up to a second, it is not suitable for normal tele­phone service where almost instantaneous replies are required. The system relies upon
the fact that there is appreciable frequency redundancy in speech waves, so that if one fre­quency segment is lost the other segments will normally carry the intelligence.
The equipment used at the transmitting site separates the speech wave into a numberof small frequency bands; for example, the centre frequencies of the filters may be at 360,
570, 900, 1430, 2270, 3600 Hz. The output of the first filter is fed directly to the transmitter,
the second filter to a time delay of one-half second, a third filter fed to a time delay of one
second, the fourth filter is fed directly to the transmitter, etc. as shown in Fig. 3.
The output of the receiver is fed to similar equipment, but in this case the frequency
segments that are not delayed at the transmitter are delayed a full second at the receiverand the frequency segments that are delayed one-half second are delayed an additional onehalf second at the receiver and finally the segments that are delayed a full second at the trans­mitter base are fed undelayed to the combiner network at the receiver . Thus, a natural sound­ing wave delayed one second results.
The system has three desirable effects:- if a fade lasts for less than a second, the bulk of the highly redundant speech wave
will be received;- there is a 6 to 7 dB measured reduction in peak level for a constant average level. The
reason for this improvement is that the peaks of the voice wave form are reduced relative
to the average level. The energy is more evenly distributed because of the time delays;- the technique provides privacy in that the reception of the signal requires decoding equip­
ment. However, if time delays of 1-5 to 2 s are used the privacy effect is for all practical
purposes eliminated. Experiments with this system indicate that to achieve thereduction in peak-to-average levels a time delay of at least 0-1 s is required. The amountof time delay required for achieving diversity gain is, of course, a function of the fading
rate and it would appear that a delay of at least 1 s is desirable if one wishes to achievea substantial reduction in the effects of fading.

4.

Audio-frequency band-splitting combiner for space diversity
In this system a combiner splits each of the two receiver audio-frequency bands into
three segments. Each segment is processed through two band-pass filters, a comparator
and two amplifiers.
The output signals from the bandpass filters are applied to the amplifiers and also to
the comparator circuit. The comparator converts the a.c. input signals into two d.c. voltages

Rep. 355

145

of opposite polarity. These voltages are compared on a continuous basis to determine
which is the stronger signal.
The comparison output drives a differential control amplifier. The type of variablegain action obtained prevents any thumps, clicks and transients of the signal applied tothe two filters for that segment. However, should the signal at Filter 1 fade by 2 dB or
more, compared with the signal at Filter 2, the selected output signal (signal at Filter 2)
will be at least 20 dB greater than the weaker signal (signal at Filter 1).
The outputs from the three segments are combined in linear addition to reproduce
the audio spectrum. The audio output response is improved over the non-diversity casefor any amount of signal fading.
B ibliography

1. K ahn , L. R., A time-diversity technique for speech transmission over rapidly fading channels(Echoplex). IRE International Convention Record, Part 8 (1962).

PQ ^<D 4 h

£ £P

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.55 ^

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P A4
'<o3 G<Uw
Pi

.0,01

0,1

1 2

5 10

30

50

70

90 95 9899

99,9 99,99

Percentage of the time that the noise isequal to or greater than the ordinate
F igure 1

Wide-spaced diversity, 16 430 kHz, June 11 to 13, 1962, 21 600 samples
Noise alone was switching criterion
Receiving stations at Manachawkin and Netcong, NJ

A: frequencychangers
B: delay lines
C: transmitter
D: receiver
E: combiner

F igure 2

Simplified block diagram o f Echoplex

10

REPORT 356 *USE OF DIRECTIONAL ANTENNAE IN THE BAND 4 TO 28 MHz(Recommendation 162-1)\(1966)

Introduction
Question 10/111 poses the problem of specifying reasonable standards for the directi­
vity of antennae in the various types of radio service, and for various distances, in the bands
between 4 and 28 MHz with due regard to economy o f cost. This Report is mainly concernedwith point-to-point circuits longer than 4000 km but, with suitable modification, could beapplied to shorter range circuits. The technique discussed requires a knowledge of thegain of the antenna under consideration and the angular widths in zenith and azimuth ofits main beam of radiation. With this information a directivity factor is derived which,used in conjunction with certain other factors, e.g. transmitter power and provision cost,
may be used to assess the suitability of an antenna for any particular application.

Proposition
An antenna possessing a given directive gain which radiated all its power in a single
beam could be regarded as having the best attainable performance of its class. Communi­
cation systems using such antennae for emission and reception could operate on a common
frequency with a given spatial distribution without risk of mutual interference, the only
condition being that each receiving antenna should “ see ” only the wanted transmitting
antenna. With such an ideal arrangement the number of systems sharing the same fre­quency would increase as a function of the gain of the antennae because of their smaller
angular beamwidth.
By making certain simplifying but justifiable assumptions, it can be shown that to ahigh degree of approximation there is a fixed relationship between the directive gain (rela­tive to an isotropic radiator) and the angular widths of this single beam (to the null) as follows:
G = Po/P = 32n2/(n2 - 4) 0O<p0 = K/Q0 (p0(1)(0O and cp0 are the horizontal and vertical angular widths respectively, in radians and P,
P0 are the total powers radiated from the ideal antenna and the isotropic radiator respectively
to produce the same field in the desired direction).
Practical antennae fall some way short of this ideal in that a proportion of the poweris radiated (or received )in directions other than in the main beam.
If the directive gain of such an antenna is G ' and the widths of its main beam are 0O',
cp0', then from (1), the power radiated in the main beam:
P' = PQ0'(f>o/K* This Report was adopted unanimously.

(2)

— 147 —Rep. 356

If this represents a fraction, q of the total radiated power,orG' = Pog/P' = Kv/Q o V(3)

q — G'Qo'qo'/K(4)I
Thus, from the measured or computed characteristics of an antenna it is possible todetermine its radiation efficiency, i.e. the fraction of the total radiated power that is directedin the main beam.
The power radiated outside the main beam of a transmitting antenna which is liable
to set up interfering signals is given by:
P o ( l- q ) /G 'If this were distributed evenly over the residual hemisphere outside the lunar arc 0O',
the average power flux would be
Po (1 - q)l(2n - Go7) G'
Since the maximum flux in the main beam is PolAn, we can write
Maximum useful signal power flux

G'(2n-Q0')

Average interfering signal power flux

(1 —q) 4n(5)

As is well known, the spatial distribution of flux outside the main beam will vary widelyand values considerably in excess of the average will be found. It would seem appropriate
to express this as a probability distribution in such a way that its effect in degrading thesignal-to-interference ratio appears as a term in the directivity factor of the antenna. To
do this would require a knowledge of the minor beam flux distributions of a large sample
of practical antennae and because insufficient information of this nature is available analternative approach must be adopted. The method used is to derive an antenna directi­
vity factor based on the assumption that all the misdirected power appears as a numberof equi-amplitude secondary beams and to apply an adjustment when individual secondary
beam amplitudes are likely to be significant to a particular problem, e.g. frequency sharing
studies.
If the same power distribution (cosine-squared) as that asuumed for the main beam isused then, for the secondary beams,/

F max \ 22tc2--------== 3-41 (5-3 dB)\ F average/n2- 4
and we can then write,
Maximum useful signal power flux
Maximum interfering signal power flux=

G' (2k —0O')(6)(1 —q) 4n x 3'4I

One further modification to the formula is necessary to take account of what has beencalled the “ propagation match ” of the antenna: various studies have shown that for long
distances (>4000 km), circuit performance improves as the vertical angle of the main beammaximum of the antenna is reduced.
A weighting factor (appropriate for vertical launching angles between about 5° and 25°)
allows for this effect and the equation for the antenna directivity factor becomes,

Rep. 356

— 148 —G' (2ti —0oO
10
M — ---------------------------(1—q)4n x 3-41 Am

For distances less than 4000 km, this factor may be omitted and instead the heightof the antenna chosen to match the propagation conditions over the route;and expressing 0O', cpo' in degrees,G' (360 -0oO
M = --------------------245-6 Am (1 -^ )

where

(7)

G 0o tpo
q = ----------176 600

G' = directivity gain of antenna expressed relative to an isotropic radiator (expressed
as a ratio unless otherwise stated),
0O' = horizontal angular width of main beam in degrees (to first minimum points),
cp0' = vertical angular width of main beam in degrees (to first minimum points),
Am = vertical angle o f main beam maximum (degrees).

3.

Application
M values for a number of actual antennae of various types are plotted in Fig. 1. The
main beam performances of all but three of the antennae considered had been exploredusing airborne equipment and for these, measured gains (power gains) were available; thesewere translated to directive gains for application in equation (7). The main beam perfor­
mances of the three exceptions (single rhombic antennae at 4, 6 and 8 MHz) were computed,
allowance being made for the reduction in directive gain due to non-uniform current in
the antenna wires.
Although interpretation of the results plotted in Fig. 1 is made difficult by the dearthof suitable data, the plot provides an indication of variation with frequency of the main
beam performance of single antennae and antenna arrays. Curves, which it is considered
represent reasonable standards of performance for these two classes of antenna have beendrawn on the diagram. The lower curve (labelled minimum standard antenna) is a best
fit to the available experimental data and may be expressed as M = 01 f 2. This is consi­
dered to be representative of the standard of performance to be expected from well-designed
single rhombic antennae operated within a frequency band in which the ratio of highest
to lowest frequency does not exceed 2.
The upper curve (Economic reference antenna) which may be similarly expressed as
M = 0-25 f 2 represents a standard of performance which will normally only be achieved
with antenna arrays. This higher standard necessarily involves a proportionally greater
expenditure on antenna plant but, as has been proposed elsewhere *, some increase above thecurrent level of expenditure can be economically justified.
For frequency planning and other allied studies the occurrence frequencies of secondary
beams having amplitudes greater than the equi-amplitude crest value may be important.
Within the range M values considered the results of the measurements made on practicalantennae indicate that not more than 10% of the secondary beams will exceed the equi* Survey o f aerials and aerial distribution techniques in the H F fixed service D. E. Watt-Carter and S. G.
Young. Proc. I.E .E ., Vol. 110, 9 (September, 1963).

— 149 —Rep. 356

amplitude crest value by 6 dB. Thus, for an antenna having an M value of 40, the ratioof the levels of the main-beam intensity and the higher secondary-beam intensity would be
10 dB. These secondary beams will usually be adjacent to the main beam.

Frequency (MHz)Curve A: Economic reference antenna
Curve B: Minimum standard antenna
•
®
*
□
x
+

Single rhombic antennae (CCIR antenna diagrams Figs. 32a, 33a, 35a)Single rhombic antenna 425765°/150'
2-stacked rhombic array2-stacked 2-interlaced rhombic array
Dipole array HR 4/4/1-0
Dipole array HR 8/4/0-5
F ig u r e 1

Antenna directivity-factor based on the measured characteristics o f HF antennae

Rep. 357

— 150 —REPORT 357 *OPERATIONAL IONOSPHERIC SOUNDINGAT OBLIQUE INCIDENCE(Study Programme 20A/III)(1966)

1.

Introduction
Study of the results from frequency soundings have led a number of workers [1, 2, 3]
to suggest that frequency sounding equipment could be used in parallel with a communi­
cations system to determine optimum, short-term operating frequencies. A number ofstudies have now been carried out [4, 5] and are being considered, which are designed todetermine the improvements that can be achieved from the use of sounding information.

2.

Operational problems encountered using frequency sounding systems
Experiments carried out so far using ionospheric sounding at oblique incidence disclose
a number of problems.

2.1 The differences in sensitivity between communication and sounding equipment.
valid information of use to communicators this difference must be allowed for.

To secure

2.2 The inaccuracies in sounder predictions which result from sounding over an ionosphericpath separated from the communication path and in the opposite direction of a non-reci­
procal path. Preliminary studies [6] suggest that for a separation of 16 km these differences
can be reduced to less than 10 dB by averaging sounding information over a number ofshort-term fading correlation periods.
2.3 The differing performance of the sounder and communication antenna systems.
2.4 The differing performance of the sounder and communication equipment in the presenceof interference.

3.

Types of sounding systems
There are a number of types of oblique incidence sounding systems but two in particu­
lar may be considered for use in connection with operational circuits.

3.1 The locally operated, independent, or semi-independent channel sampling system
A particular service adopting a channel sampling system could use its complementof allocated frequencies for both frequency sounding and communications on a time orfrequency-shared basis. The total bandwidth occupied by the emission would therefore
be relatively narrow, and the number of frequencies limited. The sounding and commu­
nication system could be co-sited, or not widely separated. This system essentially avoids
the problems mentioned in § 2.2 with the penalty of reduced propagation information, andhence reduced ability to predict propagation changes.
* This Report was adopted unanimously.

— 151 —Rep. 357,413, 414, 415

3.2 The common-user system
Stations participating in a common-user system would receive directly, or indirectly,
statistical propagation information appropriate to their communications path for time
periods of a few minutes to many hours. Prediction of statistical propagation characte­
ristics requires reliable propagation mode information, which can be obtained using a large
number of sounding frequency channels (i.e. 40-80) for high resolution across the entire
HF band, and a wide sounding signal bandwidth (i.e. 5-10 kHz) for propagation mode reso­
lution. The operational and interference problems raised by the implementation of sucha system for wide-scale use require technical consideration at the international level at theearliest possible time.

B ib l io g r a p h y

1.
2.
3.
4.
5.
6.

S a n d o z , O. A., S t e v e n s , E. E., and W a r r e n , E. S. The development of radio traffic frequency
prediction techniques for use at high latitudes. Proc. IRE, Vol. 47, 681 (1959).
D o y l e , D. J., D u c h a r m e , E. D., and J u l l , G. W. The structure of HF signal revealed by an oblique
incidence sweep frequency sounder. IRE Trans. (Antennas and Propagation) Vol. AP-8, 449(1960).
H a t t o n , W. L. Oblique-sounding and HF radio communication. IRE Trans. Communications
Systems, Vol. CS-9, 275 (1961).
J u l l , G. W., D o y l e , D. J., I r v i n e , G. W., and M u r r a y , J. P. Frequency sounding techniquesfor HF communications over auroral zone paths. Proc. IRE, Vol. 50, 1676 (1962).
E g a n , R. D., and P r a t t , D. S. Oblique sounding and HF communications. Record of Conven­tion on HF Communications. I.E.E., Savoy Place, London, U.K. (March 25-27, 1963).
J u l l , G. W., P o a p s , G. E., and M u r r a y , J. P. Prediction of HF channel characteristics with fre­quency sounding information. Presentation at Globecom VII, IEEE Communication Convention,
University of Colorado (June 7-9, 1965).

REPORT 413
OPERATING NOISE-THRESHOLD OF A RADIO RECEIVING SYSTEMREPORT 414
EFFICIENT USE OF THE RADIO-FREQUENCY SPECTRUMREPORT 415
MODELS OF PHASE-INTERFERENCE FADING FOR USE IN CONNECTION WITH
STUDIES OF THE EFFICIENT USE OF THE RADIO-FREQUENCY SPECTRUM(1966)In accordance with a decision of the X lth Plenary Assembly these three Reports will
be published separately.

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENTSTUDY GROUP i n(Fixed service systems)
Terms o f reference:1.

To study questions relating to complete systems for the fixed and allied services and terminal
equipment associated therewith (excluding radio-relay systems). Systems using the socalled ionospheric-scatter mode of propagation, even when working at frequencies above
30 MHz, are included.

2.

To study the practical application of communication theory.

Chairman: Dr. H . C . A . v a n D u u r e n (Netherlands)
Vice-Chairman: Dr. S. A r i t a k e (Japan)

INTRO D U CTIO N BY THE CHAIRM AN, STUDY G R O U P HI

1.

The scope of the work of Study Group III covers the study of world-wide radiocommunica­
tions in the fixed services, for which the H F (decametric) band is mainly used. The study
aims at recommending methods of two-day radiocommunication by means of telephony,telegraphy and facsimile. The application of such methods will enable Administrations
to interconnect their landline networks to the world-wide communication network throughradio links. The Recommendations of the Study Group contain the best solutions agreed
upon internationally for obtaining commercial quality.

2. Recommendations 75, 100, 335-1, 336-1, 338-1, 348-1 and 349-1 contain information tocarry telephony over radio links by the application of single-sideband and independentsideband systems (information concerning: system bandwidth and frequency tolerances,channel arrangements, privacy equipment and echo suppression). Studies have been started
on systems having improved bandwidth utilization (Question 9/III and Report 353) andon improvements obtainable in the quality of radiotelephone transmission (Question 13/111;
Reports 354 and 355).
3. Recommendations 106,246-1, 338-1, 342-1, 345, 346, 347, 349-1 and 436 deal with communi­
cation by means of telegraphy (information concerning: channel bandwidth, channel arran­gement and frequency tolerances, operation on FSK and twinplex channel and on ARQsystems, classification of channels and definitions on the telegraphic distortion).
The interest in further study of telegraph transmission is reflected in Questions 2/III, 6/HI,
7/III, 8/m, 12/III and 15/111 and in Study Programmes 8A/III and 17A/III. Reports
19-1, 42-1, 345, 346 and 347 contain observations and useful data on telegraph channels
capable of transmitting telegraph signals at a high transmission density. The work doneon telegraph systems giving protection against errors is intended partly to investigate thevariation in time o f error-rate for synchronous systems in general (Report 200-1) and to
study the behaviour of the efficiency of ARQ-circuits (Report 351) (see also § 9).
4. Recommendations 343-1 and 344-1 deal with facsimile transmissions of meteorologicalcharts and with the transmission of phototelegraphy on radio links connected to the— 154 —landline network. The study of remote control signals for facsimile transmission overradio links is covered by Report 201-1. D ata on the improvement' obtainable by the appli­
cation of pre-emphasis for phototelegraph transmission are given in Report 352.
5.

Operation on radio links is impaired by fading and noise under unfavourable conditionsof radio propagation, or by interference from unwanted emissions. The study of the diffi­
culties encountered and of measures to increase the time operational quality for the various
systems is covered mainly by Questions 1/III and 11 /III and by Study Programme 1A/III.
This study is continued and the fixing of protection ratios against unwanted interfering
emissions is in progress in cooperation with the I.F.R.B. (Report 197-1). Some information
is available in Recommendations 240, 339-1 and 340.
The study of the techniques of oblique-incidence ionospheric sounding has been opened for
operational purposes (Study Programme 20A/III and Report 357). Research work on propa­
gation effects has been recorded in Reports 109-1, 111 and 203.
The International Working Party established to reach the objectives of Resolution 1-1,
has produced three Reports on procedures, definitions and fading models related to the studyof an improved use of the radio-frequency spectrum (Reports 413, 414 and 415). These
Reports will be issued separately from the series of the X lth Plenary Assembly of the C.C.I.R.
Question 14/III asks for the features of automatically controlled radio systems which require
cooperation between Administrations.

6. The use of the radio path will be improved by the application of directional antennae.
Recommendation 341 gives definitions on transmission gain and loss, and Report 112 shows
the application of these concepts. Results of the study on the directivity of antennae atgreat distances are shown in Report 109-1. Further characteristics of antennae are definedin Recommendation 162-1 and discussed in Report 356.
7. Communication theory gives the basis for a better understanding of system performance.
Therefore developments in communication theory may lead to the improvement of systems.
Question 5/III and Study Programme 5A/III deal with communication theory. Report196-1 shows some applications. Practical applications were discussed by the Study Groupin the field of synchronous telegraphy (see §§ 3 and 4).
The Study Group uses the binary information unit (bit) as a standard for comparing theperformance of telegraph systems (Recommendation 166-1) and uses the normalized signalto-noise ratio for comparing radiotelegraph channels (Report 195).
8. Cooperation with the C.C.I.T.T. resulted in Recommendation 335-1 (telephony), Recommen­
dation 344-1 (phototelegraphy), Recommendations 342-1 and 345, Reports 19-1 and 351(telegraphy).
This cooperation is continued in the study laid down in Study Programme 18A/III and
Question 15/III (efficiency factor) and is reflected in the observations given in Report 201-1(remote control signals for facsimile transmission).
9. In the new and developing countries there is a need for relatively low-cost telegraph systems
with a small capacity, but nevertheless providing a degree of automatic error correction.
As a result of discussions within Study Group III, Reports 348, 349 and 350 were approved,
which go some way towards satisfying this need, and furnish a partial reply to Questions 9/IX
and 278 (Questions Nos. 4 and 6 of the Plan Sub-Committee for Asia, Geneva, 1963).

— 155 —Res. 1-1, Q. l/III

RESOLUTION 1-1
IMPROVED EFFICIENCY IN THE USE OF
THE RADIO-FREQUENCY SPECTRUM
The C.C.I.R.,(1963 - 1966)CONSIDERING(a) that knowledge and technology in the field of radiocommunications are developing rapidly;(b) that a larger number of simultaneous users of the spectrum must be accommodated in the
future;(c) that the accommodation of these additional users, without serious deterioration of thoseservices in use at present, will require careful consideration of all the many technical factors
involved in the simultaneous operation of potentially interfering systems;(d) that the available information on the wanted-to-interfering signal protection ratios andthe operating sensitivities of receiving systems needs further refinement for each of the ser­vices, to permit the most efficient planning of the use of the radio-frequency spectrum;
UNANIMOUSLY DECIDES

1.

that an International Group of Experts of the C.C.I.R.*, which would be representativeof the Study Groups interested in this problem, shall be established, to prepare a report on
definitions and procedures for the purpose of enabling the various Study Groups of the
C.C.I.R. to provide improved information on:- the required signal-to-interference protection ratios,- the minimum field strengths required for various classes of emission,
which would permit the more efficient use of the radio-frequency spectrum by the maximum
number of simultaneous users;

2.

that the co-ordination of the work of the Group should be undertaken by Study Group III;

3. that, as far as possible, the work of the Group should be conducted by correspondence.
Note. — The Director, C.C.I.R., is invited to bring this Resolution to the attention of the
U.R.S.I. for information.

QUESTION l/III **FACTORS AFFECTING THE QUALITY OF PERFORMANCE
OF COMPLETE SYSTEMS OF THE FIXED SERVICEThe C.C.I.R.,(1948 - 1966)

decides that the following question should be studied:what are the technical factors affecting the quality o f performance o f complete systems o f
the fixed service ?
* The following Administrations: U .S.A . (Chairman), France, Japan, Netherlands, Federal Republic o fGermany, United Kingdom and the U .S.S.R ., together with the E.B.U. and the I.F .R .B., have alreadyindicated their willingness to form part o f this Group.
** Formerly Question 3(111).

s.p. lA /m— 156 —STUDY PROGRAMME 1A/III *FACTORS AFFECTING THE QUALITY OF PERFORMANCE
OF COMPLETE SYSTEMS OF THE FIXED SERVICE
Signal-to-noise and signal-to-interference protection ratios
for fading signals, bandwidth and adjacent channel spacing
The C.C.I.R.,(1959- 1966)CONSIDERING(a) that the conditions for satisfactory performance of a system must take account of the needto receive signals propagated via the ionosphere, which are subject to fading and multipath
effects and are accompanied by radio noise and interference;(b) that studies requiring signal-to-noise and signal-to-interference protection ratios are closely
related, and that determination of necessary adjacent channel spacings requires, in addition,
consideration of frequency stability and bandwidth of the systems;(c) that there are a number of different techniques and systems in use in the radiotelegraph andradiotelephone services and, while it is essential to consider the most advanced state of theradio art, it is also necessary to give special study to conventional systems, either affecting
integration of landline and radio services, or of concern to the I.F.R .B .:unanim ously decides that the following study should be carried out:

1.

Classes of service
The studies concern the following classes of service in regular use in the fixed service but
should also give due regard to new techniques and systems, including those under deve­
lopment, for application to the fixed services:

1.1 Radiotelephony
1.1.1 Classes of emission: A3, A3 A, A3B, A3J, A3H, F3 (above 30 MHz only, with refer­ence to ionospheric-scatter applications);
1.2 Radiotelegraphy
1.2.1 Classes of emission: A l, A2, A7, F I, F6;
1.2.2 Modulation rates:- Al, A2, machine telegraphy 50 and 120 bauds;- A7, multi-channel VF telegraphy, 50 to 200 bauds per channel;- FI, 50 to 600 bauds;
1.2.3 Codes:- 5-unit start-stop;- synchronous error-detecting and correcting systems using two-condition signalling
codes other than the International Alphabet No. 2;-o th e r systems;* Formerly Study Programme 3A(III).

— 157 —S.P 1A/III

1.3 Facsimile, phototelegraphy, Hellschreiber
1.3.1 Classes of emission: A4, F4.

2.

Minimum conditions required for satisfactory service

2.1 Acceptable criteria and values for:2.1.1 intelligibility over radiotelephone circuits, for the various grades: just usable, operatorto-operator (order wire); marginally commercial; good commercial;
2.1.2 error-rate for characters and elements over radiotelegraph circuits (efficiency factor
for ARQ circuits);
2.1.3 legibility of copy over facsimile (phototelegraphy) and Hellschreiber circuits;- the maximum duration and percentage of the time during which performance inferior
to the standard values can be tolerated;

2.2 Performance of the system as a function of:-signal-to-noise and signal-to-interference (co-channel) ratios;-req u ired signal-to-noise and signal-to-interference (co-channel) protection ratios for theacceptable standard values of intelligibility, error-rate (efficiency factor on ARQ circuits),or legibility, for the various services *, considering:
2.2.1 signal fading, taking account not only of the amplitude distribution, but also of the
autocorrelation function and the distribution of duration of the fades;
2.2.2 diversity (space, frequency, or time) techniques: noise reducers, coding including theuse of error-correcting codes or ARQ, use of more than two signalling conditions,and optimum modulation and detection techniques;
Note 1. - It would be useful to compare the systems using the various telegraph codes, including
those of § 1.2.3, in terms of undetected or uncorrected error rate for a given power and signal­ling speed, in words per minute, and operating under the same conditions. A 5-unit startstop system may also be used as the reference system by regarding each mutilated characteras an error only. It is provisionally suggested that the ratio of error rates should be expressed
for two-circuit conditions only; namely, when the system under test is subjected to an averageof one undetected or uncorrected error per 1000 characters, and per 10 000 characters.
Note 2. - A special study is needed comparing the different systems used for voice-frequency
telegraphy on radio circuits; this is dealt with in Study Programme 18A/III
2.2.3 multipath effects;
2.2.4 interference effects of radio noise of various types, such as atmospheric, impulsive,
or Gaussian noise, as described by the wave form and amplitude distribution of theinstantaneous values of the noise;* For radiotelephone services, the signal-to-noise ratio required in the audio band must be specified, andfrom this the signal-to-noise ratio required in the radio-frequency band is established.

S.P. 1A/III— 158 —- the resulting interference effects on actual reception, taking account of the methodof detection, and of filtering prior to and following detection;
2.2.5 interference effects of co-channel signals representing the various classes of emission,
taking account of the spectral and statistical (fading) characteristics of the interfer­
ing signal;
2.2.6 monthly mean signal-to-noise ratios and signal-to-interference ratios, required forcircuits of various lengths and directions, to meet the acceptable standard values ofcircuit performance (§2.1) during the specified percentage of the time, taking into
account;- t h e distribution within an hour of the mean values of the short-term (fading) dis­tributions of signals and noise,- t h e distribution, within a month or season, for a given hour of the hourly meanvalues of the signal strengths and atmospheric noise levels (Report 322).
Note. - The monthly mean values of atmospheric noise for various time blocks, and informationon the distribution of values within the month, is given in Report 322; with regard to monthly
mean values of signal strength, and distribution of hourly values within the month, until
such time as C.C.T.R. adopts information on this subject, other standard references may
be used such as U.S. National Bureau of Standards Circular No. 462.
This study is intented to lead to revisions or replacement of Recommendations 240, 339-1
and 340.
2.3 Minimum bandwidth required for satisfactory transmission and reception of the intelli­gence, in a complete system (this is not the question of “ bandwidth necessarily occupied ”,
involving the capability of the transmitting system to avoid radiation outside the band needed
for communication, which is included in Study Programme 5A/1).
3.
3.1
3.2
, 3.3
3.4

Determination of adjacent channel signal-to-interference protection ratios, and frequency
separations between various classes of service, considering
the use of effective receiving band-pass filters no wider than necessary for satisfactory recep­
tion (see § 2.3 above, and Recommendations 237, 330 and 331-1);
the bandwidth occupied by the interfering transmission;
the frequency tolerance and stability of the wanted and unwanted signals;
the studies of § 2.2 above relating to co-channel signal-to-interference protection ratios.

Note. - The result of this study should be presented in the form indicated in the Annex.
results are intended to lead to revision of Recommendation 240.

The

ANNEXMINIMUM PROTECTION RATIOS AND FREQUENCY SERARATIONS UNDER STABLE CONDITIONS
W anted signal

Interfering signal
Al
100 bauds

Type o f service
1
dB

A1

(

24 bauds(aural)J|

50 (bauds(printer)I

120 bauds(recorder)

f

P1

2

3
kHz

FI
2 D = 400 H z
4

1
dB

2

3
kH z

F4
4

1
dB

2

A3

A3A
3

kHz

4

1
dB

2

3
kH z

4

1
dB

2

Broadcast
3

kH z

4

1
dB

2

3

4

kH z

50 bauds(printer)J " 120 bauds|(recorder)I

200 bauds(printer A R Q )F4p h ototelegrap h y

A 3A

SSB

A3

DSB
(com m ercial)

S.P. 1A/IH

Note. - Column 1 gives the limiting values in decibels o f signal-to-interference ratio, when the occupied band o f the interfering emission either falls entirely within the passband o f
the receiver, or covers it completely. Columns numbered 2, 3 and 4 indicate the frequency separation necessary between a w anted and an interfering signal when the latter is0, 6 or 30 dB higher than the wanted signal.

q . 2/m, 3/m— 160 —QUESTION 2/III *ARRANGEMENT OF CHANNELS IN MULTI-CHANNELTELEGRAPH SYSTEMS FOR LONG-RANGE RADIO CIRCUITSOPERATING ON FREQUENCIES BELOW ABOUT 30 MHz
The C.C.I.R.,(1953)CONSIDERING(a) that lack of uniformity in the arrangement and designation of the channels in multi-channel
telegraph systems, for long-range radio circuits operating at frequencies below about 30 MHz
may give rise to certain difficulties when one transmitting station has to work with morethan one receiving station;(b) that many such systems are in use, besides the multi-channel voice-frequency telegraphsystems referred to in Question 43;
unanimously decides that the following question should be studied:what is the best way of arranging and designating the channels in multi-channel telegraphsystems for long-range radio circuits, operating at frequencies below about 30 MHz ?

QUESTION 3/III **DIRECTIVITY OF ANTENNAE AT GREAT DISTANCESThe C.C.I.R.,(1948 - 1951 - 1953)

decides to study the following question:

experimental study, by Administrations and various organizations, of the directivity ofantennae realized at great distances (taking full advantage of existing transmissions), by
any suitable method, for example, by use of mechanically or electrically steered antennae.

* Formerly Question 74(111).
** Formerly Question 81(111).

STUDY PROGRAMME 3A/III.*
IMPROVEMENT OBTAINABLE FROM THE USE OF DIRECTIONAL ANTENNAE
The C.C.I.R.,(1953 - 1956 - 1959)CONSIDERING(a) that Study Programme 1A/III requires knowledge of the improvement in the signal-tointerference ratio that can be obtained by the use of directional antennae on long-distancecircuits;(b) that the Annex to Recommendation 162-1 shows median value of discrimination in the formof gains in various arcs, relative to the optimum gain for a half-wave dipole ** at the sameheight and on the correct azimuth, when the wanted and unwanted emissions are in therange 3000-10 000 km;(c) that it is also important to know the discrimination given by the antenna, when the wanted
station or the interfering station, or both, are at much shorter range;(d) that it appears practicable to obtain some reduction of interference by using a null method
at the receiver;unanimously decides that the following studies should be carried out:

1.

determination of the signal power gain in the main lobe provided by practical directional
antennae used under actual propagation conditions, relative to a half-wave horizontal dipole **at the height of the centre of the directional antenna; the median value and cumulative
distribution with time of the values of gain during short periods (as, for example, less thanan hour), should be observed; observing periods should be suitably distributed and the data
studied on a statistical basis, so as to show dependence of results on time of day and season
for normal propagation conditions, and the effect of especially critical propagation conditions
such as encountered near time of sunrise and sunset, and at times of failure of the operating
frequency near the MUF, and at times of ionospheric disturbances;2.

determination of the signal power gain in directions outside the main lobe and/or values of
discrimination provided by the antenna between the wanted and interfering signals. The data
should include the variations with time, referred to in § 1 above, and should specify directionsor the appropriate arcs shown in Fig. 1 of Recommendation 162-1;

3.

the effects of the antenna height in increasing the number of hours of useful transmission andin the reduction of interference;4.

the usefulness of a null method of minimizing the interference. The data required to evaluate
the usefulness might consist of:
4.1 logs of commercial receiving stations, showing outages due solely to interference and therelative azimuth bearing of interfering stations,
4.2 experimental data on the use of directional antenna systems and antennae with adjustabledirections of null, under conditions where interference is experienced.

* Formerly Study Programme 81A(II1).
** The median values o f the gain can also be expressed relative to the isotropic antenna.

S.P. 3B/HI— 162 —STUDY PROGRAMME 3B/III *DIRECTIVITY OF ANTENNAE FOR FIXED SERVICES USINGIONOSPHERIC-SCATTER PROPAGATIONThe C.C.I.R.,(1959)CONSIDERING(a) that systems are at present in service using ionospheric-scatter propagation, at frequencies
above 30 MHz and that extension of use of this mode of propagation may be expected in theinternational fixed services;(b) that it is desirable to establish the preferred characteristics of such systems needed to facilitate
their international connection, and that it is particularly important to have similar or matcheddirectivity of the antennae at opposite terminals of the circuit;(c) that antenna directivity, including the characteristics of radiation pattern, gain,beamwidthand direction of the main lobe or lobes, significantly affects transmission loss, and the possi­
bility of occurrence of multipath propagation and interference to and from other services;
unanimously decides that the following studies should be carried out:

studies of the desirable characteristics of the directivity of transmitting and receiving antennae
for international fixed services, using ionospheric-scatter propagation above 30 MHz, including
gain, beamwidth and direction of the main lobe or lobes, and tolerances for the radiation
pattern outside the main lobe, taking into account:- dependence on propagation characteristics of the scattering medium, including dependence
on scattering angle, size and inhomogeneity of the scattering region;- effects of meteoric ionization, and the techniques of beam slewing and beam splitting, andhow these may depend on season and time of day;- operating frequency;- diversity;- polarization;- multipath propagation, in relation to the modulation technique used;- interference to and from other services.

* Formerly Study Programme 81 B(III).

— 163 —Q. 4/IH, 5/III

QUESTION 4/III *RADIO-RELAY SYSTEMS EMPLOYING IONOSPHERIC-SCATTERPROPAGATIONThe C.C.I.R.,(1956)CONSIDERING(a) that experiments have already shown the possibility of utilizing frequencies above 27-5 MHz
for transmission by ionospheric-scatter propagation to distances well beyond the horizon;(b) that systems using this mode of propagation are already in service;(c) that it is desirable to determine the preferred characteristics of such systems needed to facilitate
their international connection;(d) that the frequency bands, which might be used for such systems, are already intensively usedby other services;
unanimously decides that the following question should be studied:1.

how do the propagation characteristics, relevant to the exploitation of systems employing
ionospheric-scatter propagation, vary with frequency;

2.

to what extent are systems employing this mode of propagation liable to interfere with eachother and with other services operating on the same or neighbouring frequencies;

3.

what are the radio-frequency and baseband characteristics of such systems, which it is essential
to specify for the transmission of telephony or telegraphy to enable two systems to be inter­
connected, and what values should be specified ?

QUESTION 5/III **COMMUNICATION THEORYThe C.C.I.R.,(1951 - 1956 - 1966)CONSIDERING(a) that for the transmission of a given quantity of information through a given telecommunica­tion channel with a given power, either in a given time using a minimum bandwidth, or witha given bandwidth in a minimum time, the theoretical formulae suggest the use of pulsecode modulation;(b) that the theoretical coding method for improving on this involves a long delay;
unanimously decides that thefollowing question should be studied :what improvement may be expected in the efficiency of existing communication systems
as a result of the application of the theory of information ?

* Formerly Question 132(111).
** Formerly Question 133(111).

S.P. 5A/III— 164 —STUDY PROGRAMME 5A/III *COMMUNICATION THEORYThe C.C.I.R.,(1951 - 1953 - 1956 - 1963 - 1966)CONSIDERING(a) that, in view of the increasing congestion of the radio-frequency spectrum and telecom­
munication circuits, it would be advantageous to discover technical methods of decreasing
the bandwidth, the transmission time or the transmitted power necessary for the transmissionof a given quantity of information;(b) that present studies seek mainly to perfect established systems, whereas recent theories seem
to show that these systems occupy several times the band widths strictly necessary for thetransmission of the required information at the required speed;(c) that, even with existing systems, it is not possible to reduce the bandwidth to that strictly
necessary because of unpredictable noise, natural and man-made interference, and complex
propagation conditions; a margin of bandwidth is necessary to decrease distortion and thefrequency of errors due to these phenomena;(d) that it is not certain that existing codes, some at least of which were not designed in the lightof phenomena peculiar to radio propagation, are making the best use of the occupied band­
width;(e) that, to assess the effectiveness of any error-detecting or error-correcting codes over radio
circuits, it is essential that realistic error statistics be known for these radio circuits;
unanimously decides that the following studies should be carried out:1.

the review of the various codes in use and the study of new codes, leading to an economy
of bandwidth or transmission time for a given quantity of information and a given qualityof transmission, taking into account the phenomena peculiar to radio propagation and therelative merits of the various existing systems of modulation from the point of view of the
bandwidth occupied in relation to the amount of information transmitted in a given time fora given power;
2. the determination of the transmission capacity obtainable in practice with regard to systems
with:
2.1 full duplex operation;
2.2 half-duplex operation (common frequency or otherwise);
2.3 simplex operation;3.

the experimental determination of error statistics for operating radio circuits. The resultof such experiments should provide a table, showing the frequency of occurrence of m errors
in a sequence of n digits {rn = 0, 1, 2, 3 . ..). Where this is possible, it may be useful togive information on the occurrence of the different types of errors. The suggested range ofvalues for n is between 7 and about 100;4.

the study, in conjunction with the U.R.S.I., of the methods of communication theory thatare best suited for practical application.
Note. - The information asked for under §§ 2 and 3 should, where possible, state the conditionsof the channel: signal-to-noise ratio, fading characteristics, special noise or channel disturb­
ances, interference from other stations, etc.

* Formerly Study Programme 133A(III).

Q. 6/III, 7/III— 165 —QUESTION 6/III *U SE O F IN T E R M IT T E N T C O M M U N IC A T IO N IN R A D IO T E L E G R A PH Y
The C.C.I.R.,(1959)CONSIDERING(a) that the method of intermittent communication is coming into use, particularly for circuits

using meteoric ionization;(b) th a t in te r m itte n t c o m m u n ic a t io n o f te n e n a b le s th e m e a n te le g r a p h sp e e d t o b e in c r e a s e d
c o n s id e r a b ly , fo r a g iv e n q u a lity o f se r v ic e , w h e n th e s ig n a ls a n d in te r fe r e n c e a t th e rec e iv e r
a re r a n d o m in c h a r a c te r ;(c) th a t in su ffic ie n t d a ta a re s o far a v a ila b le c o n c e r n in g th e fie ld s in w h ic h it w o u ld b e o p p o r tu n e
to a p p ly t h e p r in c ip le o f in te r m itte n t c o m m u n ic a t io n ;u n a n im o u s l y d e c id e s

th a t th e f o llo w in g q u e s tio n s h o u ld b e s tu d ie d :1.

u n d e r w h a t c o n d itio n s is th e u s e o f in te r m itte n t c o m m u n ic a t io n a d v a n ta g e o u s in r a d io t e le g r a p h y ;2.

w h a t a d v a n ta g e s , a s r e g a rd s te le g r a p h sp e e d , c a n b e e x p e c t e d fr o m th e u s e o f in te r m itte n t
c o m m u n ic a t io n u n d e r v a r io u s c o n d itio n s , a s c o m p a r e d w ith t h e u s u a l u n in te r r u p te d m e th o d ;3.

w h a t is th e m o s t r a tio n a l c o u r s e to b e f o llo w e d in th e c o n s t r u c t io n o f e q u ip m e n t fo r t h e u seo f in te r m itte n t c o m m u n ic a t io n u n d e r v a r io u s c o n d itio n s ?

QUESTION 7/III **IN FL U E N C E O F FR E Q U E N C Y D E V IA TIO N S A SSO C IA TED W IT H
PA SSA G E T H R O U G H T H E IO N O S P H E R E O N H F R A D IO C O M M U N IC A T IO N S
The C.C.I.R.,(1956 - 1959 - 1966)CONSIDERING(a) that Recommendation 246-1 recommends that, for frequency-shift systems working on two
conditions only and operating between 3 and 30 MHz ,the values of frequency-shift should
be 200, 400, and for modulation rates above 250 bauds, 500 Hz;(b) that preferred values for the channel spacing and frequency-shifts of multi-channel voice-frequency telegraph systems for use on H F radio circuits are given in Recommendation 436;(c) that study of frequency deviations, associated with passage through the ionosphere, has

shown that the resultant frequency variations may reach values of a few cycles per second,
while instantaneous deviations may reach much higher values (see Report 111 and the Annex
to Recommendation 349-1);* Formerly Question 180(111).
** This Question replaces Questions 181 and 182.

Q. 7/IH, 8/m— 166 —
unanimously decides th a t th e f o llo w in g q u e s tio n s h o u ld b e stu d ie d :1.

w h a t a re th e s ta tistic a l d is tr ib u tio n s o f fr e q u e n c y d e v ia t io n a s s o c ia t e d w ith p a s s a g e th r o u g h
th e io n o s p h e r e in m a g n itu d e , d u r a tio n a n d fr e q u e n c y o f o c c u r r e n c e ;2.

w h a t m in im u m v a lu e o f fr e q u e n c y -s h ift is re q u ir e d fo r fr e q u e n c y -s h ift s y s te m s o p e r a tin g b y
H F io n o s p h e r ic p r o p a g a tio n , t o t a k e in t o a c c o u n t:
- th e fr e q u e n c y s ta b ility o f th e e q u ip m e n t (s e e R e c o m m e n d a t io n 3 4 9 -1 );- th e fr e q u e n c y d e v ia tio n s referred t o in § 1 ?

QUESTION 8/III *FREQUENCY-SHIFT KEYINGThe C.C.I.R.,(1948 - 1959)CONSIDERING(a) that frequency-shift keying is employed in radiotelegraphy for the fixed services and it has
also been extended to the mobile services;(b) that it is desirable to standardize the main operating characteristics of systems employing
frequency-shift keying;(c) that various technical factors influence the choice of operating characteristics in such systems,
in particular:
c.a the overlap of marking and spacing signals due to multipath propagation (in this respecta small deviation is preferable);c.b the possible advantage of frequency diversity for reception (an advantage which increases
with deviation);c.c economy of bandwidth and the consequent necessity for controlling the shape of the trans­mitted signals;
c.d instability of frequency, which is one reason for the relatively large deviation employed inmany existing equipments;
c.e the choice of receiving systems, whether with separate filters or with frequency discriminator;
unanimously decides that the following question should be studied:1.

fixation of one or more standard values of deviation for fixed and mobile services in thevarious frequency bands, having regard to the various factors, in particular:- the frequency spectrum resulting from the keying operation;- the degree of frequency diversity desired;- economy of bandwidth;- instability of frequencies;

2.

compilation of a standard terminology regarding the characteristics of systems employing
frequency-shift keying.

* Formerly Question 183(111).

— 167 —S.P. 8A/IH, Q. 9/III

STUDY PROGRAMME 8A/III *FOUR-FREQUENCY DIPLEX SYSTEMSrhe C.C.I.R.,(1956- 1959)CONSIDERING(a) that there are in use, in the fixed radiotelegraph services, operating between 2 MHz
and 27 MHz, four-frequency diplex (or twinplex) systems, in which each of four frequencies isused to transmit one of the four possible combinations of mark and space signals correspond­
ing to two telegraph channels; it being understood that either or both of the two telegraphchannels may be sub-channelled by time-division methods and that the use of such systems
may be extended;(b) that it is desirable to standardize the main characteristics of four-frequency diplex systems;(c) that it may sometimes be necessary to employ the same radio transmitter to work with morethan one receiving station;(d) that various technical factors influence the choice of operating characteristics in such systems,
in particular:- economy of bandwidth and the consequent need to control the shape of the transmitted
signals;- a relatively wide spacing between adjacent frequencies may be necessary for high telegraphspeeds;- the signal distortion due to propagation conditions;- the instability of the characteristics of certain receiver and transmitter elements, such as
oscillators, filters or discriminators;
unanimously decides that the following study should be carried out:

the determination of the relation between the minimum frequency spacing and the telegraphspeed over the range of telegraph speeds in practical use. This should be determined for bothsynchronous and non-synchronous operations.

QUESTION 9/III **USE OF COMMON-FREQUENCY SYSTEMSON RADIOTELEPHONE CIRCUITSThe C.C.I.R.,(1963 - 1966)CONSIDERING(a) that relief of the present congestion of the H F (decametric) band is a matter of urgency;(b) that, in certain cases, the use of the same carrier frequency in both directions of a radio­
telephone circuit (in combination with techniques that prevent simultaneous transmission
in both directions) may result in economies in spectrum utilization on a radiotelephone
circuit;* Formerly Study Programme I83B(III).
** This Question replaces Question 233.

Q .9/III, 10/111
u n a n im o u s l y d e c id e s— 168 —
th a t th e f o llo w in g q u e s tio n s h o u ld b e s tu d ie d :1.

in w h ic h c a s e s d o e s th e u s e o f th e sa m e fr e q u e n c y in b o th d ir e c tio n s o f tr a n s m is s io n resu lt
in m o r e e ffe c tiv e sh a r in g o f fr e q u e n c ie s;2.

in su c h c a s e s :2.1

w h a t a re th e c h a r a c te r is tic s t o b e sp e c ifie d fo r r a d io t e le p h o n e sy s te m s u s in g th e p r in c ip le so f c o m m o n - fr e q u e n c y o p e r a tio n ;2 .2 w h a t s h o u ld b e t h e m in im u m d iffe r e n c e in le v e l a t th e in p u t t o th e r e c e iv e r , b e tw e e n th er e c e iv e d sig n a l f r o m t h e d is ta n t s t a t io n a n d sig n a ls f r o m th e n e a r b y tr a n sm ittin g s ta tio n ,t o a v o id in te r fe r e n c e b e tw e e n t h e w a n te d s ig n a l a n d th a t fr o m th e n e a r b y tr a n sm itte r o p e r a t­
in g o n th e sa m e f r e q u e n c y ;2.3

t o w h a t e x te n t w ill th e u s e o f tr a n s m ittin g a n d r e c e iv in g a n te n n a e w ith d ifferen t tr a n s m is s io n
c h a r a c te r is tic s r e d u c e th e p o s s ib ilit ie s o f a p p lic a tio n o f th is te c h n iq u e ;2.4

t o w h a t e x te n t w ill th e p o s s ib ilitie s o f a p p lic a tio n o f th is te c h n iq u e b e r e d u c e d b y t h e p r e s e n c eo f d iffe r e n t n o is e le v e ls a t th e r e c e iv in g lo c a t io n s ;2.5

w h a t o th e r fa c to r s s h o u ld b e t a k e n in to a c c o u n t w h e n p la n n in g su c h sy s te m s , fo r e x a m p le :- n o n -lin e a r itie s in th e tr a n s m ittin g a n d r e c e iv in g e q u ip m e n t,
- ca rrier -filter b a n d w id th ,- fr e q u e n c y sta b ility o f th e e q u ip m e n t ?

QUESTION 10/HI *USE OF DIRECTIONAL ANTENNAE IN THE BANDS 4 TO 27 5 MHz
Limitation of radiation outside the direction necessary for the service
THE INTERNATIONAL FREQUENCY REGISTRATION BOARD,

the request by the Panel of Experts in Recommendation No. 38 of its Final Report,
Geneva, 1963, and a f t e r c o n s i d e r i n g :‘i n v ie w o f(a) that there is serious congestion in the frequency bands between 4 and 27-5 MHz;(b) that there is a need to adopt methods and regulations for the solution of the frequency
problems with which Administrations are confronted in the use of these bands;/ c) that occupation of the radio-frequency spectrum is represented, not only in time and band­
width, but also in the spatial distribution of the radiated power;( d) that this latter distribution can be effectively controlled by the use of directional antennae:(e) that the intent of Articles 12 and 14 of the Radio Regulations, Geneva, 1959, would seem tojustify further explicit requirements for the use of directionnal antennae in the bands between
4 and 27-5 MHz, as well as for quantitative limitation of the intensity of radiation in directions
other than that required for the service;* Formerly Question 280(111).

— 169 —a n d in v ie w o f

Q. 10/HI, 11/HI

No. 180 of the International Telecommunication Convention, Geneva, 1959;d e c id e s

to submit the following urgent question to the C.C.I.R.:

what are reasonable standards for the directivity of antennae in the various types of radio
services, and for various distances, in the bands between 4 and 27-5 MHz, including the widthof the main beam and the allowable intensity of radiation (effective radiated power) in direc­
tions of azimuth outside the main beam (such standards should reflect due regard for practicalconsiderations of construction and cost) ?

Q U E ST IO N 11/III *AUTOMATIC CONTROL OF THE OUTPUT POWER
OF THE TRANSMITTERS
THE INTERNATIONAL FREQUENCY REGISTRATION BOARD,

the request of the Panel of Experts in Recommendation No. 38 of its Final Report,
Geneva, 1963, and a f t e r c o n s i d e r i n g :(a) that No. 694 of the Radio Regulations, Geneva, 1959, requires that all stations shall radiate
only as much power as is necessary to ensure a satisfactory service;(b) that nevertheless, for a considerable part of the time, stations using frequencies in the bands
between 4 and 27-5 MHz, radiate powers considerably in excess of those necessary to ensure asatisfactory service;(c) that manually operated methods of adjusting the power of transmitters are not fully adequate
to meet No. 694 of the Radio Regulations;(d) that the use of automatic control of the output power of transmitters would assist in reducing
the congestion in the H F spectrum;in v ie w o f

a n d in v ie w o f

No. 180 of the International Telecommunication Convention, Geneva, 1959;d e c id e s

to submit the following urgent question to the C.C.I.R.,

what are the most suitable methods for automatically controlling the output power of radiotransmitters operated in the H F bands to ensure, as far as is practicable, that the radiatedpower is no greater than is necessary to ensure a satisfactory service ?

* Formerly Question 281(111).

q . 12/in , 13/m

— 170 —QUESTION 12/HI
DISTORTION CHARACTERISTICS REQUIRED FOR SINGLE-SIDEBAND
AND INDEPENDENT-SIDEBAND SYSTEMS USED FOR HIGH-SPEED
DATA TRANSMISSION OYER HF RADIO CIRCUITSThe C.C.I.R.,(1966)CONSIDERING(a) that an increasing demand is noted for high-speed data transmission over H F radio circuits
and further increase in such demand may be expected;(b) that recent developments are leading to systems having greatly improved bandwidth efficiency,
i.e. a larger capacity in bits per second per unit bandwidth;(c) that it is desirable that the effects of the random variations and disturbances in the propaga­tion medium be the ultimate factors governing the performance obtainable with such systems;(d) that the characteristics of a “ 3 kHz channel” have largely been evolved from the use ofsuch channel for telephony;u n a n im o u s l yd e c id e sthat the following question should be studied:

1. what are the permissible limits of amplitude, phase and delay distortion on H F radio circuits
intended for high-speed data transmission (e.g. 2400 bits/s and above), excluding a priori
effects due to the radio propagation medium;2.

are these limits likely to be exceeded in H F systems of the fixed service currently available;

3.

should new channel arrangements for data-transmission be recommended, differing fromthe present standards for the 3 kHz channel, as defined in Recommendation 348-1 for radio­
telephony;

4.

in evaluating high-speed data transmission systems, what statistical parameters should be
used to describe the radio propagation medium and what values should be considered ?

Q U E ST IO N 13/111

IMPROVEMENTS IN THE PERFORMANCE OF
HF RADIOTELEPHONE CIRCUITSThe C.C.I.R.,(1966)

c o n s id e r in g(a) that there is a need to improve the quality of transmission of H F radiotelephone circuits;

— 171 —q . 13/m , 14/rn, is /m(b) that the use of diversity techniques may offer the prospect of such an improvement;(c) that other methods of improvement, e.g. the adaptation of compandor principles might
become available;(d) that these techniques might be used either separately or in combination;u n a n im o u s l yd e c id e sthat the following question should be studied:1.

what are the various methods whereby diversity can be obtained on H F radiotelephone
circuits;2.

what other methods are available for obtaining such improvements;

3.

what improvement of performance is to be expected with these methods ?

QUESTION 14/III
AUTOMATICALLY CONTROLLED RADIO SYSTEMSIN THE HF FIXED SERVICEThe C.C.I.R.,(1966)CONSIDERING(a) that successful development of fully automatic transmitting and receiving terminals may
offer important improvements in efficiency, reliability and economy of operation in the fixed
service;(b) that certain features of automatic control may require cooperation and exchange of informa­tion between transmitters and receivers, as for example, for change of frequency and power;
u n a n im o u s l y d e c id e sthat the following question should be studied:1.

what features of automatically controlled radio systems in the H F fixed service require
cooperation between Administrations;2.

what are the preferred methods of exchanging and utilizing such information ?

QUESTION 15/111
THE OPERATIONAL USE OF EFFICIENCY FACTOR
The C.C.I.R.,(1966)CONSIDERING(a) that the efficiency factor discussed in Study Programme 18A/III is very useful for defining
and determining the quality of a communication channel using error correction by automatic
repetition;(b) that the efficiency factor could be of use in the operation of radio telex circuits with fully
automatic switching;q . is /m , i6 /m— 172 —(c) that, however, data justifying the fixing of definite values of the efficiency factor for purposesof switching a radio channel into or out of a telegraph network have not yet been accumulated
in sufficient quantity;
u n a n im o u s l y

1.

d e c id e sthat the following question should be studied:to establish when:- a radiotelegraph channel should be switched into the network;- an operational radiotelegraph channel should be switched out of the network;

1.1 can a single value for the efficiency factor (e.g. 80%) be recommended to C.C.I.T.T. forboth cases;
1.2 if two values of the efficiency factor are necessary, what should be the preferred values;2.

are the values for the time intervals given below acceptable or are other values to be preferred;

2.1 20 s for the efficiency factor to stay above 80% before a call can be set up;
2.2 60 s for the efficiency factor to stay below 80 % before an existing call should be interrupted;
3.

what techniques should be used to evaluate whether the efficiency factor during the 20 sinterval can. be considered to have been above 80 %, or during a 60 s interval can be consi­
dered to have fallen below 80%?

QUESTION 16/111
TRANSMISSION CHARACTERISTICS
OF HF RADIOTELEPHONE CIRCUITS(1965)The INTERNATIONAL TELEGRAPH a n d
in v it e s t h e

TELEPHONE CONSULTATIVE COMMITTEE,

C.C.I.R. to study the following question:

would it be possible to improve the transmission characteristics of H F radiotelephone cir­
cuits to provide an acceptable service for automatic telephone traffic using C.C.I.T.T.
signalling systems Nos. 4 and/or 5 ?
Note 1 . - For example, a loss probability of 1/1000 due to transmission difficulties on thetelephone channel could be admitted.
Note 2. - Specifications for the two-frequency signalling system (C.C.I.T.T. System No. 4)
appear in Vol. VI of the Red Book, pages 126-135 and for the C.C.I.T.T. intercontinental
signalling system No. 5 in Doc. AP/III-No. 26, pages 22-46.
Note 3. - This Question follows on the conclusions reached by C.C.I.T.T. Study Group XIII
in regard to the use o f H F radiotelephone circuits for the routing plan for automatic tele­phone traffic:- the use of H F radio circuits in a semi-automatic intercontinental group which also includes
cable circuits is not acceptable unless the radio circuits offer a grade of service that is* Formerly Question 317(111).

— 173 —S.P. 17A/III

almost always comparable to that of the cable circuits, both from the transmission andthe signalling aspects;- for the time being, the use of H F radio circuits in automatic operation cannot be considered.

STUDY PROGRAMME 17A/III *VOICE-FREQUENCY (CARRIER) TELEGRAPHY ON RADIO CIRCUITSThe C.C.I.R.,(1951 - 1953 - 1959 - 1966)CONSIDERING(a) that different methods are now in use for voice-frequency telegraphy on radio circuits operat­
ing below 30 MHz subject to fading, noise and interference;- either using equipment normally designed for landline working and suitably adapted
for radio;- or using equipment especially designed for radio working;(b) that studies carried out so far show that it is impossible to compare transmission systems
in which the two significant conditions of modulation are obtained either by the frequency
exchange method or by the method of frequency-shift of a single voice-frequency oscillator,
without taking into account all the properties of the equipment and of the propagation
medium;(c) that experience in reception of voice-frequency telegraphy over radio circuits has shownthat frequency-modulated voice-frequency telegraph equipment for use on fadio circuits
may differ substantially from voice-frequency landline equipment; this equipment may,therefore, have to be designed and constructed with their special purpose in mind;
u n a n im o u s l yd e c id e sthat the following studies should be carried out:

1. comparisons of the different systems used to transmit and receive voice-frequency telegraphy
on radio circuits subject to the effects of fading, multipath propagation, noise and inter­
ference, with a view to standardizing their characteristics, taking into account the following
techniques and factors:- frequency-shift keying of one voice-frequency oscillator;- transmitting the two significant conditions of modulation by the two-tone method;- other modulation systems, e.g. phase-modulation systems, or systems of modulation
employing more than two significant conditions of modulation;- reception by discriminator or separate filters;
2.

influence of the modulation index (frequency shift (Hz)/modulation rate (bauds)) and thechannel spacing on the error-rate.

* This Study Programme, which replaces Study Programme 43A, does not derive from any Question understudy.

S.P. 18A/III— 174 —STUDY PROGRAMME 18A/III *EFFICIENCY FACTOR
The C.C.I.R.,(1966)CONSIDERING(a) that the efficiency factor, as defined in the “ List of definitions of essential telecommuni­
cation term s” (Part 1, 1961, No. 33.23; see also Recommendation 345), is very useful for
defining and determining the quality of a communication channel using error-correction
by automatic repetition;(b) that measurements of the efficiency factor could be of use in the operation of radiotelegraphtelex circuits with fully automatic switching;u n a n im o u s l yd e c id e sthat the following studies should be carried out:1.

the way in which measurements of the efficiency factor may be used to analyse and predictthe performance of systems with error-correction by automatic repetition;2.

the way in which measurements of the efficiency factor may be used on radio circuits which
are part of networks with fully automatic switching;3.

development of standards for appropriate equipment for assessing the efficiency factor,
taking into account the following:
3.1 measurement of the efficiency factor with time intervals appropriate to:
3.1.1 the general case of analysing the performance of systems with error-correction by auto­
matic repetition;
3.1.2 the particular case of analysing radio circuits which are part of networks with fully
automatic switching;
3.2 establishment of suitable criteria indicating the operational quality of the system or theradio circuit, and establishment of two specific conditions corresponding to the requirements
for setting up a call and the necessity of interrupting an existing call.
Note 1 . - Measurements should preferably be carried out in successive periods based ontime intervals of 10 min for long period evaluation and of 20 s for detailed analyses, conver­ted for reasons of convenience into the equivalent number of character cycles and the follow­
ing information should be recorded:- the number of telegraph signals repeated;- the number of telegraph signals incorrectly translated by the telegraph apparatus;- the total number of telegraph signals received by the telegraph apparatus;- the type of telegraph apparatus used;- the type of error-correction equipment in use, with an indication of the number of tele­graph signals in the repetition cycle and the operational conditions during the non-print
cycle;- modulation rate used in the telegraph channel and in the radio channel;- date and time of observation.
Note 2. - Measurements should be made throughout the day, using normal operating fre­quencies. If possible, an attempt should be made to determine whether a correlation exists
between the results of the efficiency factor measurements and the performance of the radio
circuit as based on observations at the radio receiving stations.
* This Study Programme, which replaces Study Programme 186, does not derive from any Question understudy.

— 175 —S.P. 18A/III, 19A/III

Note 3. - When the radio circuit is part of a network with fully automatic switching, theC.C.I.T.T. is considering:- fixing one limit (80%) for the efficiency factor on operational circuits with fully automatic
switching;- a time interval of 20 s during which this limit must be exceeded before a call can be set u p ;- a time interval of 60 s during which the efficiency factor has remained below this limit
before an existing call can be interrupted.

ST U D Y P R O G R A M M E 19A/III *IDENTIFICATION OF THE CARRIER FREQUENCY RELATIVE
TO THE ASSIGNED FREQUENCY OF AN EMISSION
The C.C.I.R.,(1963)CONSIDERING(a) that in certain classes of emission, notably single-sideband and suppressed or reduced carriertypes, the carrier frequency is not in the centre of the assigned frequency band and does
not therefore coincide with the assigned frequency;(b) that the exchange of operating information, between the terminals of a radio circuit, is faci­
litated if there is a simple method of identifying the carrier frequency of such an emission;(c) that the assigned frequency forms a convenient reference, relative to which the carrier fre­quency may be located;
u n a n im o u s l yd e c id e sthat the following studies should be carried out:

investigation of the application of the method of carrier frequency identification (seeR eport 202) and assessment of the advantages to be gained by the use of such a method.

* This Study Programme, formerly Study Programme 187(111), does not derive from any Question understudy.

S.P. 20A/III— 176 —STUDY PROGRAMME 20A/III *OPERATIONAL IONOSPHERIC SOUNDING AT OBLIQUE INCIDENCE
The C.C.I.R.,(1965- 1966)CONSIDERING(a) that sounding of the ionosphere at oblique incidence has proved to be an effective method
for observing the behaviour of H F radio waves propagated via the ionosphere;(b) that the information obtained from oblique incidence sounding may be used to improve
the performance of some long-distance radio circuits;(c) that such sounding carried out as an operational procedure may give rise to harmful inter­
ference, particularly if used indiscriminately;(d) that with increasing use difficulty may be experienced in identifying emissions from parti­
cular sounders;
u n a n im o u s l y

1.

2.

d e c id e sthat the following studies should be carried out:

the methods by which the information obtained from sounding of the ionosphere at oblique
incidence (see Study Programme 12A/VI) could be used to improve the operational efficiency
of long-distance radio circuits;Ithe limitations, if any, in such characteristics as emitted power and number of simultaneousemissions that are desirable to avoid harmful interference;3.

the measures necessary to enable such emissions to be identified;4.

the preferred characteristics of the equipment used for operational ionospheric soundingthat will promote effective co-operation between the greatest number of users.

* This Study Programme, which replaces Study Programme 208, does not derive from any Question understudy.

177 —

LIST OF DOCUMENTS CONCERNINGSTUDY GROUP III (PERIOD 1963-1966)
Doc.

OriginTitle

Reference

III/l

United Kingdom

Operational ionosphere sounding at oblique
incidence

S.P. 197(VI)III/2 andCorr.lC.C.I.R. Secretariat

Remote control signals for fascimile transmissions. Texts of the Illrd Plenary Assemblyof the C.C.I.T.T.

Rep. 201

III/3 andCorr. 1

C.C.I.R. Secretariat

Standardization of phototelegraph systems
for use on combined radio and metallic
circuits. Texts of the Illrd Plenary Assem­
bly of the C.C.I.T.T.

Rec. 344

III/4 andCorr.lC.C.I.R. Secretariat

Facsimile transmission of documentary matterover combined radio and metallic circuits.
Texts of the Illrd Plenary Assembly of the
C.C.I.T.T.

Q. 232

III/5 andCorr.lC.C.I.R. Secretariat

Voice-frequency(carrier) telegraphy on radio
circuits. Texts of the Illrd Plenary Assemblyof the C.C.I.T.T.

S.P. 43A

III/6 andCorr.lNetherlands

Draft Recommendation - Telegraph, system for isolated areas and for the mobile

S.P. 3A(III)

III/7

United States ofAmerica

Diversity techniques for HF radio-telegraphy

Q. 225(11),3(111)
S.P. 3A(III)

III/8

United Kingdom

The relative performance of telegraph sys­
tems using frequency-division multiplex on
HF radio circuits

S.P. 43A

III/9

United States ofAmerica

Draft Report - Use of common-frequency
systems on international radiotelephone
circuits

Q. 233111/10

United States ofAmerica

Draft of new Question - Use of diversity on
international HF radiotelephone circuits

III/llUnited States of.America

Use of diversity on international HF radio­
telephone circuits

111/12

United States ofAmerica

Bandwidth and signal-to-noise ratios incomplete systems

Rep. 195, Q.3
S.P. 3A(III)111/13

United States ofAmerica

Some aspects of the application of communica­tion theory

Q. 133
Rep. 196

111/14

United States ofAmericaFrequency stability required for single-side­band, independent-sideband and telegraphsystems to make the use of automatic fre­quency control superfluous

Q. 182
Rec. 349

111/15

United States ofAmerica

Draft New Question - HF radio terminal
equipment characteristics for high speed
data transmission

111/16

United States ofAmerica

Revisions for Report 109 - Radio systems
employing ionospheric scatter propagation

Rep. 109
Q. 132

111/17

United States ofAmerica

Revision of Recommendation 344 - Trans­mission of half-tone pictures over radio
circuits

Rec. 344
Q. 95

12

I

— 178 —-III/19111/20111/21

United States ofAmerica
United Kingdom
Federal Republic of
Germany
Federal Republic of
Germany

111/22 andCorr.lFederal Republic of
Germany

111/23111/25Federal Republic of
Germany
Federal Republic of
Germany
United Kingdom

111/26

Netherlands

m/27
111/28Study Group III
Japan

111/29111/30 andCorr.l111/31 andCorr.l111/32

Japan
Japan

111/33

111/35International Working
Party III/lInternational Working
Party III/l
U.R.S.I.

111/36

Canada111/37

U.S.S.R.

111/38111/39U.S.S.R.
U.S.S.R.

111/40111/41

Study Group III
United States ofAmerica
Working Group III-D

111/24111/34111/42

Title

OriginDoc.

Ill/18Japan
W.M.O.

Draft Recommendation - Measurement ofisochronous telegraphic distortion
Radiotelegraph circuits used in automatic
switched networks
Voice-frequency (carrier) telegraphy on radio
circuits
Factors affecting the quality of performanceof complete systems of the fixed services(automatic error correction) - Proposed
modifications to Recommendation 342
Factors affecting the quality of performanceof complete systems of the fixed services Draft Recommendation concerning a single­
channel ARQ system
Efficiency factor

Reference

Rec. 345
S.P. 3B(III)Q. 43
S.P. 43A
Rec. 342
S.P. 3A(III)
S.P. 3A(III)

S.P. 186

Efficiency factor

S.P. 186

Improvement obtainable from the use of
directional antennae - Measurements ofvertical angles of wave-arrival
Proposed modification to Recommenda­
tion 349
Interim Report by the Chairman
Modulation index for voice-frequency tele­graphy on radio circuits
Efficiency factor
Use of common-frequency systems on inter­national radiotelephone circuits
Relation between the density of a picture
and the degree of modulation
Standards for the facsimile transmission of
meteorological charts
Optimum use of the radio-frequency spectrum

S.P. 81A

Operating sensitivity of a radio receiving
systemCommunication theory

Res. 1

Operational oblique incidence ionospheresounding
Reliability calculation of radiocommunica­tion on short waves
Supplement to Recommendation 340
New Draft Question - Technical character­istics of automatized radiolink equipment
Summary record of the first meeting
Draft Recommendation - Use of directional
antennae in the bands 4 to 27-5 Mc/s
Draft Question - Distortion characteristics
required for single-sideband and independentsideband systems used for data transmission
over HF radio circuits

Rec. 349

S.P. 43A
S.P. 186
Q. 233Q. 95
Rep. 201
Q. 232
Res. 1Q. 133
Rep. 196
S.P. 197(VI)Rec. 340
Rec. 340

Q. 280

— 179 —ReferenceDoc.

OriginTitle

111/43

Working Group III-C

Draft Report - Operating threshold of aradio receiving system

111/44 andRev. 1
III/45 andRev. 1

Working Group III-B

Proposed modifications totion 349
Proposed modification totion 344

Working Group III-A

Recommenda­
Recommenda­

111/46

Working Group III-A

Draft Report - Remote control signals for
facsimile transmission

Q. 232111/47 andRev. 1

Working Group III-D

Proposed modifications

Rec. 166
Q. 133
S.P. 3A,
133A

111/48Working Group III-D

Draft Question - Factors affecting the qualityof performance of complete systems of the
fixed services

111/49Working Group III-A

Proposals concerning those texts of the XthPlenary Assembly which are of interest to
Working Party III-A-3

111/50C.C.I.R. Secretariat

List of documents issued (III/l to 111/50)

III/51 andRev. 1

Working Group III-B

Draft Recommendation - Arrangement ofvoice-frequency telegraph channels on radio
circuits

111/52 andCorr. 1

Working Group III-B

Draft Report - The relative performance oftelegraph systems using frequency-divisionmultiplex on HF radio circuits

111/53

Working Group III-B

Draft modification to Annex I of Recom­
mendation 342

m/54,

Working Group III-A

Report - Use of common-frequency systems
on international radiotelephone circuits

Q. 233

111/55Working Group III-D

Draft Report - Some aspects of the applica­tion of communication theory

Q. 133

111/56

Working Group III-A

Draft statement for inclusion in the reportby the Chairman, Study Group III

111/57

Working Group III-A

Draft addition to Report 107 - Directivityof antennae at great distances

111/58Working Group III-A

Draft Question - Improvements in theperformance of the HF radiotelephone
circuits

111/59Working Group III-A

Draft Study Programme - Operational iono­
spheric sounding at oblique incidence

111/60Working Group III-D

Proposed amendments(Doc. 11/36)

111/61

Study Group III

Summary record of the second meeting

111/62Working Group III-A

Draft Question - Automatic radio-links in
the HF fixed service

111/63

Working Group III-B

Draft Question - Influence on high-frequency
communications of frequency deviations
associated with passage through the ionosphere111/64

Working Group III-B

Draft Study Programme - Efficiency factor

Rev. 1 andCorr. 1

to

Draft

ReportS.P. 43A

Q. 81

— 180 —Doc.

OriginTitle

111/65Working Group III-B

Proposed modifications to Recommenda­
tion 246 - Frequency-shift keying

111/66

Working Group III-A

Draft note for inclusion in the report by the
Chairman, Study Group III

111/67

Working Group III-A

Draft note for inclusion in the report by the
Chairman, Study Group III

III/68Working Group III-A

Draft - Statement for inclusion in the reportby the Chairman, Study Group III

111/69Working Group III-A

Revision of Question 233 (III) - Use ofcommon-frequency systems on radiotelephone
circuits

111/70Working Group III-B

Draft Report - Voice-frequency telegraphy
on radio circuits

S.P. 43A

111/71,
Corr. 1 andRev.lWorking Group III-B

Draft Report - Use of radio circuits inassociation with 5-unit start-stop apparatus

S.P. 43A

111/72Working Group III-A

Draft Report - Operational ionosphericsounding at oblique incidence

111/73

Working Group III-A

Proposed modifications to Report 109 Radio systems employing ionospheric scatter
propagation

111/74

Working Group III-A

Proposals concerning those texts of the XthPlenary Assembly which are of interest to
Sub-Working Party III-A-3

III/75Working Group III-A

Text to be included in the report of the
Chairman, Study Group III

111/76

Working Group III-A

Proposed modifications to Recommenda­
tion 348

111/77

Working Group III-A

Proposed modifications totion 335

111/78Working Group III-B

Proposed amendments to C.C.I.R. texts

111/79Working Group III-B

Draft Report - Efficiency factor

111/80Working Group III-B

Draft modification to Annex I of Recom­
mendation 342

111/81

Working Group III-A

Draft Report - Use of pre-emphasis and de­emphasis for phototelegraph transmission on
HF radio circuits

S.P. 3A(III)111/82Working Group III-B

Draft Report - Single channel Simplex tele­graph system for isolated areas and for themobile services

S.P. 3A(III)111/83,
Corr. 1 andRev. 1

Working Group III-B

Draft Report - Telegraph distortion errorrate

111/84

C.C.I.R. Secretariat

Status of texts at the end of the Interim
Meeting, Geneva, 1965

111/85111/86

Study Group III
Working Group III-C

111/87

Working Group III-B

Summary record of the third meeting
Draft Report - Optimum use of the radio­frequency spectrum
Draft note for inclusion in the report by the
Chairman, Study Group III

Reference

Recommenda­

— 181 —OriginTitle

Referencem /88

Study Group III

Summary record of the fourth meeting

111/89Study Group III

Summary record of the fifth and last meeting

111/90C.C.I.R. Secretariat

List of participants

III/91

C.C.I.R. Secretariat

List of documents (111/51 to 111/91)

111/92

United Kingdom

Automatic error-correcting system for telegraph signals transmitted over radio links Comments on Doc. III/80

HI/93

United Kingdom

Automatic error-correcting system for tele- Rec. 342
graph signals transmitted over radio links Comments on Doc. 111/53

111/94

United Kingdom

Single-channel radiotelegraph system with Draft Rec.
automatic error-correction - Comments on
Doc. 111/22

111/95

United Kingdom

An improved transmission system for HF
radiotelephone circuits

Draft Q.

III/96

United Kingdom

Voice-frequency telegraphy on radio circuits Use of 120 c/s-spaced systems for 100 baud
synchronous operation

S.P. 43A

111/97

United Kingdom

Use of directional antennae in the bands 4
to 27-5 Mc/s

Q. 280111/98

United Kingdom

Draft Rec. - Use of directiona antennae
in the bands 4 to 27-5 Mc/s

Rec. 162

111/99

United States ofAmerica

Improvements in the performance of HF
radiotelephone circuits

Q. 317
Draft Q.

III/100

C.C.I.R. Secretariat

List of documents issued (111/92 to III/100)

III/101

United States ofAmerica

Proposed modifications to Recommendation 339 - Bandwidths and signal-to-noise
ratios in complete systems

Rec. 339

III/102

Italy

Tables for the computation of distorted AM
envelopes

Draft Q.
Draft S.P.

III/103

Netherlands

Automatic error-correcting system for telegraph signals transmitted over radio links

Draft Rec.

III/104

Netherlands

Factors affecting the quality of performanceof complete systems of the fixed service

Draft S.P.

III/105(H/62)

U.S.S.R.

Sensitivity and noise factor - A method of
measuring static characteristics of radiotelegraph receivers

Q. 228Draft S.P.

III/106
and Rev.lCompanhia Portuguesa
Radio Marconi

Efficiency factor

Draft S.P.

III/107(XIII/105)

Netherlands

Single-channel telegraph system for message
broadcasting with error-correcting facility

Draft S.P.
Q. 320(XIII)

Rec. 342.
Ann. II

— 182 —Doc.

OriginTitle

Reference

Ill/108

C.C.I.R.
Secretariat

Voice-frequency telegraphy on HF radio
circuits

III/109,
Add.l
and 2

Chairman,
S.G. Ill

Report by the Chairman - Fixed service
systems

III/130(XIII/113)

F.R. of Germany

Factors affecting the quality of performanceof complete systems - Full-duplex single
channel ARQ system

S.P. 3A (III)III/lll

C.C.I.R.
Secretariat

Submission of Doc. COM XIV - No. 18of the C.C.I.T.T. Transmission channels
for facsimile telegraphy

Q. 95
Q. 232
Rec. 343, 34<

III/112(H/75)

U.S.S.R.

Design of the reception channel of an iono­
spheric-scatter link

Rec. 338

m/113

C.C.I.R.
Secretariat

Submission of Doc. XIII/82 - The introduc­tion of direct printing telegraph equipmentin the maritime mobile service - A reporton trials of an automatic single-path errorcorrecting system

Draft S.P.
Q. 320 (XIII)

III/114

United States ofAmerica

Performance of high-speed data transmission
systems on HF radio circuits

Q. 3(111)

III/l 15

United States ofAmericaComments on C.C.I.R. documents relating
to error control

Draft Q.
Q. 320(XIII)

III/116

United States ofAmerica

Study of forward-acting, burst error-correct­
ing coding systems for telegraphy and datatransmission

Draft Q.
Q. 133(XIII),
320(XIII)

III/117

United States ofAmerica

Draft of an addendum to Report C.q(III),
some aspects of the application of communica­tion theory

Draft Q.

m /118

FranceArrangement of voice-frequency telegraphchannels on radio circuits

Draft Rec.

III/l 19

FranceVoice-frequency multi-channel telegraphy on
radio circuits - Influence of channel spacing

Q. 43

III/120

Study Group III

Summary record of the first meetingm/121

Study Group III

Proposed modification to Recommenda­
tion 339 - Bandwidths and signal-to-noise
ratios in complete systems

III/122

Study Group III

Draft Recommendation - Use of directional
antennae in the bands 4 to 27-5 Mc/s

m /123

Working Group
III-A

Draft Report - Use of diversity on inter­national HF radiotelephone circuits

Draft Q.

III/124

Working Group
III-A

Draft Report - An improved transmission
system for HF radiotelephone circuits

Draft Q.

III/125and Add.l

Working Group
III-A

Report by the Chairman

III/l 26

Study Group III

Proposed modification
C.u(III)

III/127

Study Group III

Draft Study Programme - Voice-frequency(carrier) telegraphy on radio circuits

III/128

Study Group III

Proposed modifications to Draft Study
Programme C.al(III) - Efficiency factor

toDraft Report

Q. 43

— 183 —Doc.

OriginTitle

Ill/129

Study Group III

Draft additions to Report 197

III/130(X/169)Ad HocCommittee X/III

Consideration of Doc. 111/43 (Rev.l), Draft
Report C.t(III), Doc. 111/86 (Rev.l), Draft
Report C.aa(III)III/131

Study Group III

Summary record of the second meeting

III/132
and Add.l

Working Group
III-B

Report by the Chairman

III/133

Working Group
III-C

Draft Report - Efficiency factor

III/134

Working Groups
III-B and III-C

Modification to Draft Study Programme
C.a.k(III) - Communication theory

III/135

Working Group
III-C

Draft Question - The operational use of
efficiency factor

III/136

Working Group
III-C

Proposed additions to Draft Report
C.q(III) - Some aspects of the applicationof communication theory

III/137
and Corr.lWorking Group
III-C

Draft Report - Performance of telegraphsystems on HF radio circuits

III/138

Study Group III

Draft Report - Use of directional antennae
in the bands 4 to 27-5 Mc/s

III/139

Working Group
III-B

Draft Report - Single-channel radiotelegraphsystems employing forward error correction

III/140

Study Group III

III/141
and Corr.lStudy Group III

Draft Report - Single-channel duplex ARQ
telegraph system
Draft Report - Voice-frequency telegraphy
on radio circuits

III/142

Working Group
III-D

Proposed new Report - Models of phaseinterference fading to be used in connection
with studies of efficient spectrum utilization

III/143

Working Group
III-D

Proposed modifications and corrigenda for
Draft Report C.t(III)III/144

Study Group III

Proposed modifications and corrigenda for
Draft Report C.aa(III)III/145

Working Group
III-D

Proposed modification to Resolution 1

III/146

Study Group III v

Summary record of the third rfieeting

m/147

Study Group III

Summary record of the fourth meeting

III/148

Study Group III

Status of texts

III/149

C.C.I.R.
Secretariat

List of documents issued (III/101 to III/149)

ReferenceI

S.P. 43A

Draft S.P.

S.P. 43A

LIST OF DOCUMENTS OF THE Xlth
PLENARY ASSEMBLY ESTABLISHED BY STUDY GROUP III
No.

Title

HI/1001

Use of diversity on international HF radiotelephone
circuits

Rep. 355

m /1002

Use of common-frequency systems on international
radiotelephone circuits

Rep. 353

III/1003

Operational ionospheric sounding at oblique incidence

Rep. 357

III/1004

Use of pre-emphasis and de-emphasis for phototelegraphtransmission on HF radio circuits

Rep. 352

m /1005

Directivity of antennae at great distances

Rep. 107-1

III/1006

An improved transmission system for HF radiotelephone
circuits

Rep. 354

III/1007

Radio systems
propagation

scatter

Rep. 109-1

III/1008

Radiotelephone systems and the use of radio links ininternational telephone circuits

Rec. 335-1

III/1009

Facsimile transmission of meteorological charts overradio circuits
Arrangement of channels in multi-channel single-side­band and independent-sideband transmitters for longrange circuits operating at frequencies below about
30 Mc/s
Influence of frequency deviations associated withpassage through the ionosphere on HF radiocom­
munications
Improvements in the performance of HF radiotelephone
circuits
Operational ionospheric sounding at oblique incidence

Rec. 343-1

HI/1010

III/1011
III/1012

III/1013
III/1014
III/1015
III/1016
III/1017
III/1018
III/1019
III/1020
III/1021
III/1022
III/1023

employing

Final No.

ionospheric-Standardization of phototelegraph systems for use on
combined radio and metallic circuits
Use of common-frequency systems on radiotelephone
circuits
Bandwidth required at the output of a telegraph or
telephone receiverFrequency stability required for single-sideband, inde­
pendent-sideband and telegraph systems to make theuse of automatic frequency control superfluous
Use of directional antennae in the bands 4 to 28 Mc/s
Principles of the devices used to achieve privacy inradiotelephone conversations
Factors affecting the quality of performance of complete
systems of the fixed service
Factors affecting the quality of performance of complete
systems on the fixed services
Yoice-frequency telegraphy over HF radio circuits
Use of radio circuits in association with 50-baud 5-unit
start-stop telegraph systems

Rec. 348-1

Q. 7/IIIQ. 13/111
S.P. 20A/III
Rec. 344-1
Q. 9/III
Rec. 338-1
Rec. 349-1
Rec. 162-1
Rec. 336-1
S.P. 1A/III
Rep. 197-1
Rep. 19-1
Rep. 42-1

III/1024

Single-channel duplex ARQ telegraph system

Rep. 350

III/1025

Telegraph distorsion, error-rate

Rep. 200-1

— 185 —Final No.

Title

No.

III/1026

Efficiency factor

Rep. 351

III/1027

Some aspects of the application of communication
theoryRep. 196-1

III/1028

Unit of quantity of information

Rec. 166-1

III/1029

Frequency-shift keying

Rec. 246-1

III/1030

Automatic error-correcting system for telegraph signals
transmitted over radio circuits

Rec. 342-1

III/1031

Arrangement of voice-frequency telegraph channels
working at a modulation rate of about 100 bauds on
HF radio circuits

Rec. 436

111/1032

Factors affecting the quality of performance of complete
systems of the fixed service

Q. l/III

III/1033

Automatically controlled radio systems in the HF
fixed service

Q. 14/111

III/1034

Efficiency factor

S.P. 18A/III

III/1035

Communication theory

Q. 5/III

III/1036

Voice-frequency (carrier) telegraphy on radio circuits

S.P. 17A/III

III/1037

The operational use of efficiency factor

Q. 15/111

III/1038
III/1039

Rep. 414 *Rep. 415 *III/1040

Efficient use of the radio-frequency spectrum
Model of phase interference fading to be used in connec­
tion with studies of the efficient use of the radio-frequency
spectrum
Voice-frequency telegraphy on radio circuits

III/1041

Remote control signals for facsimile transmissions

Rep. 201-1

III/1042

Performance of systems using phase-shift keying on
HF radio circuits

Rep. 346

III/1043

Bandwidths and signal-to-noise ratios in complete
systems

Rec. 339-1

III/1044. Distortion characteristics required for single-side­band and independent-sideband systems used for high­speed data transmission over HF radio circuits

Q. 12/111

III/1045
III/1046

Communication theory

S.P. 5A/III

Improved efficiency in the use of the radio-frequency
spectrumRes. 1-1

III/1047

Single-channel simplex ARQ telegraph system

Rep. 348

III/1048

Single-channel radiotelegraph systems employing for­ward error correction

Rep. 349

III/1049

Use of directional antennae in the bands 4 to 28 Mc/s

Rep. 356

III/1050

List of documents issued (III/1001 to III/1052)

III/1051

OperatingsystemIII/1052

Performance of telegraph systems on HF radio circuits* To be published separately.

noise-threshold

of

a

radio

receiving

Rep. 347

Rep. 413 *Rep. 345

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENT

— 187Rec. 258-1

RECOM MENDATIONS OF SECTION D (MOBILE SERVICES)

D. 1: General
RECOMMENDATION 258-1 *SINGLE-SIDEBAND AERONAUTICAL AND MARITIME MOBILERADIOTELEPHONY SYSTEMSThe C.C.I.R.,(1959 - 1966)CONSIDERING(a) that the main advantages of single-sideband systems (SSB), as compared with double-side­band (DSB), for mobile radiotelephony, are as follows:
a.a reduction of bandwidth required per channel;
a.b increase in signal-to-noise ratio, or, alternatively, reduction in transmitter power (and hence
antenna voltage), for the same signal-to-noise ratio, improvements dependent upon the degreeof carrier suppression;a.c reduction of the distortion that is due to selective fading;a.d reduction of interference, particularly that due to beat notes, between carriersdependent
on the degree of carrier suppression;a.e reduction of interference, due to cross-modulation between adjacent channel transmissions;(b) that the disadvantages of SSB compared with DSB for mobile radiotelephony, are as follows:
b.a more rigorous requirements for transmitter and receiver frequency stability;
b.b greater complexity of apparatus;
b.c higher prices of the equipment;
b.d higher maintenance costs for the equipment;b.e impracticability of conversion of existing mobile DSB equipment for SSB operation;b . f Doppler effects, that are significant for very high-speed mobile units;(c) that the MF-radiotelephony bands, used in the maritime services (i.e.world-wide
2850 kHz and additionally, in Region 1, 3155 to 3800 kHz):

1605 toc.a include the international calling and distress frequency 2182 kHz;c.b are shared with fixed services;
c.c are used by many low tonnage ships, some compulsorily and others voluntarily fitted exclu­
sively with DSB MF-radiotelephony equipment;(d) that the parts of the H F bands (i.e. 4000 kHz to 23 000 kHz for mobile maritime and2850 kHz to 24 000 kHz for aeronautical use), allocated to the respective services;
d.a do not include any international distress frequency;* This Recommendation terminates the study of Question 162.

— 188 —Rec. 258-1\

d.b are exclusively allocated to these services;(e) that in the maritime mobile services, the advantages of SSB operation predominate overthe disadvantages;(f) that although the introduction of class of emission A3J is a desirable objective it may benecessary to use class of emission A3A for public correspondence services for an indefinite
period to obtain acceptable a.g.c. performance;(g) that, in the maritime mobile services, in the interests of safety of life at sea, the introduc­tion of SSB operation should not be allowed to discourage the extension of voluntary fittingof DSB MF-radiotelephony equipment;(h) that Recommendation No. 3 o f the Final Report of the Panel of Experts, set up under Resolu­
tion No. 3 of the Administrative Radio Conference, Geneva, 1959, urges introduction of
SSB in the maritime mobile H F radiotelephony service;
UNANIMOUSLY RECOMMENDS

1.

for the maritime mobile services (see also Appendices 15 and 17 to the Radio Regulations,Geneva, 1959, and Recommendation No. 28 of the Administrative Radio Conference, Geneva,
1959);

1.1 that SSB operation be introduced in the M F and H F radiotelephony bands;
1.2 that coast stations be prepared to communicate with both DSB and SSB ship stations;
1.3 that for SSB equipment the following technical characteristics be employed:
1.3.1 in coast and ship station transmitters facilities should be provided for both class ofemission A3 A having a carrier reduction of 16 ± 2 dB below peak envelope power,
and class of emission A3J having a carrier reduction of not less than 40 dB below peakenvelope power; (Note 1)
1.3.2 the carrier frequency of the transmitters should be maintained within the following
tolerances:
1.3.2.1 for coast stations: ± 20 Hz;
1.3.2.2 for ship stations: short-term limits (of the order of 15 min) ± 40 Hz;
1.3.2.3 for ship stations: within ± 100 Hz of the reference value;
1.3.3 the carrier frequency of the receivers should be maintained within the following toler­
ances :
1.3.3.1 for coast stations: ± 20 Hz;
1.3.3.2 for ship stations the short-term limits (of the order of 15 min) ± 40 Hz; (Note 2)
1.3.4 the upper sideband should be used (see Appendix 15, Section B and Appendix 17 of
the Radio Regulations, Geneva, 1959); (Note 3)
1.3.5 the channel arrangements should be such, that two SSB channels are accommodated
within each existing DSB channel and the bandwidth of the SSB emissions should be
kept within such limits as will permit this to be done. (The precise arrangement ofthese SSB channels is scheduled to be further discussed at the World Administrative
Radio Conference, 1967. See also Appendix 17 of the Radio Regulations, Geneva,
1959);
1.3.6 the transmitter audio-frequency band should be 350 to 2700 Hz, with a permitted
amplitude variation of 6 dB; (Note 4)
1.3.7 the unwanted frequency-modulation of the SSB carrier should be sufficiently low toprevent harmful distortion;

— 189 —Rec. 258-1, 422

1.3.8 in the M F maritime mobile radio telephony bands, SSB ship stations should be able
to insert a carrier at a level sufficient to permit satisfactory reception by DSB receivers
when communicating with DSB stations;1.3.9 in the particular case of transmissions on the radiotelephone calling and distress fre­quency 2182 kHz, all transmissions should be made either by DSB, or by SSB witha carrier level sufficient to permit satisfactory reception by DSB receivers;
1.4 that the attention of Administrations should be drawn to the fact that, there would be tech­nical and operational advantages in designating certain frequencies for international common
use for ship-shore and inter-ship working;2.

that for the aeronautical mobile service, the Director, C.C.I.R., should:

2.1 advise the I.C.A.O. of this Recommendation;
2.2 renew the invitation to the I.C.A.O. to advise the C.C.I.R. of any technical and operational
problems on which they would like the assistance of the C.C.I.R.;
2.3 offer to keep the I.C.A.O. informed of progress made by the C.C.I.R. in the study of theapplication of SSB working in the maritime mobile services;
2.4 request the I.C.A.O. to keep the C.C.I.R. informed of progress made by the I.C .A D . inthe study of the application of SSB working in the aeronautical mobile services.
Note 1. - The normal method of operation for each coast station should be indicated in
the I.T.U. “ List of Coast Stations
Note 2. - This value may be maintained either manually or by other means.
Note 3. - Exceptionally, in the bands between 4 and 23 MHz independent-sideband (ISB)
may be used by special arrangement between Administrations.
Note 4. - These limits may need to be modified when selective calling is introduced.

RECOMMENDATION 422 *P U L S E T R A N SM ISS IO N F O R R A D IO D IR E C T IO N -FIN D IN G
The C.C.I.R.,(1953 - 1963)CONSIDERING(a) that certain studies, extending over many years, of the errors of direction finders show that,
under ideal conditions of site, equipment and operation, the use of pulse transmissions offers
only a slight improvement in accuracy over the use of continuous-wave transmissions;(b) that, in practice, unavoidable departures from the ideal conditions referred to in § (a) would
tend to reduce this improvement in accuracy;(c) that pulse transmissions occupy wide bandwidths;* This Recommendation replaces Recommendation 126.

/

Rec. 422, 423-1— 190 —UNANIMOUSLY RECOMMENDS

that the use of pulse transmissions for radio direction-finding at frequencies below 20 000 kHz
is generally undesirable.
ANNEX
The following errors in high-frequency direction-finding can occur:
1. observational errors introduced by the operator;
2. instrumental errors, including polarization errors and those due to deficiencies of the direc­
tion-finder site;
3. errors due to radiation scattered from topographical features many wavelengths distantfrom the direction finder;
4. errors due to lateral deviation in the ionosphere;
5. errors due to wave interference caused by convergence of rays and by different modes of
propagation.
The advantage of a pulse emission over a continuous-wave emission lies in its ability toallow signals arriving over different paths to be separated, and so to reduce errors arisingfrom sources 4 and 5 above.
The degree of accuracy to be expected from the use of pulse emissions for radio direction
finding has been studied, and it is estimated that in most favourable circumstances, for afrequency of about 8000 kHz, the standard deviation of a single rapidly observed bearing might
be about 3° for a continuous-wave emission and about 2° for a pulse emission. The corres­
ponding figures for the mean of ten such bearings taken in a period of five minutes are:continuous-wave 2-5°, pulse 1-7°.

RECOMMENDATION 423-1
USE OF 8364 kHz FOR RADIO DIRECTION-FINDING
The C.C.I.R.,(1951 - 1956 - 1959 - 1963 - 1966)CONSIDERING(a) Nos. 994, 997 and 1179 of the Radio Regulations, Geneva, 1959;(b) that land stations keep watch during their hours of service on the band 8354 kHz to 8374 kHzof which 8364 kHz is the centre;(c) that Regulations 12 and 13 of Chapter IV of the Safety of Life at Sea Convention, London,
1960, indicate minimum specifications for automatic distress transmitters;(d) that tests and operational experience have shown that radio direction-finding at 8364 kHz
may be a valuable aid (in conjunction with direction-finding at 500 kHz), in finding theposition of both aircraft and ships in distress and survival craft;(e) that complete coverage cannot be obtained with direction-finding on only one frequency in
the H F (decametric) band because of the limitations caused by radio-propagation conditions;

— 191 —Rec. 423-1(f) that H F (decametric) radio direction-finding requires apparatus as free as possible from local
site error and polarization error;(g) that the accuracy of the bearing will depend upon the field strength of the signal and thesignal/noise ratio;(h) that in view of the rapid variation of the apparent azimuth of the bearing which is frequently
observed in H F (decametric) radio direction-finding, measurements should be made over
several minutes to obtain a more accurate mean bearing; and that the bearing and fix may
be improved subsequently by a further series of measurements;(i) that standardized distress transmissions are desirable;(j) that it is essential to have a means of rapid communication between the watch-keeping stationand the direction-finding stations;
UNANIMOUSLY RECOMMENDS

1. that the site of the H F (decametric) radio direction-finding station should be, as far as possible:
1.1 flat and horizontal for a radius preferably of at least 200 m, with the surrounding neigh­bourhood flat and free from obstruction;
1.2 of high and uniform ground conductivity;
1.3 free from large metallic masses and objects likely to resonate at frequencies near to 8364 kHz;/

2.

that the antenna system should be as free as possible from wave polarization error (e.g. Adcock
systems and spaced-loop systems);

3.

that the bandwidth of the direction-finding receiver, used when bearings are taken, should be
as narrow as possible, compatible with the modulation and frequency stability of the signal
on 8364 kHz and that a broader bandwidth position should also be incorporated in thereceiver for watch-keeping purposes;

4.

that the sensitivity of the direction-finding equipment should be such that it operates satis­
factorily with a field-strength as low as 5 p.V/m;

5.

that the bearing should be determined by an aural-null method or by any other method ofcomparable or better accuracy;

6.

that the direction-finding equipment should be adjusted, balanced and calibrated at frequentintervals at the frequency of 8364 kHz;7. that the signal radiated by survival craft should be as strong as possible and stable in frequency
to ensure the greatest accuracy in determining the bearings;
8. that the signals transmitted by survival craft should preferably include long dashes sent overa period of not less than five minutes for direction-finding purposes. The attention of
Administrations should be drawn to the precise form and content of such signals proposedby France, U.S.A. and the United Kingdom, given in Doc. 39 (France), 43 and 99 (U.S.A.)
and 44 (United Kingdom), Geneva, 1951, and to the question of whether it would bedesirable to use a common form of signal for both 500 kHz and 8364 kHz;9. that, to give as great accuracy of fix as possible, several widely-spaced and interconnected
direction-finding stations should be employed (see Annex);
10. that the attention of Administrations concerned should be drawn to the advantage of theirstudying further:
10.1 the most suitable type of network for providing rapid communication between directionfinding stations and plotting centres;Rec. 423-1, 437— 192 —

10.2 the most suitable way in which information should be exchanged between different stations
or networks (e.g. use of “ Q ” code);
10.3 the best way to evaluate the most probable fix (position) from bearings supplied by the
direction-finding stations;11. that the attention of Administrations should also be drawn to the fact that world-wide direc­
tion-finding coverage cannot be obtained with only one frequency in the H F (decametric)
band.
ANNEX
A CCURACY OF BEARINGS AT

8364 k H z

At distances greater than about 1200 km the root-mean-square (r.m.s.) bearing error to
be expected with a modern H F (decametric) direction-finding system is of the order of 3° to 5°
At distances less than 1200 km the error progressively increases with decrease of distanceto values of the order of 5° to 10°; at small distances, less than about 100 km, the error may
be even greater than 10°.
The above figures refer to the arithmetic mean of bearings spread over an interval of not
more than about 10 min.

RECOMMENDATION 437 *PUBLICATION OF THE “ CODES AND ABBREVIATIONS FOR THE
INTERNATIONAL TELECOMMUNICATION SERVICES ” BY THE
INTERNATIONAL TELECOMMUNICATION UNIONThe C.C.I.R.,_(1966)CONSIDERING(a) that the second edition of the “ Codes and Abbreviations for the International Telecommuni­
cation Services ”, published by the International Telecommunication Union was issued
in 1963;(b) that Administrations have been asked to consider whether there is an operational need forthe unification of codes, in accordance with Opinion 20, § 3;(c) that no Administration has expressed a need for the unification of codes;(d) that at the Interim Meeting of Study Group XIII of the C.C.I.R., 1965, Administrations
agreed that there was, in fact, no operational reason for attempting to unify the codes;
UNANIMOUSLY RECOMMENDS

1.

that no further action should be taken concerning the unification of the “ Codes and Abbre­
viations for the International Telecommunication Services ” ;2.

that the Director, C.C.I.R., be invited to bring this Recommendation to the attention of
the Director, C.C.I.T.T.

* This Recommendation cancels Opinion 20.

— 193 —Rec. 45

D . 2 : M a r itim e m o b ile s e r v ic e
RECOMMENDATION 45
AVOIDANCE OF INTERFERENCE FROM SH IPS’ RADARTO OTHER RADIOCOMMUNICATION APPARATUS ON BOARD
The C.C.I.R.,(1951)CONSIDERING(a) that experience has proved that, with well-designed and properly installed radar, the possibilityof interference occurring in practice is very remote;(b) that the possibility of interference to radio reception and to direction-finding on a vessel,
other than that upon which the radar is located, is exceedingly remote and that no instancesof such interference have been reported;(c) that, in the unlikely case where radar interference might result to radio reception aboard aradar equipped vessel, the presence of such interference may readily be detected and identified
by listening on the radio receiver or direction-finder;(d) that, where interference has occurred to radio reception aboard ships equipped with welldesigned radar, in each case the cause of the interference has been faulty initial installationand has been removed by correcting the installation;
UNANIMOUSLY RECOMMENDS

1. that Administrations shall see to it that radar equipment placed aboard ships is well designed
and properly installed, so as not to cause interference to radio reception aboard the radar
equipped vessel. In this regard, particular attention shall be paid to shielding, bonding andto fitting line filters, especially in the modulator circuits, for the conductors which are routed
between the major components of the installation;
2.

13that the absence of interference shall be assured, either by test procedures of prototypes orby installation inspection procedures, whereby an investigation is made to determine whether
or not there exists any noticeable interference to ships’ radio receivers or direction-finders,
under practical conditions of installation and operation.

Rec. 76

— 194 —

RECOMMENDATION 76
VOICE-OPERATED^DEVICES FOR SHIP STATIONSAND CARRIER-OPERATED DEVICES FOR SHORE STATIONSThe C.C.I.R.,(1951)CON SID ERIN G(a) that the essential characteristics of the devices controlled by voice currents and acting on
the carrier wave in radiotelephone stations on board ships and of the carrier-operated devices
in receivers of coast stations are their “ operate ” and “ release ” times;(b) that the operate times of the devices should be short to minimize clipping, and their releasetimes should be sufficiently long to enable the devices to remain operated in the intervals
between words in normal speech;
U N A N IM O U SLY RECOMMENDS

1.

2.

that the operate and release times of the voice-operated carrier switching unit on the shipshould be as follows:
N et operate tim e(N ote 2)

N et release tim e(N o te 3)less than 25 msless than 15 ms

between 75 and 170 ms
between 75 and 170 ms

that the operate time ( Note 4) of the carrier-operated device in the coast station receiver,Should be as short as practicable to allow somewhat longer operate times in the ship’s
apparatus and should not exceed 5 ms when the carrier level at the input to the receiver ismore than 1 dB above the level just necessary to operate the device. The required value of
release time ( Note 5), is dependent on several factors, including the time constants of theautomatic gain control of the radio receiver and a value between 10 and 50 ms is generally
suitable.

Note 1. - Input level refers to the level of a test sinusoidal signal of frequency, corresponding to
the middle of the voice-frequency range relative to that producing 100% modulation.
Note 2. - Net operate time is the time which elapses between the instant the test signal is applied
to the input to the modulator of the transmitter, and the instant when the carrier reaches
50% of its maximum amplitude.
Note 3. - Net release time is the time which elapses between the instant when the test signal is dis­connected and the instant the carrier is reduced to within 5 dB of the maximum carrier sup­pression achieved.
Note 4. - Operate time of the carrier-operated device is the time which elapses between the sudden
application of a test signal simulating the carrier wave from the ship and the instant of openingof the receiving channel (the instant when the attenuation of the receiving channel is within 5 dBof the final value of attenuation for the receiving condition).
Note 5. - Release time of the carrier-operated device is the time which elapses between the cessa­tion of a test signal simulating the carrier wave from the ship and the instant of blocking of
the receiving channel (the instant when the attenuation of the receiving channel is within
5 dB of the final value of attenuation in the blocked condition).

— 195 —Rec. 77-1

RECOMMENDATION 77-1
CONDITIONS NECESSARY FOR INTERCONNECTION
OF MOBILE RADIOTELEPHONE STATIONS(FOR INSTANCE, AUTOMOBILES, AIRCRAFT AND SHIPS)AND INTERNATIONAL TELEPHONE LINESThe C.C.I.R.,(1951 - 1966)

CO N SID ERIN G(a) that the conditions concerning which international agreement is necessary appear to be few
in number;(b) that these conditions, if met, would permit suitable interconnection between mobile radio­
telephone stations and international telephone lines;
U N A N IM O U SL Y RECOMMENDS

1. that mobile radiotelephone circuits, intended for connection to international telephonesystems, should terminate (on a two-wire basis, for the present at least) in such a way that they
may be connected to international lines in the same manner as other landline connections;2.

that the mobile radiotelephone circuits should accept from and deliver to the landline system
speech volumes conforming, as far as possible, to the C.C.I.R. and C.C.I.T.T. standards forconnections to international circuits;

3.

that the attenuation-frequency characteristics of the radio system (including the landlines tothe radio receiver and radio transmitter) should be such that the grade of transmission is not
unduly affected; and, in particular, the effectively transmitted band should be not less than
300 to 2600 Hz (for single-sideband aeronautical and maritime radiotelephone equipment,
see Recommendation 258-1, § 1.3.5.);

4.

that the noise from a radio circuit, connected to an international circuit, should not be unduly
great and should be insufficient to operate echo suppressors or other devices on domestic
or international circuits frequently;

5.

that, for mobile radiotelephone stations, which may have to communicate with land stations
in more than one country, consideration be given to the necessity for agreement as to a methodof signalling for use between the land mobile stations.

Rec. 218

— 196 —

RECOMMENDATION 218 *PREVENTION OF INTERFERENCE TO RADIO RECEPTION ON BOARD SHIPS **The C.C.I.R.,(1951 - 1956)

C ONSIDERING(a) that the Maritime Regional Radio Conference, Copenhagen, 1948, recommended that the
C.C.I.R. study the question of interference to radio reception caused by electrical instal­lations on board ship;(b) that the Safety of Life at Sea Conference, London, 1960 (Chapter IV, Regulation 9), requested
that all steps be taken to eliminate, as far as possible, the causes of radio interference from elec­
trical and other apparatus on board ship;(c) that electrical interference is caused by the unwanted excitation of the radio receiving equip­
ment, including the antenna, by fluctuating electromagnetic fields set up by other electricalinstallations;(d) that the fluctuation of electromagnetic fields, which gives rise to interference, is caused byabrupt changes in current in the source of interference, and by abrupt changes in the resistanceof conductors situated in electromagnetic fields;(e) that electrical interference may be transmitted by direct radiation and induction from thesource of interference itself, and also by re-radiation and induction from conductors whichcarry interfering currents;
U N A N IM O U SLY RECOMMENDS

1.

that the design, construction and installation of electrical equipment in ships should be suchthat interference is minimized at its source (see also No. 959 of the Radio Regulations, Geneva,
1959);

2.

that electrical equipment installed in ships should be efficiently maintained to prevent any
increase in the level of interference which it causes;

3.

that antennae used for transmission or reception should be erected, as far above and as far
away as possible from electrical machinery and from parts of the ship’s structure such as
funnels, stays and shrouds;

4.

that the down-leads of antennae which are used exclusively for reception should be screened;that the screen should extend continuously from the receiver to a point which is as high aspracticable above the ship’s structure, and that the screen should be effectively connectedto the earth terminal of the receiver;5.

that frame or loop antennae used for direction-finding, should be effectively screened againstelectrostatic interference;

6.

that the radio receiving room should be effectively screened and situated as high as practicablein the ship;

7.

that power converting plant, within the radio receiving room, should be housed in a separate
screened enclosure, unless the plant is self-screened;

8.

that the radio receiving equipment should be designed so that it is effectively screened;* This Recommendation replaces Recommendation 78. Certain references to the Radio Regulations havebeen inserted subsequently.
** Interference from radar and other electronic equipment has not been specifically considered in framing
this Recommendation. The prevention o f radar interference is covered by Recommendation 45.

Rec. 218, 219-1— 197 —

that suppressor filters, to prevent the propagation of interference, should be fitted at thesources of interference, preferably built into the interference-producing equipment, andthat in particular:
9.1 the electrical ignition systems of internal-combustion engines, including those which may
be installed in lifeboats, should be fitted with suppressors;
9.2 the navigational instruments and associated equipment, which are installed in the neighbour­hood of the receiving antennae or the radio receiving room should, if necessary, be fittedwith suppressors, be screened, and the screen effectively earthed;9.

10. that cables in the vicinity of the receiving antennae or the radio receiving room, and cables

within the radio room, should be screened by enclosing them in metal conduits, unless thecables themselves are effectively screened;
11. that twin cables should be used wherever possible: if single-core cable is necessary, the “ lead ”
and “ return ” conductors should be fixed, as close to one another as possible, to avoid theformation of loops;
12. that suppressors should be fitted to cables at their point of entry into the radio receivingroom, unless they terminate close to the point of entry in equipment which itself provides
adequate screening and suppression;
13. that cables, ducts and pipes which do not terminate in the radio receiving room, should

preferably not be installed in the radio receiving room; if it is essential for them to passthrough the radio receiving room, the ducts and pipes and the screening of the cables shouldbe effectively earthed;
14. that a copper earth-busbar should be fixed along the bulkheads and bonded at several points

to the ship’s structure and to the metal structure or screening of the radio receiving room;
the screens of cables within and near to the radio receiving room, as well as the screens ofapparatus in the radio receiving room, should be effectively connected to the busbar;
15. that rigging should be either insulated from or bonded to the ship’s structure (stays thatare subject to considerable tension can more conveniently be bonded);
16. that, for smaller vessels and those constructed of wood, the principles recommended should

be applied as far as is practicable;
17. that particular care should be taken to minimize interference on the frequency bands used

for distress, safety and direction-finding in the maritime service;
18. that Administrations should bring the above recommendations to the attention of naval

architects, shipbuilders and those responsible for the manufacture, installation and main­
tenance of electrical equipment.

RECOMMENDATION 219-1
ALARM SIGNAL FOR USE ON THE MARITIME RADIOTELEPHONY
DISTRESS FREQUENCY OF 2182 kHz
The C.C.I.R.,(1951 - 1953 - 1956 - 1966)CONSIDERING(a) that it is desirable and practicable to establish an internationally agreed alarm signal foruse on the calling and distress frequency of 2182 kHz (see Art. 36 of the Radio Regulations,Geneva, 1959);(b) that the alarm signal should be such as to:- provide reliable operation of automatic alarm equipment;

— 198 —Rec. 219-1- provide a distinctive signal, which is readily recognized aurally, when received on a loud­speaker or headphones;- be capable of being received through interference from speech transmissions, throughother kinds of interference, and through noise;- avoid false responses when received either aurally or by automatic means:- be capable of being produced by a simple manual device, as well as by automatic means;(c) that the alarm signal should be such as to permit the construction of alarm equipment which

is rugged, dependable, stable in performance, of low cost, of easy production, of long life
with a minimum of maintenance, and which can be used with existing maritime radiotelephoneequipment;(d) that to help in clearing the calling and distress frequency channel of emissions from otherstations the alarm signal and detecting device should be effective beyond the range at whichspeech transmission is satisfactory;(e) that the automatic alarm equipment should be capable of operating, in as short a time as

possible, consistent with the avoidance of false responses;(f) that the results of the further examination of this problem by the Administrations which

participated in Study Programme 29, Geneva, 1951, are sufficiently conclusive to determine
the essential characteristics of the signal, including tolerances that should be recommended
for international adoption;(g) that it is possible to specify the minimum performance standards for automatic alarm equip­

ment, for both transmission and reception, to such an extent that future progress and develop­
ment are not hampered;(h) that it is undesirable that the specification of performance standards for automatic alarm

equipment should exceed in scope the requirements already established by international
agreement for automatic alarm devices, intended for the reception of the international alarm
signal or the international distress signal in radiotelegraphy, normally transmitted on thefrequency 500 kHz (see Nos. 1475 and 1476, and Appendix 20, § 1 of the Radio Regulations,Geneva, 1959; and Chapter IV, Regulation 10 of the Convention for the Safety of Life atSea, London, 1960);
UNANIMOUSLY RECOMMENDS

1.

that the alarm signal described below should be adopted internationally, for use on the mari­time radio telephony calling and distress frequency of 2182 kHz;

1.1 the alarm signal shall consist of two substantially sinusoidal audio-frequency tones, trans­mitted alternately. One tone shall have a frequency of 2200 Hz and the other a frequencyof 1300 Hz. The duration of each tone shall be 250 ms;
1.2 the tolerance of the frequency of each tone shall be ± 1-5%; the tolerance on the durationof each tone shall be ± 50 ms; the interval between successive tones shall not exceed 50 ms;
the ratio of the amplitude of the stronger tone to that of the weaker shall be within the range
1 to 1-2;
1.3 when generated by automatic means, the alarm signal shall be sent continuously for a periodof at least 30 s but not exceeding one minute; when generated by other means, the signal
shall be sent as continuously as is practicable over a period of approximately one minute;2.

that the automatic-devices, intended for the reception of the alarm signal in question, should
fulfil the following conditions:

2.1 the frequencies of maximum response of the tuned circuits, and other tone selecting devices,shall be subject to a tolerance of ± 1-5% in each instance; and the response shall not fall
below 50 % of the maximum response for frequencies within 3 % of the frequency of maximum
response;

— 199 —Rec.219-1, 224

2.2 in the absence of noise and interference, the automatic receiving equipment shall be capableof operating from the alarm signal in a period of not less than four and not more than six
seconds;
2.3 the automatic receiving equipment shall respond to the alarm signal, under conditions ofintermittent interference caused by atmospheric and powerful signals other than the alarm
signal, preferably without any manual adjustment being required during any period of watch
maintained by the equipment;
2.4 the equipment shall not be actuated by atmospheric or by strong signals other than the alarm
signal;3.

that the automatic alarm equipment for both transmission and reception, on the callingand distress frequency of 2182 kHz, shall fulfil the following conditions:
3.1 the equipment shall be effective beyond the range at which speech transmission is satisfactory;
3.2 the equipment shall be capable of withstanding vibration, humidity, changes of temperatureand variations in power supply voltage equivalent to the severe conditions experienced
on board ships at sea, and shall continue to operate under such conditions;
3.3 the equipment should, as far as practicable, give warning of faults that would prevent theapparatus from performing its normal functions during watch hours;
4.

that, before any type of automatic alarm equipment for transmission and reception on thecalling and distress frequency of 2182 kHz is approved for use on ships, the Administrations
having jurisdiction over those ships should be satisfied by practical tests, made under operat­
ing conditions equivalent to those obtaining in practice, that the equipment complies withthe provisions of §§ 1, 2 and 3 of this Recommendation.

RECOMMENDATION 224 *TESTING OF 500 kHz RADIOTELEGRAPH AUTO-ALARM
RECEIVING EQ UIPM EN T ON BOARD SH IPSThe C.CJ.R.,(1956)CONSIDERING

that, it is important for the. safety of life at sea, that radiotelegraph auto-alarm receiving
installations (including the antenna) are always in good working order on board ships at sea;
UNANIMOUSLY RECOMMENDS

in addition to the requirements of Chapter IV of the International Convention for the Safetyof Life at Sea, London, 1960;
1.

that all radiotelegraph auto-alarm receiving equipment, for use on the international callingand distress frequency of 500 kHz should, wherever practicable, be provided specificallywith means for automatic warning of the following:
1.1 failure of any valve filament, whether the cathode is directly or indirectly heated;
1.2 major variation or sustained failure of any source of voltage which is used for supplying, valve elements, where this would seriously affect the proper functioning of the apparatus,
as laid down in Chapter IV, Regulation 10 of the said Convention;* This Recom m endation terminates the study o f Question 108. The references to the International Conven­tion for the Safety o f Life at Sea, London, 1960, have been inserted subsequently.

— 200 —Rec. 224, 227

1.3 any drop in voltage, or complete failure, of the main power supply to the auto-alarm equip­
ment that would seriously affect the proper functioning of the equipment and where suchwarning is not already given by other means;
2. that provision should be made for listening to the output of the auto-alarm receiver;
3. that the proper functioning of auto-alarm installations should be checked periodically bylistening to signals on the auto-alarm receiver with its normal antenna connected, and byobserving similar signals received on 500 kHz on the ship’s main receiving installations;4. that measures should be taken to ensure that the auto-alarm antenna is always ingood condition;
5. that the design of auto-alarm equipment should be as simple as possible, consistent withreliable and efficient operation;
6. that, wherever practicable, measures should be taken to permit reception on the auto-alarm
installation when the radio direction-finder is being used;
7. that live test transmissions of the radiotelegraph auto-alarm signal should not be made.

REC OM M ENDATION 257 *SELECTIVE CALLING DEVICES FOR USE IN THE INTERNATIONAL VHF(METRIC) MARITIME MOBILE RADIOTELEPHONE SERVICE(Question 3/XIII)The C.C.I.R.,(1959)CONSIDERING(a) that selective calling from coast stations to ship stations would expedite handling of traffic,

particularly in public correspondence services;(b) that aselective calling system is faster and more positive than calling by voice;(c) that it
overcomes the disadvantage and annoyance caused by vessels being requiredto listen
to all calls;(d) that it permits concentration of aural watches on the safety and calling channel 156-80 MHz;(e) that a selective calling system is not subject to language difficulties;
UNANIMOUSLY RECOMMENDS

1.

that aserviceselective calling system for the international VHF maritime mobile radiotelephone
be standardized as soon as possible;

2.

that this selective calling system should have an international numbering system for such
public correspondence services;3.

that the system and the numbering plan should be capable of providing a sufficient numberof individual non-conflicting codes;* The reference to the Radio Regulations has been inserted subsequently.

— 201 —Rec. 257, 425

4.

that the bandwidth required for the transmission of the code signals should not exceed the
maximum permissible emission bandwidth specified by regulations governing the maritime
services;

5.

that the time required to select and transmit the code signal should be of the shortest possible
duration consistent with reliable operation;

6.

that the system should be capable of satisfactory operation, with signal-to-noise ratios atleast equivalent to the minimum acceptable for satisfactory two-way speech transmission;

7.

that the individual signalling combinations must be sufficient for adequately identifying
ships using selective signalling, considering that it might be possible to repeat codes in suffi­
ciently separated geographic areas, taking into account ships’ itineraries;

8.

that the selective signalling, at any given coast station, should not be limited to vessels regu­
larly using that coast station. The numbering system should be planned so as to makethis unnecessary;

9.

that the number code, assigned to a ship, should be distinctive and should be permanently
associated with that ship;

10. that the call should not be prefixed by a long dash or other special signal, to attract attentionof vessels not fitted with a selective calling device, as such calls should be made, preferably,on the frequency of the common calling and safety channel 156-80 MHz;
11. that the attention of Administrations should be drawn to the desirability of their reaching
agreement upon the channel, or channels, that should be used for selective calling. Atten­
tion should also be drawn to Note 8 of Annex 1 of the Agreement on the international VHF
maritime mobile radiotelephone service, The Hague, 1957 (see also Nos. 1214,1361 and
1362 of the Radio Regulations, Geneva, 1959).

R E C O M M E N D A T IO N 425
TE C H N IC A L C H A R A C T E R IST IC S O F F R E Q U E N C Y -M O D U L A T IO N V H F(M E T R IC ) M A R IT IM E M O B IL E E Q U IP M E N T(Q uestions 107, 161 and 164)
The C.C.I.R.,(1956 - 1959- 1963 - 1966)CONSIDERING(a) that Nos. 1359 to 1379 inclusive and Appendix 18 of the Radio Regulations, Geneva, 1959,
stipulate the general procedure for the world-wide use by the international maritime mobile
service in the band 156-174 MHz;(b) that the use of VHF (metric) equipment in the maritime mobile service could reduce the use
o f M F (hectometric) maritime bands and thus tend to reduce congestion in these heavily
loaded bands;(c) that the early introduction of the world-wide use of equipment operating at the frequency
156-8 MHz and other channels specified in Appendix 18 of the Radio Regulations, Geneva,
1959, could contribute to the safety of life at sea;Rec. 425

— 202 —(d) that it would be desirable to reach agreement upon essential technical characteristics forfrequency-modulation VHF (metric) radiotelephone equipment for use in international
maritime services to expedite the international use of such equipment;(e) that, in the informal agreement on standardization of VHF (metric) channels for international
maritime radiotelephone services that was reached among certain countries during the Baltic
and N orth Sea Radiotelephone Conference, 1955 (see I.T.U. Circular letter 1683/55/R, dated
December 1955), it was considered that the equipment should employ frequency-modulation
and be capable of operating ultimately with a frequency spacing of 50 kHz;(f) that, without some further measure of agreement on channel allocations, it is not possible todecide all the technical characteristics needed to facilitate the design of equipment for inter­national VHF (metric) maritime mobile services;(g) that the International Maritime VHF Radiotelephone Conference, The Hague, 1957, hadagreed, among other matters, upon a frequency allocation table using 4-6 MHz separation for
duplex operation in the VHF inter national maritime mobile radiotelephone service;
UNANIMOUSLY RECOMMENDS *1.

that the following characteristics for frequency-modulation VHF (metric) radiotelephoneequipment for the international maritime mobile services operating at 156-8 MHz andother channels specified in Appendix 18 to the Radio Regulations, Geneva, 1959, should
be adopted by Administrations;

1.1 that, at present, the frequency deviation should not be greater than ± 1 5 kHz and the
maximum deviation should be reviewed later if it is found in practice that unacceptableadjacent channel interference occurs, particularly as the loading of the channels increases;
1.2 that all receivers should be capable of receiving satisfactorily emissions having a maximum
deviation of ± 15 kHz;
2.

that vertical polarization should be used;

3.

that, in the absence of fading and local screening, the protection ratio for common-channel
operation should be such that the desired signal level exceeds the interfering signal level byat least 10 dB. Each Administration should provide for a further allowance, where appro­
priate, for fading and for fluctuations o f a local nature (for instance, reflections from theterrain, sea, ships, docks, etc.);

4.

that the equipment should be designed for a frequency separation between adjacent channelsof 50 kHz;

5.

that the frequency separation between the transmitting and receiving frequencies for duplex
working should be 4-6 MHz;

6.

that further study of the means of selective calling is required. For this purpose, reference
is made to Question 3/XIII, Report 320-1 and Resolution 19-1;

7.

other essential parameters;

7.1 frequency modulation with a pre-emphasis of 6 dB/octave should be used (phase-modulation)with subsequent de-emphasis in the receiver;7.2 the output power of the ships’ transmitters should generally not exceed 20 W except in
special circumstances to be determined by individual Administrations;
7.3 spurious emissions:7.3.1 the mean power of spurious emissions due to harmonics of the carrier frequency should
not exceed 25 pW measured at the antenna terminals of the transmitter when loadedwith a resistance equal to the nominal antenna impedance;* See also Appendices 3, 4 and 19 to the Radio Regulations, Geneva, 1959.

— 203 —Rec. 425, 427

7.3.2 the mean power of spurious emissions falling in any other international VHF maritime
mobile channel due to products of modulation should not exceed 10 gW, measured
at the antenna terminals of the transmitter or receiver when loaded with a resistanceequal to the nominal antenna impedance;
7.3.3 the mean power output of any other spurious emission on any discrete frequency
within the international VHF maritime mobile band should not exceed 2-5 gW,
measured at the antenna terminals of the transmitter or receiver when loaded with aresistance equal to the nominal antenna impedance;
7.3.4 in cases where Administrations permit exceptionally the use of higher powered transmit­
ters, proportionate increases in the level of these spurious emissions may be permitted.
7.4 the audio-frequency bandwidth should be limited to 3000 Hz;
7.5 the frequency tolerance of the transmitter should not exceed 0-002%;
7.6 to minimize interference, special attention should be paid to the following receiver charac­
teristics :- stability,- selectivity,- receiver radiation,- intermodulation;
8.

equipment should be designed so that frequency changes between assigned channels can be
carried out rapidly, e.g., within a few seconds;

9.

that care should be taken in the choice of intermediate frequencies for VHF receivers to avoid
interference from other services and, in particular, care should be taken to avoid interference
from other maritime mobile services, especially those in the 500 kHz and 2 MHz bands.

RECO M M EN D A TIO N 427 *INTERFERENCE DUE TO INTERM ODULATION PRODUCTS IN THE
VHF (METRIC) M ARITIM E M OBILE RADIO TELEPHONE SERVICE(Q uestion 164)
The C.C.I.R.,(1959 - 1963)CONSIDERING(a) that intermodulation products may cause serious interference in the operation of th e VHF
mobile maritime radiotelephone service;(b) that intermodulation products may be generated and radiated at receiving stations andtransmitting stations, in the radio equipment itself or at external points (such as antenna
systems), where there is electrical non-linearity;(c) that practical measures can be taken to minimize the generation of such intermodulation
products and to mitigate their harmful effects;* This Recom m endation replaces Recom m endation 256.

— 204 —Rec. 427, 428-1
UNANIMOUSLY RECOMMENDS

1.

that Recommendation 218, particularly §§ 3, 4 and 15, should be followed for the purposeof minimizing the generation of intermodulation products at points on ships external to thereceiver;2.

that antennae, rigging, stays and structures, likely to cause intermodulation products, should bemaintained in such condition as to minimize the generation of intermodulation products;

3.

that care should be taken, in the design and development of receivers, to minimize the possi­
bility of interference due to the generation of intermodulation products in the receivers
themselves;

4.

that the range of interference, due to radiated intermodulation products, should be limited
to sea areas that are not normally navigated by ships and to shore areas that are clear ofcoast receiving stations;5.

that the siting of coast stations should take into account the factors mentioned in § 4 above(see also No. 695 of the Radio Regulations, Geneva, 1959);

6.

that frequency assignments in the VHF mobile maritime radiotelephone band should, as far
as possible, take into account the possibility of interference from intermodulation products(see also No. 695 of the Radio Regulations, Geneva, 1959);

7. that where the service area permits, coast stations should use directive antennae (see also
No. 695 of the Radio Regulations, Geneva, 1959);
8. that care should be taken in the use of the single-frequency channels to minimize interference,
due to intermodulation products, to the common calling and safety channel of 156-80 MHz
and to the other channels specified in Appendix 18 to the Radio Regulations, Geneva, 1959
(see also No. 1363 of the Radio Regulations, Geneva, 1959);
9.

that frequency assignments to other services should, as far as possible, take into accountthe possibility of interference to the VHF mobile maritime radiotelephone service due to thegeneration of intermodulation products; in particular, powerful emissions from stations nearcoastal areas and with frequencies differing by about 4-6 MHz from one another, should be
avoided if possible.

R EC O M M ENDATION 428-1
DIRECTION-FINDING IN THE 2 M Hz BAND ON BOARD SH IPS(Question 2/XIII)The C.C.I.R.,(1963 - 1966)CONSIDERING(a) that, according to the Convention for the Safety of Life at Sea, London, 1960, the medium
frequency radiotelephony calling and distress frequency of 2182 kHz will become of increas­
ing importance to the safety of life at sea;(b) that, in most distress cases, merchant ships and fishing vessels and other surface craft
participate in search and rescue;

— 205 —Rec. 428-1(c) that in addition to ships between 500 and 1600 tons gross tonnage, which are already required
to be fitted with medium frequency radiotelephone equipment if they do not carry medium
frequency radiotelegraph equipment, ships between 300 and 500 tons gross tonnage will
also be required to fit such equipment, in accordance with Chapter IV, Regulation 4 of theConvention for the Safety of Life at Sea, London, 1960;(d) that a large number of ships of more than 1600 tons gross tonnage (which are compulsorily
fitted with medium frequency radiotelegraph equipment), are voluntarily fitted with medium
frequency radiotelephone equipment and that the number of such ships is increasing;(e) that the majority of deep-sea fishing vessels are fitted voluntarily with medium frequency
radiotelephone ■equipment;(f) that an increasing number of ships are being fitted with direction-finding equipment capableof taking bearings in the 2 MHz band;(g) that direction-finding and especially homing by ships is important in cases of distress;(h) that Recommendation No. 31 of the Convention for the Safety of Life at Sea Conference,
London, 1960, drew the attention of contracting governments to the studies being undertaken
under Question 2/XIII by the C.C.I.R.,(i) that technical studies in several countries have shown:i.a that direction-finding, or at least homing, is usually possible in the 2 MHz band on manyships;
i.b that compared with the problems of direction-finding by ships in the lower parts of the medium
frequency band, the main cause of error in direction-finding in the 2 MHz band is re-radiationfrom various parts of the ship’s super-structures, masts, downleads, halyards, stays, derricks,
etc., and from other antennae;
i.c that errors caused by re-radiation effects, however, should be constant if the disposition andelectrical conditions of the re-radiators are constant and that such errors can be taken into
account by calibrating the direction-finder;
i.d that direction-finding and homing is easier on board small ships than on larger ones, because
an increase in the size of ships and their superstructures, masts, etc., as given in § i.b, leads
to an increase of disturbing resonance effects;
i.e that a reliable direction-finder calibration can be more readily obtained if it is restricted toa specific frequency such as 2182 kHz, instead of a wide frequency band;i.fthat even where omnidirectional direction-finding, even on a specific frequency, is difficult
or impossible (such as on board large vessels with strong re-radiation effects), homing will
nearly always be possible;
UNANIMOUSLY RECOMMENDS

1.

that the following technical measures and precautions should be observed when installing
direction-finders capable of taking bearings in the 2 MHz band:

1.1 the antenna system, including the sense antenna, of the direction-finder should be erected
as far as possible away from any re-radiators;
1.2 the direction-finder antenna system should, preferably, be installed on the fore-and-aft lineof the ship;
1.3 if the direction-finder antenna system is fitted on a mast, it should, preferably, be installed
symmetrically on top of the mast and not to one side of it;
1.4 if the resonnance frequency of a mast and its rigging is within approximately ± 20 % of thefrequency used for direction-finding, then the antenna system of the direction-finder should
not in general be mounted on or near the top o f the mast, unless the antenna system is one

Rec. 428-1— 206 —

which is not influenced by the mast resonance. The calculation or assessment of the resonancefrequency should take into account the effect of the antenna system of the direction-finder;
1.5 that the sense antenna should be mounted on or as near as is practicable to the central axisof the antenna system of the direction-finder;
1.6 the effects caused by re-radiating antenna wires can be minimized by providing properly
located isolating switches for the antennae;
1.7 re-radiation from the rigging (e.g. stays, wire ropes, etc.) should be reduced by the insertionof insulators such that the resonance frequency of the longest portion is considerably above
the highest frequency used for direction-finding;
1.8 the formation of “ closed loops ”, e.g. by the rigging, should be avoided by inserting insula­tors at appropriate points;
1.9 to avoid electrically-doubtful connections, the connecting points of movable parts of the
rigging, and connections between masts and derricks, wire ropes, etc., should be short-circuited
as far as possible;
2.

that the following measures and precautions should be observed in the calibration of direc­
tion-finders for the 2 MHz band:

2.1 the rigging, downleads, derricks, halyards, etc., should be in their sea-going positions;
2.2 any antennae that affect the direction-finder should, preferably, be isolated and other antennae
which cannot be isolated (for example, because of operational requirements), should be in thesame condition as they will be when bearings are being taken at sea; the condition and elec­
trical arrangement of all antennae should be noted on the direction-finder calibration charts;
2.3 calibration should be carried out in an area well clear of the shore and of other ships. If
a shore-based transmitter is used, calibration should be carried out on a line passing throughthat station and crossing the coast-line approximately at right angles. The transmitting
antenna should radiate vertically polarized waves from a single element, and care should betaken to avoid re-radiation from any object in the vicinity. The distance between the trans­mitting antenna and the direction-finder should be great enough to avoid the calibration being
affected by the induction field of the transmitting antenna;
2.4 care should be taken to ensure that the direction-finder gives the correct sense on all bearings
and frequencies concerned;
2.5 the direction-finder calibration should, as a general rule, cover the full 360° and, as far as
possible, should be made at sufficiently small bearing intervals (say, in steps of a few degrees),
to detect any sudden changes in the calibration curve (for example, re-entrant portions where
two or more different corrections exist for the same indicated bearing);
2.6 calibration at 2182 kHz should be carried out at a frequency as near as possible to 2182 kHz,
special attention being paid to No. 1325 of the Radio Regulations, Geneva, 1959, and to
the avoidance of interference to established operations in adjacent channels;
3.

that the calibration should be checked periodically, especially if the condition of the rigging,etc., has been altered since the last calibration;

4.

that on board ships equipped with a direction-finder, the frequency range of which includes
the 2 MHz band, a calibration should be made to determine if the direction-finder could
be used without modification for omnidirectional direction-finding, or at least for homingon the frequency of 2182 kHz;

5.

that when Administrations encourage the use of direction-finders on board ship, capableof operating in the 2 MHz band, or at least on the international radiotelephony distress and— 207 —Rec. 428-1, 429-1

calling frequency of 2182 kHz, they should also encourage the provision of suitable facilities
for the calibration of such direction-finder equipment;
6. that the Director, C.C.I.R. should be invited to bring this Recommendation to the attentionof the I.M.C.O. Reference is made to Recommendation No. 31 of the Convention for the
Safety o f Life at Sea, London, 1960;
7. that Administrations should bring the above Recommendations to the attention of those
responsible for the provision, installation, and maintenance of direction-finders on ships;
8. that Administrations should continue the study of Question 2/XIII.
ANNEX
When the above precautions and technical measures have been taken, under good condi­
tions an accuracy of about =b 2° can be attained in taking bearings in the 2 MHz band byreception of “ ground ” waves on board ships of less than about 800 tons gross tonnage.
In unfavourable conditions, for example, when the ship is pitching and rolling, an accuracyof about dz 5° can be obtained. On larger ships, the accuracy may be worse, but in mostcases it should usually be possible to use the direction-finder for homing purposes on 2182 kHz.
Bearings taken by reception of skywaves, although variable in azimuth and sharpness, areuseful for homing into the ground wave range by utilizing their average value.

R E C O M M E N D A T IO N 429-1
IN T E R F E R E N C E LEV EL O N T H E R A D IO T E L E G R A PH D IST R E SS
FR E Q U E N C Y
The C.C.I.R.,(1963 - 1966)CONSIDERING(a) that the Safety of Life at Sea Conference, London, 1960, adopted the following Recom­
mendation (No. 27):
“ The Conference, recognizing that at present there is a tendency to increase the maximum
power of radiotelegraph installations, and that this may lead to an increase in the interference
level on the radiotelegraph distress frequency, which may considerably impair the use ofthis frequency for safety purposes, recommends that the International Telecommunication
Union should be invited by the Organization - (i. e. Intergovernmental Maritime Consult­ative Organization) - to consider what measures can be taken to prevent such an increasein the interference level ” ;(b) the provisions of the relevant Radio Regulations, Geneva, 1959;(c) the experience of coast station radio operators and ships’ radio officers;
UNANIMOUSLY RECOMMENDS

1. that the following measures should be taken to reduce interference at 500 kHz;
1.1 messages prefixed by the Safety Signal, TTT, should be sent on a working frequency after
an initial announcement at 500 kHz in accordance with Nos. 1107 and 1492 of the Radio
Regulations, Geneva, 1959;* This Recom m endation terminates the study o f Study Programme 171.

Rec. 429-1, 438— 208 —

1.2 coast stations should use their working frequencies to reply to calls from ships at 500 kHz,in accordance with Nos. 1116 and 1117 of the Radio Regulations, Geneva, 1959;
1.3 coast stations making calls to ships at 500 kHz should request ships to reply on their working
frequencies, as permitted by Nos. 1023 and 1116 of the Radio Regulations, Geneva, 1959;
1.4 No. 1092 of the Radio Regulations, Geneva, 1959, which forbids “ CQ ” calls to be made incongested areas, should be enforced by Administrations;
1.5 greater use should be made o f the facilities provided under No. 972 of the Radio Regula­tions, Geneva, 1959, for reducing power at ship stations, and coast stations as far as practi­
cable should use the minimum necessary power, particularly at night, in accordance with
No. 694 of the Radio Regulations, Geneva, 1959;
1.6 steps should be taken by Administrations to prevent unnecessary signalling at 500 kHz, part­icularly during distress, in accordance with Nos. 693, 1107 to 1113 inclusive, and 1445 of
the Radio Regulations, Geneva, 1959;
1.7 for Class A2 emissions at 500 kHz the note frequencies used by various stations should, as
far as practicable, be spread over the range 450 to 1350 Hz;
1.8 prolonged calling at 500 kHz by ships endeavouring to establish contact with distant coaststations should be avoided by greater use of H F channels or by relaying of messages;
1.9 in areas where considerable use is made of 500 kHz for calls and replies, the calling frequencies
assigned to coast stations should be spread over the band 497 to 503 kHz in accordancewith No. 1115 of the Radio Regulations, Geneva, 1959;
1.10 in Regions 1 and 3, the frequency of 512 kHz may be used as a supplementary frequency
for calls and replies when 500 kHz is being used for distress, in accordance with Nos. 1125
to 1129 inclusive of the Radio Regulations, Geneva, 1959.

R EC OM M ENDATION 438 *USE OF CLASSES OF EM ISSIO N A2H AND A3H
ON TH E DISTRESS FREQUENCIES 500 kHz AND 2182 kHz RESPECTIVELYThe C.C.I.R.,(1966)CONSIDERING(a) that, for distress and safety purposes, the Convention for the Safety of Life at Sea (SOLAS)
prescribes the use of classes of emission as assigned by the Radio Regulations, Geneva,
1959, (SOLAS London, 1960, Chapter IV, Regulations 9 (e), 9 Qi) (0, 12(6), 12 ( / ) , 13 (c),13 (/), 15 (6) and 15 (/));(b) that for distress and safety purposes, the Radio Regulations, Geneva, 1959, prescribe forships and survival craft:- Class A2 emission at 500 kHz (see Nos. 974, 994, 995 and 1134);- Class A3 emission at 2182 kHz (see Nos. 984, 994, 996 and 1337); .
* This Recom m endation terminates the study o f Question 273, and should be brought to the attention o f
the Maritime World Administrative Radio Conference o f the I.T .U ., 1967.

— 209 —Rec. 438, 439(c) that, to the maximum extent possible, amplitude-modulation systems should use single­
sideband (SSB) emissions having characteristics in accordance with the relevant C.C.I.R.
Recommendations (No. 670 of the Radio Regulations, Geneva, 1959) and that SSB opera­tion be introduced as far as operationally required for radiotelephony in band 6 and band 7(Recommendation No. 28 of the Administrative Radio Conference, Geneva, 1959);(d) that in several countries, new marine transmitters are being designed which make use of
SSB techniques;(e) that SSB transmitters may easily and economically be adapted for Class A2H and ClassA3H emission;(f) that unless SSB emission is universally adopted in the MF maritime mobile service, there
will be a need for communications between DSB and SSB stations;(g) that practical and laboratory tests have proved that class of emission A2H on 500 kHz is
as effective as class of emission A2, and class of emission A3H at 2182 kHz is as effective
as class of emission A3 for alarm, distress, urgency and safety signals when received bystations equipped for DSB reception by aural means or automatic receiving equipment;
UNANIMOUSLY RECOMMENDS

1.

that for alarm, distress, urgency and safety signals class of emission A2H at 500 kHz should
be considered as effective as class of emission A2.
Note. - To ensure the correct operation of all types of radiotelegraphy automatic alarm
equipment, both the carrier and modulating tone should be keyed;2.

that for alarm, distress, urgency and safety signals class of emission A3H at 2182 kHz should
be considered as effective as class of emission A3.

RECOM M ENDATION 439
EMERGENCY POSITION-INDICATING RADIO BEACONSOPERATING AT THE FREQUENCY 2182 kHz(Q uestion 318)
The C.C.I.R.,(1966)CONSIDERING(a) Recommendation No. 48 of the International Conference on Safety of Life at Sea, London,
1960;(b) Report of the Inter-Agency Working Group, June, 1962, on Coordination of Safety at Sea
and in the Air, reproduced in Doc. 393, Geneva, 1963;(c) the Resolution A. 91 (IV), adopted on 27 September 1965 by the Fourth Session of the Assem­
bly of the Inter-Governmental Maritime Consultative Organization (I.M.C.O.) and repro­
duced in Doc. XIII/71, 1963-1966;(d) the Report of the Fourth Air Navigation Conference of the International Civil Aviation
Organization (I.C.A.O.) (Montreal, 9 November - 3 December, 1965) and reproduced inDoc. XIII/103, 1963-1966;
14

Rec. 439

— 210 —(e) that there is an urgent need for a beacon to indicate the position of survivors and to facili­tate search and rescue operations at sea,(f) that ships compulsorily fitted for radio telephony are required to keep continuous watch
at the frequency 2182 kHz (see Regulation 7, Chapter IV of the International Convention
for the Safety of Life at Sea, London, 1960);(g) that it is desirable for the beacon signal to be received on the loudspeakers of the receiver
which is equipped with filters for the two-tone alarm signal (1300 Hz and 2200 Hz respec­tively) and which is used for watch-keeping at 2182 kHz. This alarm signal is described in
Recommendation 219-1 and Recommendation No. 33 of the International Conference of
Safety of Life at Sea, London, 1960;(h) that the type and sequence of the signal to be transmitted by the beacon should facilitatehoming by ships as well as by SAR aircraft taking into account their different speeds;(i) that the signal emitted by the beacon should as far as practicable be clearly distinguishable
from the radiotelephone alarm signal transmitted by ships still afloat or by portable radio
apparatus;(j) that the signal emitted by the beacon should not create harmful interference to other distresscalls and messages;( k) that in the interest of high reliability and minimum expense the electronic and mechanicaldesign of the beacon and especially of its keying device should be as simple as possible;(I) that national and international trials under operational conditions have already been carriedout successfully with such beacons;
UNANIMOUSLY RECOMMENDS

1.

that emergency position-indicating radio beacons operating at the frequency 2182 kHzshould be divided into two classes;

1.1 low-power beacons designated “ Type L ” producing a field strength equal to or less than
10 |iV/m at a distance of 30 nautical miles at sea level;
1.2 high-power beacons designated “ Type H ” producing a field strength greater than 10 gV/m
at a distance of 30 nautical miles at sea level;
2. that for both classes of beacon, class of emission A2 should be used;
3. that for both classes of beacon, the depth of modulation should be between 30% and 90%;
4. that the keying signal for “ Type L ” beacons should consist of a keyed emission modulated
by a tone of 1300 Hz ( ± 20 Hz) having a ratio of the period of the emission to the periodof silence equal to or greater than 1, and an emission duration between 1 and 5 s;*
5.

that the keying signal for “ Type H ” beacons should either consist of the radiotelephone
alarm signal (Radio Regulations, No. 1465) or be the same as in § 4 above; if the radio­
telephone alarm signal be used, the Morse letter “ B ” and/or the call sign of the ship towhich the beacon belongs, should be included by keying a carrier modulated by a toneof 1300 Hz ( ± 20 Hz) or of 2200 Hz ( ± 35 Hz);*

6.

that for “ Type L ” beacons, the keying signal should be transmitted continuously;* Beacons carried by ships o f the U .S.A . may use, instead o f the signals given in §§ 4 and 5, a tone sweep­
ing from 1400 H z to 300 H z not faster than twice a second.

— 211 —Rec. 439, 440

7.

that for “ Type H ” beacons, the keying cycle should consist alternately of the keying signal
having a duration between 30 and 50 s, followed by a period of silence having a duration
between 30 s and 60 s;

8.

that the keying cycles given in §§ 6 and 7 may be interrupted by speech transmission if Admin­
istrations permit such an additional facility;

9.

that the minimum initial field strength produced by “ Type L ” beacons should be 2.5 gV/m
at a distance of 30 nautical miles at sea level;

10. that after a period of 48 hours continuous operation the radiated power should not be lessthan 20% of the initial power;
11. that the beacons should be designed for the following temperature ranges:- when stowed, at least—20°C to + 55°C;- when operating in the open air, at least —10°C to + 45°C;- when operating afloat, at least—3°C to + 35°C (water temperature);
Note. - Exceptionally, for radio beacons carried by ships operating in limited areas only,
other temperature ranges may, due to special conditions in such areas, be accepted.
12. that if the beacons are designed to come into operation automatically when floating, thenoverriding facilities should be provided to enable them to be switched on and off manually;

13. that beacons should be tested about every 12 months, care being taken to ensure that false
alarms are not caused by radiating the signal;

14. that primary batteries for the beacons should have a minimum storage life of about 2 years,
and primary batteries in the beacons should be replaced at intervals of about half the storagelife;

15. that the mechanical design of the beacons should be such that it is small, light-weight; float­
able, watertight and shock-resistant;

16. that the Administrations be invited to make provision in the Radio Regulations for the opera­tion of emergency position-indicating radio beacons at the frequency of 2182 kHz;
Note 1. - The Director, C.C.I.R. is requested to transmit this Recommendation to the Inter­governmental Maritime Consultative Organization (I.M.C.O.) and to the International Civil
Aviation Organization (I.C.A.O.).
Note 2. - This Recommendation, together with Opinion 25 terminates the study of Question 318
and cancels Opinion 21.

RECOM M ENDATION 440
THE INTRODUCTION OF DIRECT-PRINTING TELEGRAPH EQUIPM EN T
IN THE M ARITIM E M OBILE SERVICE(Question 5/XIII)The C.C.I.R.,(1966)CONSIDERING(a) that there is a requirement for communication in the maritime mobile service by meansof direct-printing telegraph techniques for exchanging message and data information;

Rec. 440

— 212 —(b) that various systems have already been proposed to meet this requirement and tests havebeen carried out by different Administrations (see Report 361);(c) that further systems, especially forward acting error indicating and correcting systems, may
be proposed;(d) that, therefore, it is not yet possible to recommend a specific system to be applied in themaritime mobile service;(e) that whilst Study Group III has to deal with such systems from the point of view of the fixed
services, Study Group XIII has to consider the special aspects concerning their applicationin the maritime mobile service;(f) that it is expected that direct-printing telegraph systems will be introduced into the mari­time mobile service between the World Administrative Radio Conference, 1967, and asubsequent Administrative Radio Conference;(g) that the World Administrative Radio Conference, 1967, may need guidance in planning
the appropriate radio channels;
UNANIMOUSLY RECOMMENDS

1. that a direct-printing telegraph system for the maritime mobile service should be suitablefor:
1.1 exchanging messages and low-speed data information between two stations, i.e. betweena coast station and a ship station or between two ship stations; and1.2 broadcasting from one station to several other stations, i.e. from a coast or ship station toseveral other stations;2. that the system should accept signals conforming to C.C.I.T.T. Code No. 2 and should
provide similar signals at its output for extension to the Public Telegraph Network (seeI.T.U. List of Definitions, Part I, Item 01.12) and vice versa;
3. that bearing in mind the variations in the propagation path, the lowest modulation rate ,compatible with the grade of service required should be used; in any case it should not exceed
100 bauds;
4. that, bearing in mind that the bandwidth required per communication channel need notexceed 340 Hz and that some Administrations may require more than one channel, the World
Administrative Radio Conference, 1967, should consider allocating to Administrations,for this service, blocks of frequencies not exceeding 1-5 kHz wide;
5. that the performance of the system should provide a sufficiently small character error-rate
to meet operational requirements but shipborne equipment should not be unduly complex.

D. 3: Land mobile service
No Recommendations in this Sub-section.

— 213 —Rec. 441

D. 4: Aeronautical mobile service
RECOM M ENDATION 441
SIGNAL-TO-INTERFERENCE RATIOS AND M INIM UM
FIELD-STRENGTHS REQUIRED IN THE M OBILE SERVICES
Aeronautical mobile services above 30 M Hz
(Question 1/XIII)The C.C.I.R.,(1966)CONSIDERING(a) that the Administrative Radio Conference, Geneva, 1959, in Recommendation No. 3, invited
the C.C.I.R. to continue its study of signal-to-interference ratios and minimum field-strengths;(b) that there are partial data relating to interference protection ratios and minimum fieldstrengths required in certain documents of conferences of the I.T.U., such as those of the
Final Acts of the International Administrative Aeronautical Radio Conference, Geneva,
1948-1949;fc) that the International Civil Aviation Organisation have adopted standards and recommended
practices for the best use of VHF frequencies and the avoidance of harmful interference;
UNANIMOUSLY RECOMMENDS

that the provisions made by the International Civil Aviation Organisation should be considered
as adequate for the planning and protection of aeronautical mobile (R) service frequencies
above 30 MHz; the provisions are contained in Annex 10, Chapter 4, § 4.1.5 to the Conven­tion of International Civil Aviation, supplemented by the instructions contained in theattachment A to Part II of the same document.

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENT

— 215 —Rep. 93

REPORTS OF SECTION D (MOBILE SERVICES)

D. 1: General
REPORT 93 *H F (DECAMETRIC) AND VHF (METRIC) DIRECTION-FINDING **(Question 159)
(1956)

1.

Introduction
Two documents, 67 (United States of America) and 232 (United Kingdom), were
submitted to the VUIth Plenary Assembly in response to Question 106. A summary of thesetwo documents, and of the discussion on them, is given below.
It was generally agreed that, whenever possible, the accuracy of bearings and positions andtheir classification, should be based on the probability concept.
The United Kingdom document expresses bearing accuracies in the form of errors thatare exceeded on only 1 occasion in 20 and the U.S.A. document gives the standard deviation
error. For ease of comparison of results, all accuracies have been expressed in a common
form in this Report.

2.

Accuracy of HF (decametric) bearings
The accuracy of H F (decametric) bearings depends principally upon the following factors:- type of direction-finding (DF) equipment, for example, Adcock type,- type of site,- frequency,- range and signal strength,- ionospheric conditions, particularly diurnal variations,- amount of interference.
- number o f bearings taken,- skill of the operator.
By day, the error which is exceeded on only 1 occasion in 20 (referred to subsequently
as the 95 % error), lies between about 3° and 10° for ranges of the order of 500 to 4000 km,
depending on the site, frequency, and whether a group of bearings is taken or only one snap
bearing. More detailed data are given in the Annex. At night, errors are somewhat greater,by amounts of up to about 1°. At distances less than 500 to 1600 km (depending on iono­
spheric conditions), the error progressively increases, and may rise to as large as 10° to 20°
until the ground wave or the E-layer mode of propagation predominates. In general, errors
are less at the higher frequencies.

3.

Accuracy of VHF (metric) bearings
In the United Kingdom, the 95 % error of VHF aeronautical direction-finding stations
is generally about 5°, but in the U.S.A. it has been found that the 95% error is usually* This Report was adopted unanimously.
** See also Appendix 23 to the Radio Regulations, Geneva, 1959.

Rep. 93

— 216 —

about 12° on transmissions from aircraft. The difference is probably due mainly to the effects
of differences of siting, since with refinements in siting, the 95 % error is reduced to about 4°
in the U.S.A. At long ranges, beyond the normal service area, VHF direction-finding bearingsin the U.S.A. have been found to be sporadic but the accuracy is sometimes as good as 6°.

4.

Accuracy of HF (decametric) position fixing
The accuracy of position fixing depends principally on the “ geometry ” of the direc­
tion-finding network, its size and its disposition with respect to the transmitting station
concerned, the degree to which the various stations can take simultaneous bearings and act
in unison, and the number of stations in the network. The greatest accuracy is obtained
when the most probable position of the transmitting station can be evaluated statistically,
although in certain applications it is recognised that statistical evaluation may not be practic­
able or of operational importance. The accuracy of a direction-finding fix can be expressedin terms of the size, position and orientation of the ellipse in which the transmitting station
lies with a given probability. Various methods for deriving and plotting probability ellipses
are given in the references in Doc. 232, Warsaw, 1956.

5.

Accuracy of VHF (metric) position fixing
The accuracy of VHF position fixing can be determined in a manner similar to that for
HF. But in the aeronautical mobile service, which is one of the main users of VHF directionfinding, there is not usually sufficient time to evaluate the accuracy of a fix because of the highspeed of the aircraft. At VHF, the problem may be simpler than at H F because the direc­
tion-finding networks, in general, will be smaller and can more easily be controlled auto­
matically and have a central automatic display.

6.

Classification of bearings in general
It was considered that it would be very advantageous to have a common classification
system of bearings for all frequency bands (MF, H F and VHF) and for all types of service, forexample, the maritime mobile and aeronautical mobile.

7.

Classification of HF (decametric) bearings
The U.S.A. proposed a subjective method of classification by the operator for describing
to the plotting centre the conditions under which a bearing has been taken. The factors thatthe operator should take into account are strength of signal, sharpness of the null, amountof fading and interference, the amount of goniometer swing required in taking the bearing andthe number of bearings that have been taken in the time available. The proposed system ofclassification is as follows:
Class A - Bearing appears good, meeting the following requirements:(1) strong signal,(2) definite indication (sharp null, etc.),(3) negligible fading,(4) negligible interference,(5) less than 3° of arc of bearing swing,(6) observed repeatedly for an adequate period of time.

Rep. 93

— 217 —Class B - Bearing appears fair, being degraded by one or more of the following factors:(1) marginal signal strength,(2) blurr (blunting) of indication,(3) fading and/or audio distortion,(4) light interference,(5) more than 3° but less than 5° o f arc of bearing swing,(6) short observation time.
Class C - Bearing appears poor, being degraded by one or more of the following factors:(1) inadequate signal strength,(2) severe blurr (blunting) of indication,(3) severe fading and/or audio distortion,(4) strong interference,(5) more than 5° of arc of bearing swing,(6) insufficient observation time.
The United Kingdom proposed that the accuracy of a bearing should be evaluated statis­
tically from a knowledge of the five component variances which make up the total varianceof the bearing, namely, instrumental, site, propagation, random-sampling and observational
components. The bearing would then be classified as follows:
Class A: Probability of less than 1 in 20 that the error exceeds

2°,Class B: Probability o f less than 1 in 20 that the error exceeds

5°,Class C: Probability of less than 1 in 20 that the error exceeds 10°,Class D : Bearings whose accuracy is less than that of Class C.

8.

Classification of VHF (decametric) bearings
It was considered that time alone prevents the classification of VHF bearings taken on
transmissions from aircraft and it is not possible for the operator to classify bearings. But
the United Kingdom suggested that it would be helpful if VHF aeronautical stations wereclassified, based upon flight-checking procedures. All bearings would then be given theclassification of the station, unless they were taken under conditions inferior to those underwhich the station was calibrated.

9.

Classification of HF (decametric) position-fixes
It was generally agreed that the accuracy of a fix-position should, whenever time permits,
be given in terms of probability ellipses. The United Kingdom proposed that no formalclassification be adopted since the size and shape of the ellipse for a given probability depends
upon the “ geometry ” of the network and the transmitting station, the ionospheric conditions,etc. Where time is important, the U.S.A. proposed that the most probable fix-position
would be given in degrees and minutes of latitude and longitude and should be classified
as the equivalent circle in which the transmitting station probably lies:
Classification

Lim it of areas

Good
Fair
Poor
Estimated

40 km, radius, or less
80 km, radius, or less
120 km, radius, or lessmore than 120 km radiusRep. 93

— 218 —

10. Classification of VHF (metric) position-fixes
For the aeronautical mobile service, it was considered that classification in terms ofprobability ellipses was not likely to be practicable or useful. The United Kingdom madeno proposals on this point; the U.S.A. proposed the following classification:
Classification

Limit o f areaGood
FanPoorEstimated

4 km, radius, or less
8 km, radius, or less
12 km, radius, or lessmore than 12 km radius

11. Aeronautical aspects
It was considered that since VHF direction-finding stations are widely used in civil
aviation, Administrations should be invited to seek the advice of the International Civil
Aviation Organization on all the aeronautical aspects of VHF direction-finding and positionfinding.

12. Type of signal for VHF (metric) direction-finding
In general, the signal for VHF direction-finding purposes should include long dashes ofat least 5 s duration, but the direction-finding station should also be permitted to specify
the duration of the signal in certain circumstances. In the aeronautical mobile service, theprocedure laid down by the I.C.A.O. has been found satisfactory. This specifies two dashesof plain carrier, each of approximately 10 s duration, followed by the call sign of theaircraft, unless another signal has been requested or is known to be required by the directionfinding station.
ANNEX
A p p r o x im a t e e r r o r (i n d e g r e e s ) w h i c h m a y b e e x p e c t e d
TO BE EXCEEDED ON ONLY 1 OCCASION IN 20

Conditions: - H F Adcock direction-finder
Daylight- Ranges between about 500 and 4000 km.
3 M Hz6 M Hz9 M HzSingle snap
bearing

M ean o f
10 bearings
taken in
5 min

Single snap
bearing

Mean of10 bearings
taken in
5 min

Single snap
bearing

M ean of10 bearings
taken in
5 min

Very good

7

6

6

5

6

4

Good, average

10

9

8

7

7 ■•

6

Type o f siteRep. 358

— 219 —R E P O R T 358 *SIGNAL-TO-INTERFERENCE PRO TECTION RATIOSAND M IN IM U M FIELD STRENGTHS REQUIRED IN THE M OBILE SERVICES **(Question 1/XIII)(1966)
1.

The following documents were submitted to the Xlth Plenary Assembly, Oslo, 1966, in reply
to Question 272 (subsequently designated Question 1/XIII):Doc. XIII/25 (United Kingdom)Doc. XIII/41 (F.R. of Germany)
Doc. XIII/88 (Japan)
Doc. XIII/95 (I.R.F.B.)

2.

VHF and UHF maritime and land mobile services
Man-made noise and natural noise have not been considered in this section.

2.1 The signal-to-interference protection ratios given in Table I were tentatively suggested for
VHF and U H F maritime and land mobile services.
T a b leI

W anted emission

Unwanted emission

R F protection ratio (dB)

F3
F3
A3
A3

F3
A3
F3
A3

7
17
19

'

8

This Table is based on the degradation of the wanted signal at the output of the receiverfrom a signal-to-noise ratio of 20 dB to a signal-to-noise plus interference ratio of 14 dB.
The Table is based on interference transmission as follows:- for class of emission A3, 70% modulation by a tone of 1000 Hz;- for class of emission F3, a frequency deviation of 70 % of the maximum by a tone of1000 Hz, the receiver passband being adapted to the devia­
tion used and the information transmitted.
Under these conditions, class of emission A3 requires protection ratios about 10 dB
higher than F3.
2.2

The median values of the field strengths to be protected, for an average grade of service,
are given in Table II.
The values given in Table II take into account receiver sensitivities, antenna effectivenessand feeder losses over the various frequency bands.
* This Report was adopted unanimously.
** The aeronautical mobile service above 30 M H z is dealt with in Recommendation 441.

— 220 —Rep. 358

TABLE II
Frequency band(MHz)

M edian value o f the fieldstrength to be protected(dB rel. 1 pV/m)

30 to 50
50 to 100
100 to 200
400 to 470

8
14
20
28

Higher grades of service, such as those normally provided for connection to the public
telephone network, may require to be protected for 90 % of time and location. The relevant
field strengths can be derived from the curves given in Recommendation 370-1 andReport 244-1.
2.3 Some information on protection ratios and minimum field strength may also be found in
the “ Special Agreement between the Administrations of Belgium, the Netherlands and theFederal Republic of Germany relating to the use of metric and decimetric waves for fixed
and mobile services in border areas, Brussels, 1963 ”, and in the Final Acts of the Special
Regional Conference, Geneva, 1960.
2.4 Doc. XIII/88 (Japan), 1963-1966 also deals with the above questions for signal-to-noise
ratios of 30 and 40 dB at receiver output.

3.

HF maritime mobile service
In Doc. XIII/95 (where the expected values of natural noise and of man-madenoise at a quiet receiving location have been taken into account), the I.F.R.B. gave an
extract from the Technical Standards used by the Board when examining, in accord­
ance with Article 9 of the Radio Regulations, notices of frequency assignments to coaststations in the H F bands.
It indicated for both radiotelephony and radiotelegraphy the protection ratio values
which it applies and the minimum field strength to be protected, in characteristic maritime
areas.
The purpose was to inform Administrations, as the World Administrative Maritime
Radio Conference, 1967, draws near, of the Technical Standards used by the Board.

4.

Conclusions
Considerable additional work concerning §§ 2 and 3 is necessary to determine more
fully the appropriate protection ratios and the values of the field strengths to be protected,
and also to determine and record the measurement methods which should be adopted.

— 221 —Rep. 318

D. 2: Maritime mobile service
REPORT 318 *M ARINE IDENTIFICATION DEVICES(Question 158)
(1956 - 1963)

1.

GeneralTwo documents, 53 (United Kingdom) and 71 (United States of America), were submitted
to the VUIth Plenary Assembly in answer to Question 105 on the identification of a response
on a marine radar display.
This Report summarizes the nature of the problem, the work that has been done, as
described in the two documents, and the main points arising out of the discussions at the
VUIth Plenary Assembly.

2.

Nature of the problem
There is a growing use of radar on ships to assist navigation and to prevent collision.
Ideally, it would be desirable for radar to give the navigator the same kind of informationthat he would obtain visually in clear weather. But, in the present state of radar development
experience has shown that the radar information might, with advantage, be. supplemented
by additional information, although there is not, as yet, uniformity of opinion among thoseconcerned with marine navigation, on the type of additional information that would be mosthelpful to the navigator.
The radar installation on a ship gives, at any instant, only the bearing and position o f theother ships. The course and speed of another ship by this means can then be obtained only
by plotting; and, in any case, the radar cannot give the future intentions of the other ship.
This points to the need for an appropriate communication link as an element of any effective
marine identification device employing the types of radar installation in current use.
An identification device should be unambiguous and should be at least as good as theresolution of the associated radar, so that there would be no confusion concerning the iden­tification of two adjacent echoes on the same bearing or at the same range. The additional
information required, for example, might be the call letters of the other ship, so that commu­
nication could be established; or it might be the course and speed, or the aspect, of the othervessel.
So far, research has been directed towards the development of devices that would iden­
tify uniquely a particular echo of a ship on the radar screen of another ship or of a shorebased station. Various proposals, e.g. the use of transponder techniques, have been givenin the two documents mentioned and are described briefly in §§ 3 and 4.

3.

Summary of Doc. 53 (United Kingdom)

3.1 Harbour radar identification
It was considered that suitable devices of the transponder type might facilitate the move­
ment of vessels in the approaches to a port or in a harbour, so that the echo of the ship could
be identified on the harbour radar and communication established as required. Identification* This Report, which replaces Report 92, was adopted unanimously.

Rep. 318

— 222 —

in range and bearing would be essential, so that identification, by the use of normal direc­
tion-finding (bearing only), would not normally be sufficient. There is less likelihood ofconfusion in harbour radar identification, because ships would be identifying themselves
to a single harbour radar.
These transponder devices are used in conjunction with a radiocommunication link
between the ship and the shore. On the ship either portable equipment or the ship’s own
radio installation may be used.
Portable radar transponders have been developed which operate in the 3 cm band of
the harbour radar. The transponders and, if necessary, the portable radiocommunicationequipment, are taken on board the ship by the pilot. Identification is established by the
Harbour Controller requesting the pilot to switch on the transponder, when the response
is seen on the harbour radar as a bright line on the bearing of the ship’s echo, with a gap,
corresponding to 1 mile range, commencing at the ship. The ship is thus identified in range
and bearing. The range of the “ black-gap ” transponder is about 17 nautical miles.
This system would be suitable for use with any harbour radar operating in the 3 cm
band and no modification of the harbour radar would be required.
Another type of equipment has also been developed in which the output of a crystal
receiver is used to modulate a VHF “ walkie-talkie ” transmitter which also serves to provide
communication with the shore. At the harbour station, the VHF response from the ship
is fed into the video stage of the harbour radar. This gives a long radial echo along
the bearing of the ship, commencing at a range slightly greater than the ship’s echo.
3.2 Inter-ship radar identification
The former type of transponder mentioned above would not be satisfactory for inter­ship identification, because it might well be impossible to establish communication witha particular unknown ship to request that the transponder be switched on; and, moreover,ambiguity would be unavoidable, when several independent identification processes weretaking place on the same channel.

4.

Summary of Doc. 71 (United States of America)

4.1 Doc. 71 (United States), Warsaw, 1956, is based upon limited experience in the use ofmarine radar identification devices but also covers considerable study of the problem by
the R.T.C.M., whose report thereon is attached to the document cited as Annex 3.
In summary it is observed that:
4.1.1 there are a number of technical methods for the identification of a radar response
as coming from a particular source. All known methods, however, require that thesource have an active radar beacon to co-operate with the calling vessel. One solu­
tion might be in the direction of a system similar to that used by the military (IFF,
Identification Friend or Foe) and now coming into use for civil aviation in the UnitedStates of America for identification of aircraft to airport radars.
4.1.2 In this type of system, each ship-borne radar should be capable of emitting a parti­
cular calling or interrogating pulse or code. All vessels would maintain a beaconon continuous alert so that, on receipt of the interrogating pulse, each beacon would
reply with a specific code identifying the vessel. This code, when displayed on theinterrogating vessel’s PPI adjacent to the radar echo from the vessel carrying the
beacon, would positively identify that echo. Having identified all ships in the vicinity,a radar observer could then contact any one of them directly by whatever commu­
nication means are available. Considerable experimentation has been carried out
to realize a simplified version of this method.

— 223 —Rep. 318

4.1.3 The use of a radar beacon system of the IF F type for marine identification would
require considerable expansion of the coding and display features of any equipment
known to be currently available. It appears that no attempts to do this have as yet
been made in the commercial marine field.
The relatively simplified technique where identification is obtained by energizing
the radar beacons one at a time in response to a demand via a communications link,has been reduced to a practical method and considerable related experimentation
has been carried out in connection with harbour radar installations. The feasibilityof this system has therefore been demonstrated, although the necessary beacons are
not yet commercially available.
4.1.4 The principal practical aspect is, that there is no need to identify a particular radar
echo unless it is desired to communicate with the vessel associated with the echo. In
narrow congested waters this must be practically instantaneous. This seems to requirea radiotelephone circuit connecting the observer of the ship-borne radar directly to
his counter-part on the bridge of the associated vessel. Ocean-going vessels, however,are not generally equipped with such means of communication. Further, the mul­
tiple language problem requires consideration in any international study of this sub­ject. The Great Lakes area of N orth America, where nearly all merchant ships are
fitted with radar and radiotelephone and navigators speak the same language, isan outstanding exception. Operational investigations of ship-to-ship identification
devices have been carried out therefore only in this area.
4.1.5 The number of vessels involved poses a technical difficulty in adapting an IF F system
for marine use, if each vessel were to have a distinct identifying code.
4.1.6 A system of the IF F type in its present form, due to its cost even in a comparatively
simple version, presents an economic factor of importance. The complexity of the
microwave components which contribute most to the cost of such equipment would
be double that required for primary radar alone. The economic factor, however,will undoubtedly be eased as time passes and new technical developments occur, as
they have, for instance, in the field of television.
4.2 A number of different types of devices or methods suggested for accomplishing identificationof a positive or limited nature are outlined in the R.T.C.M. study referred to above. These
include:- responder beacons of various design,- passive devices,- D F identification using radar antennae,- suggestions other than identification.
For further details on such types of devices, see Annex 3 to Doc. 71 (Warsaw).

5.

Discussion of documents
The discussion of the documents has brought out certain important differences in inter­ship identification and shore-based radar identification. In the former case, after the identityof the unknown ship has been established, there may well be difficulty in establishing com­munication because of differences in language, type of radio installation and watch-keeping.
At present, there is no international code on navigational manoeuvres, and “ navigationby communication ” would probably necessitate revision of the International Rules for
the Prevention of Collision at Sea; it would probably raise new legal problems, if,for example, a ship were involved in a collision while executing a manoeuvre agreed inadvance with another ship. On the other hand, the type of identification which is employedfor harbour control does not usually involve such difficulties because the ship has on board
a pilot who is receiving advice from, and may communicate with, his own harbour radar
station. Rapid identification is also very desirable in all such devices.

Rep. 318

— 224 —

An inter-ship identification system would only become effective when the majorityof ships were suitably equipped; and it should be borne in mind that the ship does not receive
any direct benefit from its own identification device. Thus, ships which themselves do
not carry radar are not likely to fit identification devices, particularly if the cost of the device
is comparable with that of a radar installation.
6.

Future work
It was generally agreed in the discussions that it would be most desirable for the C.C.I.R.
to obtain from responsible shipping and administrative authorities, their views on the navi­
gational requirements that should be met by radar identification devices. However, at
the IXth Plenary Assembly, Los Angeles, 1959, the responsible authorities had not, in fact,advised the C.C.I.R. of any operational requirements for such devices and consequently
the studies were terminated.
B i b l io g r a p h y

1.
2.
3.
4.
5.
6.

7.
8.

9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.

E. C. Marine traffic coordination. NFAS-ION-RTCA-RTCM Assembly, New York
(September, 1950).
J a n s k y , Jr., C. M., J a n s k y and B a il e y . The retarded state of the science of marine navigation. IONRTCM Assembly, New York (September, 1950).
Merchant Marine Council Proceedings (September, 1951).
W y l ie , F. J. The use of radar for preventing collisions at sea. Radio Advisory Service, Journal of
the Institute of Navigation (British), 6, 271 (1953).
W y l ie , F. J. Use of radar to avoid collision. Radio Advisory Service, Lloyds List & Shipping Gazette(January 5, 1954).
M i l w r i g h t , A. P. L. A beacon for ship identification. Royal Naval Scientific Service, Journal of
the Institute of Navigation (British) (April, 1954).
I s b is t e r , E. J. and G r i s w o l d , W. R. Shore-based radar for harbour surveillance. Sperry GyroscopeCo., Electrical Engineering, 71, 12, 1072-77 (December, 1952).
P h i l i p s , E. C., NFAS and I s b is t e r , E. J. Marine identification. Sperry Gyroscope Co., RTCM Spring
Assembly Meeting, New York (May, 1952).
Shore-based radar for New York harbor, a report, Port of New York Authority (August, 1952).
H a r p e r , R. B. Pilot boat identification, harbor radar systems. Sperry Gyroscope Co., Paper presented
before Western Regional Meeting, Inst, o f Nav., Los Angeles, January 23, 1954, published in
Navigation.
Symposium papers, of the panel “ Radar plus what ”, delivered at RTCM Assembly Meeting, Boston,
Mass., 56-70 (October 13-15, 1954).
R o b e r t s , A. Radar beacons. M IT Rad. Lab. Series, Vol. 3, McGraw Hill (1947).
I s b is t e r , E. J. RADENT beacon evaluation trials. Fall Assembly Meeting, RTCM, Chicago (1953).
S t o c k m a n , H. Communication by means of reflected power. Proc. IRE, 36, 1196-1204(October, 1948).
RAMARK beacons, U.S. Coast Guard.
I s b is t e r , E. J. and B u s b y , J. W. RAMARK beacons. Sperry Gyroscope Co., Navigation, 2,
357 (June, 1951).
MICROWAVE POLARIS, U.S. Coast Guard.
You may have the answer. Merchant Marine Council Bulletin, U.S. Coast Guard (September, 1953).
Unpublished paper of Earl D. G r a y , McKeel Machine Co., Phila., Pa.
AUDAR Technical Bulletin, Radio Industries Corp.
K a m d r o n , Capt. R. Janus course broadcasting instrument (Bulletin), Seattle, Washington.
Marine identification problem, Final report, Special Committee, No. 16, Radio-Technical Commission
for Marine Services, Washington, D.C. (See also Annex 3, Doc. 71, Warsaw, 1956).
P h il ip s ,Rep. 320-1— 225 —REPORT 320-1. SELECTIVE-CALLING SYSTEMS FO R THE INTERNATIONAL
M ARITIM E M OBILE SERVICES(Question 3/XIII, Study Programme 3A/XIII)(1963 - 1966)

1.

Study Programme 3A/XIII states that Recommendation 257 does not give a full reply to
Question 271 and the trials of selective calling systems, described in Docs. XIII/10, XIII/18,
XIII/26 and 189, Los Angeles, 1959 were carried out with a view to coming to a decisionon the type of system that should be adopted internationally.
The Administrations of the Federal Republic of Germany and the U.S.A. carried out
comparative tests. Reference is made to Docs. 229 and 235, Geneva, 1963.
Study Group XIII studied the results of these tests during the session of the Xth Plenary
Assembly, and took into consideration Docs. XIII/6, 8, 9, 11, 15, 19 and 21, Geneva, 1963.
The results of further tests carried out by several Administrations are given in the reportof an International Working Party set up by the Xth Plenary Assembly (Doc. X III/19,
1963-1966).

2.

The Study Group has further studied the subject during the session of the X lth Plenary
Assembly, on the basis of the work of the International Working Party on selective callingdevices, and took into consideration further information contained in additional documents
considered at the Interim Meeting of Study Group XIII, Geneva, 1965, listed in the Con­clusions of that meeting, and documents submitted to the X lth Plenary Assembly, listed in
the Chairman’s Report (Doc. XIII/107, 1963-1966).

3.

Study Group XIII has come to the conclusion that it is important that the operational andtechnical characteristics of a world-wide maritime selective calling system should be standar­
dized as soon as possible.
No decision can -be taken at present regarding the selective calling system to be adopted
on a world-wide basis. The operational requirements should be defined more precisely
and further tests including tests, under practical operating conditions, should be made.
Account should be taken of the fact that different national selective calling systems,
already in operation on a limited scale, may expand in the absence of early international
agreement and, for economic reasons, preclude international standardization.
To expedite agreement on a world-wide basis, the studies must be continued without
delay and attention is drawn to Resolution 19-1.

4. The discussions during the Xth Plenary Assembly made it clear that all selective callingsystems tested by the Administrations of the Federal Republic of Germany (Doc. 229) andthe U.S.A. (Doc. 235) are capable of operating satisfactorily in the VHF band with classof emission F3.
They also indicated that it would be advantageous for the world-wide selective callingsystem to be suitable for operation in the radiotelephone maritime M F and H F bands, having
regard to the probable additional requirement for SSB operation in accordance with Recom­
mendation 258-1.

5. Discussions at the X lth Plenary Assembly showed the desirability for the system to be suit­able for operation in both the maritime radiotelegraph and radiotelephone services.
addition, a different type of system was described in Doc. XIII/76 (U.S.A.).
15

In

Rep. 320-1, 359— 226 —

6.

After discussion, it was decided that operational requirements and technical characteristics
should be defined more precisely and that further tests should be carried out and that forthis purpose an International Working Party should again be set up (see Resolution 19-1).

7.

The requirements of the further tests to be carried out may be summarized as follows:

7.1 as far as possible, the tests should be extended to include all classes of emission used in
the maritime mobile services;
7.2 tests should also be carried out under practical operating conditions, including the effectsof fading, interference and atmospherics, and the report should contain information withregard to:
7.2.1 reliability (ratio of calls received to calls transmitted), for high and low field strengths;
7.2.2 immunity against false calls (ratio of false calls received to calls transmitted), causedby such phenomena as speech modulation, intermodulation, etc. and interference
from other selective calls;
7.2.3 an indication of the complexity of the different receiving selectors, such as numberof tubes, transistors, relays and frequency-selective elements; also whether any com­ponents used are special or critical, especially as regards adjustment and maintenance;
7.2.4 an indication of the relative cost of typical equipment tested should, as far as possible,
be given.
8.

An indication of the patent situation should be included in the report by the International
Working Party.

REPORT 359 *USE OF A CONTROL TONE ** FOR AUTOMATIC GAIN CONTROL OF
RECEIVERS IN SINGLE-SIDEBAND RADIOTELEPHONE SYSTEMSOPERATING IN THE HF M ARITIM E M OBILE BANDS(1966)In Question 282, the C.C.I.R. has been asked to consider what arrangements should
be adopted in an A3J emission to control the gain of the receiver in the absence of speech.
This problem was considered at the Interim Meeting of Study Group XIII, Geneva 1965
(see Docs. X III/12 (United Kingdom), XIII/32 (Japan) and XIII/44 (Federal Republic of
Germany), 1963-1966). The following conclusions have been reached:1.

For some Administrations, and for some types of ship equipment, it is essential that continous information should be available in SSB transmissions on which the gain (and in somecases frequency) of the receiving equipment can be automatically controlled, and in thosecases the following arrangements should be adopted:

1.1 In the direction ship-shore this information should be in the form
at a level of approximately - 16 dB relative to peak envelope power.

of a continuous signal* This Report, which was adopted unanimously, can, together with Recommendation 258-1, be considered
as an answer to Question 282, which is thereby terminated.
** The Study G roup’s interpretation o f the Question is that the term “ control tone ” means “ control
signal ”.

— 227 —Rep. 359, 360

1.2 In the direction shore-ship the information should also be in the form of a continuous signal
at a level of approximately - 16 dB relative to p.e.p.
1.3 In both directions the information should be emitted at a radio-frequency corresponding
to the nominal carrier frequency.

REPORT 360 *OPERATIONAL PROCEDURES FOR SINGLE-SIDEBAND (SSB)
RADIOTELEPHONE SYSTEMS IN THE HF M ARITIM E M OBILE BANDS(Question 4/XIII)(1966)
Question 319 was adopted by correspondence after the Interim Meeting, Geneva, 1965,
and was subsequently designated Question 4/XIII.
Since Question 319 was adopted, two documents have been submitted: Doc. XIII/73(Senegal) and Doc. XIII/75 (U.S.A.), 1963-1966.
Doc. XIIII73 (Senegal) suggests that initial arrangements for radiotelephone calls at
H F should be made by prior arrangement over a radiotelegraph channel. It is suggested
that the ship also use initially a continuous identifying signal for the benefit of the coaststation. A carrier 20 dB below peak envelope power is considered necessary. (Recommend­
ation 258-1 recommends a carrier level of — 16 ± 2 dB relative to p.e.p.). In the direction
shore-ship similar procedures are proposed.
Doc. X III 175 (U .S.A.) proposes that a carrier 16 dB below peak envelope power becontinuously provided in both the ship-shore and shore-ship directions.
To assist the World Maritime Administrative Radio Conference, 1967, further studyof Question 4/XIII is urgently required, and the possibility of the introduction of selective
calling should be borne in mind.

* This Report was adopted unanimously.

— 228 —Rep. 361

REPORT 361 *THE INTRODUCTION OF DIRECT-PRINTING TELEGRAPH EQUIPM ENT
IN THE M ARITIM E M OBILE SERVICE(Question 5/XIII)(1966)

1.

Introduction
At the Interim Meeting of Study Group XIII, Geneva, 1965, the following papers were
submitted and discussed: Doc. XIII/38 (Norway); Doc. XIII/45 (C.C.I.R. Secretariat)
containing Doc. 111/82 (Netherlands). This resulted in Question 5/XIII being formulated
and adopted by correspondence.
The following additional documents were submitted to the X lth Plenary Assembly(Oslo): Docs. XIII/73 (Senegal); XIII/82 (U.K.); XIII/93 and XIII/94 (Canada); XIII/105,
XIII/106, XIII/119 (Netherlands); XIII/113, XIII/114 (Federal Republic of Germany);
XIII/120 (Norway), 1963-1966. Reference should also be made to Report 349.

1.1 Doc. X III 173 (Senegal) proposes that the direct-printing system should be an error indicat­
ing type, that the maximum modulation rate should be 50 bauds, that the radio circuit should
use class of emission F I and that the quality of transmission should be 1 error
per 10 000 characters.
1.2 Doc. XIIII82 (United Kingdom) describes an automatic one-way error-correcting systemused for ship-shore and shore-ship transmission of messages, data and press. The system
accepts start-stop signals which conform to C.C.I.T.T. standards and produces similar signals
at the receiver output.
The ten-unit code used for transmission consists of the 5 elements of the International
Teleprinter Code No. 2 followed by 5 parity check elements. The 5 parity elements are either
an erect or an inverse repetition of the information elements, depending on whether the Z countin the information elements is odd or even. This system is capable of correcting all single
element errors in the characters in the text and of detecting all double element errors as well
as most multiple element errors introduced by the transmission path. Errors which aredetected, but cannot be corrected, are indicated by the printing of “ error ” symbols, usuallycombination 31 or 32. A synchronous mode of transmission is employed. The modulation
rate is then 62-3, 68-5 or 102 bauds for teleprinter circuits operating at modulation rates of45-45, 50 and 75 bauds respectively. At the lower modulation rates the system is capableof extension over the public telegraph network using conventional 50-baud circuits.
No special phasing signals are required as the system is capable of fully automatic phasing
during periods of traffic as well as during periods of idling.
‘The system reported in Doc. XIII/82 is currently in commercial service. Over the period
7 August 1965 to 27 November 1965 a total number of 1099 data tapes, each containing bet­
ween 1500 and 1800 characters, were transmitted from ships at sea to an office in London,
Of these, 889 were accepted without need for later re-transmission (i.e. contained no errors).
It is further reported that tests between ship and shore stations with plain language
messages, and ship-borne reception of broadcast services (e.g. press transmission) wereconsidered satisfactory, provided some measure of diversity reception is used.
* This Report was adopted unanimously.

_ 229 —Rep. 361

1.3 Doc. XIIII93 (Canada) proposes an addition to the considerings of Question 320 (XIII).

1.4 Doc. X lilj94 ( Canada) proposes specific families of tones for mark and space (including pro­vision for frequency diversity). A unidirectional system with an error indicating and correct­
ing 10-unit code is preferred to an ARQ system. An average error-rate of 1 in 1000 charac­ters at the C.C.I.T.T. preferred standard of 50 bauds is proposed. Suggestions for operational
procedures are given.

1.5 Doc. XIII145 (Netherlands) describes a single-channel simplex ARQ system according toReport 348 which is used for ship-shore communication to pass messages, data and press.
It accepts signals in any 5-unit code and produces similar start/stop signals at the receiver
output at a modulation rate of 50 bauds, and a 150 ms character cycle. The code used fortransmission consists of seven elements per character with a constant A to Z ratio. This
code is used for error detection. All detected errors are automatically corrected by meansof ARQ.
A synchronous mode of transmission is employed at a modulation rate of 100 bauds.
The system provides automatic, error-free phasing, within one second. In addition,
the phasing signals are used to provide selective calling facilities. The system provides for
rapid reversal of traffic flow thus enabling the user of this system to participate in the telex
network.
The system is capable of using one frequency for both the transmission paths. It isin commercial service and has been for about 4 years.

1.6 Doc. XH If 105 ( Netherlands) is a report on a one-way system for message broadcasting witherror-correcting and indicating facilities. The system accepts and produces at the receiverthe 5-unit start-stop International Telegraph Alphabet No. 2, at a modulation rate of 50 bauds.
For radio transmission, the start-stop code is converted into a synchronous, 7-unit code ata modulation rate of 100 bauds. Each character is transmitted twice with an interval of
350 ms, thus giving a time diversity effect. At the receiving terminal, the first characteris checked for correct 3/4 ratio of A/Z elements, and if correct, is fed to a delay storage circuit.
If the character is mutilated, the second transmission is examined, and if correct, is printed.
If both transmissions are mutilated, then a space symbol is sent to the teleprinter. Before start­
ing the transmission of information and in the idle time between successive messages ormessage blocks, the transmitting station emits idle time signals which are also used for phasing.
Equipment designed for a 3-character ARQ system (see Docs. XIII/45 or 111/82, 1963-1966)
has been modified to include the new unidirectional transmission system. Its performance
when tested in the laboratory, under conditions simulating various types of fading, is shown
in Report 349.

1.7 Doc. XIII1106 (Netherlands) contains proposed answers to Question 5/XIII, based on
Docs. XIII/45 and XIII/107, 1963-1966. In particular, it is proposed that the system should
be suitable for communication between ships and one coast station, and from one coaststation to a number of ships; the modulation rate should be about 100 bauds; the classof emission F I, with a shift between 85 and 400 Hz or class of emission A3J, and the average
efficiency should be between 70% and 100%.

1.8 Doc. X IIIjll9 (Netherlands) tabulates the results of ship-shore and shore-ship tests witha simplex-ARQ system described in § 1.5 Details of the equipment used are given. The
undetected error-rate was better than 1 x 10~5. The mean efficiency factor was generallyof the order of 80%. These figures indicate that the undetected error-rate is better thanthat obtained with conventional ARQ systems used in the fixed service.

Rep. 361

— 230 —

1.9 Doc. X H ll 113 (Federal Republic o f Germany) observes that, when duplex operation is pos­sible, a conventional ARQ system on a single channel basis as described in Report 350
is preferred.
1.10 Doc. XIIII114 (Federal Republic o f Germany) expands on Doc. X III/113 as far as duplex
and simplex operations are concerned; it concludes that the ARQ method is preferred toforward error correction. It also concludes that transmission quality is improved if themodulation rate is not more than 100 bauds and that class of emission FI is preferable. It
is suggested that the efficiency factor should not fall below 70-80%.
1.11 Doc. X lllj 120 (Norway) describes tests between ship and shore and shore and ship, using
the two systems described in Docs. XIII/82 (U.K.) and XIII/45 (Netherlands) 1963-1966.
The equipment used is listed. The results are tabulated. For the forward error-correcting
system, the undetected error-rate was of the order of 3-5 x 10~4. For the ARQ system
the average error rate is approximately 2-6 x 10~5 and the average efficiency 75-77%. The
tests with both systems are being continued.

2. Conclusions
Whilst the information so far available does not permit a complete answer to Ques­
tion 5/XIII, the following interim conclusions may be reached:
2.1 Tests of the systems tried even at this stage show that direct telegraph printing is feasible
in the maritime mobile service for messages, data and news, and for interconnection withthe public telegraph network (See I.T.U. List of Definitions, Part I, Item 01.12.). However,more operational experience is required for defining the type of system to be used in themaritime mobile service, and the standards to be attained, taking into account economic
factors.
2.2 The systems so far described and tested do not require a higher modulation rate
than 100 bauds.

*>

— 231 —Rep. 319-1

D. 3: Land mobile service
REPORT 319-1 *CHARACTERISTICS OF EQ UIPM EN T AND PRINCIPLESGOVERNING THE ALLOCATION OF FREQUENCY CHANNELS BETWEEN
25 AND 500 M Hz FOR LAND M OBILE SERVICES(Question 7/X III)
(1963 - 1966)
1.

The following documents have been submitted in reply to Question 163 (subsequently design­
ated Question 7/XIII):
1.1 To the IXth Plenary Assembly, 1959:
XIII/4 (New Zealand), XIII/2 and XIII/11 (F.R. of Germany), XIII/30 (Japan),
XIII/32 (United Kingdom), 180 (Sweden).
1.2 To the Xth Plenary Assembly, 1963:
XIII/1 (F.S.R. of Yugoslavia), XIII/4 (Greece), XIII/10 and 259 (P.R. of Poland),
XIII/24 (F.R. of Germany), 222- (Australia).
1.3 To the Xlth Plenary Assembly, 1966:
XIII/24 (United Kingdom), XIII/29 (Japan), XIII/33 (P.R. of Poland), XIII/39 (Rev. 1)
and XIII/83 (F.R. of Germany), XIII/86 (Denmark), XIII/96 (Switzerland), X III/110
and X III/111 (Japan), X III/116 (France), XIII/121 (New Zealand), XIII/123 (U.S.A.).
2. The technical information contained in these documents, together with other information
submitted direct during the Plenary Assemblies are given in the Annex to this Report. The
data arranged according to the separation between adjacent channels adopted in the various
countries are given in Table III. Tables I and II give these separations, the names of coun­tries being replaced by the symbols used for them in Table I of the Preface to the International
Frequency List.
It would be desirable for frequency tolerances and spurious emission levels to be expressedin absolute values in future.
The information given in this Annex shows that it is difficult at present to reach complete
international standardization of the performance characteristics of land mobile equipment
operating between 25 and 500 MHz. However, it is desirable that countries with common
borders should reach agreement on some common characteristics, which would be helpfulin planning for the land mobile services.
3. Doc. XI11I24 ( United Kingdom) lists characteristics of transmitters and receivers which aresignificant in causing interference and proposes methods of measuring these characteristics.
Administrations are invited to furnish similar information with a view to reaching interna­
tional agreement on methods of measurement. This could then lead to a revision of thedata in the Annex on a uniform basis, preparatory to consideration by the C.C.I.R. of thelimits to be specified for such characteristics.
At a later stage similar consideration could be given to those characteristics of receivers
that give protection against interference.
4. Doc. XIIII39 (Rev. 1) (F.R. o f Germany) deals with processes used for the assignment andco-ordination of frequencies.
Some special information concerning the co-ordination of frequencies on a multi­
lateral basis is given in the “ Special Agreement between the Administrations of Belgium,
the Netherlands and the F.R. of Germany relating to the use of metric and decimetric waves
for fixed and mobile services in border areas, Brussels, 1963 ”.
Docs. XIIIj80 (United Kingdom) and X I H jlll (Japan) deal with certain character­istics of land mobile stations and frequency usage which affect frequency co-ordination methods.
* This Report, which replaces Report 319, was adopted unanimously.

— 232 —Rep. 319-1

Administrations are invited to examine and amplify the ideas set out in these docu­
ments.
5.

Some information concerning interference between mobile services and broadcasting
services is given in the Final Acts of the Special Regional Conference, Geneva, 1960.

6.

Resolution 20-1 invites Administrations to continue to send to the C.C.I.R. for circula­tion details of performance specifications and measuring methods and also to send detailsof practices for the allocation of channels between 25 and 500 MHz to the land mobile
services in operation in their respective countries.

7.

The study of Question 7/XIII should be continued.
ANNEX

1.

Adjacent-channel separation in the various frequency bands
TABLE I
S ep a ra tio n s now in use b u t considered o ut o f date

Channel Separation(kHz)

Frequency ranges (MHz)25-50

50-100 ’

100-200

200-500

10

12-5
15
20

25

NZLC1)

30

NZL/1)J-

40

50

NZLC1)JBEL-DNK-FPOL-S(3)-SUIBEL-D-DNKF-NOR-NZLC1)S(2)-SUIBEL-D-DNKNOR-NZLC1)POL-S(3)-SUIJ-SUI-USA

66

100

D-NOR-SUI(*) An interleaved channel allocation plan is used and only alternate channels are allocated in any one geographical area.
Consequently, the equipment is designed for double the channel separation shown above.
(2) N o new assignments have been made since 1959. Old stations are permitted to stay until 1970.
(3) N o new assignments have been made since 1960. Old stations are permitted to stay until 1971.

Rep. 319-1— 233 —
T ableII

Separations for present and/or future use.
Frequency ranges (MHz)Channel separation(kHz)

25-50(450-100(4100-200

6-25

NZL(2)

NZL(2)

NZL(2)

10

D *-DNK-DNK *NOR *-S *-SUI *USA200-500

NZL(2)

12-5
15
20

25

D-USA

DNK-F-NORPOL-S(5)-SUIJ

USA(2)

D-BEL(3)

BEL(3)D-F-J

BEL(3)-D

BEL(3)-DNKNOR-POL-S(5)SUI

BEL(3)-JNOR-SUIUSA

BEL(3)-DNK-FNOR-S(4)-S(4) *SUI

USA

30
40

USA*

50

BEL

BEL(3)-DNKF-NOR-POLS(6)66100(!) When a country symbol is followed by an asterisk, the value given for the separation refers to low-power
portable equipment.
(2) An interleaved channel allocation plan is to be used and only alternate channels allocated in any one geographical area.
Consequently the equipment is designed for double the separation shown above.
(3) The choice between the separation 20, 25 and 50 kH z is still under study.
(4) In use since 1959.
(5) In use since 1960.
(6) In use since 1965.

Rep. 319-1
2.

Technical characteristics of equipment

I
TABLE I III (8) (»)
Receiver

3

4

5

10

25-50

D

(O)

PrivateS

9

0-1 (m)

A3
F3

0

(5)

7

Occupiedbandwidth

6

Frequency tolerance±(2>

Spurious
emissions(3> (4>

(hV)

ts

2

Sensitivity(e.m.f.)

X

1

(W)

(2)

•52

(MHz)

X Max. deviation(kHz)

Typicalmean
powerClass of emission

t1)

PublicorPrivateSeparation otransmit amreceive frequen

Doc.

gj
X
IS

Frequency
range

Countries

Transm itter

ChannelSepa­
rationRep. 319-1— 235 —

— 234 —

10

11

7
7

1-5 kHz
1-5 kHz

13a

12

For a
signalto-noise
ratio of(dB)

Selectivity

13b

14

Frequency
tolerancert(2)

Spurious
responses

Spurious
radiations

(dB)

(pW)

16

17

(dB)
15

Rem arks(10)18

2 X 10-3

4 x 10-3 pW inbands:
47-68 MHz174-230 470-790
In all other bands
10 pW

DNK

X11I/86(O)

Private0

0-1 (M)A3

6

1-5 kHz4 x 10-3

4 x 10-3
inbands:
47-68 MHz174-230, 470-790

In frequency
band
27-12 MHz± 0 -6 % only\

In all other bands:
10 uW

15

50-100

Max: 5input(B, M)

A3

6

3 kHz

Input up to 1 W:
-4 0 dB
Input up to 5 W:
-5 0 dBNOR(O)

Private

0

0-5

A3

6

1-5 kHz

RR

S

(O)

Private

00-5(niMB)
5
(mMB)

A3

6

50 x 10-6

20 ^*W \- 4 0 dB /0-2 pW i—60 dB /SU1(O)Private0

0-5 (m)J(O)

PublicandPrivate

2

50

4-5

F3

5

001

In frequency
band
29-731-7 MHz only

RR

(H)
K)
(

40*

5 kHz

8 pW

16

0-6 kHz—80dB (IB)—60dB (OB)In frequency
band
26-30 MHzSuper-regenerative receivers not permitted
'

2

20

—70 at12-5 kHz

0-6 kHz-8 0

0 02 (H)2 x 10-3(NH)* between—40 dB points

4 x IQ-3(2S)(IB) = in band(OB) = out
bandRep. 319-1

D o c.
C1)

Separation o ftransmit andreceive frequencies

Countries

Frequency
range

PublicorPrivateReceiverTransmitterT ypicalm ean
pow er

(2)

e
.o

C

'1o

>
o

-o

n

s

C
m
o

o
X
C3

To3-a-*-**EL*>^s isj

Sensitivity(e.m.f.)Frequency tolerance±(2)

Spurious
emissions(3) (4>

(UV)

For a
signalto-noise
ratio of(dB)

Selectivity

13b

14

Frequency
tolerance

±

( 2)

(dB)

Spurious
responses

Spurious
radiations

(dB)

(pW)

16

17

(M H z)12

4100-200

USA

X11I/123
(O)

25-50

USA

XI11/123(O)

PrivateandPublic0-5-8

330 (B)
100 (M)F3

5

20

20 x 10-«

50 pW

[0-6]

12

[—80 at [20 X 10G]
20 kHz]*’50-100D

XIII/83(O)

Private

9-8

1
6

F3

4

14

1-2 kHz

20 pW (H)0-2 pW (NH)

[2]

20

- 7 0 at
20 kHz

12 kHz-7 0

2 x lO-3

100-200

D

XIII/24
G

Private

4-6

1
6

F3

4

14

1-6 kHz (M)
0-8 kHz (B)
1-8 kHz (m)20 pW (H)0 2 pW (NH)

[2]

20

—70 at20 kHz

16 kHz (M)
0-8 kHz (B)
1-8 kHz (m)-7 0

2 x IQ*3

F

XIII/116(O)

PublicandPrivate

4-6 -

30 (M)
50 (B)

F3

4

14

1-6 kHz (M)
0-8 kHz (B)RR

20-8 0 at
20 kHzJ(O)

PublicandPrivate

2
4-5

50

F3

5

16

1-5 kHz-80 dB (IB)-60 dB (OB)20

-7 0 at12-5 kHz

1-5 kHz-80

4 X lO-3

200-500

D

XIII/83(O)

Private

10

1
6

F3

4

14

2-5 kHz (mM)
10 kHz (B)20 pW (H)0 2 pW (NH)

[3]

20

—70 at20 kHz2-5 kHz (mM)
10 kHz (B)-7 0

2 x lO-3

25-50

AUS

222 (G)

Private25 (M)
50(B)

A3
and
F3

20 x 10-6

Less than 2-5 pW
at 50 kHz fromcarrier

11

10—80 at25 kHz

5

6
or
16

20

25

5

g>
25
.n,

(kHz)

w

ChannelSepa­
rationRep. 319-1— 237 —

— 236 —(W )0

(kH z)(kH z)

6

7

8

9

10

11

12

13a

15

Rem arks( 10 )

18

Tjie 15 kHz
separation is
occasionallypermitted butwith the sameequipmentcharacteristic
as for the
30 kHzseparation—*S+N+D
N+D** 2-signal testwith 6 dB
degradation of
12 dB
S+ N + D
N+D

100

-6 0

- 8 0 to 25 kHz(2S)(IB) = in-band(OB) = outband

— 238 —Rep. 319-1— 239 —

S3

2

3

4

5

6

7

DNK

X1II/86(O)

Private

0-6-5

25

F

XIII/116(O)

Private

4-4

NOR

(O)

Private

5-10(0PublicorPrivate

5?

U

S

25

Doc.

50-100

AUS

DNK

(O)

222 (G)

Private

8

9

10

A3
or
F3

3 kHz (M)

5

6
or
16

30 (M)
50 (B)

F3

5

16

0-8 kHzRR

2

20

25 (M)
100(B)

A3
or
F3

1 kHz

2-5 pW (H)
0-25 pW (NH)

1-5

10

(2)

0

40 (M)
70(B)Private25 (M)
50(B)16

20 x 10 « (M)
10 X lO-6 (B)20- 4 0 dB \j
0- 620 dB \J

516

1-6 kHzRR

2

3-0 KHz (M)1-5 kHz (B)

2-5 pW

5

6
or
16

6

1-5 kHz25(e.r.p.)

A3
or
F3

A3
or
F3

A3

5

1

3 kHz (M)
1-5 kHz (B)

(pW)

16

17

—70 at25 kHz-7 5 at 25 kHz

001—80 at25 kHz

-6 0

14

15

-7 0 at
22 kHz

1 kHz—80 at25 kHz

20 x lO-8 (M)10 x lO-6 (B)

(10)

18

(2S)

002

-7 0

001

(2S)

001

(2S)

- 8 0 at
25 kHz- 8 0 at 25 kHz—70 at25 kHz- 7 5 at 25 kHz

20—80 at25 kHz

-6 0

5

10

—70 at25 kHz3.0 kHz (M)1-5 kHz (B)-7 0

2-5 pW (H)
0-25 pW (NH)

1-5

10

—70 at
22 kHz

1-5 kHz-7 0002

2-5 pW

2-5

10—70 at25 kHz3 kHz (M)
1-5 kHz (B)

-7 0

002

16

6

(dB)

(2)

13b

10

Remarks
Spurious
radiations

(dB)

(H)
w
(NH)
MNhU

Frequency
tolerancert

Spurious
responses

Selectivity(dB)

1-5 kHz (B)

5

4-8
to
13-5

For a
signalto-noise
ratio o f

2.5 pW

2-5 pW

Private1

13a

3 kHz (M)
1-5 kHz (B)XIII/32(L.A.)

25

12

6
or
16

G

4

ii

A3
or
F3

F3

Publicandprivate

(MV)

(kHz)

6
5

(3) (4)530 (M)
50 (B)(O)(2)

Less than 2-5 pW
at 50 kHz fromthe carrier

4-05-5

NZL

f f

Spurious
emissions

20 X lO-6

Private25 (M)
100(B)

Frequency tolerance
i

6
or
16

A3
or
F3

XIII/116
(O)

5-10

1*

16

F

PublicandPrivateSensitivity(e.m.f.)*o"S.Si *05

Private

(0)

25

A3
and
F3

XIII/86
(°)

NOR

0-6-5

Receiver£ Max. deviation

1

(W)

Ju
c3
0

j

Class of emission(MHz)

Separation otransmit andreceive frequem(kHz)

Typical
mean
power

►
j

Frequency
range^

ChannelSepa­
rationT ransm itter

Rep. 319-1

(2S)

(2S)

Rep. 319-1

1

2

Separation o ftransmit andreceive frequencies

Countries
3

4

5

s

180 (L.A.)

Publicandprivate(O)

SUI

XIII/96

Public

XIII/86
(O)

G

NOR

NZL

S

XIII/32(L.A.)

(O)

(O)

(O)

Typical
mean
power

fiO
.2
o>
•o
C3

(W)

a
O

(kHz)

(kHz)

6

7

8

9

10

11

40 (M)
70(B)

F3
and
A3

5

16

0 -6

20 X 10-6 (M)10 X lO-6 (B)

0
4-8
50
10

l

8 i- 2e ^Frequency tolerance

Spurious
emissions(3) (4)

±
(2)

s

12
- A

(nV)

13a

For a
signalto-noise
ratio o f(dB)

Selectivity

13b

14

} w

Frequency
toleranced r'(2)Spurious
radiations

(dB)

(aW)

15

16

17

—80 at25 kHz

20 x 10-0 (M)10 x lO-6 (B)

-7 0

001

(2S)

—60 at20 kHz2 kHz

2 X 104(2S)

no specifications

2 X 10-3(dB)

20 (M)
50(B)25

Publicandprivate4-9

Private

4-8
to
13-5

25
(e.r.p.)Publicandprivate4-5

25 (M)
100(B)

Publicandprivate4
andPublicandPrivate

0
and

25

2

40 (M)
70(B)8

1-5 kHz
A3
or
F3

A3
or
F3
A3
or
F3
A3
or
F3
A3
or
F3
F3
and
A3

4-5

2 0

5

or
16

5

or
16

5

or
16

5

or
16

5

16

6

6

6

6

8 pW(H)
2 pW (NH)

1

20

2 kHz

XIII/96(O)

20 (M)
50(B)Public10*
Private18—70 at25 kHz-7 5 to 25 kHz

3 kHz (M)
2-5 kHz (B)

2-5 pW

3-0 kHz (M)1-5 kHz (B)

2-5 pW510- 7 0 at
25 kHz3 0 kHz (M)1-5 kHz (B)-7 0

3 0 kHz (M)
1-0 kHz (B)

2-5 pW(H)0-25 pW (NH)

1-5

10

- 7 0 at
22 kHz3 0 kHz (M)10 kHz (B)

-7 0

002

2 kHz (M)
1 kHz (B)

2-5 pW

2-5

10—70 at25 kHz2 kHz (M)
1 kHz (B)

-7 0

002

(2S)

- 8 0 at
25 kHz

10 X lO-6 (M)5 x lO-8 (B)

-7 0

001

(2S)
In the band
100-103-5 MHz
the values
given in co­lumn 7 must be
replacedby“ 3 ” and incolumns 11
and 15 by:
20 x lO-6 (M)10 X 1O-0 (B)—60 at20 kHz

2 kHz

10 x 10 ° (M)5 x 1 0 -0 (B)“ A} <h )001

10 (M)
20(B)

1-5 kHz
A3
or
F3
4-5

2 0

8 pW (H)
2 pW (NH)

1

20

2 kHz
no specifications

1
16

(2S)

(2S)

- « ! d B } <N»>

SUI

Rem arks(10)

Spurious
responses^ 7 b }<N H )10 (M)
20(B)8Sensitivity(e.m.f.)

a •a

(2)

X

Rep. 319-1

Receiverjo5
oj!

PrivateDNKTransm itter

co
■o§
u-o

(O)

1 0 0 -2 0 0— 241 —gg

(M Hz)

PublicorPrivate

■
!S

(kHz)

o^

Frequency
range

O h

ChannelSepa­
ration— 240

2 X 10-4 * A separationof 4-6 MHz
is planned
2 X lO-3<2S)

Rejp. 319-1

8

9

10

• Public.4 (M)
100(B)

F3

5

16

XIII/111(O)

Private

50

,F3

5

16

(O)

Public20 (M)
50(B)

2

3

4

200-500

J

(O)

5

(2)

10

30

50-100100-20040

100-200

AUS

222 (G)

Private10 (M)
20 (M)

Private25 (M)50(B)J

XII1/30(L.A.)(O)

PublicandPrivateAUS

222 (G)

Private

2-4-5

A3
or
F3

4-5

Sensitivity(e.m.f.)Spurious
emissions

Frequency tolerance±(2)(3) (4)

(MV)

nj
S

1

Typicalmean
power

Occupiedbandw idth
(5)

J Max. deviation

7(M Hz)

PublicorPrivatehi.

Class of emission

6

I1)

(kHz)

SUI

Separation o ftransmit andreceive frequencies

(W)

D oc.

Receiver

T ransm itter

gg
gj
.n,

Frequency
range

Countries

ChannelSepa­
rationRep. 319-1— 243 —

— 242 —

11For asignalto-noise
ratio o f(dB)

Selectivity

14

(dB)

(pW)

16

17

0-9 kHz (B)
2-3 kHz (M)-6 0 dB

1-6

20-7 0 at
0-9 kHz (B)
15 kHz 1 2-3 kHz (M)-8 0

4 x 10-8

2-3 kHz

- 6 0 dB

2-5

20

—70 at
15 kHz2-3 kHz-8 0

4 x lO-3

1-5 kHz

8 pW (H)
2 pW (NH)1

20—60 at20 kHz2 kHz

2 x 10-4

no specifications

2 x l0 -3

15

<10)

18

(2S)

(2S)

20

1-5

10

—76 at30 kHz5'

Less than 2-5 pW
at 50 kHz fromcarrier

1026

1-2 kHz- 8 0 dB (IB)
- 6 0 dB (OB)2

20

-7 0 at
25 kHzA3orF3

20 X lO-8 (M)10 X lO-8 (B)Less than 2-5 pW
at 60 kHz fromcarrier2-5

10-7 2 at
26 kHz56or16

25 (M)
50(B)

(dB)

13b

20 X 10-«

F3

Spurious
radiations

13a

6
or
. 16

50

±

(2)

R em arks
Spurious
responses

12

2 kHz

A3
or
F3

Frequency
tolerance—76 at30 MHz

1-2 kHz4 x 10-3(2S)(IB) = in-band,(OB)= outband- 7 2 at 26 kHz

USA

XIII/123(O)

PublicandPrivate0-55-26330 (B)
100 (M)F3

520

5 x lO-8

50 pW

0-8

12 *

[—80 at
30 kHz][5 x 10 ®]J

XI1I/30(L.A.)(O)

PublicandPrivate

2-4-5

50

F3

12

30

2 kHz

-8 0 dB (IB)
-6 0 dB (OB)2

20

—70 at25 kHz

3 kHz

1

-8 0

1

*S+N+D
N+D** 2-signal testwith 6 dB
degradation of
12 dB
S+ N + D
N+D

[-95]

-8 0

4 X lO-3|(2S)(IB) = in-band(OB) = outband

Rep. 319-1

I1)

PublicorPrivateSeparation o ftransmit andreceive frequencies

Doc.

Transm itter

Typical
mean
power

(2)

(kHz)

(M Hz)

(W)

1

2

3

4

5

6

7

50

25-50

F

XIII/116(O)

Private

4-4

POL

XIII/10and259 (G)
XIII/33(O)

PrivateS

180(L.A.)(O)

Private

(O)

S

SUI

50-1 CM) NZL -

E
u
O

1cs

>
0
•o
1

s

si
!4 €

8

9

10

30 (M)
50 (B)F3

15

36

20 (M)
50 (B)F3

15

0

25 (M)
50(B)

F3
and
A3

15

PublicandPrivate

4

25

A3

180
(L.A.)(O)

PublicandPrivate025 (M) '
50(B)

F3
and
A3

XIII/96(O)

Public20 (M)
50(B)
10 (M)
20(B)

A3
or
F3

15

15

Frequency tolerance

±
(2)

«J
(kHz)

10

100-200e .
.0Receiver

1(kHz)

Private1120—80 at50 kHz42

2 kHz

25 pW (M)
- 6 0 dB (B)220- 7 0 at
50 kHz36

100 x 10-«

-4 0 dB (M)-6 0 dB (BM)65 kHz (M)
1-5 kHz (B)

2-5 pW36

100 x 10-8

- 4 0 dB (M)- 6 0 dB (MB)3 kHz

8 pW (H)
2 pW (NH)36

2-5 kHzG

XIII/56(O)

Public4-5

25 (M)
100(B)

F3

15

36

NZL

(O)

PublicandPrivate

4

25

A3
or
F3

6

or
16
42

Rem arks
Spurious
responses

Spurious
radiations

(dB)

(MW)

16

17

18

-6 0

2 kHz

-6 0

2-5

10

- 7 0 at
50 kHz5 kHz (M)
1-5 kHz (B)-7 0Receiver selec­
tivity and spu­
rious responses
with 2-signal
test

002

(2S)

(2S)

1

20

2 kHz

2 X 10-4

no specifications

2 X 10-8—60 at40 kHz

20 pW (H)0-2 pW (NH)2

20

-7 0 at
50 kHz2-5 kHz

3 kHz (M)
2 kHz (B)

2-5 pW2

20-7 0 at
50 kHz3 kHz (M)
2 kHz (B)

5 kHz (M)
1-5 kHz (B)

2-5 pW

2-5

10-7 0 at
50 kHz5 kHz (M)
1-5 kHz (B)-7 0

25 pW (M)
-6 0 dB (B)220- 7 0 at
50 kHz

3 kHz

-6 0

3 kHz

(10,

(2S)

5 kHz

15

15

15

2

F3

±

(dB)

RR.

40

Frequency
tolerance
(2)

2 kHz

10 (M)
20 (B)

F3

Selectivity

14

4-5

20 (M)
50(B)

(uV)

For a
signalto-noise
ratio o f
(dB)
13b

PublicPrivateSpurious
emissions(3) (4)13a

XIII/83(O)

XIII/10and259 (G)
XIII/33(O)

Sensitivity(e.m.f.)

12

D

POL

Rep. 319-1— 245 —gj
*Xj

Frequency
range

Countries

ChannelSepa­
ration— 244 —

-7 0

(2S)

2 x lO-2

'

(2S)

002

(2S)

Receiver selec­
tivity and spu­
rious responses
with 2-signal
testRep. 319-1

R eceiver:

1

2

.;,o
• ;C3.
*>o*oK

Occupiedbandw idth
(5)

c
.0

C

Typical
mean
power
(2>

1o
0

(W)

a
U

: (kHz)

33
s

(MHz)

PublicorPrivate. D oc.
I1)

gj

(kHz)

js
"C
c
3
0
O:

tS

Frequency
range

Separation otransmit andreceive frequen

Transm itter

ChannelSepa­
ration

Pj

S

4

5

6

7

8

‘9

10

S

180
(L.A.)(O)

PublicandPrivate0and825 (M)
50(B)

F3
and
A3

15

36

'

Sensitivity(e.m.f.)Frequency tolerance
rt
(2)

.

Spurious
emissions.'(*> (4)

■

3

V.

Rep. 319-1— 247 —— 246 —

11

100 x 10-0

12

(pV)

13a

For a
signalto-noisa
ratio o f(dB)

Selectivity

>13b

14

.

Frequency
tolerance
dr
C2)

(dB)

is

R em arks
Spurious
responses

Spurious
radiations

(dB)

0»W)

16

17

(iO)

18

(2S)
In the band
100-103 5 MHz
the values
given incolumn 7 must
be replaced by:-4 0 dB (M)- 6 0 dB (MB)

“ 3 ”

SUI

XIII/96(O)

Public20 (M)
50(B)

A3
or

10 (M)
20(B) '

F3

250

3 kHz

8 nW(H)
2 pW (NH)1

20—60 at40

2 x 10-4 * A separationof 4-6 MHz
is planned

2 kHz

10*
Private200-500'

DNK

XIII/86(O)

Private

8-15

F

XllI/116(O)

Private

12-5

G

XllI/56. (O)Private

5-5
to .
6-5

15

40

5 kHz

A3
or
F3

5 kHz (M)
3-5 kHz (B)

25 pW

15

6
or
36

F3

15

36

5-6 KHz (M)3-3 kHz (B)

*

2

A3
or
F3

5 kHz (M)
3-5 kHz,(B)

25 pW

15

6
or
16

50

F3

12

30

9-4 kHz

15

36

15

6
or
36

50
(e.r.p.)J

XII1/29(O)

PublicandPrivateNOR(O)

Private5

15 (M)
50 (B)

F3

NZL

(O)

PublicandPrivate

10

50

A3
or
F3

l

no specifications

2 x 10-3

(2S)

001

(2S)

—70 at50 kHz-7 5 at 50 kHz

20—80 at50 kHz-6 0* Same tolerance
as RR for the
30-235 MHz
band

10

10

—60 at50 kHz5 kHz (M)
3-5 kHz (B)

-6 0

(2S)

- 6 0 dB

2-5

20

- 7 0 at
30 kHz

9-4 kHz-8 0

4 x 10-3

5 kHz (M)
3 kHz (B)

2-5 pW

1-5

10- 7 0 at
50 kHz5 kHz (M)
3 kHz (B)

-7 0

002

5 kHz (M)
2-5 kHz (B)

2-5 pW

2-5

10- 7 0 at
50 kHz5 kHz (M)
2-5 kHz (B)

-7 0

002

Single signal
selectivity.
See also Notes(6) and (7)(2S)

Rep. 319-1— 248 —

1

2

3

4

5

POL

XIII/10and259 (G)
XIII/33(O)

PrivateS(O)

PrivateSUIXIII/96(O)

Public6

7

XIII/123(O)

PublicandPrivate. s

Spurious
emissions(3) (4)910

15 (M)
50(B)

F3

12

30

3 kHz

25 pW(M)-6 0 dB (B)

15

F3

15

36

10 x 10® (M)
5 x lO-6 (B)20 pW \ /m
-4 0 dB / (H)
0-2 pW 1 m u )- 6 0 dB j U

3 kHz

8 pW (H). 2 pW (NH)20 (M)
50(B)
10 (M)
20 (B) ,,5■ -aFrequency tolerance
db
(2)

8

10

USA

•o

250 (B)
50 (M)

A3
or
F3

F3

ReceiverSensitivity(e.m.f.)

(kHz)

0
7
10
15
21
30

Private.2.2*>

Occupiedbandw idth(5)

Separation otransmit ant
receive frequen(W)

Typical
m ean
power
(2)

'

C

fi
&

(MHz)

PublicorPrivateClass of emission

(kHz)

c
•a
■O '
U

D o c .’
(x)

aj
pq
.n,

.3
Frequency
range-

Transm itter

M

ChannelSepa­
rationRep. 319-1— 249 —

11

15

40

5 kHz

15

40

5 x 10"®

12

50 pW

For a
signalto-noise
ratio o f(dB)

Selectivity

13a

13b

14

2-5

20

-7 0 at
50 kHz(UV)Frequency
tolerance

rfc
(2)

(dB)
15

3 kHz

[1,4]

20

12*

Spurious
radiations

(dB)

(uW)

16

17

100-200

GRC

XIII/4(G)

Private20 (M)
50 (B)

F3

15

36

3 kHz

-7 0 dB

0-5
1

100

25-50

YUG

XIII/1(G)

Private

20

F3

15

36

15x10"®

-3 0 dB

1

(2S)

2 kHz

2 x 10-4(2S)

no specifications

2 x 10-3—60 at40 kHz[-7 0 at
50 kHz](J) L.A. = Los Angeles, 1959; G = Geneva, 1963; O = Oslo, 1966.
(") B — base station; M ~ mobile vehicle station; ni = mobile portable station.
;(®) H = on harm onic frequencies; N H — on frequencies dther than harmonics.
/(4) R R — R adio Regulations, Geneva (1959).
(5) In some cases, the bandw idth is specified a t the 20 dB points.
(8) U nder the condition o f injecting the desired frequency signal which is 6 dB higher than the 20 dB noise quieting level, theundesired frequency signal in the adjacent channel that is injected to the receiver and makes again 20 dB noise Quieting, shall be
above 80 dB (1 pV = 0 dB).

12 (M) —86 at
12 (B) 60 kHz
10

18

001

[5 X 10 «]

[-90]

**

66

(i°,

Receiver selec­
tivity and spu­
rious responses
with 2-signal
test

-6 0

-7 0

- 7 0 at
50 kHz1

R em arks
Spurious
responses- 8 0 at
100 kHz

3 kHz*S+N+D
N+D** 2-signal testwith 6 dB
degradationof
12
dB
S+ N + D
N+D-7 0

50 x 10 ®

(7) In the absence o f the desired signal and when the undesired signals o f the adjacent and next adjacent channel frequencies are
injected to the receiver a t a level o f 65 dB (1 pV = 0 dB), the noise quieting o f the receiver shall be less than 20 dB.
(8) It would be desirable for data relating to a new colum n “ Interm odulation ” to be supplied by A dm inistrations; this new colum nwould be inserted between the present colum ns 17 and 18.
(9) The values given in square brackets [ . . . ] w e considered optional by the A dm inistrations which have supplied them.
(10) (2S) = receiver selectivity with 2-signal test.

— 250D . 4 : A e r o n a u tic a l m o b ile s e r v ic e
No Reports in this Sub-section.

— 251 —STUDY GROUP XIII
(Mobile services)
Terms o f reference:
To study technical and operating questions concerning the aeronautical, maritime, land tmobile, radiolocation and radionavigation services (except services that involve the use of earth
satellites which, at present, are the concern of Study Group IV).

Chairman:Vice-Chairman:

Mr. G. H. M. G l e a d l e (United Kingdom)
Mr. J. So b e r g (Norway)

IN TRO D U CTIO N BY THE CHAIRM AN, STUDY G R OU P XIII

1.

Opinion 20 and Report 317: Codes and abbreviations for the International Telecommunica­tion Services.
Opinion 20 asked Administrations to consider whether there was an operational needfor the unification of the codes used in the international telecommunication services. No
Administration, in fact, expressed a need for such unification and therefore it has been agreed
in Recommendation (437) that no further action should be taken concerning the unificationof codes. Report 317 has now been deleted.
2.

Resolution 19, Question 271 (XIII), Study Programme 271A (XIII), Report 320, Recom­
mendation 257 : Selective calling devices for use in the international maritime mobile radio­

telephone services.
At the Interim Meeting, Geneva, 1965, a draft Recommendation was prepared for aselective-calling system employing the principle of sequential single frequencies (s.s.f.c.)so that each digit of the code number of a ship was represented by a single frequency. Thissystem had been tested extensively by the International Working Party. However, subsequent
to the Interim Meeting, a different kind of system, a digital system, was proposed by theUnited States of America. In addition, further discussions at the X lth Plenary Assembly
showed that there would probably be a need in the future for selective calling in other mari­time services in addition to the radiotelephone service; for example, in conjunction withdirect-printing radiotelegraph systems or radioteleprinter systems. It was also felt thatthe selective calling system should also provide an indication of the coast station that had
called and/or the channel on which the ship should reply. It was finally decided that theInternational Working Party should be set up again (Resolution 19-1) to attempt to define
more precisely the operational requirements and to supervise comparison tests of the new
digital system and the s.s.f.c. system. The Question and Study Programme were amended
accordingly (see Question 3/XIII and Study Programme 3A/XIII) and the Report was brought
up to date (See Report 320-1). The Netherlands Administration again undertook to act
as Chairman of the International Working Party and to carry out tests. The International
Working Party has been asked to prepare a progress report by 1 April 1967 for discussion
at an Interim Meeting in 1967, so that as much information as possible on this subject will
be available in time for the Maritime World Administrative Radio Conference, September
1967.
Recommendation 257 was left unchanged for the time being.

— 252 —3.

Question 163 (XIII), Resolution 20, Report 319: Characteristics of equipment and prin­ciples governing the allocation of channels in the VHF (metric) and U FH (decimetric) land
mobile services.

3.1 The Question has been replaced by Question 7/XIII to extend the frequency range down­wards to 25 MHz, so as to cover, inter alia, small portable equipment operating at frequencies
in the neighbourhood of 27 MHz.
3.2 The Resolution has been replaced by Resolution 20-1 which now includes, in § 3, a reference
to the relevant measuring methods, to facilitate a better understanding of the technicalspecifications in use by various Administrations.
3.3 The main Table of the Report (Report 319-1) has been considerably enlarged and brought
up to date by the addition of fresh data from various Administrations. The main Table(Table III) has been rearranged so that the data is tabulated according to the separation bet­
ween adjacent channels adopted by Administrations. Two other Tables, I and II, havebeen added to show the channel separations (I) now in use but out of date, and (II) separa­tions for present and future use. Administrations are invited to furnish information to
enable the tables to be completed.
3.4 Administrations have also been invited to furnish information on their specifications thatappertain to the characteristics of transmitters and receivers that cause interference andon the methods of measurement of such characteristics. At a later stage the characteris­tics of receivers that give protection from interference could be considered. It was hopedthat agreement on methods of measurement would lead eventually to a uniform presenta­tion of the data on specifications in the new Table III.
3.5 The lattice-plan principle for the co-ordination of frequency assignments for land mobile
services was also discussed. Although it was attractive for planning broadcast services
where uniform coverage of an area was desired, some Administrations were doubtful whether
the principle would be helpful in planning land-mobile services where the transmitting sta­tions were often crowded together in large cities or industrial areas. Further study of theprinciples of planning mobile services and frequency usage would be desirable.
3.6 Three new Study Programmes deriving from Question 7 (XIII) were adopted, namely:
Study Programme 7B/XIII: Minimum channel separation and optimum modulation
systems for land mobile systems between 25 and 500 MHz.
Study Programme 7A/XIII: Technical characteristics of land mobile equipment bet­
ween 25 and 500 MHz.
Study Programme 7C/XIII: Interference due to intermodulation products in the land
mobile services between 25 and 500 MHz.
3.7 A new Question 8/XIII was adopted, concerning the preferred technical characteristics of
single-sideband equipment for the M F and H F land mobile services. This question isof particular concern to those administrations where land mobile services have to operateover much greater area's than can be covered by VHF and U H F services.

4.

Question (206 XIII) and Recommendation 428: Direction-finding by ships in the 2 MHzband.
The Question was replaced by Question 2/XIII, particularly for further study of mini­
mum technical measures for “ homing ”. The Recommendation was improved by the addi­
tion of new §§ 1.4, 1.5 and 1.7 containing fresh information.

— 253 —5.

Opinion 21: Emergency position-indicating radio beacons.
Question 318 was adopted by correspondence after the Interim Meeting, Geneva 1965,
after considering the replies from I.C.A.O. and I.M.C.O. to the questions addressed to themin Opinion 21.
, Recommendation 439, concerning beacons for operation on 2182 kHz, has been approved;
and in view of the action already taken by Fourth Air Navigation Conference of I.C.A.O.,
a new Opinion (25), has been addressed to I.C.A.O. asking whether I.C.A.O. wishes the
C.C.I.R. to consider beacons operating at 121.5 and 243 MHz.
Opinion 25 and Recommendation 439 terminate the study of Question 318.

6.

Question 272 (XIII): Signal-to-interference protection ratios and minimum field-strengths
required in the mobile services.

6.1 Recommendation 441 has been approved to give recognition to the provisions containedin the Convention of International Civil Aviation, Annex 10, Chapter 4, concerning theplanning and protection of Aeronautical Mobile (R) Service frequencies above 30 MHz.
6.2 A preliminary Report 358 has been prepared concerning the VHF and U H F maritime andland mobile services and the H F maritime mobile service. Considerable additional data
is required to determine appropriate protection ratios and values of field strength to be pro­tected for these services.

7.

Question 273 (XIII): Use of classes of emission A2H and A3H at the distress frequencies
500 kHz and 2182 kHz, respectively.
Recommendation 438 has been approved. At 500 kHz, class of emission A2H is con­sidered as effective as class of emission A2 for alarm, distress, urgency and safety signals;
and on 2182 kHz, class of emission A3H is considered as effective as class of emission A3.
The new Recommendation terminates the study of Question 273 and doubtless the Recom­
mendation will be taken into account at the Maritime World Administrative Radio Confer­ence, 1967.

8.

Question 274 (XIII): Facsimile transmission of meteorological charts for reception on
board ships.
Opinion 24 has been addressed to the W.M.O., asking that Organization to consider
the provision of facsimile transmission of meteorological charts specifically intended forreception on board ships. To simplify ships’ equipment, the Opinion also asks W.M.O. toconsider the use of one standard drum-speed and index of co-operation, the use of class ofemission F4 only, and to minimize the number of radio channels. The study of Ques­
tion 274 has been terminated.

9.

Question 282 (XIII): Use of a control tone for automatic gain control of receivers in single­
sideband radiotelephone systems operating in the H F maritime mobile bands.
Question 282 has been terminated by Report 359, in conjunction with new Recommenda­
tion 258-1 (which replaces Recommendation 258 on single-sideband systems in the maritime
and aeronautical services). In brief, the Report recommends a continuous control signal,
at a level of — 16 dB relative to peak envelope power, for ship-shore and shore-ship trans­missions when automatic gain control of receivers is required.

— 254 —10. Recommendation 258: Single-sideband aeronautical and maritime mobile radiotelephoneequipments.
This recommendation has been replaced by Recommendation 258.-1. The main changes
are that both coast and ship station transmitter should have facilities for both classes ofemission A3J (suppressed carrier) and A3 A (reduced carrier), so that the use of A3 A andA3J are of equal standing, and it is intended that the type of emission used by coast stations
should be included in the I.T.U. “ List of Coast Stations ”. A new § (f) recognizes that,
although the use of class of emission A3 J is a desirable objective, it may be necessary to use
emission A3 A for an indefinite period to obtain acceptable automatic gain control in recei­vers. A long-term frequency tolerance of ship stations transmitters has been adopted as± 100 Hz in all H F bands.
The references to the aeronautical services (§ 2) have been brought up to date.

11. Question 319 (XIII): Operational procedures for single-sideband radio telephony systems

in the H F maritime mobile bands.

(Question 4/XIII).

This new Question was adopted by correspondence after the Interim Meeting, Geneva,
1965. A short Report (360), has been prepared, but further study is necessary. This
Question is closely bound up with selective calling and the channels and methods thatshould be used for calling. It is hoped that further consideration can be given to thesematters at the next Interim Meeting in 1967, prior to the maritime W.A.R.C.

12. Question 320 (XIII): The introduction of direct-printing telegraph equipment in the mari­time mobile service.
This new Question was adopted by correspondence after the Interim Meeting, Geneva,
1965. It has been revised and replaced by Question 5/XIII. Report 361 has been prepared,
which summarizes the eleven documents submitted to the X lth Plenary Assembly. Refer­ence should also be made to Report 349. Report 361 concludes that even at this stage it
appears that direct printing telegraphy for the maritime service is feasible.
Certain broad recommendations have been made in a new Recommendation 440. In
particular it points out that the system must be suitable for operation between pairs of sta­tions and also for broadcasting from one station to several stations; it also recommends
that the modulation rate should not exceed 100 bauds and that channel allocations to Admin­
istrations for this service should be in frequency blocks 1-5 kHz wide.
Further study and tests are necessary before a firm recommendation can be made ona system for international adoption for maritime purposes.

13. New Question 6/XIII: Self-supporting antennae for use on board ships.

The object o f this Question is mainly to extend the table of metre-amperes in the Conven­tion for the Safety of Life at Sea, 1960 (Chapter IV, Regulation 9, § (g)), which is usedin the determination of the “ normal range ” of the ship’s wireless installation. The present
table does not cater for the new types of self-supporting antennae.

14. Cancelled Recommendations:

Recommendation 424: Bearing and position classification for direction-finding: now
covered by Appendix 23 of the Radio Regulations.

— 255 —Recommendation 426: Spurious emissions from frequency-modulated VHF (metric)
maritime mobile equipment: now included in Recommendation 425.
15. Cancelled Reports:
Report 317: Publication of service codes in use in the international telegraph service:
redundant; see also Recommendation 437.
16. Amended Recommendations:
Recommendation

77:

Reference added to new Recommendation 258-1 on single­
sideband maritime and aeronautical radio telephony systems.
Recommendation 219: § 1.1: deletion of “ for minimum period of 6 s ”.
Recommendation 429: § (a) : misquotation from Safety of Life at Sea Conference
corrected.
All Recommendations were amended where necessary to bring references up to date.
17. Terms of Reference of Study Group XIII: The terms of reference were not changed.
T exts o f S t u d y G r o u p

Subject

M aintained

RevisedDeletedOpinion 20
Report 317

Codes

Selective calling

M inoreditorialchanges

XIII

Rec. 257

Land mobile
equipment

New

Remarks

Rec. 437

Res. 19
Q. 271
SP 371(A)Rep. 320

Res. 19-1
Q. 3/XIII
S.P. 3A/XIII
Rep. 320-1

Q. 163Res. 20
Rep. 319

Q. 7/XIIIRes. 20-1
Rep.319-1
S.P. 7B/XIII

Channelseparation
Technical
S.P. 7A/XIII characteristics
S.P. 7C/XIII Inter­
modulation
Q. 8/XIII
MF and HF
SSB

2 MHz DFQ. 206
Rec. 428

Emergency
position-indicating
radio bacons

Q .318 *Signal-tointerference ratios

Q.'272

Q. 2/XIII
Rec. 428-1
Op. 21

Rec 439
Op. 25* Q .318 has
been terminatedby Rec. 439
and Op. 25

Rec. 441 *Rep. 358* Aeronauticalservice— 256 —Subject

M aintained

RevisedM inoreditorialchanges

DeletedNew

A2H, A3H

Q. 273Rec. 438

Facsimile

Q. 274

Op. 24Control tone
for SSB

Q. 282

Rep. 359 *Single-sideband

Rec 258

Rec 258-1

Operational
Procedures* See also
Rec. 127

Q. 4/XIII
Rep 360
Q. 320

Direct-printing
telegraphy

Q. 5/XIII
Rec 440
Rep 361

Self-supporting
Antennae

Q. 6/XIIIClassificationof bearings

Rec 424

Spurious emissions
from VHF
equipment

Rec 426

Interconnections
RT alarm signal
8 MHz DFVHF FMequipment
500 kHz inter­
ference HF-DF
Radar interference
Voice-operated
devicesInterference onships
500 kHz auto
alarm
Pulse-DFVHF inter­
modulation
Radar
identification

Remarks

Rec 77
Rec 219
Rec 423
Rec 425
Rec 429
Rep 93
Rec 45
Rec 76
Rec 218
Rec 224
Rec 422
Rec 427
Rep 318-

— 257 —Op. 24OPINION 24 *FACSIM ILE TRANSM ISSION OF M ETEOROLOGICAL CHARTSFOR RECEPTION ON BOARD SHIPSThe C.C.I.R.,(1966)CONSIDERING(a) that meteorological charts are being transmitted extensively over radio circuits;(b) that the transmissions concerned are mainly intended for exchange of meteorological infor­
mation in the fixed services;(c) that, however, it is desirable to adopt a more uniform practice for facsimile transmissionsof meteorological charts intended for ships;(d) that Chapter V, Regulation 46 (ii), of the Convention for the Safety of Life at Sea, London,
1960, requests contracting Governments to encourage the transmission of suitable facsimile
weather charts for ships;(e) that there is a need for the reception on board ships of suitable meteorological charts;(f) that an increasing number of ships is being fitted with equipment for receiving meteorolo­
gical charts;(g) that the World Meteorological Organization (W.M.O.), in collaboration with the C.C.I.T.T.,
has standardized the equipment used for international meteorological transmissions (seethe following W.M.O. Documentation: Recommendations 60 and 61 of the third sessionof the Commission for Synoptic Meteorology (C.S.M.) and § 7.15 of the report of the fourth
session of C.S.M.);(h) that the W.M.O. standards provide for various drum-speeds and indices of co-operation;
the choice, which depends on the type of charts transmitted, is left at present to the discretionof meteorological services;(i) that certain characteristics, concerning meteorological facsimile transmissions by radio,
are contained in Recommendation 343;
IS UNANIMOUSLY OF THE O PINION

1.

that consideration should be given to the provision of facsimile transmission of meteorolo­
gical charts specifically intended for reception on board ships (see Recommendation 16-IVof the W.M.O. Commission for Maritime Meteorology);

2.

that the layout of such charts, the minimum size of letters, figures and symbols, and thethickness of lines, should be standardized throughout the world, to facilitate theirinterpretation by ships’ personnel when using small size recording equipment;

3.

that the appropriate signals for preliminary tuning should be transmitted for about 120
seconds prior to the commencement of facsimile transmission of meteorological charts
intended for ships;

4.

that direct frequency-modulation (F4) should be employed for the facsimile transmissionof meteorological charts over radio circuits, with the following characteristics:(a) Decametric waves (3 MHz — 30 MHz)Centre frequency (corresponding to the assigned f r e q u e n c y ) .................. f 0
Frequency corresponding to b l a c k ................................................... . . . fo — 400 Hz
Frequency corresponding to w h i t e ................................................................. fo + 400 Hz* This Opinion terminates the study o f Question 274.

17

Op. 24, 25— 258 —(b) Kilometric waves (30 kHz — 300 kHz)Centre frequency (corresponding to the assignedf r e q u e n c y ) ................ f 0
Frequency corresponding to black................ ...................................... fo — 150 Hz
Frequency corresponding to white.......................................................f 0 + 150 Hz
5.

that consideration should be given to the use of onestandard drum speed and one standard
index of cooperation in facsimile transmissions specifically intended for reception by ships;

6.

that consideration should also be given to keeping to a minimum throughout the world
the number of radio frequencies employed for facsimile transmissions intended for reception
by ships;

7.

that the Director, C.C.I.R. should bring this Opinion to the attention of the W.M.O. forconsideration by that Organization.

O P IN IO N 25 *E M E R G E N C Y P O S IT IO N -IN D IC A T IN G
R A D IO B EA CO N S
The C.C.I.R.,(1966)CONSIDERING(a) that Recommendation 439 defines the characteristics of Emergency Position-Indicating
Radio Beacons operating on the frequency of 2182 kHz; to indicate the position of survivors
and to facilitate search and rescue operations;(b) that Doc. XIII/71, 1963-1966, contains Resulotion A. 91 (IV) adopted on 27 September
1965 by the Fourth Session of the Assembly of the Inter-Governmental Maritime Consul­
tative Organization (I.M.C.O.) confirming the views of the Maritime Safety Committee;
and that, in particular, 2182 kHz is recommended as a first choice operational frequency,
but it rests, however, with Administrations to determine whether the beacon should allow
for the use of a second or more frequencies;(c) that Doc. XIII/103, 1963-1966, contains the Report of the Fourth Air Navigation Con­
ference of the International Civil Aviation Organization (I.C.A.O.), Montreal, 9 November 3 December 1965 in which the frequencies of 121.5 MHz and 243 MHz and certain technicalchacracteristics are recommended for Survival Radio Equipment;
IS UNANIMOUSLY OF THE OPIN IO N

1.

that the International Civil Aviation Organization be invited to advise C.C.I.R. if they wish
the C.C.I.R. to study characteristics of Emergency Position-Indicating Radio Beacons operat­ing on the frequencies of 121.5 MHz and 243 MHz;

2.

that the Director, C.C.I.R. be invited to transmit this Opinion to I.C.A.O.

* This Opinion, together with Recom m endation 439, terminates the study o f Question 318.

— 259 —Q. 1/XIH, 2/XIIIQUESTION 1/XIII *SIGNAL-TO-INTERFERENCE PRO TECTION RATIOS AND M INIM UM
FIELD-STRENGTHS REQUIRED IN THE M OBILE SERVICES
The C.C.I.R.,(1963)CONSIDERING(a) that full effect should be given to the studies which the Administrative Radio Conference,
Geneva, 1959, in its Recommendation No. 3, invited the C.C.I.R. to continue for all services;(b) that for certain kinds of mobile services, partial data relating to interference protection
ratios and minimum field strengths required, exist in documents of some Conferences of
the I.T.U., for example, in the Final Acts of the International Administrative AeronauticalRadio Conference, Geneva, 1948-1949 and of the Special Regional Conference, Geneva,
1960;(c) that such documents, however, do not constitute a complete and consistent set of data relat­
ing to all kinds of mobile services operating in all frequency ranges, particularly with respect
to VHF mobile services;u n a n im o u s l y d e c id e sthat the following question should be studied:1.

what are the signal-to-interference protection ratios which define the threshold of harmfulinterference for the several mobile services;2.

what are the signal-to-noise ratios and the minimum field-strengths required for satisfactory
reception of the different classes of emission in the several mobile services;

3. what are the appropriate fading allowances in the several mobile services ?
Note 1 . - The above studies should be continued simultaneously and with the same urgency.
Note 2. - Particular attention should be given to those studies which will assist the further refine­ment of the technical standards used by the International Frequency Registration Board.
Note 3. - The above-mentioned studies should be carried on permanently and recommendations
and possible revisions be published as soon as practicable.

QUESTION 2/X III**
DIRECTION-FINDING AND H O M IN G IN THE 2 MHz BAND ON BOARD SH IPSThe C.C.I.R.,(1959 - 1966)CONSIDERING(a) that the use of radiotelephony in the 2 MHz band on board ships is increasing;(b) that an increasing number of ships are being fitted with direction-finding equipment capableof taking bearings in the 2 MHz band;_A -----------* Formerly Question 272(XIII).
** This Question replaces Question 206.

— 260 —Q. 2/XHI, Res. 19-1(c) that the taking of accurate bearings, and especially homing, on board ships is importantin cases of distress;u n a n im o u s l yd e c id e sthat the following question should be studied:1.

what special technical measures and precautions should be taken in the design and the ins­
tallation of 2 MHz direction-finding equipment for use on board ships for taking bearings;

2.

what are the minimum technical measures that need be taken for homing at the radiotele­phony distress frequency of 2182 kHz;3.

what is the order of accuracy to be expected from 2 MHz direction-finding equipment onboard ships, particularly at the international distress frequency of 2182 kHz ?

Note. - For the purposes of this Question “ homing ” means the taking of direction-finding
bearings without ambiguity of sense within an arc of 30° on either side of the bow.

RESOLUTION 19-1
SELEC TIV E-C A LLIN G SY STEM S F O R U SE IN T H E IN TE R N A TIO N A L
M A R IT IM E M O B IL E SERV ICES(Study Programme 3A/XIII)The C.C.I.R.,(1963 - 1966)CONSIDERING(a) Question 3/XIII, Study Programme 3A/XIII, Recommendation 257 and Report 320-1;(b) that the results o f the tests carried out by several Administrations are given in the Reportof the International Working Party on selective-calling devices (Doc. X III/19, 1963-1966);(c) that additional documents considered at the Interim Meeting of Study Group XIII, Geneva,
1965, listed in the conclusions of that Meeting, and documents submitted to the X lth Plenary
Assembly, listed in the Chairman’s Report (Doc. XIII/107, 1963-1966), give further infor­
mation;(d) that so far, it has not been possible to make a decision on the system that should be adopted
internationally;(e) that the selective-calling system should be suitable for operation in all maritime mobile
services;(f) that it is important to standardize, with the least possible delay, the operational and techni­
cal characteristics of an international maritime selective-calling system;
UNANIMOUSLY DECIDES

1.

that an International Working Party should again be convened for the purpose of further
studying selective calling for the maritime mobile service. Reference is made to Question
3/XIII, Study Programme 3A/XIII and Report 320-1, §§ 6, 7 and 8;

— 261 —2.

Res. 19-1, Q. 3/XIII

that the following Administrations and International Organizations should be invited toparticipate in this International Working Party;
Netherlands (Chairman),
Belgium,
Canada,Denmark,
United States of America
FranceJapan,

Norway,Federal Republic of Germany,
United Kingdom,
Union of Soviet Socialist Republics,
Comite International Radio Maritime,
International Chamber of Shipping;

3. that the Netherlands Administration should be invited to be responsible for conducting
the tests mentioned in Report 320-1, § 7;
4. that a progress report should be sent, by 1 April 1967, to the Chairman, Study Group XIII
and to the Director, C.C.I.R. for circulation to participants in the work of Study Group XIII.

QUESTION 3/XIII *SELECTIVE-CALLING SYSTEMS FOR USE IN THE INTERNATIONAL
M ARITIM E M OBILE SERVICES
The C.C.I.R.,(1956 - 1963 - 1966)CONSIDERING(a) Recommendation 425-1, in answer to Question 107, concerning VHF (metric) FM equipmentin the maritime mobile service;(b) that there may be advantages in the use of selective-calling systems in the operation of theinternational maritime mobile services;(c) that a selective-calling system should provide for a sufficiently large number of individual
non-conflicting signalling combinations;(d) that the frequency bandwidth required for signalling should not exceed that required forthe transmission of speech;(e) that the signalling equipment should operate reliably under poor transmission conditions;(f) that the signal receiving units should be capable of operating with the radio receiving equip­
ment commonly available in ships;(g) that the transmission of a complete call should be accomplished in as short a time as possible;(h) that the equipment should be low in cost and capable of operation for long periods under
shipboard conditions;u n a n im o u s l yd e c id e sthat the following question should be studied:1.

is there a need for a world-wide selective-calling system in the maritime mobile services,and to what extent, and for what purposes can selective calling be used with advantage;2.

what are the advantages and disadvantages in the use of the same selective-calling system
in all maritime bands;

3.

what are the operational requirements that should be met by any selective-calling systemthat could be used for the purposes recommended in answer to § 1;
* This Question replaces Question 271.

S.P. 3A/XIII, Q. 4/XIII— 262 —

4.

what auxiliary facilities are available in existing selective-calling systems;

5.

what are the essential technical characteristics of selective-calling systems on which inter­national agreement is required;6.

what types of selective-calling systems fulfil the operational and technical requirements
in answer to §§ 3 and 5 ?

STUDY PRO G R A M M E 3A/XIII *SELECTIVE-CALLING SYSTEMS FOR USE IN THE INTERNATIONAL
M ARITIM E M OBILE SERVICES
The C.C.I.R.,(1959 - 1963 - 1966)CONSIDERING(a) that Recommendation 257 does not give a full reply to Question 271;(b) that the essential technical characteristics of a selective-calling system to be agreed uponneed further study, in accordance with Resolution 19-1 and Report 320-1;(c) that it is desirable to standardize technical and operating characteristics;
u n a n im o u s l y d e c id e s

1.

that the following study should be carried out:

trials of selective-calling systems, with a view to coming to a decision on the type of systemthat should be adopted internationally;

2. consideration of the number of individual code combinations required and the principles
to be adopted in their allocation;
3. determination of those technical and operating characteristics of the selective-calling system
which require international standardization;

4.

degree of immunity of the systems from false operation and degree of their response to wanted
signals.

QUESTION 4/XIII **OPERATIONAL PROCEDURES FO R SINGLE-SIDEBAND RADIOTELEPHONESYSTEMS IN THE H F M ARITIM E M OBILE BANDSThe C.C.I.R.,(1965 - 1966)CONSIDERING(a)the desirability of encouraging the rapid conversion of the radiotelephone service in the
H F maritime mobile bands from-double sibeband (DSB) to single-sideband (SSB) operation(in accordance with Recommendation 258-1);* This Study Programme replaces Study Programme 271 A.
** Formerly Question 319(XIII).

— 263 —Q. 4/XIH, 5/Xin(b) the lack of uniformity of operational procedures among the coast stations that provide
this service;(c) the increasing trend towards the use of unattended or remotely-controlled receivers at coaststations;(d) the desirability of standardizing, as far as possible, the technical facilities necessary on ships
for communicating with different coast stations;(e) the studies undertaken by the C.C.I.R. in connection with Question 282 on the subject ofautomatic gain control systems;(f) the possible use of selective calling devices, particularly in the direction of shore-to-ship(Question 3/XIII);u n a n im o u s l yd e c id e sthat the following question should be studied:1.

what special emissions should be made by ship stations using single-sideband equipment
when initiating a radiotelephone call to a coast station in the H F maritime mobile service;2.

what further signals, if any, should be sent at the beginning of such a call to enable coaststation receivers to be correctly adjusted;3.

is there a need for any supplementary control signals to be sent by the ship station during
the radiotelephone call for the purpose of controlling the radio circuit between the ship andthe coast station;

4.

what special signals or emissions, if any, should be sent by a coast station to initiate a callto a ship station;

5.

what special signals or emissions, if any, should be sent by a coast station at the beginningof a radiotelephone call to a ship, to facilitate rapid and accurate adjustment of the ship
station receiver;6.

is there a need for any supplementary control signals to be sent by the coast station during
a radiotelephone call, for the purpose of controlling the radio circuit between the ship andthe coast station ?

QUESTION 5/XIII *TH E INTRODUCTION OF DIRECT-PRINTING TELEGRAPH
EQUIPM EN T IN THE M ARITIM E M OBILE SERVICEThe C.C.I.R.,(1965 - 1966)CONSIDERING(a) that there is a requirement for communication in the maritime mobile service by meansof direct-printing telegraph techniques;(b) that the same information may need to be transmitted simultaneously from one coast sta­tion to a number o f ship stations;(c) that ship stations may need to transmit messages and data to. coast stations;(d) that the modulation rates and the telegraph codes used in the telegraph equipment should
conform to C.C.I.T.T. standards;* Formerly Question 320(xiII).

Q. 5/XIH, 6/XIH— 264 —(e) that the use o f an error-indicating, an error-indicating and correcting, or an error-correct­
ing system for such circuits may be necessary and that the characteristics o f such systems
need to be agreed upon;(f) that any special operating procedures necessary for such a service should be agreed;
unanimously decides that the following question should be studied:1.

what types o f error indicating, error indicating and correcting, or error correcting systemshould be recommended for use over the radio paths;

2.

what is the maximum modulation rate that should be used over the radio paths;

3.

what types o f modulation should be used over the radio paths; *4.

what overall quality of transmission (error rate or transmission efficiency factor) is required
for this service.

5.

what operational procedures should be recommended for such a service ?

QUESTION 6/XIII
SELF-SUPPORTING ANTENNAE FOR USE ON BOARD SH IPSThe C.C.I.R.,
CONSIDERING(1966)
0(a) that conventional main wire-antennae, suspended between the masts of merchant vessels,
impede cargo-handling operations;(b) that repeated dismantling and re-rigging of main wire-antennae in harbours leads to increased
wear and tear and consequently decreases the reliability of the antenna system;(c) that the superstructure of modern ships makes it more and more difficult to install main
wire-antennae of sufficient height and clearance;(d) that, therefore, the use on board ships of self-supporting main antennae is increasing;(e) that for several years, efforts have been made to improve the radiation properties and theefficiency of self-supporting antennae, to meet the requirements of the minimum normal
range of ship stations in the M F band (Convention for the Safety of Life at Sea, 1960, Chap­
ter IV, Regulation 9, § (g))\(f) that the table of metre-amperes, which appears in the aforementioned Convention and which
gives an indication of the normal range obtainable with an installation including a conven. tional main wire-antenna, cannot be applied to self-supporting antennae;(g) that experimental work has shown that, in the frequency band 405-535 kHz, self-supporting
antennae have, in general, poorer radiation properties than conventional main wire-antennae;(h) that properly constructed and installed self-supporting antennae, however, have better radia­
tion properties in the 2 MHz bands and H F bands compared with conventional main-wireantennae;(i) that it is important that antennae and transmitters be suitably rnatched;

— 265 —u n a n im o u s l y

1.

d e c id e s

Q. 6/XIII, Res. 20-1

that the following question should be studied:what advice should be offered to the Inter-Governmental Maritime Consultative Organiza­tion by the C.C.I.R. on the additions to be made to the table of metre-amperes given in
the Convention for the Safety of Life at Sea, 1960, Chapter IV, Regulation 9, § (g), to include
self-supporting antennae;

2. what practical methods should be used to assess the properties of self-supporting antennae
installed on board a ship in regard to radiation under different conditions, e.g. ship’s draught,
humidity, precipitation, location and configuration of the antennae;
3. to what extent will it be possible to use the dimensions of the antenna and its height above thedeepest load waterline in assessing compliance with the requirements of the said Convention ?

RESOLUTION 20-1
CHARACTERISTICS OF EQ UIPM EN T AND PRINCIPLES GOVERNING THE
ALLOCATION OF FREQUENCY CHANNELS IN TH E LAND M OBILE SERVICES
BETWEEN 25 AND 500 M Hz
(Q uestion 7/XIII)The C.C.I.R.,(1959 - 1963 - 1966)CONSIDERING(a) that land mobile services of various kinds are growing rapidly;(b) that, in border areas, difficulties may arise between the services of different Administrations;(c) that it would be advantageous if there were a sufficient measure of agreement, where neces­sary, between Administrations on the characteristics of equipment and on the principles
adopted in the planning for land mobile services;
UNANIMOUSLY DECIDES

1.

that Administrations should consult together as necessary to resolve any difficulties concern­
ing their land mobile services and for the purpose of improving such services;2.

that those Administrations which are interested in the provision of common land mobile
services should consult together and should advise the C.C.I.R. of any technical and opera­
tional problems that require international study;

3.

that Administrations should continue to submit technical specifications of land mobile
equipment and the relevant measuring methods used in their respective countries to the
Chairman, Study Group XIII and the Director, C.C.I.R., for circulation;

4.

that Administrations should submit information on practices adopted for the allocationof channels between 25 and 500 MHz for land mobile services to the Chairman, Study GroupXIII and the Director, C.C.I.R., for circulation;

265 aSTUDY PRO GRAM M E 6A/XIII
SELF-SUPPORTING ANTENNAE FOR USE ON BOARD SHIPS
Performance at 500 kHz(1967)The C.C.I.R.,
CONSIDERING(a) that there are now radically different physical and electrical configurations of self-supporting
antennae as compared with the 500 kHz antennae to which Chapter IV, Regulation 9, § (g),of the International Convention for the Safety of Life at Sea, 1960, was intended to apply;.
(b) that to provide an adequate answer to Question 6/XIII, additional data are needed as to thedesign, installation and performance of self-supporting antennae, in order that a proposal
might be made for modification of Regulation 9, § (g), to be applicable to self-supporting
antennae, while ensuring that such installations will meet the minimum normal ranges specified
for ship stations;d e c id e sthat the following studies should be carried o u t :data on performance of self-supporting antennae should be collected and communicated to
the Director, C .C.I.R .:1.

Description

1.1 Characteristics and dimensions of antennae as mounted on board ship, e.g. overall height
above deepest load line, etc., including simple diagrammatic sketches where appropriate;
1.2 design criteria for base insulator (physical and electrical characteristics, e.g. shunt capacitance,,physical dimensions, material, etc.), top loading and loading coil, if any;
2.

Performance

2.1 Current, as measured with class of emission A0;
2.1.1 current delivered to the antenna system by the transmitter;
2.1.2 current at the base of the antenna;
2.2 Capacitance of the antenna system as seen from the transmitter (at approximately 500 kHz);.
2.3 field strength measured over sea water at a distance of at least three nautical miles and adjusted
to a reference value at one nautical mile in accordance with Recommendation 368;
2.4 weather conditions on board ship during the measurements;
3.

Installation details, for example :3.1 location on ship;
3.2 separation from nearby objects;
3.3 protection from adverse weather effects.

Res. 20-1, Q. 7/XHI— 266 —

5. that Administrations which have reached agreement with adjacent countries on the opera­tion of land mobile services in border areas, should submit to the C.C.I.R. technical andoperational details of the agreement to assist other Administrations with similar problems.

QUESTION 7/XIII *CHARACTERISTICS OF EQ U IPM EN T AND PRINCIPLES GOVERNINGTH E ALLOCATION OF FREQUENCY CHANNELS IN
THE LAND M OBILE SERVICES BETWEEN 25 AND 500 M Hz
The C.C.I.R.,(1956- 1966)CONSIDERING(a) that an interchange of information on the requirements of Administrations, concerning thetechnical characteristics of equipment used in land mobile services between 25 and 500 MHz,
would be advantageous in the development of those services;(b) that an exchange of information among different countries concerning the practices applied

to the assignment of channels and the experience gained in the operation of land mobile
services between 25 and 500 MHz is of value in general;(c) that a certain measure of agreement may be desirable on the characteristics of the land mobile

equipment that are used in the border areas of neighbouring countries to minimize mutualinterference;(d) that a certain measure of agreement may also be desirable on the practices governing theallocation and use of channels in land mobile services between 25 and 500 MHz in borderareas;
u n a n im o u s ly d e c id e sthat the following question should be studied:

1. what are the technical requirements of Administrations concerning equipment used in land
mobile services between 25 and 500 MHz that are of international importance in the devel­
opment of such services, e.g. transmitter power, type of antenna, emission characteristics,
frequency tolerance;
2. to what extent would it be desirable to standardize the performance characteristics of land
mobile equipment between 25 and 500 MHz internationally;
3. what are the broad practices adopted by Administrations in the allocation of channels tothe various kinds of user in the land mobile service between 25 and 500 MHz, e.g. channel
separation, geographical spacing of stations in the same adjacent channels, frequency separa­tion for duplex operation, degree of frequency sharing in a particular service area;
4. to what extent is it desirable to reach international agreement on the practices for the alloca­
tion of channels in the land mobile service between 25 and 500 MHz ?

* This Question replaces Question 163.

— 267 —S.P. 7A/Xm

STUDY PROGRAMME 7A/XIIITECHNICAL CHARACTERISTICS OF LAND M OBILE EQUIPM ENT
BETWEEN 25 AND 500 M Hz
The C.C.I.R.,(1966)CONSIDERING(a) that Report 319-1 gives a partial answer to Question 7/XIII.
(b) that information contained in this Report will facilitate cooperation between Administrationsin the technical operation of their services;(c) that a degree of standardization is desirable, since the land mobile service connected to
the national network may form part of an international connection, as stated in Recommenda­
tion 77-1.
(d) that it is desirable to determine equipment technical characteristics, to facilitate theplanning of channel allocation in the land mobile bands;(e) that it would therefore be desirable to reach agreement upon which are the essential tech­nical characteristics for VHF and U H F radiotelephone equipment for use in the land mobile
service, in order to expedite the international interchange of data on such equipment;u n a n im o u s l y d e c id e sthat the following studies should be carried out:

determination of equipment characteristics (including methods of measurement) for thevarious land mobile services between 25 and 500 MHz which may be adopted by Adminis­
trations, in particular:
1. for frequency-modulation systems:
1.1 the maximum frequency deviation for various channel-frequency spacings;
1.2 pre-emphasis and de-emphasis characteristics;
2. for amplitude- and frequency-modulation systems:
2.1 the maximum audio-frequency bandwidth;
2.2 frequency tolerances of transmitters;
2.3 typical and maximum output powers of base and mobile-station transmitters;
2.4 mean power limits of harmonic and other spurious emissions:2.4.1 falling in any other land mobile channel,
2.4.2 falling within the bands of other radio services;
2.5 receiver characteristics, particularly- frequency stability,- selectivity,- radiation,- intermodulation,- choice of intermediate-frequency,- sensitivity,- audio-frequency response.
Note. - Study Programmes 7B/XIII and 7C/XIII should be borne in mind.

S.P. 7B/XIH, 7C/XIII— 268

STUDY PROGRAMME 7B(XIII)M IN IM U M CHANNEL-SEPARATION AND O PTIM U M
SYSTEMS OF M ODULATION FOR LAND M OBILE SYSTEMSBETWEEN 25 AND 500 M Hz
The C.C.I.R.,(1966)CONSIDERING(a) that Report 319-1 partly answers Question 7/XIII;(b) that congestion in the VHF and U H F bands is a serious problem in many countries;(c) that this is due to the rapid growthof the land mobile services;(d) that in a number of countries many base stations are operated from within a limited geo­
graphical area;(e) that the frequency tolerances given
in Table I (Column 3) of Report 181-1are now readily
achievable with equipment used in the land mobile service;(f) that in a number of countries impulse noise is at such a level as to cause serious degradation
to communications range;
unanimously decides that the following

1.

2.

3.
4.
5.

studies should be carried out:

determination of the minimum bandwidth necessary for various known modulation techniques,in particular for double-sideband amplitude-modulation, frequency modulation and single­
sideband emissions;determination of the relative advantages and disadvantages of various types of modulation
system as the occupied bandwidth approaches the minimum necessary for the transmissionof intelligence, taking into account the necessary signal-to-noise ratio at the receiver input;
determination of the minimum channel-separation achievable between base station trans­mitters located within a limited geographical area or at a common site;
determination of the minimum frequency-separation between transmitters and receivers
under conditions of duplex operation at the same site;
determination of the technical characteristics, criteria and techniques to achieve, in practice,
the channel and frequency separations in §§ 3 and 4.

STUDY PRO G R A M M E 7C/XIII
INTERFERENCE DUE TO INTERM ODULATION PRODUCTS IN
THE LAND M OBILE SERVICES BETWEEN 25 AND 500 M Hz
The C.C.I.R.,(1966)CONSIDERING(a) that Report 319-1 only partly answers Question 7/XIII;(b) that large numbers of base station transmitters and receivers may be operated within thesame limited geographical area;

— 269 —S.P. 7C/XIII, Q. 8/XHI(c)that such transmitters may produce high-level intermodulation emissions, the odd ordersof which fall within and on either side of a land mobile band, and these may fall on receive
frequencies of land mobile stations;(d)that channelling plans can be devised so as to minimize the effects of intermodulation products;(e)that receivers may have spurious intermodulation responses as a result of two or more strong
input signals;(f)that external non-linearly conducting elements may produce intermodulation products fromtwo or more signals;
unanimously decides that the following studies should be carried out:

1.

determination of the various causes of intermodulation products arising within transmitters,
receivers and external non-linear elements, and the various techniques which may be used
to minimize their production and reduce their effects, the method used being stated in each
case;

2.

determination of the maximum permissible mean power of intermodulation emissions forsatisfactory operation in the land mobile services;3.

determination of the precautions that are required against the formation of intermodulation
products in receivers and which are compatible with satisfactory operation of the land mobile
services.

QUESTION 8/XIII
MF AND HF LAND MOBILE SERVICES
Preferred technical characteristics of
single-sideband equipment
The C.C.T.R.,(1966)CONSIDERING(a)that the final report of the Panel of Experts on the reduction of congestion in the H F spectrum
has recommended the adoption of single-sideband techniques;(b)that the necessary bandwidth of single-sideband emissions is less than that for other radio­
telephone emissions;(c) that there is an increasing need for economy in the use of spectrum space;(c) that the use of single-sideband emissions in the maritime mobile service is under considera­tion;(e) that I.C.A.O. is considering the preferred technical characteristics to be adopted for single­
sideband equipment for the aeronautical mobile service;(f)that the need for the use of single-sideband systems for the fixed services has been stressed.
(See Radio Regulations No. 465 and Recommendation 100);(g)that sharing between the land mobile and other services exists in many frequency bands;

Q. 8/xni— 270 —(h) th a t in te r c o m m u n ic a tio n b e tw e e n s t a t io n s in t h e v a r io u s m o b ile se r v ic e s m a y b e n e c e s sa r y ,p a r tic u la r ly fo r se a r c h a n d r e s c u e o p e r a tio n s ;(i) th a t it is d e sir a b le fo r c o m m o n p r e fe r r e d te c h n ic a l c h a r a c te r is tic s to b e a d o p te d , a s fa r a s
p o s s ib le , fo r th e m a r itim e , a e r o n a u tic a l a n d la n d m o b ile se r v ic e s;
u n a n im o u s l y d e c id e s

th a t th e f o llo w in g q u e s t io n s h o u ld b e s tu d ie d :1.

w h a t b a s ic r e q u ir e m e n ts s h o u ld b e m e t fo r MF a n d H F la n d m o b ile e q u ip m e n t, in p a r ti­
c u la r t h e ty p e o f s in g le -s id e b a n d e m is s io n , t h e sid e b a n d w h ic h s h o u ld b e u s e d , a n d th ec h a n n e l se p a r a tio n ;2.

w h a t te c h n ic a l p e r fo r m a n c e s h o u ld b e re q u ir e d o f t h e tr a n sm itte r — in p a r tic u la r , p e a k
e n v e lo p e p o w e r , fr e q u e n c y sta b ility , m o d u la t io n fr e q u e n c y r e s p o n s e , le v e ls o f sp u r io u s
e m is s io n s , le v e l o f ca rrier su p p r e s s io n , a n d r e s tr ic tio n s o n in te r m o d u la t io n p r o d u c ts ;3.

w h a t te c h n ic a l p e r fo r m a n c e s h o u ld b e re q u ir e d o f th e r e c e iv e r — in p a r tic u la r , se le c tiv ity ,s e n s itiv ity , a u d io -fr e q u e n c y r e s p o n s e , fr e q u e n c y sta b ility , b lo c k in g a n d in te r m o d u la t io nch a r a c te r is tic s , a n d le v e ls o f s p u r io u s e m is s io n s ;4.

w h a t o th e r s p e c ia l r e q u ir e m e n ts a re n e c e s sa r y fo r s in g le -s id e b a n d e q u ip m e n t u s e d in th e
MF a n d H F la n d m o b ile se r v ic e ?

— 270 a —QUESTION 9/XIII

SELECTIVE-CALLING SYSTEM FOR FUTURE OPERATIONALREQUIREMENTS OF THE MARITIME MOBILE SERVICES(1967)The C.C.I.R.,
CONSIDERING(a) that draft Recommendation D.a * in answer to Question 3/XIII meets the immediate opera­
tional requirements of certain Administrations;(b) that future operational requirements may necessitate the development of different types of
selective calling system;d e c id e s th a t th e f o llo w in g

q u e s tio n s h o u ld b e stu d ie d :1.

what are the operational requirements for selective calling that may be necessary for future
maritime communication systems;2.

what other information, in conjunction with the selective call, may be required for the opera­tion of future maritime communication systems;3.

what are the best means for meeting these requirements bearing in mind the technical andeconomic factors and the need for frequency spectrum conservation?

QUESTION 10/XIII
REDUCTION OF FREQUENCY SEPARATION BETWEEN ADJACENTCHANNELS IN THE VHF (METRIC) MARITIME-MOBILE BAND
(1967)The C.C.I.R.,
CONSIDERING(a) that the use of the VHF (156-174 MHz) band by the maritime-mobile service is increasing;(b) that, as a result, an increased number of channels may be necessary;(c) that the number of channels available for assignment may be increased by reducing the fre­quency separation between adjacent channels;* See the Conclusions o f the Special Meeting o f Study Group XIII, Geneva, 1967.

270 b(d) that, as there are already in operation a large number of equipments conforming to Recom­
mendation 425, any reduction in frequency separation between adjacent channels needs to beconsidered, not only as regards technical characteristics but also as regards interference toexisting services;d e c id e sthat the following question should be studied:1.

if the frequency separation between adjacent channels be reduced to 25 kHz, what should be
the technical characteristics of the equipment and what would be the effects on the performanceof the radiotelephone system;

2.

what special measures would need to be taken to introduce the new frequency separation
between adjacent channels with the minimum adverse effect on existing services ?

QUESTION 11/X III
IMPROVEMENTS IN THE PERFORMANCE OF
RADIOTELEPHONE CIRCUITS IN THE MF AND HF MARITIME BANDS(1968)The C.C.I.R.,
CONSIDERING(a) that there is a need to improve the quality of transmission of MF and H F maritime radio­
telephone circuits;(b) that the adoption of new compandor principles which have recently become available mightoffer the prospect of such an improvement;d e c id e sthat the following question should be studied:1.

what are the methods by which compandor techniques can be applied to maritime radio­
telephone circuits in the M F and H F bands;

2.

what improvement in performance is to be expected with these techniques;3.

what characteristics would need to be agreed if such a technique were adopted;

4.

what changes, if any, would need to be made to the tolerances of existing equipment, etc. tosatisfactorily apply such techniques;
what measures should be taken to provide compatible operations between stations utilizing
compandor principles and those fitted with conventional equipment only?

5.

— 270 c —QUESTION 12/XIII
RADIO-PAGING* SYSTEMS(1968)The C.C.I.R.,
CONSIDERING(a) that systems for paging by means of radio are in operation in a number of countries and that
their use is extending;(b) that as the areas of coverage are increased, the possibility of interference between different
radio-paging systems, and between radio-paging systems on the one hand and other radio­
communication systems on the other hand is increased;(c) that the various systems already in use, or proposed, are not necessarily compatible one withanother;(d) that system compatibility is necessary in the case of international operation;(e) that for international operation it is desirable to agree on the parameters of the system;(f) that it is essential to make the most efficient use of the available radio-frequency spectrum;d e c id e sthat the following question should be studied:,‘1.

from a technical point of view, what frequency bands are most suitable for radio-paging
systems;2.

what overall quality of transmission (capacity, degree of immunity from false calls, successful
call ratio, etc.) should be provided by radio-paging systems;3.

what are the technical characteristics of radio-paging systems on which international agree­
ment is desirable;

4.

what operational facilities need to be specified to permit international operation of radio­
paging systems, and in what circumstances could they share frequencies with other radio­
communication systems?

* Radio paging— a one-way calling system without speech.

— 271 —LIST OF DOCUMENTS CONCERNING STUDY GROUP XIII
(Period 1963-1966)
OriginTitle

Reference

XIII/1and Corr.l

United States ofAmerica

Selective calling devices for use in the international maritime mobile radiotelephoneservice - Report of tests performed for theInternational Working Party set up under
Resolution 19

S.P. 271A

XIII/2and Corr.lFederal Republicof Germany

Selective calling devices for use in the international maritime mobile radiotelephoneservice - Report to the International Work­ing Party set up under Resolution 19

S.P. 271A

XIII/3

United Kingdom

Publication of the “ Codes and Abbrevia- Op. 20
tions for the International Telecommunica­tion Services ” by the International Tele­
communication Union

XIII/4

I.M.C.O.

Extract from the Maritime Safety Committee Report to the Council (MSC VIII/28),
8th session

Op. 21

XIII/5

United Kingdom

Tests of selectivity calling devices for use in
the international maritime mobile radiotelephone service

Res. 19
Q. 271

XIII/6

I.C.A.O.

Emergency position-indicating radio beacons

Op. 21

XIII/7

United Kingdom

Signal-to-interference protection ratios andminimum field-strengths required in themobile services - Aeronautical services

Q. 272

XIII/8and Corr.l

United Kingdom

Use of classes of emission A2H and A3H
on the distress frequencies of 500 and
2182 kHz respectively

Q. 273

XIII/9

United Kingdom

Facsimile transmission of meteorologicalcharts for reception by ships

Q. 274

XIII/10

CanadaSelective calling devices for use in the international mobile radiotelephone service Report to the C.C.I.R. International Work­ing Party on selective calling

S.P. 271A

XIII/11

CanadaSelective calling devices for use in the international mobile radiotelephone service Report to the C.C.I.R. International Work­ing Party on selective calling

S.P. 271A

XIII/12

United Kingdom

Use of control tone for automatic gain
control of receivers in single-sideband radio­
telephone systems in the HF maritime mobile
bands

Q. 282

XIII/13

FranceSelective calling devices for use in the international maritime mobile radiotelephoneservice - Report to the International Work­ing Party set up under Resolution 19

Res. 19

XIII/14and Corr.l

The Netherlands

Tests of selective calling devices for use in
the international maritime mobile radiotelephone service

Rep. 320
Res. 19

XIII/15

United States ofAmerica

Comparative tests of U.S.A., German andJapanese marine selective calling devices

Res. 19
Q. 271I— 272 —Doc.

OriginTitle

Reference

XIII/16Japan

Comments on the selective calling devices
for use in the international maritime mobile
radiotelephone service

Rep. 320
Q. 271

XIII/17Japan

Test of selective calling devices for use in
the international maritime mobile radio­
telephone service

Res. 19
Q. 271

XIII/18

Japan

Selective calling devices for use in the inter­national maritime radiotelephone service

Q. 271

XIII/19

International
Working Party

Report on selective calling devices

Res. 19
Q. 271
S.P. 271A
Rep. 320
Rec. 257

XIII/20

W.M.O.

Facsimile transmission of meteorologicalcharts for reception by ships

Q. 274

XIII/21

NorwaySelective calling devices for use in the inter­national maritime mobile radiotelephoneservice

S.P. 271A

XIII/22

United Kingdom

Direction finding by ships in the 2 MHzband - Direction finding at 2182 kHz: theuse of a 2182 kHz “ long line ” DF adaptor
for use with MF direction finders

Q. 206

XIII/23

United Kingdom

Proposed modifications to Recommenda­
tion 428 - Direction finding by ships in the
2 MHz band

Rec. 428

XIII/24

United Kingdom

Characteristics of equipments and principles
governing the allocation of channels in the
VHF (metric) and UHF (decimetric) land
mobile services - Electrical characteristics ofamplitude-modulation and angle-modulation
land mobile equipment

Q. 163

XIII/25

United Kingdom

Signal-to-interference protection ratios andminimum field strengths required in themobile services

Q. 272

XIII/26

United Kingdom

Operational procedures for single-sideband
radio telephony in the HF maritime mobile
bands

Rec. 258

XIII/27

United Kingdom

Direction finding by ships in the 2 MHzband - Direction finding at 2182 kHz

Q. 206

XIII/28

Federal Republicof Germany

Selective calling devicesfor use in the internationalmaritime mobile
radiotelephoneserviceRep. 320
Q. 271

XIII/29Japan

Characteristics of equipments and principles
governing the allocation of channels in the
VHF (metric) and UHF (decimetric) land
mobile services

Rep. 319

XIII/30

Japan

Fascimiletransmission of meteorologicalcharts over radio circuits

Q. 274

XIII/31

Japan

Direction finding by ships in 2 MHz band

Q. 206

XIII/32

Japan

Use of a control tone for automatic gain
control of receivers in single-sideband radio­
telephone systems operating in the HF
maritime mobile bands

Q. 282

— 273 —XIII/33(1/16)

OriginPeople’s Republicof Poland

Title

Reference

Proposal for the determination of tolerances
for spurious radiation at frequencies above
235 MHz

Rec. 329
S.P. 182(1)Q. 163

XIII/34

United States ofAmerica

Revision of Recommendation 258 - Single­
sideband aeronautical and maritime mobile
radiotelephone equipments

Rec. 258

XIII/35

United States ofAmerica

Use of single-sideband in the maritime
mobile service for public radiotelephoneservice to ships and aircraft

Rec. 258

XIII/36

Study Group XIIIInterim Report by the Chairman - Mobile
services

XIII/37

International
Working Party on
Selective Calling
Devices

Measurements on modified selective callingdevices working according to the sequential
single frequency code (SSFC) system of theFederal Republic of Germany

XIII/38

NorwayDraft New Question - Transmission ofdata and teleprinter signals in the maritime
mobile service

XIII/39
and Rev. 1

Federal Republic of
Germany

Characteristics of equipment and principles
governing the allocation of channels in the
VHF (metric) and UHF (decimetric) land
mobile services

Q. 163Res. 20

XIII/40

Federal Republic of
Germany

Selective calling devices for use in the inter­national maritime mobile radiotelephoneservice (Second contribution)

Rep. 320
Q. 271

XIII/41

Federal Republic of
Germany

Signal-to-interference protection ratios andminimum field-strengths required in themobile services

Q. 272

XIII/42

Federal Republic of
Germany

Use of classes of emission A2H and A3H
on the distress frequencies 500 kHz and2182 kHz respectively

Q. 273

XIII/43

Federal Republicof Germany

Facsimile transmission of meteorologicalcharts for reception by ships

Q. 274

XIII/44

Federal Republicof Germany

Q. 282

XIII/45

C.C.I.R.
Secretariat

Use of a control tone for automatic gain
control of receivers in single-sideband radio­
telephone systems operating in the HF
maritime mobile bands
Submission of Doc. III/82 - Single channel
simplex telegraph system for isolated areas
and for the mobile services

XIII/46

The Netherlands

Effectiveness of A2H emissions on 500 kHz
and A3H emissions on 2182 kHz

Q. 273

XIII/47

Japan

Comments on the German selective callingsystem

XIII/48

Summary record of the first meeting
Study Group XIII
Working Group XIII-B Submission of the following proposals to
the Interim Meeting of Study Group XIII(Part I)
List of documents issued (XIII/1 to XIII/50)
C.C.I.R.
Secretariat
Working Group XIII-D Draft Recommendation - Use of classes ofemission A2H and A3H on the distressfrequencies 500 kHz and 2182 kHz respectively

XIII/49
and Rev. 1
XIII/50
XIII/51
18

S.P. 3A(III)Q. 273I

— 274 —OriginTitle

Reference

XIII/52

Working Group

XIII-B Submission of the following proposals to
the Interim Meeting of Study Group XIII(Part II) - Direction-finding by ships in the
2 MHz band

Q. 206

XIII/53

Working Group

XIII-B Submission of the following proposals to
the Interim Meeting of Study Group XIII(Part III) - Emergency position-indicating
radio beacons

Draft Q.

XIII/54

Working Group XIII-A Draft Opinion - Facsimile transmission of
meteorological charts for reception by ships

XIII/55

United Statesof America

XIII/56

Working Group

XIII-C Draft amendments to Report 319

XIII/57

Working Group

XIII-C Draft Recomendation - Signal-to-interference
ratios and minimum field-strengths requiredin the mobile services - Aeronautical services

XIII/58

Working Group XIII-C Proposed amendments to Report 319

XIII/58

Working Group

XIII-C Draft Report - Signal-to-interference protec­
tion ratios and minimum field-strengths
required in the mobile services

XIII/60

Working Group

XIII-D Proposed modifications
tion 258

XIII/61

Working Group XIII-D Draft Question - Operational procedures for
SSB radiotelephone systems in the HF
maritime mobile bands

XIII/62

Working Group XIII-A Draft Recommendation - Selective callingsystem for use in the international maritime
mobile radiotelephone service

XIII/63

Working Group

XIII-E Draft Question - Application of direct
printing telegraph equipment to the maritime
mobile service

XIII/64

Working Group

XIII-E Draft Recommendation - Publication of Op. 20
the “ Codes and Abbreviations for the Inter­national Telecommunication Services ” by
the International Telecommunication Union

XIII/65

Working Group

XIII-D Draft Report - Use of a control for auto- Q. 282
matic gain control of receivers in single­
sideband radiotelephone systems operatingin the HF maritime mobile bands

XIII/66
and Rev.lWorking Group XIII-E Proposed revision of the texts of Study
Group XIII

XIII/67

Study Group XIII

Summary record of the second meeting

XIII/68

Study Group XIII

Summary record of the third and last meeting

XIII/69

C.C.I.R.
Secretariat
C.C.I.R.
Secretariat
C.C.I.R.
Secretariat

List of participants

C.C.I.R.
Secretariat

Correspondence
C.C.I.R.

XIII/70
XIII/71
XIII/72

Statement by the Chairman of the delegation

Q. 272

to Recommenda­

List of documents issued (XIII/51 to XIII/70)
Resolution A.91(IV) of I.M.C.O. - Emergency
position-indicating radio beacons
between

W.M.O.

andOp. 21

— 275 —Title

Reference

XIII/73

C.C.I.R.
Secretariat

Letter from the Administration of Senegal

Q. 318, 319,
320

XIII/74

United Statesof America

Proposed modification to Question 318(XIII) Emergency position-indicating radio beaconsQ. 318

XIII/75

United Statesof America

Operational procedures for single-sideband
radiotelephone system in the HF maritime
mobile bands

Q. 319XIII/76

United Statesof America

Selective calling system for use in the inter­national maritime mobile radiotelephoneserviceQ. 271,
S.P. 271A

XIII/77

United Statesof America

Draft Recommendation - Emergency posi­tion-indicating radio beaconsQ. 318

XIII/78

United Statesof America

Emergency position-indicating radio beaconsQ. 318

XIII/79

United Kingdom

Proposed modification to Draft Recommenda­
tion D.c(XIII) - Selective calling system foruse in the international maritime mobile
radiotelephone service

Draft Rec.

XIII/80

United Kingdom

Q. 163

XIII/81

United Kingdom

Characteristics of equipment and principles
governing the allocation of channels in VHF(metric) and UHF (decimetric) land mobile
services
Selective calling in the international maritime
mobile radiotelephone service

XIII/82

United Kingdom

The introduction of direct printing telegraphequipment in the maritime mobile service A report on trials of an automatic single­
path error-correcting system

Q. 320

XIII/83

F.R. of Germany

Characteristics of equipment and principles
governing the allocation of channels in the
VHF (metric) and UHF (decimetric) land
mobile services

Q. 163

XIII/84

F.R. of Germany

Facsimile transmissions of meteorologicalcharts for reception by ships

Q. 274

XIII/85

F.R. of Germany

Rep. 320
S.P. 271A

XIII/86

Denmark' Selective calling devices for use in the inter­national maritime mobile radiotelephoneservice
Proposed additions to Report 319 (Annex I)

XIII/87
XIII/88

DenmarkJapan

XIII/89
XIII/90

F.R. of Germany
CanadaXIII/91

CanadaXIII/92

CanadaDoc.

OriginEmergency position-indicating radio beacons
Signal-to-interference protection ratios andminimum field-strengths required in themobile services
Emergency position-indicating radio beacons
Proposed modification to Draft Recommenda­
tion D.d(XIII) - Single-sideband aeronauticaland maritime mobile radiotelephone systems
Use of classes of emission A2H and A3H
on the distress frequencies 500 and 2182 kHz
respectively
Selective calling devices for use in the inter­national maritime mobile radiotelephoneserviceQ. 271Q. 163
Rep. 319
Q. 318Q. 272
Q. 318Draft Rec.
Q. 273
Q. 271

— 276 —OriginT itleR eferen ce

XIII/93

CanadaProposed modification to Question 320(XIII) Introduction of direct printing telegraphequipment in the maritime mobile service

Q. 320

XIII/94

CanadaTransmission of data and teleprinter signals
in the maritime mobile service

Q. 320

XIII/95

I.F.R.B.

Memorandum by the I.F.R.B. on signalinterference protection ratios and the mini­
mum field strengths necessary in the highfrequency maritime mobile service

Q. 272

XIII/96

Switzerland

Specifications for land mobile equipment

Res. 20

XIII/97

NorwayEmergency position-indicating radio beaconsQ. 318

XIII/98

New Zealand

Draft Question - VHF and UHF land mobile
services - Minimum channel separation andoptimum modulation systems

Draft Q.

XIII/99

New Zealand

Draft Question - VHF and UHF land mobile
services - Intermodulation products

Draft Q.

XIII/100

C.C.I.R.
Secretariat

List of documents issued (XIII/71 - XIII/100)

XIII/101

New Zealand

Draft Question - Technical characteristics of
VHF and UHF land mobile equipment

XIII/102New Zealand

Draft Question - MF and HF mobile services Preferred technical characteristics of single­
sideband equipment

XIII/103

C.C.I.R.
Secretariat

Submission of the Report of the Fourth
Air Navigation Conference (I.C.A.O.) (extract)

Op. 21

XIII/104

CanadaProposed modifications to Draft Recommendation D.d(XIII) - Single-sideband aero­
nautical and maritime mobile radiotelephoneequipments - Response characteristics ofmaritime mobile radiotelephone equipment

Draft Rec.

XIII/105(III/107)

The Netherlands

Single channel telegraph system for message
broadcasting with error-correcting facility

Draft S.P.
Q. 320

XIII/106

The Netherlands

The introduction of direct printing telegraphequipment in the maritime mobile service

Q. 320

XIII/107
and Corr.l

Chairman.
S.G. XIII

Report by the Chairman - Mobile services

XIII/108

Japan

Proposed modifications to Draft Recommendation D.d(XIII) - Single-sideband aero­
nautical and maritime mobile radiotelephonesystem

XIII/109

Japan

Emergency position-indicating

XIII/110Japan

Characteristics of equipment and principles Q. 163
governing the allocation of channels in the
VHF (metric) and UHF (decimetric) land
mobile services

XIII/111

Japan

Characteristics of equipment and principles Q. 163
governing the allocation of channels in the Res. 20
VHF (metric) and UHF (decimetric) land
mobile services

Draft Rec.

radio beacons Q. 318

— 277 —Doc.

OriginTitle

Reference

XIII/112d/51)(VI/189)

C.C.I.R.
Secretariat

Submission of the memorandum of the
I.F.R.B. - Radio noise in ships

XIII/113(III/110)

F.R. of Germany

Factors affecting the quality of performanceof complete systems - Full-duplex single­
channel ARQ system

S.P. 3A(III)XIII/114

F.R. of Germany

The introduction of direct printing telegraphequipment to the maritime mobile service

Q. 320

XIII/115

C.I.R.M.

Draft Question - Self-supporting antennae
for ships

XIII/116

FranceCharacteristics of equipment used in the
VHF (metric) and UHF (decimetric) land
mobile services

XIII/117

FranceEmergency position-indicating radio beaconsQ. 318

XIII/118

FranceSingle-sideband aeronautical and maritime
mobile radiotelephone equipments

Draft Rec.

XIII/119The Netherlands

Results of practical tests with a full ARQ
direct printing telegraph system in the maritime
mobile service

Q. 320

XIII/120

NorwayDirect printing telegraph equipment for use
in the maritime mobile service - A reporton experimental transmission

Q. 320

XIII/121

New ZealandAnnex to Draft Report D.m(XIII)

XIII/122

Working Group XIII-B Draft Opinion - Facsimile transmission of
meteorological charts for reception by ships

XIII/123

United Statesof America

Characteristics of equipment and principles
governing the allocation of channels in the
VHF (metric) and UHF (decimetric) land
mobile services - Electrical characteristics ofland mobile equipment

XIII/124

Study Group XIII

Summary record of the first meeting

XIII/125
and Rev.lWorking Group
XIII-C

Draft Report - Signal-to-interference pro­tection ratios and minimum field strengths
required in the mobile services

XIII/126

Study Group XIII

Draft Recommendation - Emergency posi­tion-indicating radio beacons operating on
the frequency of 2182 kHz

XIII/127

Working Group
XIII-A

Draft amendment to Recommendation 258 Single-sideband aeronautical and maritime
mobile radiotelephony systems

Q. 162

XIII/128

Working Group
XIII-C

Draft Study Programme - Interference due
to intermodulation products in the land
mobile services between 25 and 500 MHz

Q. 163

XIII/129Working Group
XIII-C

Draft Study Programme - Technical charac­
teristics of land mobile equipment between
25 and 500 MHz

Q. 163

XIII/130

Working Group
XIII-C

Draft Study Programme - Minimum channel
separation and optimum modulation systems
for land mobile systems between 25 and
500 MHzQ. 163Q. 163Res. 20

Draft Op.
Q. 274Q. 163

Q. 272

— 278 —D oc.

Origin

XIII/131

Working Group
XIII-D

Draft Question - Self-supporting antennae
for use by ships

XIII/132

Study Group XIII

Report - The introduction of direct printing
telegraph equipment in the maritime mobile
service

XIII/133

Working Group
XIII-A

Draft Report - Operational procedures for
SSB radiotelephone systems in the HF
maritime mobile bands

XIII/134

Working Group
XIII-A

Draft Question - MF and HF land mobile
services - Preferred technical characteristics
of single-sideband equipments

XIII/135

Working Group
XIII-B

Draft Opinion - Emergency position-indicat­
ing radio beacons

Title

Reference

Q/319

Q. 318

XIII/136

Study Group XIII

Summary record of the second meeting

XIII/137

Working Group
XIII-C

Draft amendment to Resolution 20 - Charac­
teristics of equipment and principles govern­
ing the allocation of channels between 25
and 500 MHz for land mobile services

XIII/138

Working Group
XIII-D

Proposed revision of the texts of Study
Group XIII

XIII/139

Working Group
XIII-B

Draft Recommendation - The introductionof direct printing telegraph equipment in
the maritime mobile service

Q. 320

XIII/140

Working Group
XIII-C

Report - Characteristics of equipment andprinciples governing the allocation of frequency
channels between 25 and 500 MHz for land
mobile services

Q. 163

XIII/141

Study Group XIII

Draft Resolution - Selective calling systems
for use in the international maritime mobile
service

XIII/142

Study Group XIII

Draft Study Programme - Selective callingsystems for use in the international maritime
mobile service

XIII/143

Study Group XIII

Draft Report - Selective calling systems forthe international maritime mobile service

XIII/144

Study Group XIII

Draft Question - Selective calling systems
for use in the international maritime mobile
service

XIII/145

Working Group
XIII-C

Draft Question - Characteristics of equip­
ment and principles governing the allocationof channels in the land mobile services bet­
ween 25 and 500 MHz

XIII/146
and Corr.lStudy Group XIII

Summary record of the third meeting

XIII/147

C.C.I.R.
Secretariat

Submission of Docs. III/114, III/115 andIII/116

XIII/148

Study Group XIII

Summary record of the fourth meeting

XIII/149

Study Group XIII

Summary record of the fifth meeting

XIII/150.

C.C.I.R.
Secretariat

List of documents issued (XIII/101 to XIII/151)

XIII/151

Study Group XIII

Status of texts

Q. 163

Q. 271 and
S.P. 271A

— 279 —LIST OF DOCUMENTS OF THE Xlth PLENARY ASSEMBLYESTABLISHED BY STUDY GROUP XIII
Doc.

Title

Final text

XIII/1001

Use of a control tone for automatic gain control of receivers in single-sideband radiotelephone systems operat­
ing in the HF maritime mobile bands

Rep. 359

XIII/1002

Facsimile transmission of meteorological charts for reception by ships

Op. 24

XIII/1003

Signal-to-interference ratios and minimum field-strengths
required in the mobile services - Aeronautical services
above 30 MHz

Rec. 441

XIII/1004

Publication of the “ Codes and abbreviations for theinternational telecommunication services ” by the Inter­national Telecommunication Union

Rec. 437

XIII/1005

Use of classes of emission A2H and A3H on the distressfrequencies 500 kHz and 2182 kHz respectively

Rec. 438

XIII/1006

Direction-finding in the 2 MHz band aboard ships

Rec. 428-1

XIII/1007

Direction-finding and homing by ships in the 2 MHz
band
Emergency position-indicating radio beacons operatingon the frequency of 2182 kHz

Q. 2/XIII

XIII/1008

Rec. 439

XIII/1009

Emergency position-indicating radio beaconsQ. 318

XIII/1010

Operational procedures for SSB radiotelephone systems
in the HF maritime mobile bands

Q. 4/XIII

XIII/1011

Operational procedures for SSB radiotelephone systems
in the HF maritime mobile bands

Rep. 360

XIII/1012

Selective calling systems for the international maritime
mobile service

Rep. 320-1

XIII/1013

Technical characteristics of land mobile equipment between 25 and 500 MHz

S.P. 7A/XIII

XIII/1014

Minimum channel separation and optimum modulation
systems for land mobile systems between 25 and 500 MHz

S.P. 7B/XIII

XIII/1015

Self-supporting antennae for use by ships

Q. 6/XIII

XIII/1016

Emergency position-indicating radio beacons

Op. 25

XIII/1017

Characteristics of equipment and principles governing the allocation of channels between 25 and 500 MHz
for land mobile services

Res. 20-1

XIII/1018

Signal-to-interference protection ratios and minimum Rep. 358
field strengths required in the mobile services

XIII/1019

Single-sideband aeronautical and maritime mobile radiotelephony systems

Rec. 258-1

XIII/1020

Interference due to intermodulation products in theland mobile services between 25 and 500 MHz

S.P. 7C/XIII

XIII/1021

MF and HF land mobile services - Preferred technicalcharacteristics of single-sideband equipment

Q. 8/XIII

XIII/1022

Selective calling systems for use in the international maritime mobile service

Res. 19-1

XIII/1023

Selective calling systems for use in the international
maritime mobile service

S.P. 3A/XIII

— 280 —XIII/1024
XIII/1025
XIII/1026
XIII/1027
XIII/1028
XIII/1029
XIII/1030

Title

Final text

Selective calling systems for use in the international
maritime mobile service
The introduction of direct printing telegraph equipmentin the maritime mobile service
The introduction of direct printing telegraph equipmentin the maritime mobile service
Characteristics of equipment and principles governing
the allocation of frequency channels between 25 and
500 MHz for land mobile service
The introduction of direct printing telegraph equipmentin the maritime mobile service
Characteristics of equipment and principles governing
the allocation of channels in the land mobile services
between 25 and 500 MHz
List of documents issued (XIII/1001 to XIII/1030)

Q. 3/XIII
Q. 5/XIII
Rep. 361
Rep. 319-1
Rec. 440
Q. 7/XIIIRECOMMENDATIONS OF SECTION H (STANDARD-FREQUENCIESAND TIME-SIGNALS)

RECOM M ENDATION 374-1
STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONS(Question 1/VII)
The C.C.I.R.,(1951 - 1953- 1956- 1959- 1963 - 1966)CONSIDERING(a) that the Administrative Radio Conference, Geneva, 1959, allocated the frequency bands
20 kHz ± 0 05 MHz, 2-5 MHz ± 5 kHz (2-5 MHz ± 2 kHz in Region 1), 5 MHz ± 5 kHz,
10 MHz ± 5 kHz, 15 MHz ± 10 kHz, 20 MHz ± 10 kHz and 25 MHz ± 10 kHz,requesting the C.C.I.R. to study the question of establishing and operating a world-widestandard-frequency and time-signal service;(b) that additional standard-frequencies and time-signals are emitted in bands 4 to 9;(c) the provisions of Article 44, Section IV, of the Radio Regulations, Geneva, 1959;(d) the opinions relating to standard-frequency and time-signal emissions expressed by theInternational Union of Geodesy and Geophysics (I.U.G.G.) by the International ScientificRadio Union (U.R.S.I.) and by the International Astronomical Union (I.A.U.) and conveyed
for information to the Chairman, Study Group V II;(e) that the standard for measurement of time interval designated by the International Com­mittee of Weights and Measures is based temporarily on a frequency corresponding to a
hyperfine energy transition o f the Caesium atom given by:/(Cs) = 9 192 631 770 Hz;

UNANIMOUSLY RECOMMENDS

1.

that the time-signals emitted from each transmitting station should bear a known relation
to the phase of the carrier;2. that the carrier frequency should be maintained constant with reference to the internatio­
nally designated standard for measurement of time interval and that the average daily frac­tional frequency deviations from the adopted value should not exceed ± 1 x 10~10;
3. that adjustments in the epoch of the time-signals should be made, with or without a fractional
offset in carrier frequency, to maintain the epoch of the time-signals within about 100 ms
of Universal Time UT2;
that, where a fractional offest is adopted, the value of the offset should bethat announced
by the B .I.H .:4.1 that the value of this offset should be changed, when necessary, at 0000 h UT on 1 January
of any year;
4.2 that the offset should have the value zero or a positive or negative integral multiple of
50 x 10-10;
4.3 that adjustment in the epoch of the time-signals should be made at the dates announced
by the B .I.H .;4.4 that these adjustments should be made, when necessary, at OOOOh UT on the first day ofany month, and should be ± 100 ms;
4.5 that the various emissions of this type should be mutually coordinated;4.

— 282 —Rec. 374-1, 375-1
5.

that where the carrier frequency is not offset, the time signals should conform to one of
the two following schemes:
5.1 the rate of the time signals is offset; in which case the time signals should be coordinatedwith those referred to in § 4;
5.2 the rate of the time signals is not offset; in which case mutually coordinated experimental
emissions should be made, with epoch adjustments made when necessary as announced
by the B .I.H .; these adjustments should be made at 0000 h UT on the first day of any monthand should be a positive or negative integral multiple of 100 ms;
6. that the B.I.H., after consultation with the observatories and laboratories concerned, should
announce the adopted value of the offset;
6.1 that the B.I.H. should also announce the dates and values of adjustments in the epoch of
the time-signals;
6.2 that all such announcements should be made by the B.I.H. to the controlling authorities
at least six weeks before the changes are to be made;7. that when corrections are necessary to the epoch of the time-signals emitted from any trans­mitting station, to maintain an agreed coordination, such corrections should not be madeat the same time as the adjustments referred to in §§ 4 and 5;
7.1 that the B.I.H. will suggest to controlling authorities, if necessary, the magnitude and dateof such corrections; that all such corrections should be reported subsequently to the B.I.H.
and also published as soon as possible.

RECOM M ENDATION 375-1
STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONSIN ADDITIONAL FREQUENCY BANDS(Q uestion 2/VII)
The C.C.I.R.,(1959 - 1963 - 1966)CONSIDERING(a) that precise intercontinental frequency comparison has already been achieved by the useof the frequency-stable emissions operating in band 4;(b) that for many purposes a world-wide time (epoch) synchronization with an accuracy greaterthan 1 ms is required;(c) that synchronization to 1 gs may be extended to ranges greater than 2000 km by meansof pulsed ground-wave signals;(d) that line-of-sight transmissions in bands 8 and 9, and predominantly ground-wave signals
in band 5, provide a stable means of distributing time-signals and standard-frequencies;
UNANIMOUSLY RECOMMENDS

1.
2.

3.
4.

that information on the results and methods of measurement of phase stability over paths
in bands 4 and 5, should be disseminated as widely as possible;that advantage be taken of the stability and precision of pulsed ground-wave navigation
systems, for establishing intercontinental and possibly world-wide time synchronization;that appropriate stations, existing in bands 5 and 6, should be employed as much as possiblefor distributing standard-frequencies by precise control of their carrier frequencies;that existing FM sound-broadcasting stations and television stations in bands 8 and 9 shouldbe employed as much as possible for distribution of standard-frequency and time-signals,

— 283 —Rec. 375-1, 376-1

which can be added to, or make use of, the existing modulation, without interference to thenormal programme;
5. that two bands of 100 kHz, in bands 8 and 9 respectively, are suitable for an effective lineof-sight standard-frequency and time-signal service.

RECOM M ENDATION 376-1
AVOIDANCE OF EXTERNAL INTERFERENCE W ITH EM ISSIONSOF THE STANDARD-FREQUENCY SERVICE IN THE BANDS
ALLOCATED TO THAT SERVICE(Question 1/VII)
The C.C.I.R.,(1959 - 1963 - 1966)CONSIDERING(a) the importance and increasing use of standard-frequency and time-signal emissions in the
allocated bands;(b) that interference reduces the usefulness of the standard-frequency and time-signal service
to a serious degree;(c) that, despite the efforts made by Administrations and the I.F.R.B. to clear the standardfrequency bands, some registered users, and many unnotified emissions, remain in thesebands, which continue to cause interference with the standard-frequency services;(d) Recommendation No. 31 of the Administrative Radio Conference, Geneva, 1959;
UNANIMOUSLY RECOMMENDS

1. that to avoid external interference, Administrations and the I.F.R.B. should continue theirefforts to clear the standard-frequency bands;

2. that, in the territory under its jurisdiction, each Administration should make every effort
to prevent all users of the radio-frequency spectrum from operating other stations in thestandard-frequency bands, capable of causing harmful interference to the standard-fre­quency service;
3. that national monitoring stations should carry out a regular search for external interfering
stations in the standard-frequency bands and should make every effort to identify eachinterfering station, if necessary with international cooperation;
4.

that, in each case of external interference, the users of standard-frequency emissions should
request the monitoring service of their own country to identify the interfering station;

5. that, in cases of external interference with the standard-frequency service, Administrations
should apply the provisions of Articles 14, 15 and 16, of the Radio Regulations, Geneva,
1959, and, if desired, should send a copy of relevant correspondence to the I.F.R.B.;
6. that, when interference is observed in the standard-frequency bands, even if the source cannot
definitely be identified, representatives of Administrations, participating in the work ofStudy Group VII, should exchange information from users of standard-frequency and timesignal transmissions and from the monitoring service. This may later permit identificationof the interfering station.

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENT

— 285 —Rep. 267-1

R EPO R TS O F SECTIO N H (S T A N D A R D -F R E Q U E N C IE S A N D T IM E -SIG N A L S)REPORT 267-1 *STANDARD-FREQUENCIES AND TIME-SIGNALS(Question 1/VII)(1956- 1959- 1963- 1966)
This Report outlines the work of Study Group VII since the Xth Plenary Assembly.
Study Group VII, following opinions received from the I.A.U., I.U.G.G. and U.R.S.I.,
has continued to study the problem of meeting the need for time-signals based on an atomic
time scale, as well as for time-signals related to Universal Time. Interference is still a press­
ing problem and discussions were held between representatives of countries radiating standardfrequency signals in bands 6 and 7 in the European area. Some stations have reduced theperiods of audio frequency modulation which can interfere seriously with time-signal
reception. Demands for increasing precision posed many technical questions and useful
discussions ensued on the possibilities of exploiting new techniques both at low frequencies
and in the field of modern communication systems, as indicated in various Study Programmes
and Reports.
Recommendation 374-1 concerning standard-frequency and time-signal emissions has
been revised with the intention of providing, on the same emission, for the needs of users
who require uniform frequency and those requiring time information. Noting that theInternational Committee of Weights and Measures has now designated a standard for meas­
urement of time interval in terms of an atomic transition, it is recommended that the emitted
frequencies be maintained constant to ± 1 x 1 0 10 throughout each year by reference toatomic standards. The time-signals should be maintained within about 100 ms of UT2either by means of step adjustments or by a combination of frequency offset and step adjust­ments. The B.I.H. is charged with deciding, after due consultation, the extent of the offset
in the rate of the time-signals in each year and the magnitude and epoch of the step adjust­ments and corrections in the offset system. A new Study Programme 1C/VII has beenformulated providing for the active study of methods of indicating both the epoch of UT2
and the international unit of time interval in the same emission. Recommendation 374-1
also provides for the coordination of experimental transmissions which do not maintain
an offset in carrier frequency but whose time-signals remain within ± 100 ms of UT2. Co­
ordination of such transmissions will be provided by the B.I.H.
Electromechanical and electronic phase shifters for generating an offset frequency
have been used during the last ten years at a number of laboratories and observatories.
The development of a pulse operated electronic and solid state phase shifter is noted. Thus
there is no technical difficulty in converting from the atomic time scale to another scalewith fixed offset, or vice-versa, with negligible error.
In Table I are schedules giving, where appropriate, the daily and hourly patternsof transmission and modulation of stations in the allocated bands. The diagrams of modu­
lation characteristics show why mutual interference exists in many areas: it is particularly
severe in Western Europe and in the Far East. Report 269-1 refers to the reduction or
elimination of periods of audio-frequency modulation by a number of European transmitters.
* This Report was adopted unanimously.

Rep. 267-1— 286 —

Other stations JJY, IAM and WWVH retain audio-frequency modulation but reduce inter­
ference by introducing gaps in the modulation adjacent to the time-signal pulses. It is
hoped that Administrations will continue to make mutual adjustment of their emission andmodulation schedules and thereby attempt to secure better use of the standard-frequency
bands. Resolution 14-1 indicates the procedure to be followed to avoid the possibilityo f interference from any new standard-frequency stations and indicates that the informationreferred to in this Resolution should be published by the I.T.U. and distributed directly
to the participants in the work of Study Group VII.
The characteristics of stations operating regular services at controlled frequencies outside
the allocated bands are given in Table II. It includes a number of very high-power naval
transmitters in band 4 and also a number of emissions in bands 5 and 8.
The Droitwich transmitter at 200 kHz has extended its period of operation to 22 hours
per day and has improved the accuracy of the carrier frequency.
Table II includes MSF, which now operates continuously at 60 kHz and the new station
HBG, which transmits experimentally at 75 kHz. It is desirable that the HBG time emissions
be made regular. Bands 8 and 9 provide a useful means of achieving a local distribution
o f time and frequency by line-of-sight services and new Opinion 27 suggests that Adminis­
trations should reserve 2 bands 100 kHz wide in these bands for this purpose.
In addition to the mutual interference discussed above, effective use of the service isimpaired by other transmissions. Interference continues even though the efforts of Admi­
nistrations and of the I.F.R.B. have effected a considerable clearance of registered transmitters.
Recommendation 376-1 urges Administrations to clear the bands by monitoring and if possi­
ble identify interfering stations as well as by applying Articles 14, 15 and 16 of the Radio
Regulations, Geneva, 1959. In Opinion 28, the I.F.R.B. is asked to increase thenumber of special monitoring programmes per year and it is also considered desirable that
direction-finding information should be obtained on the position of interfering stations.
Report 271-1 concerns the results of propagation studies on a microwave link and also
the results obtained in measurements of the phase stability of stations in bands 4 and 5,
received at long ranges. In addition it contains information on the fluctuations of reception
times of signals received from stations operating in bands 6, 7 and 9.
In the course of examination of the documents submitted it was found that, at present,
it is not easy to provide with artificial earth satellites for a general distribution of standardfrequencies and time-signals. The use of standard communication satellites has proved,
however, an interesting system for clock synchronization. Study Group VII learned withinterest that the communication satellite Relay II had been used in February 1965 to relateclocks in the U.S.A. and Japan with an accuracy of 0-1 gs.
Question 4/VII asks what new techniques would have to be considered for an evenbetter dissemination. Study Programme IB/VII has been introduced to investigate further
the advantages of single-sideband operation with full carrier. Report 362 points out someadvantages of this system and indicates the present situation. Study Programme 4A/VII
notes the advantages of.utilizing existing emissions in the broadcasting bands to disseminate
standard-frequencies and time-signals over ground wave range by stabilizing the carrier
frequencies and recommends that related studies be made.
Study Programme 3B/VII has been introduced as a result of the increasing precisionin several fields of frequency measurement: it is necessary to specify, in convenient and precise
terms, the various forms of frequency and phase instability, as, for example, in Report 364.

— 287 —Rep. 267-1

Some of the work of U.R.S.I. is closely related to improvements in standards and mea­
surement techniques and in the determination of errors introduced in propagation of standardfrequency and time-signals. Other scientific unions, such as I.A.U., I.U.G.G. and I.U.P. A.P.
are also discussing problems closely related to Study Group VII, so some advantages areforeseen in arranging discussions (see Resolution 14-1) in collaboration with these Unions.

TABLE I
Characteristics o f standard-frequency and time-signal emissions in the allocated bands, valid as o f 1 September 1966

StationCall sign

Approximate
location

Antenna(e)LatitudeLongitude

Type

Carrier
power
(kW)

3O
Period ofoeoperation
"5.2
V
>S»
2 ’! ■(0
C
Oc je
3.
u3
»o- —
2
.o
C3
0
g
Q
a
3

z

Standard-frequencies used

D uration o f emission

Carrier(MHz)

M odulation(Hz)

Time-signal(min)

Audio-modu­
lation (min)10) 1/7C3£ Ho<o*-».H^e
O.3
>»C
o.E

M ethod ofadjustm ent
o f timesignal

§■§3
-< «

ATA

New Delhi,
India

28° 34' N Horizontal
dipole77° 19' E

2

1

5

5

10

I; 1000

continuous

4 ineach 15±200

Steeringby thefrequency

FFH 0

Paris,
France48° 32' N Radiating
mast
02° 27' E

5

1

5(6 8 ]/ 2

2-5

1; 1000

30 ineach 60

25 ineach 60±2

Steps of
100 ms

HBN0

Neuchatel,
Switzerland

47° 00' N Horizontal
dipole06° 57' E

0-5

1

7

24

5

1

5 in
each 10nil±1

Steps of
100 msIA M 0

Roma,
Italy

41° 52' N Vertical 7J4
12° 27' E

1

1

6

1

5

1; 1000

10 ineach 15

4 ineach 15±1

Steps of
100 msIBF(13)

Torino,Italy

45° 02' N Vertical X/4
07° 46' E

5

1

7

23/4

5

1

continuous

nil

±1

Steps of
100 msJG 2A R 0

Tokyo,
Japan

3

1 50

2 ( 7)

002

10

continuous

nil

±1

Steps ofof 100 ms

JJY 0

Tokyo
Japan

35° 42' N Omni­
139° 31' E directional
35° 42' N Vertical 7J2
139° 31' E dipoles;(XI2 dipole,
top-loadedfor
2-5 MHz)

2

4

24(9)

2-5; 5;
10; 15l(i°);
1000(0continuous

27 ineach 60±1LOL0
M S F0

Buenos Aires, 34° 37' S
Argentina
58° 21' W
Rugby,
52° 22' N Horizontal
United01° 11' W quadrant
Kingdom
dipoles;(vertical
monopole,
2-5 MHz)OMA

Praha,
Czechoslovak
S.R.

50° 07' N
14° 35' E

RWM-RESMoskva,U.S.S.R.

55° 45' N
37° 18' E

W \W (I)

T

7

2

3

6

5

5; 10; 15

1; 440;1000

4 ineach 60

4 ineach 5

0-5

3

7

24

2-5; 5;10

1

5 ineach 10nil

Steps of
100 ms±200

Steps of
100 ms±1

Steps of
100 ms

1

1

7

24

2-5

1;1000(12)

15 ineach 30

4 ineach 15±10

Septs of
50 ms

20

1

7

19

5; 10;
15

1; 1000

10 ineach 1200

51/4
hours/day(4)±50Multiplesof
10 ms

Fort Collins, 40° 41' N Vertical %I2 2-5
Colorado
105° 02' W dipoles
to 10
U.S.A.

6

7

24

2-5; 5;
10; 15;20; 25

1; 440;600

continuous ‘0

2 ineach 5±0-5

Steps of
100 ms20° 46' N Vertical X/2
156° 28' W dipoles;(vertical i.14
for 2-5 and
5 MHz

1 to
2

4

7

24

2-5
5; 10; 15

1; 440;600

continuous

3 ineach 5±1

Steps of
100 msFort Collins, 40° 41' N Top-loaded
Colorado
105° 03' W vertical
U.S.A.

1-8

1

7

24

002

nil

nil

nil

±0-2

nil

ZLFS

Lower Hutt, 41° 14' S
New Zealand 174° 55' E

0-3

1

1

3

2-5

nil

nil

nil

±500

nil

ZU O 0

Olifantsfontein, 25° 58' S
Republic of 28° 14' E
South Africa

Verticalmonopole

4

1

7

24

5

1

continuous

nil

±5

Steps of
100 msZUO0Johannesburg, 26° 11' S
Republic of 28° 04' E
South Africa

Horizontal
dipole

0-25

1

7

24

10

1

continuous

nil

±5

Steps of
100 msWWVH(i)

WWVL(i)

Maui,
Hawaii,U.S.A.

N otes to Table /The daily transmission schedule and hourly m odulation schedule is given, where appropriate, in the form o f Figs. 1 and 2 supplemented by the following notes :i 1) These stations have indicated their participation in the international coordination of time and frequency. The time signals rem ain within about 100 ms o f UT2,
and the frequency is m aintained as constant as possible by reference to atom ic or molecular standards, and at the offset from the nom inal value announced for each yearby the Bureau international de l’H eure.
0 M easured with respect to the announced offset in frequency.
( 3) Time-signals are radiated according to the following program m e :M inutes past
odd hour
45-46
46-50
50-55
55-®)
60-61
61-66

Transmission
Call sign
Seconds, preliminary signal
N o m odulation
Seconds
Call sign
R hythm ic signals, 61 p er minute

The signals a t 06, OS, 10 and 12 hours are transm itted by m odulated carrier (A2 signals). A t all other times, telegraphic (A l) signals are emitted.
R W M -R E S does not operate from 0607 to 1345 U T on the first and third Wednesday o f each m onth.
(4) From 0500 to 0807 U T at 5 M H z and from 0830 to 1207 U T a t 15 M Hz, excluding periods o f time-signal transmissions.
.
(5) in addition to o th er tim ing signals and time announcements, a special tim ing code is radiated 10 times per hour. Consisting o f 36 bit, 100 pulse/sec. binary-coded decimal code, it
gives the second minute, h o u r and day o f year. A complete time frame lasts one second and the code is broadcast for one m inute in each 5-minute period, except the first after
the hour. The code contains 100 H z, 10 H z a n d 1 H z markers, which are locked to the frequency and time-signals.
(8) M onday to Friday.
(7) From 0530 to 0730 UT.
( 8) Interruption for 5 ms.
(*) Interrupted from 25-34 minutes o f each hour.
(10) puise consists o f 8 cycles o f 1600 H z tone. First pulse o f each m inute preceded by 655 m s o f 600 H z tone.
(11) 1000 H z tone m odulation between th e minutes 0-10, 20-25, 34-35, 40-45 and 59 - 60 except 40 ms before and after each second’s pulse.
( 12) In the period from 1800-0600 UT, audio-frequency m odulation is replaced by time-signals.
(13) N o offset in the carrier, coordinated time signals.

— 290 —Rep. 267-1

TU 0

8

+ -H

10

1

12

i-H

14

16

18

20

22

24 UT

» I «

ATA
NEW D E LH I

10 M Hz: M onday
to Friday

FFH
PA RIS

2-5 M Hz: Monday
to Friday

HBN
N E U C H A T EL********************************************************************************

5 M Hz5 M Hz; not
Sunday

IAM
ROM A

JBF
TO R IN OI

5 M H z: emission from45-60 minutes

Im m n~n~rr

J JY
TOKYO

ru n

2-5, 5, 10, 15 M Hz

5, 10, 15 M Hz:
not Sunday

LO L
BUENOS AIRES********************************************************************************

RUGBY

2-5, 5, 10 M Hz

OMA
PR A H A

2-5 M HzRWM - RESMOSKVA

15 M Hz
10 M Hz5 M Hzwwv
WASHINGTON

2-5, 5, 10, 15, 20,
25 M HzWWVH
HAW AII

2-5, 5, 10, 15 M Hz

2-5 M Hz:
Tuesday:
carrier only

ZL F S
LO W ER H U TT

I I 1 I I I II I I I I I I I I 11 I 11 IJ 510MHzJOHANNESBURG

TU 0
1

2
I

1

4
I

Stationoperating

I

6
I

t

8

10

12

14

■f - - l - <- - 1— 1— I - l -

■ ■

l

16
i

l

18
t

- 1

Stationnot operating
F ig u r e 1

D aily em ission schedule

20
I

1

22
1

I

24 UT
I— I

1 Emission in*******1 alternate five-minuteperiods

— 291 —Rep. 267-1

Hour
+

Min

0

10

5

15 20

II I I | I I I I | I

25

30

35

40

45

50

60

55

Form of second and minute signals morse andvoice annoucements (A)I I I | II I I | I I I I | I I I I | l-44 I | I I I I | I I I I | I t H | I I I I | I H -f

1O00

WO

1O00

Pulse o f 5 cycles of 1000 Hz tone, length­
ened to 100 ms at the beginning of eachminute. Call sign and time (UT) in Morse

1000

\

1000

Pulse of 5 cycles o f 1000 Hz tone: minutepulse followed by 500 H z tone for 500 ms.
Call sign in Morse and voice announcement.

1000

1000

1 ms carrier break repeated 5 times every
second and 250 times at minute, exact time
being start o f first break. Call sign in Morse.

HBN

Pulse o f 5 cycles of 1000 Hz tone; minutepulse of 20 cycles o f 1000 H z tone. Callsign and time (UT) in Morse, voice identifica­tion.
Pulse o f 5 cycles o f 1000 H z tone repeated
7 times at minute. Call sign and time (UT)in M orse; voice identification at the beginn­
ing and end of emission.

jjy"m v 1 ~

\

1000

440

ihOOOi;::

1000

1000

440

440

1000

440

1000

Pulse o f 8 cycles of 1600 H z tone, minutepulse is preceded by a 600 Hz tone o f 655 ms
duration. Call sign and time (JST) in Morseand voice. Radio propagation warnings inletter code: N (normal), U (unstable) or W
(disturbed).

o440

Pulse o f 5 cycles of 1000 H z tone, 59th pulse
omitted. Call sign in M orse: identificationand time (U T-3 h) in voice.

1000

Pulse o f 5 cycles o f 1000 Hz tone, 100 ms
pulse at minute. Call sign in M orse andvoice announcement.

1000

1000

A
IWDS

|4 l0 j
A

1000

A
RPF

[bOO
A
R PF

A

1000

Pulse o f 5 cycles o f 1000 H z tone, 59th pulse
omitted and 60th repeated 100 ms later. Radio
propagation forecasts given in M orse during
each announcement period. Geoalerts given
in M orse during first half of 19th minute ofeach hour. Time code (second, minute, hourand day o f year) 10 times per hour. Callsign and time (UT) in M orse; time (U T-5 hours)in voice.

A
IWDS

iM H HA
IWDS

Pulse of 5 cycles o f 1000 H z tone, 100 ms
pulse at minute and 500 ms pulse every 5th
minute. Last 5 pulses in each quarter hour
100 ms long. From minute 55-60 in every
3rd hour 100 ms pulses lengthened to 500 ms
at minutes. Call sign in Morse.

A

69o|

§410

tk

A

|sao{
A
R PF

| |
A
IWDS

|eo o |

[440

A

A

A

Pulse o f 6 cycles o f 1200 H z tone, 59th pulse
omitted and the 60th repeated 100 ms later.
Geoalerts given in morse during first half of
49th m inute of each hour. Call sign andtime (UT) in M orse; time (U T-10 hours) invoice.
Pulse of 5 cycles o f 1000 Hz tone, length­
ened to about 0-5 s at minute.

+

0

5

10

15

20

25

30

35

40

45

50

H M I 1 I 1 I 1 | I I I I 1 I I I I | I I I I | I I I I | I II I | I I I I j 1 H I | I I I I | I
Hour□

C arrier only

Min
Second pulses

F ig u r e

440

2

Audio
frequency, Hz— Hourly modulation schedule

N o emission

M odulation
with DSB andinterrupted
carrierIRep. 267-1

TABLE II
Characterictics o f standard-frequency and time-signal emissions in additional bands, valid as o f 1 September 1966

Station

3
oO
«c« r

Antenna(e)Carrierpower(kW)

Period o foperation

Standardfrequencies used

Duration o f emission

11
Zo gs o
UCS
>
e3.
E
P
3
z

3.
30
a

Carrier.
(kHz)

Modulatior(Hz)

Time-signal
(min)

CS

Audio­
modulation
(min)

c£
g,rt©
£o uo ©
-* Method of«~.Ec adjustmento •o f timesignal>*P-rotj .Eb3gu 0.

Approximate
location

LatitudeLongitude

Type

(31)

Allouis,France47° 10' N
02° 12' E

Omnidirectionnal

500

1

7

24

164

nil

nil

continuous
A3

±05

nil

CHU0

Ottawa,Canada45° 18' N
75° 45' W

Foldeddipoles andrhombic

0-3;
3; 5

3

7

24

3330;
7335;
14 67010

continuous

nil

±50

Steps of
100 ms

DCF77(24)Mainflingen,
F.R. of
Germany

50° 01' N
09° 00' E

Omni­
directional

12

1 60

60

77-5

1; 200;
440

0

0

(0

Steps of
200 ms(3!)

Droitwich,
UnitedKingdom

52° 16' N
02° 09' W

T

400

1

7

22

200

nil

nil

A3 broad­
cast contin­
uously±5nil

GBR(i)

Rugby,
UnitedKingdom

52° 22' N
01° 11' W

Omni­
directional

300
40(3)

1

7 2 2 (016

1 (04 X5 (0per daynil±1

Steps of
100 msHBG(34)

Prangins,
Switzerland

46° 24' N
06° 15' E

Omni­
directional

20

1

7

75

1(32)

continuous

nil

±0-2

Steps of
100 ms

JJM-6
JG2AS

Kemigawa,
Chiba CJapan

35° 38' N
140° 04' E

Omni­
directional

10

1

7

24

40

nil

nil

nil

±0-5

nil

MSF(34)

Rugby,
UnitedKingdom

52° 22' N
01° 11' W

Omni­
directional

10

1

7

24

60

1 (0

continuous

nil

±1

Steps of
100 msLoran-C

Carolina
Beach, N.C..
U.S.A.

34° 04' N
I T 55' W

Omni­
directional

30)

1

7

24

100

20(16)

continuous

nil

±0-5

Steps of
50 ms

N A A 0(25)Cutler,
Maine
U.S.A.

44° 39' N
67° 17' W

Omni­
directional

2000
10000

1

7

24

17-8

nil

nil

nil

±0-5

nil

NBAOX26)

Balboa,PanamaCanal Zone,
U.S.A.

09° 04' N
79° 39' W

Omni­
directional

300
300

1

7

24(0

24

1 (0

continuous

nil

±0-5

Steps of
100 ms

NPG/NLK Jim Creek,
Washington,
0
U.S.A.

48° 12' N
121° 55' W

Omni­
directional

1200
2500

1

7

24

18-6

nil

nil

nil

±0-5

nil

M PM 0

Lualualei,
Hawaii,U.S.A.

21° 25' N
158° 09' W

Omni­
directional

1000
1000

1

7

24(18)

26-1

nil

nil

nil

±0-5

nil

NSS0

Annapolis,
Maryland,
U.S.A.

38° 59' N
76° 27' W

Omni­
directional

1000
1000

1

7

24

21-4

nil

nil

nil

±0-5

nil

OMA

Podebrady,
Czechoslovak
SR

50° 08' N
15° 08' E

T

5

1

7

24

50

1 (0

23 hours
per d ay (0

nil

±10

Steps of
50 ms

RWM-RESMoskva,U.S.S.R.

55° 45' N
37° 18' E

20

1

7

21(20)

100

1

40 in
each 120

nil±50

Multiplesof 10 ms

SAZ(24)

Enkoping,
Sweden59° 35' N
17° 08' E

Yagi(12 dB)

01
(ERP)

1

7

24

100 000

nil

nil

nil

±50

nil

SAJ(24)

Stockholm,
Sweden59° 20' N
18° 03' E

Omni­
directional

006
(ERP)

1

1

2(22)

150 000

nil

nil

10(23)±1nil

VNG(27)

Lyndhurst,
Victoria,
Australia

38° 00' S
145° 12' E

Omni­
directional

20-5;0-5-10;10724(28)

5425;
7515;
12 005

i;
1000

(29)

nil

±10

continuous

Steps of
100 msWWVB(24) Fort Collins,
Colorado,
U.S.A.

40° 40' N
105° 03' W

Toploadedvertical

13

1

7

24

60

10

continuous

nil

±0-2

Steps of
200 ms26° 11' S
28° 04' E

Directional
to Olifantsfontein

005

1

7

24(30) 100 (MX)1;
100 000

continuous

nil

±5

Steps of
100 mszu oJohannesburg,
Republic ofSouth Africa

24

(33)

(21)

_ 292

Call signRep. 267-1

NOTES TO TABLE II— 294(4) These stations have indicated their participation in the international coordination o f time and frequency. The time-signals remain within about 100 ms of UT2, |and thefrequency is maintained as constant as possible by reference to atomic or molecular standards, and at the offset from the nominal value announced each year byThe Bureau
international de l ’Heure.
(2) Measured with respect to the announced offset in frequency.
(3) Figures give the estimated radiated power.
(4) Time code used which reduces carrier by 10 dB at the beginning o f each second.
(5) Pulses o f 200 cycles o f 1000 H z tone : the first pulse in each minute is prolonged.
(6) M onday to Saturday.
(7) Transmission extends essentially from 0645 to 1035 and 1900 to 0010 U T (1 November - 28 February) and from 1900 to 0210 U T (1 M arch - 31 October).
(8) International type A l telegraphy time-signals from the Deutsche Hydrographische Institut from 0700 to 0710, 1000 to 1010, 1900 to 1910, 1930 to 1940, 2000 to 2010 U T andduring the minutes 00 to 10 o f each h our until the end o f transmission (see (7)).
A l telegraphy time-signals (carrier with second pulses) from the Physikalisch-Technische Bundesanstalt from 0728 to 0735, 1028 to 1035, 1911 to 1929, 1941 to 1959 U T and during
the minutes 57 to 59 o f each hour until the end o f the transmission (see (7)).
Carrier with pulses every 2 minutes from the Physikalisch-Technische Bundesanstalt from 0645 to 0659 and 0736 to 0959 UT.
(9) Carrier modulated with 440 Hz tone from 0711 to 0727 and with 200 Hz tone from 1011 to 1027 UT.
(10) The frequency o f the controlling oscillator varies by some parts in 1010 and increasing slowly at the rate of about 1part in 109 in one month.
(1:L) Maintenance period from 1300 to 1430 U T each day.
(12) A l telegraphy signals.
(13) From 0255 to 0300, 0855 to 0900, 1455 to 1500 and 2055 to 2100 UT.
(44) Maintenance period from 1300 to 1600 U T on the first Sunday of each month.
(15) Carrier interrupted for 100 ms at each second and 500 ms at each minute; from 1430-1530 UT, A2 pulses are transmitted in the same form as for M SF 2-5, 5 and 10 MHz.
(16) Time pulses occur in groups o f 8, one millisecond apart; 20 groups per second.
(17) Except from 1300 to 2100 U T on Wednesday.
(18) Except from 1800 to 2300 U T on Wednesday.
(19) From 1000 to 1100 U T, transmission w ithout keying except for call-sign OMA at the beginning o f each quarter-hour.
(20) Transmission is interrupted from 0007 to 0100, 1207 to 1300 and 1607 to 1700 U T each day and from 0607 to 1345 U T on the firstand third Wednesday o f each month.
(21) Each Friday.
(22) From 0930 to 1130 UT.
(23) 5 minutes a t the beginning and 5 minutes at the end o f the transmission for identification purposes only.
(24) N o offset, either on carrier or on time-signals.
(25) FSK is used, alternately with CW, for various intervals each day. It is planned to control the FSK transmissions so that the phase can be tracked, as is now possible for CW.
(26) From November, 1965.
(27) The time-signals are transmitted according to the international coordination. The frequency shall be coordinated at a later date.
(28) Except from 1200 h to 1215 h and 2200 h to 2215 h.
(29) Except first minute o f each hour.
(30) N o transmissions between 15 and 25 minutes past each hour.
(31) Carrier without offset.
(32) Interruption o f the carrier during 100 ms at the beginning o f each second; double pulse each minute; triple pulse each hour.
(33) In absence o f telegraph traffic.
(34) Experimental emission; no offset in the carrier, coordinated time-signals.

— 295 —Rep. 269-1

REPORT 269-1 *REDUCTION OF MUTUAL INTERFERENCE BETWEENSTANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONS(Question 1/VII)(1963 - 1966)
The appreciable amount of mutual interference between standard-frequency and timesignal emissions continues to detract from the value of the services operating on the fre­quencies allocated. The participation of a larger number of stations in the international
system for time and frequency coordination, though a most welcome development, has
nevertheless caused difficulty in the identification and use of synchronization signals emanat­
ing from different stations in the same, small geographical area, in which there is an intervalof only one or two milliseconds between the various signals. The position in Western Europe,
where this applies, has been improved by the decision of HBN and MSF to coordinate theirrespective transmission programmes.
The emissions of the time-signals in band 5 (DCF at 77-5 kHz, HBG at 75 kHz, MSF
at 60 kHz and OMA at 50 kHz) offer a new way of reducing interference in band 7.
Use of continuous audio-frequency modulation in a number of emissions is a very fre­quent source of interference with time-signal reception. Audio-frequency modulation, by
its very nature, is essentially confined to uses which do not require a high standard of accuracy
and it would seem highly desirable to restrict the use of this type of modulation. HBN,
IBF and MSF have already eliminated all audio-frequency modulation periods from theirprogrammes. OMA is replacing audio-frequency modulation by time-signals during theperiod from 1800 to 0600 hours UT. IAM (5 MHz) has reduced the number of audio­
frequencies used from three to one (1000 Hz) and the total period of modulation from 40
to 16 minutes per hour.
Other means of finding a solution to the problem of the co-existence of several standardfrequency stations are under study. During the last three years, for instance, WWV and
WWVH, in addition to steadily reducing the time allotted to audio-frequency modulation,
have introduced a break of 40 ms in continuous modulation, during which time-signals
are transmitted.
IAM has also introduced a 40 ms break in continuous modulation, during which time
signals are transmitted. In this way there will be neither carrier nor modulation duringthat interval. This technique has also been employed in Japan, by JJY, the length of the
break in modulation being extended to 85 ms to enable time signals to be received fromsome other synchronized station without interference due to audio-frequency modulation.
This method enables sinusoidal modulation to be emitted simultaneously with pulse-modulation without major mutual disadvantages, but it also requires the use of relatively more com­plex equipment at the receiving station, if the time information is to be satisfactorily extracted.
Though the X lth Plenary Assembly of the C.C.I.R. provided the opportunity for useful
discussion between Administrations, it must be stressed that bi- or multi-lateral negotiations
between the agencies operating a standard-frequency service might lead to a more direct
solution of the problem of interference in restricted areas. If the Chairman and Vice-Chair­man, Study Group VII, the Director, C.C.I.R. and the I.F.R.B. were kept informed of suchnegotiations, they could cooperate in whatever action is to be undertaken.

* This Report was adopted unanimously.

Rep. 270-1— 296 —REPORT 270-1 *FREQUENCY SPECTRUM CONSERVATION
FOR H IG H PRECISIO N TIME-SIGNALS(Study Programme 3A/VII)(1963 - 1966)
There is an increasing number of applications requiring the use of a very precise timereference. In an effort to achieve greater precision, it is to be expected that the system oftime distribution will tend to make use of an increased bandwidth up to the limits imposedby the width of the allocated band, the instabilities of the propagation path or by considera­
tions of noise and interference. An increased bandwidth is also appropriate where pointto-point links are used to establish a precise (1 ps or less) time relation between remotestations.
An example of a system developed to exploit fully the characteristics of earth-ionosphere
propagation is the navigational system known as Loran-C operating at 100 kHz. This sys­
tem has been shown to be capable of high precision for the distribution of a time reference.
The rate of rise of the leading edge of the signals is chosen to be sufficiently rapid and thelength of the pulse is sufficiently short that it is possible to distinguish between the time ofarrival of the ground wave and the first ionospheric wave returned from the D-layer. The
relative separation of these two components at a distance of about 2000 km has been foundexperimentally to be 25 to 30 us. This delay determines the characteristics of the pulse
waveform which, necessarily, occupies a total bandwidth of ± 10 kHz.
As a further development, a 1 Hz pulse on Universal Time UT2 has been added experi­mentally to the transmissions of the Cape Fear station of the Loran-C chain operating on
the East Coast of the U.S.A. Similar pulses have been added to the Johnston Island Loran-C
station. The purpose of these signals is to make available the time distribution capacityo f Loran-C in those cases where the repetition period of the navigational signals is not a
simple fraction of a second and these signals cannot, therefore, be easily related to standard
time generators.
At high frequencies, where long-distance propagation is wholly dependent upon theionosphere, the precision with which time-signals can be received is limited by the charac­
teristics of the propagation medium. The bandwidths in use have been largely determinedby administrative rather than technical or scientific considerations. It is to be noticed inReport 267-1 (Table I) that all stations, with the exception of HBN and RWM-RES, now
make use of an audio-frequency sub-carrier for the time-signal waveform. This takes theform previously recommended by C.C.I.R., and consists of n cycles of 200 n Hz audio­
frequency modulation, leading to a pulse of constant length equal to 5 ms. The value ofn can be varied conveniently to distinguish the various emissions. Thus WWV and several
other stations have adapted a pulse waveform with n = 5, i.e. 5 cycles of 1000 Hz. For
WWVH, n = 6 has been chosen while JJY has recently adopted a pulse with n — 8. The
use of this form of pulse does not make it possible to resolve the several components of asignal received by more than one path (multipath propagation), but it is reasonably economicalof bandwidth, and disturbed propagation conditions produce easily recognizable distortionsof the pulse waveform.
A method of precise time dissemination which does not require the use of excessively
wide bands has recently been investigated [1]. It makes use of the interference between
two closely-spaced phase coherent carrier frequencies to generate a coarse time reference.
When this can be realized with sufficient stability it serves, in effect, to identify one particular
cycle of the carrier frequency and a precise time reference can then be obtained from measure­ments of the carrier phase. Experiments making use of the carrier frequencies of 19-9 and20-0 kHz have shown that at a distance of 1400 km, and with an averaging time of a few hours,* This Report was adopted unanimously.

— 297 —Rep. 270-1, 271-1

that the envelope or group delay variations will cause an instability in the coarse time indica­tion of less than ± 50 ps. This means that a particular cycle of the 20-0 kHz carrier canbe “ marked ”, and used thereafter to provide “ microsecond ” timing.
In an endeavour to obtain, by means of VLF emissions, a comparable accuracy in themeasurement of time epoch as is achieved in the measurement of time interval, studies havebegun on the precision which may be attained using very narrow bandwidths (Doc. VII/65(Italy), 1963-1966).
Two new procedures have been investigated. The first necessitates generation of aparticular waveform, which can be interpreted as the product of two sinusoidal signals of
the same amplitude, having frequencies in an integral ratio with a convenient phase rela­tion. It takes advantage of the precise timing given by the typical “ phase jump ” of theradio-frequency signal [2,3] (not of the envelope). The second uses periodic phase inversionsof the carrier wave. The theoretical results already obtained are satisfactory and instru­
ment development is in progress.
Another method [4,5] employs, in the same emission (but not necessarily simultaneously),
two nearby frequencies. It takes advantage of the precise timing obtainable by a suitablephase-tracking and comparison procedure.
B ib l io g r a p h y

1.

M o r g a n , A. H. and B a l t z e r , O. J. A VLF timing experiment. Radio Science, 680, 11, (November,2.

E g i d i , C. and O b e r t o , P. Modulazione d’ampiezza con le tre righe spettrali aventi ampiezze e fasi

3.

E g i d i , C. and O b e r t o , P. Generally distorted three spectral lines amplitude-modulation, Archiv El.

1964).
qualunque. Alta Frequenza, 33rd, 144-156, particularly Fig. 11 (1964).
Vbertragung, 18th, H.9, 525-536, particularly Fig. 10 (1964).
4.
5.

F e y , L. and L o o n e y , C. H. A dual frequency VLF timing system. Submitted to IEEE Trans, on Inst,and Meas. (December, 1966).
C h i , A. R. and W i t t , S. N. Time synchronization of remote clocks, using dual VLF transmissions.
Proc. of 20th annual Frequency Symposium, Atlantic City (April, 1966).

REPORT 271-1 *STABILITY AND ACCURACY OF STANDARD-FREQUENCYAND TIME-SIGNALS AS RECEIVED(Q uestion 3/VII)(1963 - 1966)
1.

Stability of standard-frequency in the VLF and LF bands (bands 4 and 5)

Several reports have been presented on the propagation of VLF signals [1, 2, 3, 4, 5,
6]. The phase of the received signals undergoes a diurnal change due to the altitude varia­
tion of the ionospheric D-layer. Consequently, for frequency comparison purposes, thephase should be measured at intervals o f 24 hours or multiples thereof.
It has been observed, though, that for great distances the phase-shift accumulated during
a 24-hour interval does not necessarily cancel, but can be ± 2tc or a multiple thereof. Thisis due to an interference between two signals of different propagation paths. If the stability* This Report was adopted unanimously.

Rep. 271-1— 298 —of the local frequency standard is sufficient, this situation is easily recognized and taken
into account. Such effects have been observed for the signals of GBR, NBA and NPM
in Australia and the signals of NBA and NPM in France.
The new time service provided experimentally by the transmitter HBG located near
Geneva (see Report 267-1, Table II) reaches a large part of Central Europe. Experiments
have shown that the time signal of HBG can be received by simple receivers with a disper­sion of less than 01 ms at the distance of 1000 km. The phase of the carrier is typicallystable to better than ± 2 ps at the distance of 500 km for ground wave reception.

2.

Stability of time-signals in bands 6 and 7 as received
The results of time-signal comparisons carried out at the Tokyo Astronomical Observa­
tory for the years 1961, 1962 and 1963 have been reported [2]. When using a comparison
system whose accuracy is + 0 01 ms, the standard deviation for a single reception has beenfound to vary from ± 0-01 ms at a distance of 4 km to about ± 0-5 ms at distances of about
18 000 km. Most signals have been found to exhibit little seasonal variation except thosefrom WWV and DAM, when reception becomes poor in thenorthern hem isphere winter.

3.

Stability of time-signals in band 9 as received
Measurements have been made in Italy [7] to determine the causes of reduced stability
and accuracy of time-signals as received by the users and to establish the statistical distribu­
tion of the instability values. The results show that, when using non-specialized equipment,
the overall accuracy obtainable is several parts in 10®, with approximately three consecutive
measurements of 1000 seconds duration.

4.

Stability over a line-of-sight radio-relay link (band 10)
Experiments have been made [8,9] on the instability introduced by propagation overa 50 km line-of-sight radio-relay link. The results can be summarized as follows:
Concerning the phase of the transmitted wave, the stability degradation due to propa­
gation is less important than the inherent fluctuations in the signal due to the generator
noise. For a measurement time period of 1 s, the contribution of instability due to the
propagation can be represented by a fractional standard error of about 3 x 10~12 which
decreases to 1 x 10~14 as the averaging time is increased to 106 s.
Concerning the precision in the transmission of time intervals, the contributionof instability introduced by propagation results in a standard error of about 1 x l(h8 sfor time intervals of 1 s and of 2 x 10~6 s for time intervals of 106 s.

5.

Clock synchronization via satellite
Two experiments have been performed using radio transmissions via artificial satellites
to synchronize clocks in different continents. TELSTAR I was used between U.S.A. andU.K. in August 1962, and an accuracy of 1 ps was achieved [10]. Comparisons between
U.S.A. and Japan in February 1965 were made using RELAY II and employing the methodof retransmission of pulses [11]. An accuracy of synchronization of 0-1 ps was achieved.
B ibliography

1. C.C.I.R. Doc. VII/7 (Australia), 1963-1966.
2. C.C.I.R. Doc. VII/21 (Japan), 1963-1966.
3. T hompson, A. M., A rcher, R. W. and H arvey, I. K. Some observations on VLF standard-frequency
transmissions as received at Sydney N.S.W. Special 1963 International Issue of IEEE, Vol. 51, 11(November, 1963).
4. C.C.I.R. Doc. VII/11 (France), 1963-1966.
5. D ecaux, B. and G abry, A. Some particular observations on diurnal phase variations of VLF trans­missions received in Paris. Radio Science Journal of Research NBS/USNC-URSI Vol. 68D, 1 (January,1964).

— 299 —
6.

7.
8.
9.
10.
11.

Rep. 271-1, 362

R e d e r , F. H., A b o m , C. J. and W i n k l e r , G. M. R . Precise phase and amplitude measurements on

VLF signals propagated through the arctic zone. Radio Science Journal of Research NBS/USNCURSI, Vol. 68D, 3, (March, 1964).
C.C.I.R. Doc. VII/28, (Italy) 1963-1966.
N o r t o n , K. A., B a r r o w s , E. C., T h o m p s o n , M. C. Jr. and J a n e s , H.B . Variance of radio-frequency
caused by turbulence on line-of-sight transmissions. Trans. IRE, P.G.I. (December, 1962).
C.C.I.R. Doc. VII/19 + Amend+ Corr., (U.S.A.), 1960-1962.
S t e e l e , J. M., M a r k o w it z , W. and L i d b a c k , C.
A. Telstartimesynchronization,
IEEETrans,onInstrumentation and Measurement. Vol. IM-13, 4, 164 (December, 1964).
M a r k o w it z , W., L i d b a c k , C. A., U y e d a , H. and M u r a m a t s u , S . Clock synchronization via Relay II
satellite. IEEE Trans, on Instrumentation and Measurement (December, 1966).

REPO RT 362 *SINGLE-SIDEBAND OPERATION FO R THE
STANDARD-FREQUENCY AND TIME-SIGNAL SERVICE(Study Programme 1B/VII)(1966)
Single-sideband (SSB) operation with full carrier is a special form of emission for reduc­ing mutual interference and has the following advantages:- the use of an ordinary receiver for the reception of a single transmitting station,- the possibility, using more elaborate receiving apparatus, of distinguishing between two
stations transmitting on the same carrier frequency but using, respectively, the upper orthe lower sideband,- a certain degree of spectrum economy,- the reduction of second-harmonic distortion, if the carrier is subject to fading.
For a number of years station WWV has been transmitting 440 Hz and 600 Hz audio­
frequencies using the standard-frequency carriers of 2-5, 5, 10, 15 and 20 MHz and the uppersidebands only. All other modulations, time pulses and announcements in voice or incode, were produced by double-sideband amplitude-modulation.
A recent survey of users of WWV indicated that there was insufficient usefulness of
the upper single-sideband with full carrier audio-frequency transmissions to justify theequipment necessary to continue the service. Conventional double-sideband audio-fre­quency transmissions were commenced on 1 March, 1965.
Plans exists to rebuild the station WWV, and perhaps the station WWVH, includingtransmitters which will be able to furnish the entire programme by single-sideband emissions
with full carrier. If found desirable it would then be feasible to operate WWV on the upper
sideband and WWVH on lower sideband, thereby making it possible, with appropriate
receivers, to differentiate between the two stations.
The Italian station IAM (5 MHz) is continuing the experimental emission of a standard
frequency with a 1000 Hz modulation using double-sideband with suppressed carrier. Recep­
tion results are satisfactory.

* This Report was adopted unanimously.

Rep. 363, 364— 300 —REPO RT 363 *INTERCOM PARISONS OF TIM E SCALES BY VARIOUS M ETHODS(Study Programme 3C/VII)(1966)
A number of intercomparisons of standard-frequency generators has been made inrecent years. Some of these have employed radio signals. Examples are given in refer­ences [1, 2, 3]. Other methods involve the direct comparison of standards, some of whichhave been carried from one country to another [4, 5]. The results have conclusively shown
the value of making such direct comparisons both for checking the effects of propagationon the accuracy of radio transmissions and for studies which may ultimately lead to aninternational atomic time scale system. Statistical studies of this problem are also being
made [6].
B ibliography

1.

B o nanom i , J., et al. A comparison of TA1 and the NSB(A) atomic time scales. Proc. IEEE 52, 4

2.

M o r g a n , A. H., C ro w , E. L. and B lair ,

3.

4.
5.
6.

(April, 1964).

B. E. International comparison of atomic frequency
standards via VLF radio signals, Radio Science Jour, o f Research NBSIUSNC-URSI, Vol. 69D,
7 (July, 1965).
B eehler , R . E ., M ockler , R . C. ,and R ic h ar dso n , J. M . Cesium beam atomic frequency standards.
Metrologia, Vol. 1, 1, 126 and ff, (July, 1965).
B eehler , R . E., et al. An intercomparison of atomic standards. Proc. IEEE, 54, 2, p. 301 (February,1966).
B odily , L. N. Correlating time from Europe to Asia with flying clocks. Hewlett Packard Journal,
16, 8.
C ro w , E. L. The statistical construction of a single standard from several available standards. IEEE
Trans, on Inst, and Meas., IM-13, 4, 180-185 (December, 1964).

REPORT 364 *INSTABILITY OF STANDARD-FREQUENCY GENERATORS(Study Programme 3B/VII)(1966)In the last years the results of a large number of studies have appeared on the instabilityof standard-frequency generators. Theoretical aspects of the problem, definitions andexperimental procedures for measurements have been widely investigated.
Several studies [1, 2, 3] have shown that the measurement of the short-term frequency
instability of highly stable oscillators is much influenced by low-frequency noise, some ofwhich is known as 1/f noise.
A study [4] of quartz crystal oscillators has shown the existence of several components
of frequency instabilities. The use to which an oscillator may be put determines the relative
importance of these components. In this study, both long-term (over two months) andshort-term characteristics of current good quality oscillators were observed. Corresponding
studies have been made for atomic frequency standards [5].
* This Report was adopted unanimously.

Rep. 364, 365— 301 —

A special issue of the Proc. IEEE has been devoted to the frequency stability of oscilla­
tors and radio-frequency sources [6] and can be consulted for information.
B ib l io g r a p h y

1.
2.
3.
4.
5.
6.

Interim proceedings of the Symposium on the definition and measurement of short-term frequency stability.
Goddard Space Flight Center, Greenbelt, Maryland (23-24 November, 1964).
Symposium Report. Definition and measurement of short-term frequency stability. Frequency, 3, 1,
26 (January-February, 1965).
Y a s u d a , Y . and Y o s h im u r a , K. Measurement of short-term frequency instability and frequency
spectra of highly stable oscillators. Journal of Radio Research Laboratories, 11, 58 (November, 1964).
C.C.I.R. Doc. VII/25 (United Kingdom), 1963-1966. Instability of standard-frequency generators.
B e e h l e r , R . E., M o c k l e r , R . C., and R i c h a r d s o n , J. M . Cesium beam atomic time and frequency
standards. Metrologia, 1, 3 (July, 1965).
Proc. IEEE, 54, 2 (February, 1966).

REPORT 365 *COMPARATIVE STATISTICS CONCERNING THE PRO PERTIESOF UT AND AT RADIO EM ISSIONS(Study Programme 1C/VII)(1966)
It is important to determine the best system for supplying both the international unitof time interval and the epoch of UT2 on the same emissions. Two systems which yieldsuch information have been compared for 1965 [1]. This Report presents a summary ofsome of the results of this study.
The time scales of these systems, UTC (universal coordinated time) and SAB (stepped
atomic scale as WWVB), underwent adjustments in their epochs: three for UTC, and four
for SAB. If one compares the deviations of the mid-points of the steps from the UT2 scale,the statistical data tabulated in Column 2 in Table I are obtained. If, on the other hand,
one compares the deviations from UT2 on weekly basis, the data given in Column 1 in Table I
are obtained.
T able I
Column 2

Column 1
Deviations o f scale
markers from UT2

Weekly averages :Carrier offset

Mid-point averages.

Mean Dev.
(ms)

Mean Abs.
Dev. (ms)Mean Dev.
(ms)

1

Mean Abs.
Dev. (ms)UTC - UT2-150 x 10-10

25-3

34-9

18-6

22-9

SAB - UT2

0

4-1

50-6

81

13-1

If one also measures the percentage of the time during the year that the respective scales
deviated from UT2 by the amounts given in Column 1 of Table II, one obtains the percentages
shown in Column 2 of Table II.
There is little difference in the choice of system on the basis of these statistical data.
* This Report was adopted unanimously.

Rep. 365, 366— 302 —
T able II
Column 1

Column 2
By the percentage

Scale deviation from UT2 exceeded

0
25
50
75
100
125

UTC

SAB

100

100
75-5
47
23
7-5
0

68

28
4
0
0

B ib l io g r a p h y1.

H u d s o n , G. E . Scientific aspects of universal and/or atomic time and frequency transmissions, pre­sented to U.R.S.I., Commission I, Washington D.C. (April, 1966) (to be published).

R EPORT 366 *A M ETHOD FOR CLASSIFYING SYSTEMS W H ICH YIELD TIM E AND
FREQUENCY INFORM ATION FRO M THE SAME RADIO EM ISSION(Study Programme 1C/VII)(1966)

1.

Introduction
After the Interim Meeting of Study Group VII, Monte Carlo, 1965, Study Programme
1C/VII was adopted by correspondence. It decided that studies and experiments should bemade to provide both epoch of UT2 and the international unit of time interval in the sameemission. The present document proposes a method for classifying time and frequency
information emission systems chosen for study or adoption.
The Chairman, Study Group VII is requested to communicate with the Chairmen of
the appropriate commissions of the U.R.S.I., I.A.U., I.U.G.G. and I.U.P.A.P. It is suggested
that anyone having a proposal of a system should submit it in written form to the Chairmanof C.C.I.R. Study Group VII for his information and use. After a number of systems
have been classified according to the presently suggested scheme [1-6], it may become appa­
rent that some have distinct advantages (simplicity, clarity, completeness of information)over others. At this point, it will be necessary to determine, on the basis of practical tests
and stated user needs, which system or systems best meet the needs of users. The Table
included in this Report may be used as a guide by proposers of systems.

2.

Definitions

2.1 By carrier offset is meant an intentional fractional frequency deviation from the nominal
carrier frequency value as determined in terms of the frequency:/ ( Cs) = 9 192 631 770 Hzof the Cesium transition, which has been designated as the international standard of fre­quency to be employed temporarily for the physical measurement of time. Carrier offset* This Report was adopted unanimously.

— 303 —Rep. 366

adjustments may be made only on the first of the year for TIC (international coordinatedtime) emission systems. These are systems which are coordinated by the B.I.H.
2.2 By time interval offset is meant an intentional fractional deviation of a period of the broad­
cast time scale interval from its nominal value in terms of the second of time. Adjustments
in time interval offsets may only be made on the first of the year for TIC systems.
2.3 By an epoch step is meant an intentional discontinuity introduced at some instant in an other­wise uniform sequence of time intervals, whereby a sequence of intervals following the step
does not have the same epoch as that preceding it. Epoch steps may be made only on thefirst of the month for a TIC system. We classify them into those greater than or equal to
0-2 s., and those less than 0-2 s.
2.4 By the term UTC marked is meant sequences of time markers which are offset in time intervaland coherent with the offset carrier frequency, and into which epoch adjustments may beintroduced, so that they approximate to the UT2 scale within about 0-1 s.

3.

Tabular entries
The following instructions are given to help make entries in the Table of § 5. A system
which employs more than one carrier or time scale will necessitate the use of more than
one table.

f‘

3.1 If a carrier offset is not present, designate the corresponding entry opposite A in the Tableby 0. Otherwise designate it by 1. Some carrier signals employed for time dissemination
do not have sufficient stability or they have other technological characteristics so that theirfrequencies do not need to be offset from nominal. In some cases it may not be appropriate
to specify the offset to describe the method.
3.2 If a time interval offset is not present, designate this fact by writing 0 opposite entry B, andotherwise by writing 1.
3.3 If epoch steps 0-2 s or less are used, indicate this opposite entry C by 1, and otherwise by 0.
3.4 If UTC markers are not present, designate this fact opposite D by 0, and otherwise by 1.
Note that if the entries under B and C are both 1, then the entry under D is 1 only if the
purpose of the adjustments noted in B and C is to follow UT2 and if the carrier frequency
is offset according to the UTC marking method. However, the purpose may be to clarify
the signal coding. Hence it is always necessary to make the entry under D explicit.
3.5 If voice or code broadcasts are not present for the purpose of giving more accurate UT in form ation, then enter 0 under E, and otherwise 1.
3.6 If it is not necessary or appropriate to specify a property to classify the system, then thecorresponding entry should be left blank (-).
3.7 As examples, the TIC system coordinated by the B.I.H. in 1966 employs the UTC scale
and is designated (1111 —) according to this classification method. The SAB scale [7] emitted
by WWVB in 1965 and 1966 according to a stepped atomic system approximates UT2 within
about 01 s. It is designated (00101). The offset atomic system employed by HBG during
1966 employs a scale whose time intervals are offset. It is designated (01100).

4.

Scale marker trends
To assist in making the sketch in § 5 according to a uniform method, a few words ofclarification are given. A time scale consists of a sequence of markers, often nominal seconds(or minutes). At convenient intervals, count the number of such scale markers and subtract
the number of atomic seconds (or minutes) which have occurred since some initial epoch.
Plot this number as ordinate, labelled “ scale minus time ”, against the elapsed time (in months,

— 304 —Rep. 366

or years, as convenient) as abscissa. Do this for each time scale present in the system andlabel the curves clearly. Also choose the appropriate units on the axes.
The slopes of the resulting trends are proportional to the corresponding offsets, in therates of the time-signals.
5.

Classification form
Please prepare items I to V as follows and send the form to the Chairman, C.C.I.R.
Study Group VII.
I. Name o f system (two words)
II. Name and address o f originator
III. Table
Property

Entry (0 or 1)

Additional remarks

A : Carrier offset
B: Time interval offset'

C: Epoch steps
D: UTC marked
E: UT2 \ , T .
,UT1 f ^ ° ice or rodeO)

1 Cross out UT2 or UT1 as appropriate and cross out Voice or Code as appropriate. Also do this for the label on
the UT curve below.

IV.

Sketch o f scale marker trends(Be sure to indicate the appropriate units on the axes)

Scale
minus
time
(seconds,
minutes)Time (years, month)V.

Brief general description o f system

— 305 —Rep. 366

B ib l io g r a p h y

1.
2.
3.
4.
5.
6.
7.

C.C.I.R. Doc. VII/70 (U.S.A.), 1963-1966. Some systems for obtaining time and frequency informa­tion on radio emissions.
C.C.I.R. Doc. VII/71 (U.S.A.), 1963-1966. Possible modifications to the present system of emissionsof time and frequency.
C.C.I.R. Doc. VII/72 (U.S.A.), 1963-1966. A system for obtaining time and frequency information
on radio emissions.
C.C.I.R. Doc. VII/73 (U.S.A.), 1963-1966. A simple system for obtaining time and frequency infor­
mation on radio emissions.
C.C.I.R. Doc. VII/74 (U.S.A.), 1963-1966. A method for classifying systems which yield time andfrequency information on radio emissions.
C.C.I.R. Doc. VII/77 (Italy), 1963-1966. Standard-frequency and time-signal emissions - Proposals
for a complete signals schedule.
H u d s o n , G. E. Scientific aspects of universal and/or atomic time and frequency transmissions,presented to U.R.S.I., Commission I, Washington D.C. (April, 1966). To be published.

I

20

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENT

— 307 —STUDY GROUP YII(Standard-frequencies and time-signals)
Terms o f reference:
Organization of a world-wide service of standard-frequency and time-signal emissions.
Improvement of measurement accuracy.
Chairman:
Mr. B . D e c a u x (France)
Vice-Chairman: Professor M. B o e l l a (Italy)

I n t r o d u c t io n b y t h e C h a ir m a n , S t u d y G r o u pVIIAt the X lth Plenary Assembly, Study Group VII brought up to date a number of texts
which required amendment owing to the very rapid evolution of the questions they dealt
with. It took account of the increasing demands made by users of standard-frequencies
and time-signals and of the development of methods for the more accurate production andtransmission of such signals. Report 267-1 reviews the work done since the Xth Plenary
Assembly; the main points are brought out below.

1. Greater accuracy in transmission and reception
1.1 Recommendation 374-1 reduces the tolerance for the emitted frequency from ± 5 x 10~10
to ± 1 x 10-10.
1.2 The same Recommendation indicates the steps to be taken to coordinate such emissions,either by an offset between the frequency emitted and the nominal frequency, so that the
time-signals given by the emitted frequency correspond approximately to Universal Time,or without an offset.
1.3 Recommendation 374-1 also extends the role of the B.I.H., which will in future fix for eachyear not only the value o f the offset but also the date on which adjustments in the epochof the time-signals are to be made.
1.4 The problem o f providing UT and the international unit of (atomic) time interval in thesame emission is also dealt with in Opinion 26, which advocates on this point the international
cooperation already requested in Resolution 14-1. Report 366 gives a method of classifying
emissions. Report 365 gives comparative statistics for certain systems now in use.
1.5 Study Programme 3B/VII and Report 364 deal with the definition and improvement ofstandard-frequency generator stability. Question 4/VII and Study Programme 3C/VII
envisage new techniques for international comparison of such generators. Report 363
lists examples of comparisons already performed.
1.6 To avoid any loss in accuracy due to propagation phenomena, Question 2/VII raises thequestion of the use of bands other than bands 6 and 7. Recommendation 375-1 makes
certain recommendations in this connection. Study Programme 4A/VII, supported by
Report 271-1, envisages stabilization of the carrier frequencies of sound and television broad­casting stations for this purpose. Lastly, Opinion 27 considers that Administrations shouldreserve two special bands for standard-frequency and time-signal emissions in bands 8 and 9.
1.7 Greater precision in the distribution of time-signals could be obtained by employing newtransmission techniques, such as signals of special form using a narrow VLF band (Study
Programme 3A/VII and Report 270-1) or artificial satellites (Study Programme 2A/VII and
Report 271-1).

— 308 —2.

Reduction of interference with standard-frequency services.

Such interference is of two kinds:
2.1 Mutual interference between standard-frequency stations working on the same frequency.
Study Programme 1A/VII and Report 269-1 envisage remedies for this, notably by trans­mitter time-sharing. Study Programme 1B/VII and Report 362 contemplate employing single
sideband operation for this purpose. The use of certain bands, as envisaged in § 1.6
above, might also make the position easier.
2.2 Interference caused by stations other than standard-frequency stations. Recommenda­
tion 376-1 impresses once more on Administrations the urgent need to clear the 'standardfrequency bands. Opinion 28 requests the assistance of the IFRB in this field.
3.

Tables of emission characteristics.

See Report 267-1

— 309 —Res. 14-1, Op. 26

RESOLUTION 14-1
STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONS(Question 1/VII)
The C.C.I.R.,(1963 - 1966)CONSIDERING

the provisions of Article 44, Section IV, of the Radio Regulations, Geneva, 1959;
UNANIMOUSLY DECIDES

1.

that, whenever an assignment to a station operating standard-frequency emissions is put
into service, the Administration concerned shall notify this assignment to the I.F.R.B., in
accordance with the provisions of Article 9 of the Radio Regulations, Geneva, 1959; however,no notice should be submitted to the I.F.R.B. until experimental investigations and coordina­tion have been completed, in accordance with Article 44, Section IV, of the Radio Regula­tions ;

2.

that each Administration should send all pertinent information on standard-frequency sta­tions (such as frequency offset, changes in the phase of time pulses, changes in transmission
schedule, etc.), to the Chairman o f Study Group VII for forwarding, via the Director, C.C.I.R.
to the I.T.U. for official publication;

3.

that Study Group VII should cooperate with the I.A.U., the U.R.S.I., the I.U.G.G., theI.U.P.A.P. (International Union of Pure and Applied Physics) and the B.I.H.

OPINION 26
STUDIES AND EXPERIM ENTS CONCERNED W ITH
TIME-SIGNAL EM ISSIONS(Question 1/VII)
The C.C.I.R.,(1966)CONSIDERING(a) that frequency and epoch may be provided in the same emission;(b) the present necessity for providing both the epoch of UT and the international unit of timeinterval in the same emission;(c) the possible future utilization of an epoch of the atomic time scale in time-signal emissions;
IS UNANIMOUSLY OF THE O PINION

1.

that the International Scientific Radio Union (U.R.S.I.), the International Astronomical
Union (I.A.U.), the International Union of Geodesy and Geophysics (I.U.G.G.), and theInternational Union of Pure and Applied Physics (I.U.P.A.P.) should be asked to cooperate

Op. 26, Q. 1/VH, S.P. 1A/Vn— 310 —

with C.C.I.R. Study Group VII in pursuing studies and experiments relative to the following
problems:
1.1 how to provide both the epoch of UT and the international unit of time interval in the sameemission;
1.2 how the various essential requirements could be met by the emission of a single uniform
time scale;2.

that the Chairman, Study Group VII should communicate with the Chairmen of the appro­
priate Commissions of the U.R.S.I., the I.A.U., the I.U.G.G., and the I.U.P.A.P., to initiate
consultations and that the Director, C.C.I.R. should be informed of the progress of thestudies.

QUESTION 1/VII *STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONSThe C.C.I.R.,(1948 - 1951 - 1953 - 1956 - 1963)CONSIDERING(a) that the Administrative Radio Conference, Geneva, 1959, called for the study of the estab­lishment and operation of a world-wide standard-frequiency and time-signal service;(b) that a number of stations are now regularly emitting standard-frequencies and time-signals

in the bands allocated by this Conference;(c) that some areas of the world are not yet adequately served;(d) that the use of more stations than are technically necessary would diminish the utility ofthe service by producing harmful interference;u n a n im o u s l yd e c id e sthat the following question should be studied:1.

what measures can be recommended for increasing the effectiveness of the existing standardfrequency and time-signal service in the bands allocated by this Conference;2.

what measures can be recommended for the reduction of mutual interference between standardfrequency and time-signal stations operating on the same frequency and whose service areas
overlap ?

STUDY PR O G R A M M E 1A/VII **STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONSThe C.C.I.R.,(1965)CONSIDERING(a) that Question 1/VII and Recommendation 374-1 call for information on methods for improv­

ing the usefulness of the existing standard-frequency and time-signal service;(b) that standard-frequency stations are operated simultaneoulsy on the same carrier frequency;* Formerly Question 140(VII).
** Formerly Study Programme 140C(VII).

— 311 —u n a n im o u s ly

d e c id e ss.p. iA /v n , ib / v h , i c / v nthat the following studies should be carried out:

1.

an investigation of the possibilities of reducing mutual interference between emissions inthis service by:
1.1 shortening the programme of continuous tone modulation and of announcements;
1.2 use of a modulation which gives the required information and accuracy with minimum
bandwidth;
1.3 staggering the emissions in the allocated bands and using a convenient type of modulation;
1.4 a convenient coordinated time-sharing of frequencies for those areas where there is mutualinterference;:2.

collection of information on how standard-frequency emissions in bands 6 and 7 may becoordinated with emissions in other bands to give the best overall world-wide service.

STUDY PRO G R A M M E 1B/VII *SINGLE-SIDEBAND OPERATION FO R THE STANDARD-FREQUENCYAND TIME-SIGNAL SERVICEThe C.C.I.R.,(1965)CONSIDERING

the measures taken by the I.T.U. urging Administrations to accelerate the conversion of
their double-sideband systems, in the frequency bands below 30 MHz, to single-sideband
systems and to complete such conversions by 1967 or earlier if possible to reduce thecongestion in these bands;
u n a n im o u s l yd e c id e sthat the following studies should be carried out:

the improvements that may be obtained in the distribution and use of standard-frequency
and time-signal emissions by the use of single-sideband operation, with full carrier, parti­
cularly in the 2-5; 5; 10; 15; 20 and 25 MHz bands.

STUDY PRO G R A M M E 1C/VII **TIME-SIGNAL EM ISSIONSThe C.C.I.R.,(1965)CONSIDERING(a) the necessity for providing both epoch of UT2 and the international' unit of time intervalin the same emission;(b) that the epoch of UT is determined by the angular position of the Earth about its axis andis required for various scientific and technical purposes;* Formerly Study Programme 140D(VII).
** Formerly Study Programme 140E(VII).

S.P. 1C/VH, Op. 27, Q. 2/VII
u n a n im o u s ly

d e c id e s— 312 —
that the following studies should be carried out:

the possibility of developing an improved method by active pursuit of studies and experiments
to provide both epoch of UT2 and the international unit of time interval in the same emis­sion.
Note. - The international unit of time interval is the second as adopted by the General
Conference on Weights and Measures. See also Recommendation 374-1, § (e).

O PINION 27
STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONSIN ADDITIONAL FREQUENCY BANDS(Question 2/VII)
The C.C.I.R.,(1966)CONSIDERING(a) that in certain areas, particularly in industrial centres, it is not always possible to obtainan adequate signal-to-noise ratio with the existing standard-frequency and time-signal service;(b) that a better service is needed in certain areas and this service may be given by use of fre­quencies in band 8 and higher;
IS UNANIMOUSLY OF THE OPIN IO N

that each Administration should, as far as possible, provide for the distribution of standardfrequencies and time-signals, on a local basis, two bands 100 kHz wide in bands 8 and 9 res­pectively, the centre frequencies of which should be whole multiples of 5 MHz.

QUESTION 2/VII *STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONSIN ADDITIONAL FREQUENCY BANDSThe C.C.I.R.,(1956- 1963)CONSIDERING(a) that in certain regions, particularly in industrial centres, it is not always possible to obtainan adequate ratio of the wanted signal to the noise level with the existing standard-frequency[H and time-signal service;(b) that the bands allocated for standard-frequency and time-signal emissions are more usefulfor long-distance distribution than for local distribution;(c) that a better service is needed in certain areas and this service may be given by use of fre­quencies in band 8 and higher;* Formerly Question 249(VII).

— 313 —Q. 2/VH, S.P. 2A/VII, Q. 3/VH(d) that high accuracy frequency and time comparisons between distribution centres can bemade using frequencies in bands 4 and 5;
u n a n im o u s l yd e c id e sthat the following question should be studied:what can be recommended for the distribution of standard-frequencies and time-signals,
above 30 MHz and below approximately 100 kHz ?

STUDY PRO G RA M M E 2A/VII *STANDARD-FREQUENCY AND TIME-SIGNAL EM ISSIONSFRO M ARTIFICIAL EARTH SATELLITESThe C.C.I.R.,(1963)CONSIDERING(a) that continuing advances in communications, particularly in space communications andassociated science and technology, have increased the requirements for accuracy and service
range of standard-frequency and time-signal emissions;(b) that the work of Study Group IV describes radiocommunication systems making use ofearth satellites which can be expected to give extensive coverage and good stability of signals
over the earth’s surface;u n a n im o u s l yd e c id e sthat the following studies should be carried out:

what are the technical factors to consider in recommending frequencies and in determining
the transmitting, modulating and receiving techniques, which are important to the develop­
ment of standard-frequency and time-signal emissions from artificial earth satellites ?

QUESTION 3/VII **STABILITY OF STANDARD-FREQUENCY AND TIME-SIGNALEM ISSIONS AS RECEIVED
The C.C.I.R.,(1956 - 1959 - 1963)CONSIDERING(a) that the standard-frequency and time-signal emissions as received are less stable than at
the source, owing to phenomena occurring in the propagation of radio waves, e.g. the Doppler
effect, diurnal variation and multipath interference;(b) that errors, which occur during propagation, depend on the geographical location of boththe transmitter and receiver, as well as on the nature and condition of the medium, andgenerally differ in different regions of the radio spectrum;(c) that special techniques of standard-frequency and time-signal emissions may improve theaccuracy with which they can be received;* Formerly Study Programme 249A(VII).
** Formerly Question 250(VII).

Q. 3/y n , S.P. 3A/VII, 3B/VH(d)— 314 —

that the accuracy with which standard-frequency and time-signal emissions can be received
may depend upon the design of the receiving equipment;

unanimously decides that the following question should be studied:
1. what are the causes of the reduction in the stability and accuracy of the standard-frequencies
and time-signals as received by the users;

2. what is the magnitude in statistical terms of the instability introduced by these causes;
3. what are the most suitable techniques for transmitting and receiving standard-frequencies
and time-signals to obtain the best results in the reception of:- standard-frequencies and time-signals as used by those requiring moderate accuracy;- standard-frequencies and time-signals as used by those requiring the maximum possible
accuracy ?

STUDY PRO G R A M M E 3A/VII *FREQUENCY-SPECTRUM CONSERVATION
FO R H IG H PRECISIO N TIME-SIGNALSThe C.C.I.R.,(1959)CONSIDERING(a) that higher precision in the radio distribution of time-signals necessitates, using present
techniques, the use of an increased bandwidth;(b) that newly developed techniques may, nevertheless, effect a considerable bandwidth economy;
unanimously decides that the following studies should be carried out:

1. an investigation of the relationship between bandwidths required, and precisions obtainableat present for various carrier-to-noise ratios as may be encountered in practice;i
2. an investigation of narrow-band techniques to generate and broadcast high precision time
markers;3.

an investigation of the characteristics of the radio paths involved that limit the accuracyof time-signals as received, and how these radio-path parameters affect the choice of an opti­
mum method.

STUDY PRO G R A M M E 3B/VII *INSTABILITY OF STANDARD-FREQUENCY GENERATORSThe C.C.I.R.,(1965)CONSIDERING
that the employment of high quality frequency standards in a wide range of applications
has given rise to a need to specify, in convenient and precise terms, the various forms offrequency and phase instability which limit performance in relation to the increasingly strin­
gent requirements;* Formerly Study Programme 250A(VII).
* Formerly Study Programme 250C(VII).

— 315 —unanimously decides

S.P. 3C/VII, Q. 4/VH

that the follow ing studies should be carried out:

1.

how may the various forms of frequency and phase instability, inherent in a standardfrequency generator, be qualitatively described;

2.

how may the limitations of precision, imposed by various forms of frequency and phaseinstability in a standard-frequency generator, be quantitatively expressed ?

STUDY PRO G RA M M E 3C/VII *INTERNATIONAL COM PARISON OF STANDARD-FREQUENCYAND TIME-SIGNAL EM ISSIONSThe C.C.I.R.,(1965)CONSIDERING(a) that many stations participate in the international coordination of frequency and time;(b) that U.R.S.I. Resolution No. 2 adopted in Tokyo, 1963, at its XlVth General Assembly
and the I.A.U. resolutions adopted at Hamburg, 1964, during its X llth General Assembly,
recommend that international comparisons be made between the scales of time in use;
unanimously decides that the following studies should be carried out:

international comparisons between standard-frequency and time-signal emissions by different
methods (exchange of standard-frequency and time pulse generators, transmissions overradio-relay links, transmission by artificial earth-satellites, etc.).
'

QUESTION 4/V II**
DISSEM INATION OF STANDARD-FREQUENCIES AND TIME-SIGNALSThe C.C.I.R.,(1965)CONSIDERING •(a) the needs for increased accuracy of standard-frequency and time-signals;(b) that the present standard-frequency and time-signal emissions as received are less accurate
than the source, due to effects in the propagation of the radio waves, such as diurnal varia­
tions and the Doppler effect;
unanimously decides that the following question should be studied:what additional techniques can be employed for disseminating standard-frequencies andtime-signals by radio-transmissions (for example: by reflections from meteor trails, utiliza­tion of existing broadcasting facilities and laser techniques) ?
* Formerly Study Programme 250D(VII).
** Formerly Question 289(VII).

S.P. 4A/VH, Op. 28— 316 —STUDY PROGRAMME 4A/VII
DISSEM INATION OF ST AND ARD-FREQUEN CiES BY CARRIER-FREQUENCYSTABILIZATION OF BROADCASTING EM ISSIONSThe C.C.I.R.,(1966)CONSIDERING(a) the need for investigation of-additional techniques for the dissemination of standardfrequencies and time-signals;(b) that broadcasting of standard-frequency signals is carried out in some countries by stationsin the broadcasting bands;(c) that certain advantages may be obtained by the technique of stabilizing the carrier-frequencies
of broadcasting stations, namely:- the possibility of providing good ground-wave coverage, free of Doppler-effect errors,
at centres of population and industry;- the rapid comparison of frequencies at receiving locations by the use of such sufficiently
high carrier-frequencies; and- the use of relatively simple receiving equipment;u n a n im o u s l yd e c id e sthat the following studies should be carried out:

1. determination of the accuracy and stability of received signals from such broadcasts;
2.

investigation of the influence of the location of transmitting stations on convenience of use
and on propagation characteristics of signals;

3.

determination of the desirability of establishing a service of this nature;

4. investigation of the relative merits of amplitude- and frequency-modulation as related tothe dissemination of time-signals and of the use of the broadcasting bands for the disse­mination of standard-frequencies by carrier-frequency stabilization.

O PINION 28
SPECIAL M ONITORING CAMPAIGNS BY THE I.F.R.B.
W ITH A VIEW TO CLEARING TH E BANDS ALLOCATED EXCLUSIVELYTO THE STANDARD-FREQUENCY SERVICEThe C.C.I.R.,(1966)CONSIDERING(a) Recommendation No. 31 of the Administrative Radio Conference, Geneva, 1959, and theresults of the special monitoring campaigns organized by the I.F.R.B., with a view to clearing
the bands allocated exclusively to the standard-frequency service;(b) the need for achieving a more complete clearance of those bands;

— 317 —Op. 28(c) the difficulty experienced by the I.F.R.B. in identifying stations not belonging to the standardfrequency service, but operating in the standard-frequency bands;
IS UNANIMOUSLY OF THE OPINION

1.

that the I.F.R.B. should be asked to increase, as far as practicable, the number of special
monitoring programmes per year, covering the bands allocated exclusively to the standardfrequency service;2.

that the I.F.R.B. should urge Administrations of countries where direction-finding facilities
are available to take bearings with a view to determining the position of the stations observed.

— 318 —Q U E ST IO N 5/VII

HIGH PRECISION STANDARD-FREQUENCY AND TIME-SIGNAL EMISSIONS *(1968)The C.C.I.R.,
CONSIDERING(a) that there is a growing need, particularly in aviation, for accuracies of standard-frequency
and time-signal emissions that exceed those currently available;(b) that to achieve world-wide uniformity, timing requirements for aviation should be closely
coordinated with the International Civil Aviation Organization (I.C.A.O.);d e c id e sthat the following question should be studied:what methods can be internationally adopted to provide, on a world-wide basis, standardfrequency and time-signal emissions with synchronization uncertainties of 0’5 ms or less (3a)?

* See draft Report H.n (VII).

— 319 —LIST OF DOCUMENTS CONCERNING STUDY GROUP VII(Period 1963-1966)
Doc.

Origin

Title

VII/1

C.C.I.R.
Secretariat

Resolution 15 of the International Associationof Geodesy

VII/2

United Kingdom

Standard-frequency and time-signal emissions

Q. 140

VII/3

United Kingdom

Standard-frequency and time-signal emissions

S.P. 140A

VII/4

United Kingdom

Single-sideband operation for the standardfrequency and time-signal service

S.P. MOB

VII/5

United Kingdom

Standard-frequency and time-signal emissionsin additional frequency bands

Q. 249

VII/6

C.C.I.R.
Secretariat

Resolution 21 of the International Associationof Geodesy

VII/7

Australia

Accuracy of reception of VLF emissions

Q. 250VII/8

Australia

Stabilized frequency emissions and monitor­
ing facilities in bands 4 and 5

Proposedmod. toRep. 268

YII/9

FranceStandard-frequency and time-signal emissions

Rec. 374
Q. 140VII/10FranceStandard-frequency and time-signal emissions

Rec. 376
S.P. 140A

VII/11

FranceRec. 375
Q. 249VII/12

C.C.I.R.
Secretariat

Standard-frequency and time-signal emissionsin additional frequency bands
Clarification and Resolutions of the Interna­
tional Astronomical Union

VII/13

U.R.S.I.

Resolution 1 of the XlVth General Assembly,
Tokyo, 1963, Commission I-R adio standards
and measurements

U.R.S.I.
Res. 1

VII/14

U.R.S.I.

Resolution 2 of the XlVth General Assembly,
Tokyo, 1963, Commission I - Radio standards
and measurements

U.R.S.I.
Res. 2

VII/15

United Statesof America

Standard-frequency and time-signal emissions

Proposedmod. toRes. 14

VII/16and Corr.l

United Statesof America

Dissemination of standard-frequencies andtime-signals

Draft
S.P.

VII/17

United Statesof America
United Statesof America

Time-signal emissions

Draft Q.

Studies and experiments concerned with
time-signal emissions

Draft Op.

International comparison of
frequency and time generators

standard-

Draft
S.P.

VII/20

United Statesof America
Japan

JJY standard-frequency
emissionstime-signal

Q. 140VII/21Japan

Stability of standard-frequency and timesignal emissions as received

Q. 250VII/22Japan

Measurement of short-term instability andfrequency spectra of highly stable quartz
oscillators

Q. 250VII/18VII/19and Corr.l

Referenceand— 320 —
Doc.

Title

OriginReference

VII/23Chairman
Study Group, VII

Interim Report by the Chairman, Study
Group VII (Standard-frequencies and timesignals)

VII/24

United Kingdom

Standard-frequency and time-signal emissions
from artificial earth satellites

S.P. 249A

VII/25

United Kingdom

Instability of standard-frequency generators

S.P. 250B

VII/26

United Statesof America

Standard-frequencies and time-signals

Q. 140
Proposedmod. toRep. 267

VII/27

United Statesof America

Standardized frequency emissions and moni­
toring facilities in bands 4 and 5

Q. 249Rec. 375
Proposedmod. toRep. 268

VII/28Italy

Time-signal reception in band 9

Q. 250VII/29Italy

Improved distribution of time-signals

Rec. 375
Q. 249S.P. 250A

VII/30I.F.R.B.

Special monitoring programmes covering thefrequency bands allocated exclusively to thestandard-frequency service

VII/31Italy

The new IBF schedule

VII/32

Study Group VII

Summary record of the first meeting

VII/33

Working Group VII-B

Deletion of Report 258

VII/34

Working Group VII-B

Revision of Recommendation 376

VII/35Working Group VII-A

Single-sideband operation for the standard
frequency and time-signal service

VII/36

Working Group VII-B

Standard-frequency and time-signal emissions

VII/37

Working Group VII-B

Revision of S.P. 140A(VII)Mod.
to Res. 14

YII/38Working Group VII-B

Draft Opinion

YII/39Working Group VII-B

Studies and experiments concerned with
time-signal emissions

Y11/40Workinh Group VII-A

Draft Study Programme-Time-signal emissions

Draft S.P.

VII/41

Working Group VII-A

Standard-frequency and time-signal emissions

Draft Rec.

VII/42Working Group VII-A

Instability of standard-frequency generators

Draft S.P.

VII./43

Working Group VII-A

Frequency spectrum conservation for highprecision time-signals

Draft Rep.

VII/44

Working Group VII-A

Instability of standard-frequency generators

Draft Rep.

VII/45Working Group VII-A

Dissemination of standard-frequencies andtime-signals

Draft Q.

VII/46

Working Group VII-A

Stability and accuracy of standard-frequency
and time-signals as received

Draftmod. toRep. 271

VII/47

Working Group VII-B

Standard-frequency and time-signal emissionsin additional frequency bands

Draft Op.

VII/48Working Group VII-B

International comparison of standardfrequency and time-signal transmissions

Draft S.P.

Draft Op.

— 321 —Doc.

OriginTitle

Reference

VII/49Working Group YII-A

Standard-frequency and time-signal emissionsin additional frequency bands

Draft Rec.

VII/50C.C.I.R.
Secretariat

List of documents issued (VII/1 to VIII/50)

VII/51

Working GroupYII-ASingle-sideband operation for the standardfrequency and time-signal service

Draft Rep.

VII/52Working Group VII-B

Reduction of mutual interference between
standard-frequency and time-signal emissions

Draft Rep.

VII/53

Study Group YII

Summary record of the second meeting

VII/54

Study Group VII

Modifications to Table I

Rep. 267

YII/55

Study Group VII

Standard-frequencies and time-signals

Draft Rep.

VII/56

Study Group VII

Summary record of the third and last meeting

VII/57(IV/166)(VIII/67)(IX/159)

C.C.I.R.
Secretariat

List of participants - Interim meetings (MonteCarlo, 1965)

VII/58C.C.I.R.
Secretariat

List of documents issued (VII/51 to VII/58)

VII/59Czechoslovak
S.R.

Elimination of tone modulation of station
OMA on 2-5 MHz

Rep. 269
Rep. 267
S.P. 140A
Q. 140VII/60

United Kingdom

Dissemination of standard-frequencies andtime-signals

Q. 289Draft Rep.

VII/61

United Kingdom

Standard-frequency and time-signal emissionsin additional frequency bands

Q. 249Draft Rep.

VII/62and Corr.l

United Statesof America

A precision pulse-operated electronic phaseshifter and frequency translator

S.P. 140E

VII/63and Corr.l

United Statesof America

Draft Study Programme - Dissemination ofstandard-frequencies by carrier-frequency
stabilization

VII/64Italy

IBF station

S.P. 140C

VII/65Italy

Time-signal emissions with spectrum conserva­
tion in the VLF bandQ. 249S.P. 250A

YII/66

Japan

Report on an experiment on clock-pulse
synchronization using “ Relay II ” satellite

Q. 250
S.P. 250D

VII/67

Japan

Proposed modifications to Draft Report
H.d(VII) - Standard-frequencies and timesignals

Draft Rep.

VII/68Japan

Report on standard-frequency broadcast at
station JJM-6/JG2AS

Draft Rec.
Draft Rep.

V II/69

A ustralia

Proposed modification to Draft Recommendation H.a(VII) - Standard-frequency and timesignal emissions

Draft Rec.

21

I

— 322 —Doc.

OriginTitle

Reference

VII/70

United Statesof America

Some systems for obtaining time and frequency
information on radio emissions

S.P. 140E
Draft Op.

VII/71

United Statesof America

Possible modifications to the present systemof emissions of time and frequency

S.P. 140E
Draft Op.

VII/72

United Statesof America

A system for obtaining time and frequency
information on radio emissions

S.P. 140E
Draft Op.

VII/73

United Statesof America

A simple system for obtaining time andfrequency information on radio emissions

S.P. 140E
Draft Op.

YII/74

United Statesof America

A method for classifying systems whichyield time and frequency information fromthe same radio emission

S.P. 140E

VII/75Chairman,
Study Group VII

Report by the Chairman, Study Group VII Standard-frequencies and time-signals

VII/76

SwitzerlandStandard-frequency and time-signal trans­missions by HBG

Q. 140VII/77

Italy

Standard-frequency and time-signal emissionsProposals for a complete signals schedule

Draft S.P.
140E
Draft Op.

VII/78Study Group VII

Summary record of the first meeting

VII/79Working Group
VII-A

Draft Study Programme - Dissemination ofstandard-frequencies by carrier frequency
stabilization of broadcasting and televisionemissions

VII/80Working Group
VII-A

Modification to Draft Report H.i(VII) Single-sideband operation for the standardfrequency and time-signal service

S.P. MOB

VII/81

Working GroupVII-A

New text Draft Report H.g(VII) - Stability
and accuracy of standard-frequency andtime-signals as received

Q. 250VII/82and Corr.lStudy Group VII

Draft Report - Intercomparisons of timescales by various methods

S.P. 250D

VII/83

Study Group VII

Proposed new text of Draft Report H.h(VII) Instability of standard-frequency generators

S.P. 250B

VII/84

Study Group VII

Proposed modifications to Draft Recommen­
dation H.a(VII) - Standard-frequency andtime-signal emissions

VII/85and Rev.l

Study Group VII

Draft Report - Comparative statistics concern­
ing the properties of UT and AT radio
emissions

S.P. 140E

VII/86and Rev.l

Study Group VII

Draft Report - A method for classifying
systems which yield time and frequency
information from the same radio emission

S.P. 140E

VII/87and Rev.l

Study Group VII

Proposed
H.f(VII)

VII/88Working Group
VII-B

Draft Opinion - Studies and experiments
concerned with time-signal emissions

VII/89Working Group
VII-B

Proposed ammendments to Draft Report
H.e(VII)

amendments

to-Draft Report
Q. 140

— 323 —OriginV II/90

VII/91
VII/92
VII/93
VII/94
VII/95Working Group
VII-B
Working Groups
VII-A and VII-B
Study Group VII
Study Group VII
Study Group VII
C.C.I.R.
Secretariat

Title

Proposed amendments to Tables I and II
of Draft Report H.d(VII)
Draft Report H.d(VII) - Standard-frequencies
and time-signals
Summary record of the second meeting
Summary record of thethird meeting
Status of texts
List of documents issued (VII/59 to VII/95)

Reference

Q. 140I

LIST OF DOCUMENTS OF THE Xlth PLENARY ASSEMBLYESTABLISHED BY STUDY GROUP VII
Doc.

Title

Final text

VII/1001
VII/1002

Standard-frequency and time-signal emissions
Avoidance of external interference with emissions of
the standard-frequency service in the bands allocatedto that service
Standard-frequency and time-signal emissions in additional frequency bands
Standard-frequency and time-signal emissions in additional frequency bands
Special monitoring campaigns by the I.F.R.B. with aview to clearing the bands allocated exclusively to thestandard-frequency service
Stability and accuracy of standard-frequency and timesignals as received
Single-sideband operation for the standard-frequency
and time-signal service
Intercomparisons of time scales by various methods
Reduction of mutual interference between standardfrequency and time-signal emissions
Instability of standard-frequency generators
Studies and experiments concerned with time-signal
emissionsStandard-frequency and time-signal emissions
Dissemination of standard-frequencies by carrier-frequency
stabilization of broadcasting emissions
Standard-frequencies and time-signals
Comparative statistics concerning the properties of UT
and AT radio emissions
A method for classifying systems which yield time andfrequency information from the same radio emission
Frequency spectrum conservation for high precisiontime-signals
List of documents issued (VII/1001 to VII/1018)

Res. 14-1
Rec. 376-1

VII/1003
VII/1004
VII/1005
VII/1006
VII/1007
VII/1008
VII/1009
VII/1010
VII/1011
VII/1012
VII/1013
VII/1014
VII/1015
VII/1016
VIII/1017
VII/1018

Rec. 375-1
Op. 27
Op. 28
Rep. 271-1
Rep. 362
Rep. 363
Rep. 269-1
Rep. 364
Op. 26
Rec. 374-1
S.P. 4A/VII
Rep. 267-1
Rep. 365
Rep. 366
Rep. 270-1

— 325 —Rec. 182-1

RECOMMENDATIONS OF SECTION J (MONITORING OF EMISSIONS)RECOM M ENDATION 182-1
AUTOMATIC M ONITORING OF OCCUPANCY
OF THE RADIO-FREQUENCYSPECTRUM(Q uestion 9/VIII)
The C.C.I.R.,(1956 - 1966)CONSIDERING(a) that the increasing demand of radio services requires the most efficient use of the radio­frequency spectrum;(b) that the most efficient use of the spectrum can be arranged only when the distribution intime, magnitude and direction of the signals occupying it is known;(c) that automatic monitoring equipment is now in use by Administrations and that further
development in automatic observation is foreseen, including methods for the analysis ofrecords;(d) that, by the use of automatic monitoring equipment, a number of parameters can be eva­
luated which are of considerable value in enabling more efficient utilization of the spectrum;
UNANIMOUSLY RECOMMENDS

1.

that, although automatic monitoring equipment will not completely replace manual observ­
ations, it is a valuable aid. Administrations should be encouraged to undertake the use
and further development of such equipment;

2.

that, although further study is needed to enable Administrations and frequency-planning
authorities to derive the greatest benefit from the records produced, it is desirable that equip­
ment should possess the following principal characteristics:- total frequency range- minimum 2 to 30 MHz;
desirable 10 kHz to 30 MHz or more;- swept frequency range
variable, typical range 20 to 1000 kHz;- number of sweeps per hourvariable, 30 to 180;
- maximum rate of sweeping
variable; dependent on the desired frequency
resolu­tion for the band being swept and the class or classesof emission being recorded;- sensitivity'
1 pV/m or better;- resolving power
variable; approximately 100 to 5000 Hz;- signal characteristics recorded- carrier frequency,- bandwidth^- field-strength,- duration of occupancy;- size of records
paper chart 20 cm x 32 cm for twenty-fourhours;
calibration at intervals of 1, 10 or 100 kHz as appro­
priate.
Note. - Frequency resolving-power is the smallest frequency difference between two stable
carriers of the same level which can be distinguished. For equipment using oscilloscopes,

Rec. 182-1, 377-1— 326 —

this power is the limit to which two stable carriers of the same level can be observed
separately with a difference of 3 dB between the peak levels of the emissions and theminimum level between those peaks (see Fig.).
3.

that it is desirable that the records should also contain, if possible, the following informa­tion :- name and location of monitoring station;- date and period of recording;- frequency band;- signal identification, as appropriate;- class of emission, as appropriate;- direction of signal;- noise level.

Carrier A Carrier B
Frequency
F ig u r e

RECOM M ENDATION 377-1
ACCURACY OF FREQUENCY MEASUREMENTS
AT M ONITORING STATIONS(Question 1/VIII)
The C.C.I.R.,(1948 - 1956 - 1959 - 1963 - 1966)CONSIDERING(a) the requirements of the Administrations, of international organizations carrying out moni­
toring observations and of the I.F.R.B., in respect of the frequency measurements necessary
for the efficient performance of their duties;(b) the general availability of suitable monitoring equipment for frequency measurements;

— 327 —Rec. 377-1(c) that it is desirable that the errors of frequency measurement shall not exceed one-tenth of
the frequency tolerances specified in Appendix 3 to the Radio Regulations, Geneva, 1959;
UNANIMOUSLY RECOMMENDS

that monitoring equipment and procedures shall be such that frequency measurements shallbe made with an accuracy equal to, or better than, that specified in the following Table:
Type o f measurement

Accuracy

Measurements of the frequencies of stations, except
broadcasting stations, operating in the band 10 kHz
to 4000 kHz±5 parts in 106 (or, where this would
be less than ±1 Hz, to an accuracy of±1 Hz)

Measurements of the frequencies of broadcastingstations, operating in the band 10 kHz to 4000 kHz±1 Hz

Measurements of the frequencies of stations, except
television broadcasting stations, operating in theband 4000 kHz to 500 MHz±1-5 parts in 106

Measurements of the frequencies of stations, except
television broadcasting stations, operating in theband 500 MHz to 10-5 GHz±1 part in 105

Measurements of the frequencies of television broad­casting stations, operating in the band 30 MHz to1000 MHz±100 Hz

Measurements of the frequencies of stations, operat­
ing above 10-5 GHz±5 parts in 105

Note 1. - It is realized that, while the accuracies quoted above are sufficient for international
monitoring, higher accuracies may be needed to meet national requirements.
Note 2. - For frequency measurements made solely to investigate occupancy of frequency
channels, the permissible error for stations operating in the band 10 kHz to 30 MHz is ± 3
parts in 105.
Note 3. - When compared with the table of ultimate tolerances for transmitters adopted in
Geneva, 1963 (Report 181-1, Table I, Column 4), it is apparent that, if and when these ulti­
mate tolerances are made part of the Radio Regulations, the accuracies of measurement
as indicated in the above Table will, in some cases, be inadequate to maintain the desired
1 to 10 ratio of measurement error to station tolerance.

Rec. 378-1— 328 —

RECOMMENDATION 378-1

ACCURACY OF FIELD-STRENGTH MEASUREMENTS
AT MONITORING STATIONS(Q uestion 3/VIII)
The C.C.I.R.,(1953 - 1956 - 1963 - 1966)CONSIDERING(a) that field-strength measurements are made at monitoring stations in the frequency range
10 kHz to 1 GHz;(b) that accurate measurements, for use in connection with the international registration andassignment of frequencies, may be desirable;(c) that the publication of such data from monitoring stations is also desirable;
UNANIMOUSLY RECOMMENDS

1. that, to obtain the accuracies specified in § 2, the field-strength measuring equipment atmonitoring stations should be installed and operated in accordance with the Annex to thisRecommendation;
2. that, except where there are limitations due to receiver noise-level, atmospheric noise or
external interference, the accuracy to be expected in field-strength measurements, at values
above 1 gV/m, should be:
Frequency band (MHz)Below 30
30 to 1000

. Accuracy of measurement (dB)±2± 3

3. that when, because of limitations of measuring instruments, interference, signal instability
or for other reasons, the accuracies shown in § 2 are not obtainable, the measurements should
nevertheless receive due consideration commensurate with the accuracy indicated.
ANNEX
1. Fixed antenna installation
1.1 Frequencies o f 30 M H z and below
It is recommended that, for frequencies of 30 MHz and below, vertical antennae shorter
than one-fourth wavelength should be used, with ground systems consisting either of buried
radial conductors at least twice the length of the antenna and spaced 30° or less apart, orof an equivalent ground screen.
It is necessary to ensure that no significant distortion of the field being measured iscaused by obstructions, buildings, buried pipes, etc.
Vertical antennae, as described above, are recommended as standard for field-strength
measurement by monitoring stations, for ionospheric signals at frequencies of 30 MHz
and below for the following reasons:1.1.1 it is generally accepted that random variations in polarization of ionospheric waves
are such that the vertically polarized component is, in general, substantially equal
to the horizontal component;

— 329 —Rec. 378-1

1.1.2 the response of a vertical antenna, shorter than 1/4 of a wavelength, is substantiallyindependent of frequency.
1.2 Frequencies above 30 M H z
Antennae for field-strength measurement at frequencies above 30 MHz are recommended
to conform to the following conditions:1.2.1 The receiving antenna must have the same polarization as the transmitting antenna.
For these frequencies, short monopole antennae, half-wave dipoles and high-gain
antennae are appropriate.
1.2.2 It is preferable that the antennae be located at a height of 10 m above ground.
1.2.3 Consideration should be given to environmental conditions (e.g. terrain and obstruc­tions), to minimize factors reducing accuracy.
1.3 Antenna factor
The error in the determination of the antenna factor should be kept within 1 dB. The
antenna factor takes into account coupling or mismatch losses between the antenna andthe receiver, in the parts not common to the measuring and calibrating circuits.
2.

ReceiverThe receiver should have high inherent stability with respect to gain, frequency, band­
width and attenuation. Particular attention is drawn to the desirability of using voltage
regulators and crystal-controlled oscillators to limit the effect of the receiver on the overall
accuracy of field-strength measurements.

3.

Calibration
The field-strength-measuring installation should be calibrated as required to maintainthe accuracies given in § 2 of this Recommendation. A suitable method of calibration,
which takes into account the requirements of § 1.3, involves comparison of the indicatedsignal levels observed with the measuring equipment with the actual field strength, as deter­
mined by a calibrated field-strength meter of known accuracy, of emissions from stations
operating on or near the frequency on which regular field-strength measurements are to be
performed. Where such measurements are made over an extended frequency range, a cali­
bration curve may be prepared based on comparison measurements at frequent intervals
over the frequency range of interest. When performing these comparisons, the monitoringstation antenna and the field-strength meter antenna should have the same polarization (e.g.
both antennae adjusted for reception of vertically-polarized emissions, or both for hori­zontally-polarized emissions). To insure against variations in receiver gain, it is desirable
to check the receiver at frequent intervals (e.g. daily) with a radio-frequency standard-signal
generator of known and stable characteristics.

B ib l io g r a p h y

1.
2.

t
Recommendations U.R.S.I., Commission 1 (1960).
S e lb y , M. C. Accurate RF voltages, Trans. A.I.E.E., (Communications and Electronics), 6, 158—
164 (May, 1953).

I

Rec. 379-1— 330 —

RECOM M ENDATION 379-1
IDENTIFICATION OF RADIO STATIONS(Question 14/VIII)
The C.C.I.R.,(1951 - 1953 - 1956 - 1959 - 1963 - 1966)CONSIDERING(a) that the Radio Regulations, Geneva, 1959, Article 19, set forth requirements for transmis­
sions of call signs and state that each radio station provided with a call sign from the inter­national series must, unless otherwise provided, transmit this call sign during the courseof its emission;(b) that certain types o f radio stations are exempted from the necessity of having an internationalcall sign, for example, stations which are identified by other means;(c) that, in some cases, the requirement to transmit the identifying signal by interrupting thetraffic imposes difficulties;(d) that methods for identifying certain complex types of emission have been evolved;
UNANIMOUSLY RECOMMENDS

1. that for the purpose of identification, the identifying signal should be transmitted, using:
1.1 International Morse code with classes of emission A l, A2, FI or F2, preferably transmitted
at manual speed; or
1.2 five-unit code (International Telegraph Alphabet No. 2) with classes of emission A l, A2
or F I, at the standardized speed of 50 bauds; or
1.3 speech in clear;
2.

that, if the station does not desire to interrupt traffic for identification, it should superimpose
the identifying signal on the traffic by using the following methods:

2.1 Class o f emission FI (especially for high-speed or multi-channel operation): additional modula­tion (frequency or phase) of the carrier by the identifying signal in International Morse code;
2.2 Single- or independent-sideband emissions: amplitude keying of the reduced carrier or someother pilot frequency;
2.2.1 keying o f the reduced carrier, with a difference in level of 5 dB, gives a satisfactory
compromise between an acceptable degree of distortion of the traffic signals and thesuitability for identification purposes, especially if the identifying signal is repeated;
Note. - With reduced-carrier emissions the above-mentioned method can only beapplied if receivers without automatic frequency control are used.
2.2.2 keying a pilot frequency lower than the lowest traffic modulation frequency provides
a satisfactory means of identification for suppressed carrier emissions;
2.3 Facsimile transmissions employing class o f emission A4: amplitude-modulation, at a frequency
below the lowest used for the facsimile modulation. When single-sideband transmission
is used, amplitude keying, as in § 2.2 may be used;
3.

that, to avoid additional complexity in the equipment and operation of transmitting sta­tions, every reasonable effort should be made to provide monitoring stations with equip­
ment suitable for the reception of identifying signals of all stations;

— 331 —4.

Rec. 379-1, 442, 443

that Administrations should be encouraged to cooperate directly with one another in carryingout tests of identification methods. Administrations are also invited to inform the I.F.R.B.,
in advance of such tests, of new methods of identification to facilitate cooperative observa­
tions and also to afford other Administrations the opportunity to become acquainted withsuch methods for the identification of radio stations.

RECOM M ENDATION 442
EXPEDITIOUS M ETHOD OF DETERM INING FIELD STRENGTH AT
M ONITORING STATIONS(Question 4/VIII)
The C.C.I.R.,(1966)CONSIDERING(a) that stations participating in the international monitoring system, as a part of their normal
work, need to make expeditious measurements of the field strength of harmful interference;(b) that a lower degree of accuracy than that specified in Recommendation 378-1 can be accepted,
in the frequency band from 12 kHz to 30 MHz,UNANIMOUSLY RECOMMENDS

that, for the expeditious measurement of field strength at monitoring stations, a method
either of substitution or of overall calibration of the measurement system, providing an
accuracy better than ± 6 dB be adopted from among the methods specified in Report 368.

RECOM M ENDATION 443
BANDW IDTH MEASUREMENTS AT M ONITORING STATIONS(Question 5/VIII)
The C.C.I.R.,(1966)CONSIDERING(a) the need for the measurement of bandwidths of emissions at monitoring stations to promote
efficient use of the radio-frequency spectrum;(b) that the equipment for measuring bandwidths at transmitting stations does not produce
accurate measurements when employed at monitoring stations;(c j the slow progress of studies concerning the best equipment and methods for bandwidth
measurements;(d) the need for a uniform estimate of bandwidths at monitoring stations, to enable the I.F.R.B.
to compare the results obtained by different monitoring stations;(e) Report 275-1;

— 332 —Rec. 443
UNANIMOUSLY RECOMMENDS

that, until a method of measurement in monitoring stations can be devised that will conformto the definition in No. 90 of the Radio Regulations, Geneva, 1959, the monitoring stations
should adopt, provisionally, as an estimation of the bandwidth, a method consistingof measuring the bandwidth at 6 dB and at 26 dB.
Note 1. - An “ x dB ” bandwidth should be regarded as that band outside of which discrete
components of the spectrum of the emission are attenuated to an amplitude x dB ormore below the level of the peak value of the emission, as indicated by a spectrum
analyser (see Report 324)
Note 2. - It is recognized that in measuring bandwidth of emissions, the results obtainedby this method may have no simple relationship to the “ occupied bandwidth ” as definedin No. 90 of the Radio Regulations, Geneva, 1959.

Rep. 272-1— 333 —REPORTS OF SECTION J (MONITORING OF EMISSIONS)REPORT 272-1 *FREQUENCY MEASUREM ENTS AT M ONITORING STATIONS(Question 1/VIII)(1956- 1959- 1963 - 1966)
Question 1/VIII seeks information on the desirable ratio of the error of frequency meas­
urement to the permissible tolerances of emission and the accuracy required for frequencies
extending up to, in certain cases, at least 10-5 GHz.
Information on equipment, accuracy of measurement and methods, is contained inDocs. VIII/1 (U.S.A.), V III/13 (Japan), VIII/18 (Japan), VIII/27 (United Kingdom) andVIII/28 (United Kingdom), Washington, 1962. The information available at present may
be summarized as follows.
1.

General

1.1 When an individual measurement of a radio station is made, its accuracy can be estimatedfrom a knowledge of all of the factors (except perhaps that of Doppler effect), which pro­
duced the error. The sources of error which should be known to the measurer, are: themaximum error in the frequency standard of reference; the maximum instability error of
the transfer oscillator and the error of setting that oscillator to zero-beat with the signal.
Inasmuch as the direction of errors, other than that of the reference standard, will not usually
be known, the errors of measurement should be provisionally estimated, until an answer
to Study Programme 1A/VIII is obtained, as if they were all in the same direction after allow­
ing for any known error of the reference standard.
1.2 It is considered, that a conservative ratio of error to tolerance as applied to the majorityof frequency measurements, is to be preferred over a ratio difficult to obtain. With a conserv­
ative ratio, the measuring equipment may be operated well within its capabilities with agreater degree of assurance that all measurements meet the desired minimum accuracy.
1.3 The ratio of 1 to 10 between the error of measurement and the tolerance appears to be areasonable criterion to be retained at least until such time as conclusions are reached in thework of Study Programme 1A/VIII. In this study, it may be desirable to adopt a statisticalmethod of arriving at the accuracy of measurement of an unknown frequency (seeDoc. VIII/18 (Japan), Washington, 1962).
2.

Accuracy of measurement

With regard to § 1 of Question 1/VIII, on the accuracy of frequency measurements which
can be accomplished at monitoring stations, the following statements may be made:2.1 The accuracy of the secondary standard of a frequency measurement installation is determinedby calibration. A stability of ± 1 part in 109 or better can be achieved with currently avail­able standards, including those designed for mobile use. The accuracy may not exceed
dt 1 part in 107 when using standard-frequency transmissions received over a sky-wave path.
However, by selecting a time of day for the comparison during which sky-wave propagation
conditions are most stable (usually around noon of the path mid-point), and by continuing
the comparison over a period of several minutes, accuracy of a few parts in 108 is readily* This Report was adopted unanimously.

— 334 —Rep. 272-1

achievable. Where ground-wave H F or usable VLF/LF emissions from standard-frequency
stations are available, the secondary standard accuracy may be maintained to better than
± 1 part in 108.
Where greater accuracy is required, either for fixed or mobile installations, use may
be made of an atomic frequency standard. Atomic standards weighing less than 20 kg,
requiring 50 W or less of operating power, and having an accuracy of ± 1 part in 109 or
better, are available.
2.2 The methods of measurement usually employed result in the determination of the instantan­
eous frequency as received. Therefore, when measuring distant stations, due regard mustbe given to frequency shifts caused by varying propagation conditions (e.g. Doppler effect).
Errors, due to the use of a stable transfer oscillator, can be reduced to a negligible amountby the use of an oscilloscope for zero-beat adjustment. In anticipation of the extensive
use of YLF/LF standard-frequency emissions, the desirability of future reduction of theerror to an appropriate smaller value should be kept in mind. This is of particular import­
ance in connection with services in which a 1 to 10 ratio of measurement error to station
tolerance cannot be achieved with a frequency standard having an accuracy of only
± 1 part in 107.
2.3 When compared with the table of ultimate tolerances for transmitters adopted by the C.C.I.R.
at Geneva in 1963 (Report 181-1, Vol. I, Table I, Column 4), it is apparent that, if and whenthese ultimate tolerances are made part of the Radio Regulations, the accuracies of meas­
urement as indicated in the following Table will, in some cases, be inadequate to maintainthe desired 1 to 10 ratio of measurement error to station tolerance.

T a b leI

Accuracy o f measurement attainable under optimum conditions at fixed andmobile monitoring stations (n is the integer equal to, or
immediately above, one thirtieth o f the measured frequency in MHz
Class o f emission

Fixed stations

Mobile stations

AO, A3, A3B±2-5 x 10-8±0-5 n Hz

± 4 x 10-8±0-5 n Hz

FI, Al±2-5 x 10-8±0-5 n Hz±2-5 Hz± 4 x 10-8±0-5 n Hz±2-5 Hz

FI, MUX±2-5 x 10-8±0-5 n Hz±10 Hz± 4 x 10-8±0-5 n Hz±10 Hz

F3 using discriminating
equipment±2-5 x 10-8±100 Hz± 4 x 10-8±100 Hz

2.4 For emissions with a discrete component at the assigned frequency, which can be identified,the accuracy is practically the same as for unmodulated emissions. For emissions having
discrete components which can be identified at other than the assigned frequency, the accuracy
is further limited by the accuracy with which the displacement is known.
2.5 Under conditions of fading, and where the measurement is made using a pattern on the screenof an oscilloscope, the measurement is performed only when there is sufficient signal strength,e.g. A l stations are measured only during on-keyed conditions and not during a field-strength
m in im u m period. Under these conditions the accuracies listed in Table I can be obtained.

— 335 —Rep. 272-1

2.6 Under conditions of interference between two amplitude-modulated stations, the frequencyof the weaker station can still be measured with the accuracy indicated in Table I, if thecarriers of the wanted and unwanted stations are spaced by at least 40 Hz. With a fieldstrength ratio between the wanted and the unwanted stations of 1 to 1, good measurements
may be made with the accuracy indicated in Table I, when the carriers are only spaced by
12 Hz. For a field-strength ratio of 2 to 1, the minimum frequency spacing at which goodresults are obtained is 2 Hz. These high accuracies of measurement are made possible,
even under conditions of interference by other stations, by visual observation of the Lissajous patterns produced on the oscilloscope screen by combining the heterodyne beat between
the received signal and the comparison frequency and a fixed standard-frequency of 1000 Hz.
By receiving mutually interfering stations on a direction-finding equipment, their ratio of
signal strengths at the receiver input can be improved, thus making possible measurementswith the accuracies shown in Table I at smaller carrier spacings.
2.7 Two interfering frequency-modulated stations can be measured for unfavourable fieldstrength ratios when the frequency separation between their carriers is at least 2 to 3 kHz.
The measurements are taken during periods of no modulation by heterodyning the wanted
carrier with the comparison frequency and observing the results on a panoramic display
screen. The accuracy will then be within ± 500 Hz. Here too, by employing a directionfinding technique, the received signal strength of the unwanted station may be sufficiently
attenuated to attain the accuracies indicated in Table I.
2.8 Measurements of carrier instability can be made, either as a series of measurements of instan­taneous frequencies employing the oscilloscope method or, with rapid variations of thecarrier frequency, the centre frequency can be determined by means of a discriminator equip­
ment, or a panoramic adaptor, resulting in an accuracy of measurement of the extreme
frequencies of about ± 50 Hz.
2.9 Keyed carriers can be measured by the oscilloscope method with the accuracies listed inTable I.
2.10 For suppressed carriers, individual frequencies o f the types listed under §§ 2.5, 2.6, 2.7, 2.8
and 2.9, which are contained in the emission spectrum, can be measured with the accuracies
listed in those paragraphs. For a carrier not completely suppressed, the measurement
can be made with the accuracy indicated in § 2.6.

3.

Equipment and methods

3.1 With regard to measurements above 50 MHz, the frequency measuring equipment of theindividual countries differs so much that it is only possible to comment generally upon them.
Administrations usually prefer to make measurements with nearly the same equipment
as that which they use for frequency measurements below 50 MHz. The extension to ahigher frequency range is effected by the use of harmonics of either a secondary standard
or a stable oscillator or by the use of a frequency synthesis method providing a single tunablefrequency. All equipment uses direct reading dials in conjunction either with electronic
counters or with visual indicators such as pointer instruments or oscilloscopes.
3.2 With regard to preferred equipment and methods for the measurement of frequency infrequency-modulated emissions, the carrier frequency may be measured by any of the usual
methods during intervals of no modulation. With modulation, it is common practice tomeasure the average frequency by means of a frequency counter. In many types of pro­gramme material, the peak excursions of an FM carrier in the positive and negative directions
may be considerably different while, at the same time, the average frequency will remain
constant. This non-symmetrical programme material may result, for example, from cer­tain combinations of a fundamental tone and its various harmonics. Then the averageover a period of several cycles at the lowest modulating frequency will approximate theunmodulated carrier frequency. Therefore, the averaging technique is valid under all normal

Rep. 272-1, 273-1— 336 —

conditions, provided the period of the frequency count is long compared with one cycle
at the lowest modulating frequency. Instabilities in the transmitter may, of course, resultin a shift in the average frequency o f the carrier, so that the frequency indicated by the counter
would differ somewhat from the unmodulated carrier frequency.
3.3 With the availability of portable battery-operated frequency standards, stable to ± 1 partin 108 per day, U H F television stations operating with ± 1000 Hz tolerance may be measured
to the recommended accuracy. A daily check against standard-frequency emissions
at the optimum time of the day as regards propagation stability will suffice to achieve an
accuracy of the standard considerably better than the ± 1 part in 107 that is required forthese measurements. For greater accuracy, such as might be involved where precision offset
techniques are used, very accurate measurements could be achieved by use of a portable
atomic standard. VLF standard-frequency emissions also provide a means of improving
the accuracy at mobile as well as fixed monitoring stations. Battery-operated equipment,
comprismg a selective VLF receiver and phase or time comparison circuitry, may be used
to permit accurate calibration of the frequency standard. Such comparison equipment,in combination with a battery-operated frequency standard and a transistorized electronic
counter, provides a convenient means of achieving a high degree of accuracy even undermobile conditions.
The importance and potential usefulness of statistical analyses of frequency measure­ment data is described in Doc. VIII/18, Washington, 1962. This document also suggests
a method of arriving at the accuracy of a measurement of an unknown frequency by obtain­
ing the standard deviation of a number of measurements made of a known frequency.
In Doc. VIII/27, Washington, 1962, the overall accuracy of frequency measurements,
attainable in the range 1 to 10 GHz, was indicated using a typical spectrum analyzer with thefollowing characteristics: varies from 8 kHz (for a 250 kHz sweep), to 100 kHz (for a 70 MHz
sweep), equivalent to ± 8 parts in 106 and ± 1 part in 104 respectively at a frequency of
1 GHz. Thus, an accuracy of ± 1 part in 105 would appear possible, in practice, for therange 1-10 GHz for the condition where the emission contains a known discrete component
whose position relative to the unmodulated carrier frequency is accurately known. Where
it is possible to obtain a beat frequency output, the accuracy of measurement may be increased
to ± 1 part in 106 or even better.
Bibliography
1.

V alet, G. and G eringer, N. Receiving and measuring stations for broadcasting purposes, European
Broadcasting Union Technical Monograph, No. 3102, Chapters III and IV (1965).

REPORT 273-1 *FIELD-STRENGTH MEASUREM ENTS AT M ONITORING STATIONS(Question 3/VIII)(1959 - 1963 - 1966)
Question 3/VIII seeks information on various aspects of the measurement of fieldstrength at monitoring stations, including the preferred methods and equipment for making
such measurements in connection with propagation studies, measurement problems peculiar
to certain special types of emissions (e.g., interrupted and reduced carriers and television
signals), measurements in the presence of noise and interference; together with determination* This Report was adopted unanimously.

— 337 —Rep. 273-1of the extent to which measurements at a distance can give useful information relative
to harmonic levels at the transmitter itself; and a determination of the most useful pro­gramme which can be carried out in fulfilling the needs of the I.F.R.B., other Study Groupsof the C.C.I.R. and other bodies.
The contributions (Docs. VIII/6, VIII/8, VIII/16, VIII/20 and VIII/22, Los Angeles,
1959, together with Docs. VIII/6 and VIII/25, Washington, 1962), are summarized herein.
In considering Question 3/VIII, reference should also be made to Report 227 which contains
useful information.

1.

Preferred methods and equipment

1.1 Methods o f measurement
A number of methods of making field-strength measurements at monitoring stations
are described, including:- continuous recording over periods of several hours;- continual sampling at short intervals (for example, for 5 s every two minutes) (see § 1.2.6
for details);- sampling at longer intervals (for example, for 10 min each 90 min).
In some instances, especially where a ground wave is being observed, a single shortperiod of measurement may suffice, depending upon the purpose for which the measure­ment is required.
In certain cases, e.g. measurements for the purpose of H F propagation studies, one
may require information concerning the overall propagation conditions over a band of
frequencies. The present method of automatic monitoring of spectrum occupancy will
yield only a very rough impression of the propagation conditions, since it does not discri­
minate between the various path directions and cannot make allowance for the difference
in distances between the transmitting stations and the location of the receiver. Therefore,
it may be expedient to make short records lasting about 10 min, over the entire high-frequency
band at intervals of about 90 min, of stations known to be working for 24 hours a day, so
chosen that the ranges of frequencies and distances of interest are well represented.
Time constants of the detector circuit for measuring non-interrupted carrier emissions
are selected according to the results desired, with values of the order of a few seconds on
both the charge and discharge cycles commonly used for average values. For quasi-peakvalues, a short charge time constant with a much longer discharge time constant is needed.
For the measurement of the quasi-peak values of field-strength of an emission withinterrupted carrier, a circuit may be employed with time-constants of 1 ms build-up timeand 600 ms decay time. When this method is not suitable (e.g. keyed pulses), because of
too long a build-up time, the measurement may be made by the substitution method using
a cathode-ray oscilloscope.

1.2 Measuring and recording equipment
1.2.1 General
A typical field-strength recording installation consists of a suitable antenna, asensitive receiver with a bandwidth appropriate to the emission to be recorded andincluding provisions for converting the received signal into a corresponding direct
current for operation of an associated recording device, and a standard signal generator
for use in calibrating the receiver in terms of radio-frequency voltage input levels.
22

— 338 —Rep. 273-1

To ensure minimum frequency drift, the conversion oscillators in the receivers are,wherever possible, controlled by quartz crystals. Stabilization of the alternating
current line voltage is provided by primary voltage regulators. Further protection
against fluctuation is obtained by stabilization of the d.c. voltages in the receiver.
Minimization of changes in receiver gain is accomplished by careful design of receivercircuits, by the aforementioned voltage stabilization and by operating the equipment
at an essentially constant temperature.
1.2.2 Antennae
For measurements in the low, medium and high frequency bands, a stub antenna
with impedance matching transformers or a wideband stub antenna with constantfeed impedance may be used. In some particular cases, however, a directional antenna
designed for a single frequency or a narrow band of frequencies may be preferred.
Field-strength measurements on VHF and U H F bands are best made by means of a
wideband dipole or a special directional antenna (e.g. a dipole installed in a cornerreflector or parabolic reflector). In the upper part of the U H F band and in the SHF
band successful use has been made of log-periodic antennae, either with or without
parabolic reflectors, so installed that near optimum results, with low standing-wave
ratios, are achieved over a frequency range of 2/1 or greater.
1.2.3 Recorders
Although ink-line, strip-chart recorders continue in common use, direct recordingof the statistical distribution of the variations in field-strength by automatic distribution
counters is also being done. Another method, reported by the Federal Republic of
Germany, makes use of magnetic tape equipment. In this method, the variations of
the d.c. yoltage on the a.v.c. line, representative of the field-strength, are transformed
to audio frequencies (50 to 300 Hz), by means of an oscillator controlled by a reactancevalve and used to modulate the amplitude of a low frequency carrier (about 5 kHz).
1.2.4 The calibrating equipment
The calibration process involves two phases:- determination of the effective height of the receiving antenna, taking into accountlosses in the connecting transmission line;- daily, or more frequent, receiver calibration, to eliminate possible errors due toprogressive changes in sensitivity.
Doc. VIII/6, Los Angeles, 1959, suggests that it is good practice to calibrate ini­
tially the field-strength meters, for use on frequencies below about 30 MHz, on a loop
antenna. The loop is placed at a small defined distance from a Lecher line whichis terminated with a resistance equal to its surge impedance, which can be coupled
to a radio-frequency source. If the current flowing in the Lecher line is known, thefield intersecting the loop can be computed.
To determine the effective height of an antenna, the input signal to the receiveris compared with the indication of a calibrated field-strength meter.
1.2.5 Frequency ranges involved
Although field-strength measurements have been made over almost the entire
usable spectrum, most of the activity up to the present has been concentrated at fre­quencies below 1 GHz. As greater use is made of the microwave frequencies forspace-to-ground transmissions, it seems likely that there will be increased activity infield-strength measurements in these higher frequency ranges. Examples of measurement

— 339 —Rep. 273-1

programmes for field-strength which are now under way, or have been concluded
in recent years, a re :- in the 540 to 1600 kHz broadcast band, continuous recordings have been madeduring the past two sunspot cycles;- VHF and U H F field-strength measurements (FM and television broadcast stations),
have been in progress since 1946 at various locations over paths having lengths from60 to 1000 km (37 to 620 miles);- certain monitoring stations in the U.S.A. are determining the field-strength of expe­
rimental U H F television stations located in aircraft. These experiments are donein connection with extending the service area;- a monitoring station in the United Kingdom is making regular field-strength record­
ings of incoming radiotelegraph signals from Accra, Bombay and Colombo, as apartial contribution to Resolution 7-1 (Sky-wave field-strength and transmission
loss at frequencies between the approximate limits of 1-5 and 40 MHz;- the station in the United Kingdom has also made long-term field-strength measure­ments of ten distant VHF (metric) and U FH (decimetric) transmitters and two
distant ionospheric-scatter transmitters and the data obtained have been summarized
and submitted to the C.C.I.R. (Doc. VIII/25, Los Angeles, 1959).

1.2.6 Analysis o f the records
Recordings made in the 540 to 1600 kHz broadcast band are analysed, to obtainhourly median values of field-strength and from these data monthly median values
may be obtained. Particular attention is given to the second hour after sunset for the
mid-point of the path between transmitter and receiver. Values for other hours andfor levels other than the median may be obtained in a similar manner.
In the HF, VHF and U H F bands, it is often desirable to determine the upper
decile (Fio), the median (F50) and the lower decile (F90 ) values. The median value, indB relative to lpV/m, is a desirable form of presentation of measurements at discrete
frequencies for propagation studies.
A system of analysis, which eliminates much of the human effort, is based upona method of recording periodic samples of signal strength, using regular equipmentwith simple modification rather than a continuous registration of signal levels. A timeswitch operated by a synchronous motor is provided in each recorder so that a contact
is closed once every two minutes for a duration of about five seconds. This contact
is inserted in an appropriate circuit in the receiver, where it will cause the recording
instrument to respond by drawing an inked line with each operation of the switch.
The recorder chart will then show a series of transverse lines. When operated at theusual speed of about 75 mm (three inches) per hour, the paper will show 4 lines per cm(10 lines per inch), each having an amplitude with a known relationship to field-strength.
It has been found that 30 samples per hour will yield an accuracy adequate for mostapplications. After the recording have been made, the charts are analysed on equip­
ment specially constructed for this purpose. This equipment may consist of aphotoelectric cell arrangement for counting the hourly number of samples withamplitudes exceeding a pre-set level, while the chart paper moves through anappropriate optical system. Hourly numbers of samples at each level are counted
automatically and printed by means of an electrical counter and a sequential countprinter. These numbers may be directly converted to equivalent percentages of time,
for all signals exceeding given levels. The data are thus available in hourly values,

Rep. 273-1— 340 —V

from which monthly and yearly distribution curves may be plotted, showing dailyand seasonal variations of field-strength at any percentile levels.

2.

Preferred equipment and methods of measurement in the presence of noise and interference
No particular problems are presented in measuring the field-strength of emissions withinterrupted carrier and of television video signals in the presence of noise and interference,as long as the noise and interference peak levels are below the level of the wanted signal,
since the quasi-peak indicating device will respond to the highest level present. However,in the case where the peaks of noise and interference are greater in intensity than the wanted
emission, other techniques must be used. In some instances, reduction of the receiver
bandwidth may be effective in eliminating unwanted emissions. The effect of high noise
peaks of short duration can possibly be avoided, by increasing the charge time-constant of
the detector sufficiently to minimize receiver response to the noise without appreciable reduc­tion in the indicated level of the wanted signal. The efficacy of such expedients would,of course, depend on circumstances and very likely would not be valid under conditionsof heavy fading. Doc. VIII/16, Los Angeles, 1959, describes a method used in Japan, forthe measurement of emissions in the presence of adjacent-channel interference, using a pano­ramic unit attached to the equipment, so that an interfering emission may be separated
from the wanted signal and the field-strength represented by the deflection of the oscilloscope
trace caused by the interrupted carrier under study, may be determined by comparison witha signal from the equipment used for calibration purposes.

3.

Determination at a distance of relative radiation levels of fundamental and harmonic frequencies
of an emission
It would appear that this matter should be considered in two parts:- conditions where both the fundamental and the harmonic emissions toarrive at the measuring point over a ground-wave or line-of-sight path;be measured- where either the fundamental or the harmonic emission, or both, arrive at the measuringsite over a sky-wave path.
» The situation as regards these two modes of propagation will be considered separately.
3.1 Measurement o f radiation levels under conditions o f ground-wave or line-of-sight propagation
Study Group V, in response to a request for assistance on this matter, has referred Study
Group VIII to Report 227. This Report contains detailed information on making andevaluating such measurements, taking into account instrument errors, differing attenuation
rates at different frequencies and other variables.
3.2 Measurements o f radiation levels where sky-wave paths are involved
Study Group I has considered this matter, as evidenced by Recommendation 329-1 andStudy Programme 7A/I. Likewise, Study Group VI, in Reports 252-1 and 257-1 reviews
progress which has been made in determining the best method of calculating the field-strength
at a distance from the transmitter (ionospheric propagation), and describes plans for further
study of this matter.
It is expected that the results of the further deliberations of Study Groups I and VI will
be of benefit to the international monitoring system in its efforts to minimize interference
from spurious emissions. Pending the outcome of these deliberations, it would be highly
desirable for stations in the international monitoring system to have certain guide-lines
which might be followed in obtaining evidence of possible excessive radiation at the harmonicfrequency. While such evidence would not be conclusive, it might serve as an indicationthat close-in measurements should be made to verify the existence of harmonics at excessive

— 341 —Rep. 273-1, 275-1

levels. Appendix 4 of the Radio Regulations, Geneva, 1959, gives power limitations on
spurious emissions as measured at the antenna transmission line input. Although theseemissions may readily be measured at that point, there is no simple means of converting
the spurious power limitations given in Appendix 4 to equivalent field-strength at a distance.
Since it is the actual radiated spurious field-strength rather than the power into the antenna
which is of primary concern as an interference source, it might be well to consider establish­
ment of a limitation on spurious emissions, in terms of the maximum unattenuated fieldstrength at about 1600 m (1 mile). Having once established such a limit, the maximum
allowable inverse-distance field could readily be determined. Since the attenuation would
actually increase more rapidly than inversely with the distance, the measured value of the
spurious emission would be a conservative index of the actual radiated field, especially if
the condition continues over a period of several days. This limitation would be in addition
to, rather than a substitute for, the limitations on spurious power input to the antenna trans­mission line specified in Appendix 4. Admittedly, the results could not be compared directlywith measurements made at the transmitter. However, it would appear that such standards
might be of help to monitoring personnel in bringing about a reduction of interference due
to harmonic radiation.

4.

Additional propagation studies that are desirable
Resolution 7-1 points out the need for experimental data in the frequency range from
1-5 to 40 MHz for paths of different lengths and directions and requests that Administrations
and Members of the C.C.I.R. render assistance to Study Group VI on this matter.
B ibliography

1.
2.
3.

C hapin , E. W. Field-strength measurements. L.D. Report 6.3.1. (1 October, 1958) Federal Com­
munications Commission, Washington, 25, D.C.
Selby, M. C. Accurate RF voltages. Trans. A.I.E.E. (Communications and Electronics), 6, 158-164(May, 1953).
V alet, G. and G eringer, N. Receiving and measuring stations for broadcasting purposes.
European Broadcasting Union Technical Monograph No. 3102, Chapters III and IV (1965).

REPORT 275-1 *BANDW IDTH MEASUREMENT AT M ONITORING STATIONS(Question 5/VIII)(1953 - 1956 - 1959 - 1963 - 1966)

1.

General discussion of measurement techniques, considering the definition of occupied band­
width-No. 90 of the Radio Regulations, Geneva, 1959

1.1 Measurement o f power ratios
The present definition of occupied bandwidth suggests the principle described in Recom­
mendation 327-1, § 1.2 of measuring the ratio of the total power to the parts remaining
outside of the bandwidth being measured. It would be necessary to locate the upper andlower edges of the band, by totalling the power in the out-of-band components on the high* This Report was adopted unanimously.

Rep. 275-1— 342 —

side until the 0-5% value is obtained and then repeating this procedure for out-of-band
components below the band, starting in each case sufficiently far from the centre frequency
so that no appreciable energy is omitted from measurement.

1.2 Limitations in the accuracy o f bandwidth measurements made at a distance from the transmitter
Although a determination of occupied bandwidth of an emission, by the method of
measuring total power and out-of-band power, can be accomplished when the measurements
are made near the transmitter, this method is not generally applicable to measurements at
a distance from the transmitter where the presence of interfering emissions or noise tend
to mask the out-of-band signal components of interest. This is particularly true in thecrowded M F (band 6) and H F (band 7) portions of the spectrum, regions of primary interest
to international monitoring stations.
In spite of the very definite limitations which observations at a distance place upon
the accuracy of measurements of occupied bandwidth, approximate determinations havebeen found of value when monitoring the spectrum for enforcement of bandwidth limitations.
However, these non-precise measurements made at a distance, which are subject to inaccu­
racies for the reasons previously enumerated, should be considered as advisory only. Where
greater accuracy is required, measurements at the transmitter may be desirable.

1.3 Bandwidth measuring method which appears to be practicable for use at international monitor­
ing stations
It is the practice of some Administrations, in evaluating spectrum occupancy of anemission from a distant transmitter, to use the method described in Recommendation 327-1,§ 1.1. In using this method, the occupied bandwidth is considered to include discrete com­ponents attenuated less than 26 dB below the peak level of the emissions. This procedure
admittedly will not give a precise measurement of occupied bandwidth in terms of the defi­
nition in the Radio Regulations, Geneva, 1959. For example, it is possible that a particularemission will have numerous low-level components on either side of the main emission such,that their sum on each side would be equal to much more than 0-5 % of the total mean power
while having none of these discrete components exceeding the 26 dB level. In such a case,the occupied bandwidth, as determined at the transmitter by measuring power ratios, would
presumably be somewhat greater than when measured at a distance by the method describedin Recommendation 327-1, § 1.1.

2. Representative bandwidth measuring equipment
2.1 A spectrum analyser, of the type described in Recommendation 327-1, §1.1, is suitablefor use at monitoring stations. With this equipment, the emission spectrum is analysed bypassing each component successively through a narrow-band filter of fixed frequency, byheterodyning the signal with an external frequency, varied either automatically or manually.
For the measurement of narrow-band emissions, a spectrum analyser having a highdegree of resolution is desirable, so that an accurate display of the emission spectral distri­bution may be obtained. A typical instrument has a maximum resolution of 10 Hz andprovides a swept frequency range adjustable from 1 kHz to 100 kHz, together with a sweep
rate adjustable from 1 to 30 sweeps per second.
For the analysis of wide-band emissions, spectrum analysers are available which incor­
porate a complete receiver as well as those designed for use with general purpose receivers. A
typical instrument covers a frequency range from 10 MHz to 44 GHz with a sweep width
continuously variable from 200 kHz or less to as much as 70 MHz (at the higher frequencies).
The sweep rate is adjustable from 1 to 60 sweeps per second.

— 343 —Rep. 275-1

A major shortcoming of spectrum analysers, which use a single filter to sweep the entire
band under surveillance, is the incompatibility between high resolution and rapid sweep
rates, especially where a band of considerable width must be studied. A fast sweep rateis necessary to obtain a representative display of transient components. However, as thesweep rate is increased, the resolution becomes poorer so that significant components ofthe emission will not be displayed accurately. A number of systems have been devised to mini­
mize the sweep-rate versus resolution limitations. One method involves the division of
the band to be observed into as many as eighteen sub-bands, each of which is individuallyswept. The eighteen outputs are then displayed one at a time on a single cathode-ray tube
or simultaneously on separate tubes.
2.2 Doc. VIII/76, 1963-1966, describes two methods of estimating the occupied bandwidth interms of the power distribution of the emission. The first of the two methods is designed
primarily for the H F portion of the spectrum, while the second is reported to be useful forcomparatively broadband emissions in the VHF bands.
2.3 An energy spectrum recorder is described in Doc. VIII/13, Los Angeles, 1959. This device
makes a chart record of spectrum occupancy in terms of available power from a standard
antenna.
2.4 A device for measuring frequency shift, especially in questions concerning the monitoringof complicated emissions and those types of emissions using a synchronous high speed multi­
channel system, is described in Doc. VIII/29, Washington, 1962. This device permits simul­
taneous measurements of frequency shift of multiplex channels as well as a visual check on
the frequency shift signals.

3.

A somewhat different approach to the measurement of bandwidth is described as follows(see Doc. VIII/10 (Federal Republic of Germany), Los Angeles, 1959):
Endeavours have been made to determine the bandwidth occupied by an emission, by
way of the signal shape instead of by analysing the spectrum. Such experiments have been
made for class of emission A l only, starting from the fact that the bandwidth occupied
is a function of the shortest build-up (and decay) time of the emitted signals (see Recommenda­
tion 328-1, § 2.1.3).
As regards the effect of fading, a comparison between 60 single measurements of Al
emissions taken at the transmitter and in the far field (up to 425 km), resulted in a maximum
deviation of 16%. The average value of the deviations amounted to 4-8%. The differencesin the results of the measurements at the transmitter and those taken far away may be explainedby the deformation due to the fading effects of the signals. Measurements made under
extreme fading conditions will not yield satisfactory results.
The effect of interference was investigated by superimposing a received non-fading Al
signal with a simulated interference signal of variable frequency generated locally. It was
found that the wanted signals could still be evaluated with a signal-to-interference ratio
as low as 35 dB. With signal-to-interference ratios lower than 35 dB, evaluation was nolonger possible, because the 10% value of the wanted signal could not then be recognized.

4.

Spectrum analysers may also be valuable in the recognition and classification of emissions,particularly complex emissions. Many types of emission have certain peculiar combina­
tions of characteristics which, when viewed on a spectrum analyser by a trained observer,
may provide valuable information leading to the recognition of the emission. Photographsof spectrum analyser displays of known emissions may be kept available to the monitoring
observer for reference and for comparison with questionable emissions.
Spectrum analysers have also been used to advantage in connection with frequency
measurements in the presence of interference, where matching of the frequency of the measur­ing equipment against the unknown frequency by aural methods is difficult. By observing
the two signals on the spectrum analyser, the frequency of the measuring equipment may
be adjusted to that of the unknown carrier or to other discrete components in the signal.

5.

Although the estimations of the bandwidths, in terms of discrete components attenuatedless than 6 dB and less than 26 dB below the peak level of the emission, may have no direct
relationship with the “ occupied bandwidth ” as defined in No. 90 of the Radio Regulations,

— 344 —Rep. 275-1, 276-1

Geneva, 1959, such estimates can be of considerable value in detecting emissions occupyingexcessive bandwidths, and which may cause interference. The use of a standard methodby all monitoring stations in reporting estimates of bandwidth to the I.F.R.B. should also
assist the I.F.R.B in evaluating reports of different monitoring stations (see Report 324).
6.

Additional information concerning measurement of bandwidth may be found in Recom­
mendation 327-1.

7.

Conclusions

To explore fully the possible accuracy of observations at monitoring stations in estimat­
ing bandwidth, studies will be required to compare such estimates with measurements per­formed in conformance to the definition of “ occupied bandwidth ” in No. 90 of the Radio
Regulations. Such comparisons should include observations on various classes of emission
under good reception conditions and in the presence of interference. Likewise comparison
data on any new methods of estimating or measuring bandwidth, which may be reported
by Administrations, will also be helpful to Study Group VIII in evaluating such methods.

REPORT 276-1 *MONITORING OF RADIO EMISSIONS FROM SPACECRAFT
AT FIXED MONITORING STATIONS(Q uestion 6/VIII)(1963 - 1966)
Question 6/VIII seeks information concerning methods and equipment desirable formeasurement at fixed monitoring stations of emissions from spacecraft and practical meansof identification by monitoring stations of emissions from specific spacecraft.
Information concerning these matters is contained in Docs. VIII/3 (U.S.A.) and VIII/15(Japan), Washington, 1962. The information in these documents may be summarized asfollows:
1.

Techniques of measurement

1.1 General
The main factors influencing the necessity for different techniques of monitoring obser­
vation and measurement of emissions from spacecraft as contrasted with observations andmeasurements of emission originating from fixed or mobile radio stations on or near theearth are, with reference to spacecraft:- the difference between received and transmitted frequency, and the varying nature of
the received frequency, caused by the Doppler effect;- the generally weaker field-strength at the earth receiving point, due to distance and lowtransmitter power;- relatively short time that a signal from a near-earth orbiting satellite is receivable at a
fixed monitoring point.
* This Report was adopted unanimously.

— 345 —Rep. 276-1

Administrations launching spacecraft will, of necessity, continue to provide for therequired accurate tracking and telemetry reception to meet their special needs. However,monitoring stations responsible for the enforcement of domestic laws and regulations andengaging in international monitoring, pursuant to Article 13 o f the Radio Regulations, Geneva,
1959, will participate in space monitoring as a natural and necessary extension of their regularmonitoring facilities, techniques and operations.

1.2 Frequency measurements
When there is a relative velocity between the spacecraft and the monitoring station,a difference of frequency proportional to the relative velocity arises between the transmitted
and received signals owing to Doppler-shift effect. The apparent frequency of the trans­mitter in the case of an active satellite, as measured by a fixed monitoring station, is higher
than the source frequency when the satellite is approaching the monitoring station andlower when it is receding. A measurement gives the source frequency only at the instantwhen the relative velocity between the source and the monitoring station is zero.
To determine the source frequency and the extent of Doppler shift, the basic require­ment is a rapid frequency-measuring technique and a means of accurately timing each measure­ment. If frequency measurements are taken every few seconds and plotted against time,a curve is obtained from which the frequency at the point where the rate of change is greatest
can be estimated with reasonably good accuracy, possibly to within ± 1 part in 106.
Doc. VIII/15, Washington, 1962, describes a frequency measuring method whichuses a discriminator, the object of vjhich is to represent on a cathode-ray oscilloscope thewaveform obtained by mixing the receiver output with a low-frequency saw-tooth wave
(e.g. 25 or 50 Hz) from a separate source. The discriminator is used to determine the trans­mitted frequency by measuring the constantly changing frequency of the Doppler shift.
When the figure remains stationary on the oscilloscope, the receiver output frequency is
an exact multiple of the standard low-frequency. From the value of this exact multiple
and the local oscillator frequency in the receiver, the exact frequency can be determined.
By measuring the frequency each time the figure on the oscilloscope becomes stationary
and plotting this against time, the curve of the Doppler shift may be drawn.

1.3 Bandwidth measurements
The apparent bandwidth of a near-earth satellite, transmitted as measured at a fixedmonitoring station, varies because of the Doppler-shift effect in the same manner as described
for the carrier frequency. Although not of practical significance at present from an inter­
ference standpoint, it should be realized that the frequency shift is slightly greater for signal
components near the upper edge of the spectrum of the emission than for those near the
lower edge. This difference could amount to hundreds of cycles per second for the wide
bandwidths proposed for some of the future spacecraft transmissions, on frequencies above
1000 MHz. This effect causes the apparent bandwidth, as observed at the fixed monitoring
point, to vary slightly. However, it is doubtful that the currently available spectrum ana­lyzers have sufficient resolution to detect it when the entire signal is being observed, underoperating conditions of weak signal and relatively high background noise.

1.4 Measurements o f power flux density
For determination of power flux density at the surface of the earth of emissions from space­
craft, two methods are under consideration (see Nos. 470 N to 470 U of the Radio Regula­tions as approved by the Extraordinary Administrative Radio Conference, Geneva, 1963):

Rep. 276-1— 346 —- by measurement, using specialized equipment;- by calculation, based upon measurement of field strength converted to power flux-density
as follows:/ = 20 logic e - 25-77
where / = total power flux-density in dB above 1 W /m2,
e = field strength in V/m.

2.

Equipment and facility requirements

2.1 GeneralIn general, as in more conventional monitoring surveillance, equipment for monitoringsignals from spacecraft must have adequate flexibility to cover a wide range of frequencies,in contrast to the spot frequency coverage that suffices for the needs of a research or operat­
ing space agency. The location of the monitoring station should be such that interference
from man-made signals and noise is at a minimum.
Automatic sweeping of a band of frequencies, by varying the receiver tuning, and auto­
matic recording of intercepted signals on a chart-type ink-line field-strength recorder, may
assist in “ acquiring ” space signals and in timing their periods of reception.
An electronic counter, providing printed frequency and time records, has been founduseful to meet the requirement of taking high-speed measurements to follow the Doppler
shift.
*For bandwidth measurements, it is desirable to employ a camera to photograph thespectrum display for later analysis. The exact time of taking the picture should be recordedon the film at the time of exposure.
Although good results have been obtained by tracking the satellite signals by manualadjustment of antenna azimuth and elevation, and by manual adjustment of the receivertuning to follow the Doppler frequency shift, automatic tracking of both is suggested, if
practicable. Further studies should be undertaken to determine practicable means to pro­vide such tracking capabilities. Automatic antenna and receiver tracking will become ofincreasing importance for satisfactory monitoring at frequencies above 1000 MHz.

2.2 Antennae
Antennae ranging from fixed dipoles to log-periodic types capable of being rotatedin azimuth and adjusted in elevation have been tested. The latter type has been employed
for frequencies between 50 and 5000 MHz and has provided good general coverage overa 10 to 1 frequency range in a simple antenna. Other antennae used successfully include
a multi-bay Yagi, single and twin helical, conical helix, dipole with corner reflector, foldedcrossed doublets with half-wave phasing stubs between the doublets, 4-element folded dipole(in-phase array), and a series of uni-directional “ V ” antennae with a selective switchingarrangement to change orientation. Studies are progressing for the use of parabolic reflectorsof up to about 8-5 m (28 ft) in diameter, for monitoring antennae to be used for frequencies
in the 4000 MHz range and higher and using various antenna elements including a wide­band log-periodic array. Because of the quite sharp directivity of such high-gain antennae,
considerable care is required in acquiring and tracking the signals from the spacecraft.
2.3 Receivers
For economic reasons, and because a general-coverage receiver is required at moni­
toring stations, the extremely low noise figures possible for fixed-frequency receivers used
for space research and operational purposes are not equalled by available monitoring receivers.
However, the receiver should have a relatively low noise figure and be capable of receiving

— 347 —Rep. 276-1

signals in the order of a few hundredths of a microvolt at the receiver input, and shouldhave a wide range of adjustable bandwidth to permit reception of both wide and narrow­band transmissions from spacecraft.

2.4 Specialized equipment
To facilitate “ acquisition ” of the signal from a spacecraft, it is desirable to be able
to sweep a narrow band of frequencies automatically and to record the received signals
both aurally and on a field-strength recorder. A sweeping device has been developed forthis purpose, using a semi-conductor diode as a voltage variable capacitor applied to thefrequency-determining circuits of the receiver. In operation, the sweeping device is set
to vary the receiver frequency over a band greater than the amount of predicted Doppler
shift.

3.

Identification of transmissions from spacecraft
Considerable thought has been given to the extent of the need by space Administrations
and by monitoring stations for a call-sign or other special identifying signal to facilitate
identification of emissions from spacecraft and of the effects of installation of equipment
for that purpose. It has been concluded that neither need is great enough at present, norlikely to be in the near future, to warrant pressing for the use of an identifying signal.
The techniques employed for space research and operations in satellite and other space­
craft tracking, and foreseen for communications and other uses of space emissions, aresuch that special identifying signals are normally not essential. There normally being no
requirement on the part of the tracker and user for identifying signals, to require their use
to facilitate monitoring observations, could impose limitations adversely affecting reliability,
weight, cost and operation of the system involved.
It has been found possible to identify emissions from particular satellites from signal
characteristics and ephemeris data. It would thus appear that the provisions of Article 19,
No. 737 of the Radio Regulations, Geneva, 1959, relating to recognized means of identi­
fication other than call-signs, will be met if Administrations launching satellites and otherspacecaft will continue to make such information currently available to monitoring
services. The following information will assist in identification:- carrier frequencies;- orbit time;- angle of inclination of orbit to equator;- equator crossing time and longitude of crossing:- perigee and apogee distances, and- signal characteristics such as type of modulation and bandwidth for each frequency.
In addition, data on the transmitter power, antenna characteristics including antennapolarization and other related parameters will be useful in the prediction of reception.
From the ephemeris data, monitoring stations have been able to calculate when a par­ticular satellite will be above the horizon for a particular monitoring station and the distances
involved, to predict reception and assist in identification. A considerable amount of pub­lished information is available, regarding the techniques of satellite and spacecraft track­ing and the problem associated therewith (see Bibliography).

Rep. 276-1— 348 —

3.1 Special aids for determining satellite positions and expected reception times
Graphical and slide-rule aids have been found useful for determining reception time
for spacecraft based on past reception data (see Doc. VIII/3, Geneva, 1962).
3.2 Direction finding as an identification aid
To supplement determination of the exact time of closest approach of a satellite toa monitoring station, by noting the centre point of the maximum rate of the Doppler shift ofthe carrier frequency, a curve can be plotted to show the change in direction of arrival of
the signal with time, as determined by direction-finder bearings or orientation of a highly
directional receiving antenna. The maximum angular rate of change will occur when thesatellite is nearest to the monitoring station during a particular pass and the information
obtained by this method should agree closely with the information obtained from the fre­quency/time curve.
3.3 Future possibilities for monitoring procedures involving transmissions from spacecraft
Procedures have been discussed herein for identification of transmissions from space­
craft, based on past experience of comparing the measured and observed signal charac­
teristics with published information, and by comparing the time of closest approach to amonitoring station - as determined from the measured Doppler shift of the carrier frequency
and from varying azimuth (bearing) - with ephemeris data. With the expectation of increased
use o f operational satellites, immediate positive identification by monitoring stations of
all intercepted spacecraft emissions by these methods may become too time-consuming.
Therefore, the following additional procedures may be necessary:- a communications system involving either passive or active satellites could be identified
by the identifying signal of the ground station reflected from or relayed by the satellite,
even if this did not immediately identify the particular satellite of a multi-satellite system,and- in enforcement-type monitoring of spacecraft emissions, particularly when noncom­
pliance with radio regulations or cases of interference are observed, monitoring stations
could log all possible information concerning frequency and bandwidth measurements,
direction of signal arrival, type of modulation and other signal characteristics, together
with accurate times of observation and measurements, and request identification, basedon these data, from identification and tracking centres.
The time that the satellite is closest to the monitoring location on a given pass, as deter­
mined from Doppler-shift measurements, and the carrier frequency as measured for thistime, will be of utmost importance to the space centre in effecting identification.
However, further consideration might be given to the incorporation of an appropriate
identifying signal.
B ibliography

1.
2.

Smithsonian Contribution to Astrophysics, Vol. 2, 10, U.S.A. Government Printing Office.
Various papers in Proc. IRE, 48 (April 1960), particularly:- H utchinson , H. P. and A rendt, P. R. Ionospheric scintillations of satellite signals.
- W eifenbach, G. C. Measurement of the Doppler-shift of radio transmissions from satellites.

Rep. 277-1— 349 —REPORT 277-1 *MEASUREMENTS AT M OBILE M ONITORING STATIONS(Question 144)
(1959- 1963 - 1966)

1.

Types of measurement

1.1
1.2
1.3
1.4

Subject to the limitations necessarily imposed by mobile operation, the size of suitable
instruments and power consumption, it is considered to be practical to employ mobile
stations to make all the measurements of emissions normally made at fixed monitoring
stations.
Typical measurements and ranges are:Frequency measurement:
10 kHz to above 10 GHz
Field-strength measurement:
10 kHz to above 10 GHz
Bandwidth measurement:
10 kHz to above 10 GHz
Direction finding - with loops:
10 kHz to 20 MHz- with dipole arrays:
20 MHz to above 1 GHz- with horns:
1GHz to 10 GHz
Automatic monitoring of occupancy:
10kHz to above 300 MHz
Percentage modulation, FM deviation:
10 kHz to 1 GHz
Video waveform measurement of television emissions:
40 MHz to 890 MHz

1.5
1.6
1.7

Mobile monitoring stations are particularly valuable for monitoring low-power
stations and stations at frequencies above 30 MHz whose range is limited.
In addition to the use of equipment installed in a vehicle, certain measurements canalso be made using portable equipment. Experience shows that separate mobile monitor­
ing units, specifically designed for selected types of measurement, lend themselves more
readily to operational use rather than a single vehicle equipped to make all classes of meas­
urement.

2.

Types of equipment
It is considered undesirable, to have to use special equipment for the mobile monitoring
service and regular stock types of equipment with small dimensions, low weight and low
power consumption are preferred. Since mobile equipment is subjected to vibration andshock, robust construction, together with shock-mounting of components, is important.
With the exception of some portable units, the equipment is normally designed for opera­tion at standard mains voltage and frequency.
It is preferred that instruments, such as frequency standards, which are sensitive totemperature changes, be designed to reach and maintain operating temperature in as shorta time as possible, so that continuous application of power will not be necessary or so that
only limited circuits will require continuous power. As an alternative, standards which arelocked in synchronizm with VLF standard-frequency emissions should prove useful.

2.1 Frequency standards and associated measuring equipment
The frequency standard should be capable of maintaining a frequency stability
one part in 108 per day or better, after nominal warm-up periods and under the operating* This Report was adopted unanimously.

Rep. 277-1— 350 —

conditions normally encountered in the mobile service. Currently available frequency
standards, specifically designed for mobile use, are capable of stabilities of ± 1 part in 108
or better under field conditions.

2.2 Field-strength measuring equipment
The extent to which field-strength measuring instruments should be provided in a mobile
monitoring station depends upon the purposes of the measurements. For regulation enforce­
ment purposes, continuous coverage up to at least 1000 MHz is desirable. For obtaining
propagation data, highly sensitive recorders operating on a fixed frequency have certain
advantages, although the instruments used for enforcement measurements may also be used
for this purpose with some compromise in sensitivity and frequency stability.
This discussion will deal only with tunable continuous coverage instruments.
Wherever possible, field-strength measurements should be made in an area where thesignal field is relatively undisturbed by local reflections and re-radiation. Where there isstrong dependence on location, measurements may be made in terms of median values, therecording being made continuously as a function of location or time.
The mobile station itself may contribute errors and the calibration includes antenna,
receiver and recording equipment. It is desirable, therefore, that the equipment be port­
able so that measurements can be made away from the vehicle. To avoid directivity effects
when measurements are made from the vehicle in motion, omnidirectional antennae areused. Since measurements of harmonic attenuation may involve comparatively weak signals,
it is desirable that the field-strength meter be capable of the measurement of signal levelsof the order of 1 pV/m. The instrument should likewise be immune to overloading fromstrong signals of 1 V/m or more. To attain satisfactory accuracies, considering that undis­
turbed fields are the exception at frequencies above 30 MHz, the errors contributed by the
instrument itself should be less than ± 2 dB. It is desirable that circuitry be incorporated
for determination of peak and quasi-peak levels of pulsed emissions, as well as for the average
field strength of amplitude- and frequency-modulated and similar emissions.

2.3 Bandwidth measuring equipment
Authorized bandwidths, for stations assigned to the various VHF and U H F services,vary from less than 1 kHz for radiotelegraph services to several MHz for television broad­
cast services. Mobile monitoring stations should, therefore, be equipped with spectrum
analysers having very flexible characteristics, including a sweep width of 20 kHz or less fornarrow-band emissions and with the capability of displaying at least 5 MHz of spectrum at atime on certain broadband emissions.
The sweep rate should be variable from about 1 to 30 sweeps per second to permit opti­
mum utility for various types of observation. Provision should be made for either linear
or logarithmic display of signal levels and calibrated scales should be provided for direct
measurement of level ratios.
Mobile measurements of bandwidth may be made by a frequency occupancy recorder,
for those types of modulation for which no measurement method of higher accuracy exists,
or when it seems impracticable to carry out such measurements in the mobile service becauseof the high technical expense involved. With telegraph signals for instance, the bandwidth
can be determined from the signal element with the shortest rise time (see Doc. V III/10,
Los Angeles, 1959). In the VHF band, estimated bandwidths can also be read off the oscillo­graph screen of a panoramic set with a calibrated frequency scale. The measurement of
bandwidth can also be made by a method of frequency analysis, using a very narrow( ± 100 Hz) filter to measure the magnitude of the spectrum components passing throughthe filter in relation to the carrier.

— 351 —Rep. 277-1

2.4 Direction-finding equipment
It is desirable that the monitoring receivers in a mobile installation also serve as receivers
for the mobile direction-finder. Light weight, compactness, high sensitivity, effective shield­
ing, stability, robust construction and low power-consumption are desirable features formobile monitoring receivers. Furthermore, receivers for mobile monitoring should provide
continuous tuning coverage of as wide a frequency range as possible. Accurate calibrationof the order of 1 kHz at 30 MHz and below, and 10 kHz above 30 MHz is highly desirable.
Accuracy of frequency resetting of the order of 1 part in 104 or better is also desir­able. Although band-switching is preferable, plug-in radio-frequency units for different
bands may reduce the circuit complexity.
The loop ro+ater should preferably be installed in the approximate centre of the roofof the vehicle, with the loop socket extending through the roof and with the azimuth scaleand rotating mechanism (usually a hand wheel) inside the vehicle at a convenient location.
A number of plug-in-loops with different electrical characteristics will permit optimum results
to be obtained over a wide range of frequencies.
Directional antennae are needed to extend the frequency range above the limits of loop
antennae. Desirable characteristics are: high directivity, broadband frequency coverage,
high gain, horizontal and vertical polarization and small size. Antennae types in use arehorizontal and vertical dipoles, Yagi-beam, helical and rotatable H-type Adcock, whileparabolic, horn type or corner-reflector antennae can be used above 300 MHz.
An antenna finding increasing acceptance above 1 GHz, is a broadband horn covering
approximately a frequency range of 2 to 1. For added gain and directivity, the horn may
be mounted in a parabolic reflector.
For antennae in the YHF/U H F range, it may be very useful to use telescopic rotating
supports controlled from inside the vehicle employed as a mobile station. With these supports,
it is possible to surmount obstacles near the place of measurement and to take measurements
at various heights with the antenna steered in different directions. The antenna height
and azimuth should be indicated accurately on the dials inside the vehicle.

2.5 Automatic monitoring o f occupancy measuring equipment
Monitoring of spectrum occupancy, at specified locations or along specified paths,
may be made in the mobile monitoring unit, by means of a frequency spectrum recorder
or by means of a panoramic adaptor.
The latter permits visual observations to be made over a relatively small band of fre­quencies while the vehicle is in motion.

2.6 Modulation measurement equipment
It is desirable to provide facilities for measurement of percentage modulation of both
amplitude- and frequency-modulated emissions. For the former, a cathode-ray oscilloscopewith a wide-band vertical amplifier usable up to 10 MHz or more is required. For measur­
ing modulation deviation of FM emissions, an instrument capable of accurate measurementof carrier deviation, over a range from ± 5 kHz or less to ± 100 kHz or more, is required
and should be capable of indicating instantaneous values. An overall accuracy of 5%
or better is highly desirable. A cathode-ray oscilloscope may be used as an indicator forthe carrier deviation meter to permit measurements of instantaneous peaks of deviationof FM stations.

2.7 Television measuring equipment
Measurements of the characteristics of the video waveform of television transmissions
can be made with instruments specially designed for the purpose. Cathode-ray oscilloscopeRep. 277-1— 352 —

display of the various portions of the video signal is desirable, so that individual picturelines or segments thereof, as well as individual synchronizing pulses, may be observed. Pro­
vision should also be made for viewing the entire picture on a screen of adequate size topermit evaluation of the picture quality.
2.8 Power supplies
To provide adequate power for large mobile monitoring units, a separate power unit
either integral with the vehicle or mounted on a trailer may be used. An engine-alternator
unit of 5 kW rating is usually adequate for this purpose. For the smaller mobile monitoring
units, an alternator of about 500 W driven by the vehicle fan belt is a useful source of power.

3.

Accuracies and limitations of measurement
Most of the measurements listed in § 1 of this Report can be as readily performed withmobile as with fixed facilities, generally with little or no compromise in desirable accuracy.

3.1 Frequency measurements
Mobile frequency standards are available which will maintain stability better thand= 1 part in 108 per day under field conditions.
By means o f frequency synthesizers or electronic counters, it is often possible to obtain
direct measurements of the frequency of emissions, without recourse to auxiliary interpolating
instruments, over a range of frequencies extending above 100 MHz. Transfer oscillator
techniques may be used at much higher frequencies, with interpolation between the transfer
oscillator and the frequency standard being made with an electronic counter or other appro­
priate means. Measurement accuracies, within the desirable limit of ± 1 part in 107, may
be accomplished under optimum conditions when the nature of the carrier is such, that a
precise zero beat may be obtained or where direct counting techniques may be used.
On FM emissions, frequency averaging techniques with an electronic counter will provide
an accuracy of 1 part in 106 or better.
3.2 Field-strength measurements
The accuracy of field-strength measurements above 30 MHz is limited, not so muchby the instruments themselves, as by the local conditions and transmission-path which tend
to distort the electromagnetic field, so that a considerable variation in field-strength overrelatively short distances may be expected. This problem may be alleviated to some extent
by making several measurements at each measuring location, moving the antenna a few
feet horizontally between measurements. Very good results can also be obtained by taking
measurements at different heights using the telescopic supports described in § 2.4 [1].
Under average conditions, even when appropriate precautions are taken to ensure
optimum accuracy, the accuracy cannot be depended upon to be better than ± 2 dB. If large
numbers of measurements are made as functions of time, location or distance, etc., the sta­tistical evaluation will yield values of the quasi-maximum, quasi-minimum and medianvalues with an accuracy of about ± 3 dB or better, depending somewhat on the distributionof field-strengths. A major limitation of portable or mobile field-strength meters is thelimited sensivity, particularly at the higher frequencies. In the lower portion of the spec­
trum, up to several MHz, atmospheric noise is likely to be a limiting factor on the usable
sensitivity, while at higher frequencies the noise introduced by the instrument! itself becomes
important. Under average field conditions and depending upon the frequency involved, theminimum field-strength, which may be measured with portable instruments with the accuracies
mentioned above, will range from about 2 to 100 pV/m in the frequency range from 10 kHz
to 1000 MHz.

— 353 —Rep. 277-1

3.3 Bandwidth measurements
Generally, the same limitations apply on measurements of bandwidth by mobile instal­lations as for measurements at fixed monitoring stations. The same measuring instruments
are applicable to both types of installation. One advantage of mobile as contrasted with
fixed installations is that, in the case of the former, measurements can often be made imme­
diately adjacent to the transmitter, eliminating some of the measurement problems (such as
those associated with interference and noise), which are mentioned in Report 275-1.
3.4 Direction finding
A major limitation of loop-type direction-finders is their polarization error in the presenceof signals with significant skywave components. A further serious limitation of a direction­finder, which depends upon the direction of arrival of the wave front, is the likelihood of
local reflections or re-radiation from nearby objects such as buildings, transmission andtelephone lines, etc. In an area where the wave is relatively free from distortion due tolocal conditions, where the path of arrival is essentially horizontal (vertically polarized wave),and taking into account possible errors introduced in orienting the direction-finder azimuth
scale, accuracies of the order of ± 5° with vehicle-mounted loop-type direction-finders
are typical, with somewhat greater accuracy at frequencies below about 5 MHz. However
where the wave has been distorted by local conditions or where skywave components arepresent, bearing nulls are likely to be obscured or to deviate widely from the true directionof the emission source.
Where the ground wave is predominant (i.e. the ratio of ground-wave to reflected waves
being at least 6 dB), direction-finding loops may be used in the frequency range 10 kHz to
30 MHz. The accuracy obtained depends upon the signal level and the equipment used.
Typical values for a direction-finding null 1° wide are:
10 kHz: 50 gV/m,1000 kHz: 15 gV/m,
20 MHz: 10 gV/m.
For the bearings of horizontally polarized signals (line-of-sight) at frequencies above
30 MHz, Yagi-beam antennae may be used in a method of maximum signal directionfinding with an angular width of bearing indication of ± 15°.
For measurements made from a vehicle in motion, no proper bearing seems possible
because of multiple reflections from nearby objects. However, when equipped with a visualindicator, mobile direction-finding sets will allow determination of a median value of thevarying indications and hence yield an approximate direction.
3.5 Monitoring o f occupancy o f the radio-frequency spectrum
The accuracy obtainable from a frequency spectrum occupancy recorder depends upon
the receiver and the overall calibration. Equipment used in the Federal Republic of Germany
has the following characteristics:- Sensitivity: better than 1 gV/m.
- Accuracy of field-strength indications: ± 3 dB at angles of incidence below 60°.
- Frequency stability of receiver: ± 5 parts in 105 ± 40 Hz (where ± 40 Hz is the band­
width of the filter).
- Accuracy of reading time-markers: ± 1 min or ± 30 s.
- Adjustable maximum frequency spread on the recording strip by choice of appropriate
gear reduction: 100 Hz per mm. When monitoring above 30 MHz by means of panoramic
sets the resolving power may be about 400 Hz.
23

— 354 —Rep. 277-1, 278-1
3.6 Percentage modulation

Cathode-ray oscilloscopes, with the desirable characteristics for measurement of per­centage modulation of amplitude-modulated signals, are available. Accuracy of such meas­
urements can usually be maintained within ± 5 %. For measurement of carrier deviation,
instruments are available which meet the desirable characteristics listed in §2.6. Selfcontained calibrators are provided to maintain an instrument accuracy better than 5%.
3.7 Television measurements
Instruments are available for performance of all desirable television measurements
and observations mentionned in § 2.7. Measurement accuracy of the various instruments
in most cases approaches or equals that of measurements which can be performed at a fixedlocation. Comparative level measurements of components of the composite video wave­
form, for example, can usually be made with an accuracy of 5 to 10%.
Measurements and observations, which may be performed with the equipment installed
in a mobile television enforcement unit in the U.S.A., include:- frequency measurements of television station carriers (including chrominance sub-carrier
frequency of colour emissions);- the precision frequency measuring equipment covers a frequency range of 20 to 1000 MHz
with an accuracy under optimum conditions of 5 parts in 107;
- measurements of synchronizing pulse waveform and timing, video waveform and ofcolour video phase relationships;- checking of video levels with respect to synchronizing pulse levels;- measurements of bandwidth of television emissions including observations of spurious
emissions at all frequencies between 54 MHz and 890 MHz;- percentage of modulation rate of vision and sound emissions;- measurements of distorion and noise level at audio frequencies.
B i b l io g r a p h y

1.

G entile, G. Measurement of field strengths of frequencies above 30 MHz. Method used by RAI
monitoring centre, Monza. E .B .U . R eview , 97-A (June, 1966).

REPORT 278-1 *AUTOMATIC MONITORING OF OCCUPANCY OF THE
RADIO-FREQUENCY SPECTRUM(Question 9/VIII)(1959 - 1963 - 1966)
This Report takes into consideration the documents presented up to the Xlth Plenary
Assembly of the C.C.I.R., Oslo, 1966.
1.

Doc V in/2 (U.S.A.), Washington, 1962

1.1 In considering the accuracy of automatic monitoring equipment in determining bandwidthsof emissions, due consideration should be given to relating measurements of narrow-band
emissions of the order of 2 kHz or less to the characteristics of the particular instrument* This Report was adopted unanimously.

— 355 —Rep. 278-1

in use. It has been determined, for example, that in some instruments which mechanicallysweep a frequency range and resolve the bandwidth presentation by selective circuits, theshape factor of the selective circuits is such as to complicate bandwidth determinations atother than accurately known comparison levels. The variation of received signal levels
due to propagation conditions, together with other factors, impose restrictions on the accuracyof indicated signal bandwidth of narrow-band signals. Consideration should therefore be
given to the need for an analysis of the relative distribution of the signals level and the resolv­
ing capability of the instrument at several input levels. For signals with bandwidths ofseveral kHz, the errors contributed by the above-mentioned equipment limitations becomeless important. Nevertheless, it may be desirable, in the interest of correlating data obtainedwith different instruments, to take into account their resolving power and the repetition
rate and duration of discrete components of the observed signals.
In determining the accuracy of field-strength measurements made by automatic devices,the polarization and directivity of the antennae are important factors. In the 3 to 30 MHz
range, where signals received over sky-wave paths contain both horizontally and verticallypolarized components to a significant extent, a decision must be made as to the component
to be measured. Since the vertical angle of arrival is most commonly less than 45°, lesserror will usually be introduced by measuring the vertically-polarized component rather thanthe horizontally-polarized component. Where greater accuracy is required, an appropriate
correction may be applied, based upon a computed value for the vertical angle of arrivalof the wave front.
Measurement of the vertically-polarized component may readily be accomplished byusing a vertical receiving antenna, the electrical length of which is appreciably less than
one-quarter wave, for the frequency band under study. To reduce errors due to non-homogeneous earth in the vicinity of the antenna, a ground screen, together with radial groundwires extending out at least 30 m (100 ft.) in all directions has been found beneficial. The
level of signal input to the recorder may be measured by comparison with a calibrated stan­
dard radio-frequency signal generator. The antenna effective height is determined bycomparison with measurements made with an accurate field-strength meter using an antennaof like polarization.
In evaluating the field-strength data thus obtained, due allowance must be made forerrors introduced by the various instruments. Allowance must also be made for fluctuations
in signal-level, since, during the sweeping process, the receiver is tuned to a particular signal
for only a small proportion of the time.

1.2 Measurement of signal-to-noise ratio primarily involves a comparison between signal andno-signal conditions making use of the same techniques as for field-strength measurements.
In this instance too, variations in signal-level due to propagation must be taken into account.
In the lower portion of the H F range, the problem is somewhat complicated, especially during
the warm months of the year, by the generally high level of atmospheric noise, which is subject
to wide variations in level, both instantaneous and over significant periods of time. The
effect of receiver bandwidth and of the bandpass characteristics will also need to beconsidered, so that satisfactory correlation between measurements made with different
equipment may be accomplished.

1.3 The preferred means of analyzing and evaluating automatic monitoring records depends
primarily upon the information desired. In some instances, it may be desirable to obtain
information concerning the direction of arrival of the various signals in the frequency band
under study; this would provide data relating to the determination of channel occupancy
with respect to the different azimuths of origin of the emissions. For example, a long-range
direction-finder may be associated with the automatic recorder in such a way that the azimuth
would be advanced a small increment (such as one or two degrees) at the start of each sweepof the automatic recorder. Signal nulls and maxima could readily be determined by inspec­tion of the chart. Additionally, data could be extracted from such recordings which would
indicate occupancy in a given azimuth at regular intervals of time. In congested bands,
the use of a directional antenna would also aid in reducing overlapping of signal traces.

Rep. 278-1— 356 —

Identification of the type of emission, by analysis of automatic recorder indications,is subject to shortcomings with narrow-bandwidth emissions, because of limitations in the
resolving power of the instrument. However, those emissions occupying a significant band­
width, such as multi-element tone printers, multiple-component multiplex, wide-shift simplex
or multiplex and certain transient types of emission, can frequently be catalogued by inspec­tion of recorder indications, together with precise frequency increment chart calibration.
1.4 The degree to which records may be analyzed by automatic means would appear to be an
economic rather than a technological matter. Because of the variety of data normallyavailable from the automatic recorder, equipment for complete automatic analysis would
necessarily be quite complicated. Such an analysing system might employ transducers toconvert chart components into digital or analogue data which could be handled by electronic
data-processing equipment.

2.

Doc. VIII/8 (Federal Republic of Germany), Washington, 1962
The method of measurement described below permits the field-strength to be recorded
continuously instead of in steps. From such field-strength recordings, the bandwidth andsignal-to-noise ratios may be readily determined.
A potentiometer is mechanically coupled to the recording head of the occupancy recorder,
supplying a d.c. voltage directly proportional to the relative position of the recording stylus
on the recording sheet. After suitable amplification, this d.c. voltage is applied to the timebase (x-plates) of a cathode-ray oscilloscope, thus providing a frequency scale exactly insynchronization with the sweep of the occupancy recorder.
The intermediate-frequency output of the receiver is connected to a multi-section analyz­
ing filter (quartz crystal), the bandwidth of which is variable in steps between 30 and 100 Hz.
After detection, the filtered signal is amplified in a logarithmic amplifier and fed simulta­
neously to the measuring (Y) plates of the oscilloscope and to the occupancy recorder. By
special arrangements, the Y-axis is calibrated linearly over a range of 80 dB. The oscillo­
scope screen, of the long-persistence type, allows direct observation during a full sweep of
the occupancy-recorder. Automatic recording is effected by photographing the screenpresentation of any individual sweep by means of a 35-mm camera. The shutter release
may be actuated automatically, by means of a special control contact in the occupancy
recorder. By means of a simple counter device, such as is used in telephone exchanges, it
may easily be arranged that each single or any «th sweep is exposed on the film. Correlation
between the photographed oscillograms and their corresponding sweep numbers is easily
ascertained by photographing the counter, together with the spectrum pattern.
Evaluation of the oscillograms may readily be performed by projecting the developed
negative on to the occupancy recording sheet, so that both frequency calibrating scales are
made to coincide. The field-strength and bandwidth of a wanted emission, as well as its
amplitude ratio relative to an unwanted signal, may thus be determined easily. The values
taken from the photographs are, of course, instantaneous values present at a particularpoint of the spectrum at the moment when the filter swept through it.
The foregoing characteristics point to the limitations of the proposed method. Setting
aside for the moment the influence of fading, which will be dealt with further below, theproposed method is suitable for recording continuous line spectra as well as periodicallyand quasi-periodically keyed emissions, i.e. practically any binary telegraph systems
encountered in practice. Some difficulties arise, however, in the representation of non­periodic pulse emissions and of classes of emission with modulation envelopes which do
not vary periodically; e.g. A3, A3 A, A3B; in these cases, however, the amplitude of thecarrier (or residual carrier) is recorded correctly.

— 357 —Rep. 278-1

The extent of the frequency range that can be explored is limited by the bandwidth of
the analyzing filter which, to assure the desired resolution characteristic, should not be larger
than 100 Hz, and by the exploration speed which should not greatly exceed 60 s per sweep.
Since, for the intended purpose, the exploration rate with a filter width of 100 Hz should
be 5000 kHz per second the time increment for any discrete spectrum component of the sweep
signal is in this case 20 ms; the scanning speed of spectrum analysers given in Annex I to
Recommendation 327-1 are considerably lower, because fine analysis of the spectrum isdesired. In most cases, however, the indication of field-strength, as found from the oscillo­grams, will be entirely adequate to give an overall picture of the conditions in the frequency
range explored. This holds true similarly for the bandwidth and signal-to-noise ratios of
the recorded emissions. In these conditions, the maximum sweep range would be
300 kHz wide. Recordings of signals subjected to fading can, of course, only show instan­taneous values : of the field-strength. The received field undergoes irregular variations
between limits that can only be estimated by taking a large number of sequential photo­graphs. Any estimate of the actual field-strength will normally be accurate within± 4 dB. The smaller the scanning range, the better the field-strength maximum will be
discernible. If, in special cases, a more accurate measurement of the statistical variationof the field-strength is desired, a conventional single-frequency recording with subsequent
analysis should be made.

3.

Doc. VIII/12 (Japan), Washington, 1962

3.1 The recording system is of the disruptive-discharge type, so that the records can be examinedin the course of recording. Moreover, the recorded lines are very thin and the field-strengthof signals can be indicated by the thickness of the lines.
3.2 Since the filter in the recording unit (the rate of sweep being taken into account), has a passband 30 Hz wide, it resolves the frequencies very well. This enables one to identify thetype of emission from the recording.
3.3 The frequency stability of the receiver unit is better than 1 part in 106 and the frequency
scale (capable of calibration against the standard frequency), can be marked at 10 kHz
intervals. Therefore, the accuracy of reading the frequency is 300 Hz;
3.4 To determine the relative field-strength of each of the vertically recorded lines, a variableattenuator is placed at the intermediate-frequency stage in the receiver unit, and is inserted
automatically step-by-step in succession at each fixed time of sweeping. Thus, the relative
field-strength can be obtained from the amount of attenuation inserted.
Furthermore, to smooth the overall gain/frequency characteristics of the equipment,
including the antenna system used, a vertical omnidirectional loaded antenna of wide band­
width is used (the structure and electrical characteristics of which are shown in Figs. 1, 2
and 3 in Report 373).
3.5 Accuracy in determining bandwidthThis equipment is to record the relative distribution of the spectra of signals above
a certain level, but it is not intended that the occupied bandwidth, as laid down in the Radio
Regulations, Geneva, 1959, should be read from the recorded lines. Therefore, as the widthof the spectrum of each signal at a certain level is considered as a bandwidth, studies werecarried out to determine the accuracy with which the bandwidth might be estimated inthis case.
This equipment, when used with a 100 kHz swept frequency range and 60 sweeps perhour, is capable of determining the bandwidth of the spectra of various classes of emission
at a given level to an accuracy of about 100 Hz.
3.6 Accuracy in determining field-strength
The method of measurement of field-strength by means of this equipment is the sameas described in § 3.4. In this case, the larger the number of sweeps per step in the attenuator,

Rep. 278-1— 358

the higher the accuracy of reading the recorded lines. Considered from the propagation
characteristics, however, because of variations in field-strength, the increase in the numberof sweeps and the prolongation of measurement brings a lack of reliability to the results.
On the other hand, in the field of reception at the monitoring stations in Japan, almost
all radio waves, excluding those in the standard broadcasting service, are less than about
55 dB (1 pV/m = 0 dB). The lowest field-strength that this equipment is capable of record­
ing is — 10 dB.
From various viewpoints above, it is concluded that it is best to complete one opera­tion of measurement in a period not exceeding 20 minutes at 60 sweeps per hour, the numberof sweeps per step of the attenuator being 2, and the attenuator having 10 steps of 6 dB
each, that is, 60 dB.
Where measurements are taken with the 100 kHz swept frequency range by the useof the equipment with the above characteristics:- the overall gain deviation of the vertical omnidirectional loaded antenna and the receiverunit within the swept frequency range is within ± 0-8 dB;- the accuracy of reading the field-strength from the result of recording is within ± 4 dB;- the error of the attenuator at the intermediate-frequency stage is within ± 1 dB.
Taken altogether, the accuracy of determination of the relative field-strength is ± 6 dB.
Further, if a suitable emission is selected from among those recorded and its field-strengthis measured individually, the relative field-strength of each emission can then be obtained.

3.7 Capability o f automatic monitoring equipment in determining signal-to-noise ratios.

4.

The lowest signal-to-noise ratio (for an equivalent noise bandwidth of 10 kHz) that
this equipment is capable of recording, is less than — 10 dB at the input terminal of thereceiver, when the equipment is in the optimum condition of recording. In case of higher
values than this, the signal-to-noise ratio can be determined by measurement of the intensities
of signal and noise in the same way as the field strength mentioned above.

Doc. V m /ll (Japan), Washington, 1962

4.1 Measurement o f relative field-strength
A variable attenuator is added to the receiver unit of the equipment, the attenuation
is automatically increased step-by-step in succession at each specified number of times ofsweeping, and the signal output is recorded. The relative field-strength of each signal isdetermined by the attenuation inserted immediately before the recorded line fades out.
The absolute field-strength is obtained as follows: the absolute value of the wanted
signal among those recorded is measured by means of a second field-strength meter, and,on the basis of this value, the absolute value of other signals is derived from the relative
field-strength.
The total attenuation should be 60 dB, to be equally divided into about ten steps. It
is desirable to make the number of times of sweeping two per step in the attenuator.
The duration of each measurement should be about 20 minutes, taking account offluctuation in field-strength due to variation in the radio propagation characteristics.
An antenna, with good frequency characteristics such as a vertical omnidirectionalloaded antenna, should be used (such an antenna is illustrated in Fig. 1, and its charac­
teristics are given in Figs. 2 and 3 in Report 373).

— 359 —5.

Rep. 278-1

Occupancy-vacancy recorderAn occupancy-vacancy recorder in use in the U.S.A. and initially described in Doc. 186(U.S.A.), Los Angeles, 1959, has been modified especially for use on 30 to 470 MHz, although
it may also be used for 500 kHz to 30 MHz coverage if desired. The basic unit consistsof a receiver mechanically tuneable from 500 kHz to 30-5 MHz in steps of 1 MHz. Opera­tion at VHF and U H F is obtained by the use of converters changing the frequency being
recorded to frequencies between 15-5 and 30-5 MHz. The converters are normally operated
with crystal frequency control although occasionally synthesizers have been utilized.
A common drive mechanism drives both the receiver tuning mechanism and the record­ing chart. After the 1 MHz band is scanned the receiver and chart are returned to thestarting frequency at high speed. The frequency axis is along the 122 cm (48 inch) lengthof the chart and the pen moves across the 30-5 cm (12 inch) width of the chart in 48 hours.
When a signal is received above a level determined by the sensitivity setting of the receiver,
the recording pen drops against the paper and marks. (During the high-speed return span
the pen is lifted from the paper.) The resulting record is a sheet 30-5 x 122 cm (12" x 48")
with the occupancy information for a given frequency appearing transversely on the chart.
If desired there is provision for changing the receiver sensitivity on the 2nd and 3rd scans
and returning it to the original value on the 4th scan.
The present mode of operation is as follows:
Bandwidth covered per sweep:
1 MHz
Time of sweep and return (total):
5-5 min6 dB bandwidth of recorder:
6 kHz
Presentation: paper and ink, 30-5 x 122 cm (1 x 4 feet)
Sensitivity: approximately 1 pV across 50 £2
Antennae: Vertical stacked omnidirectional antenna for 148-172 MHz and 450-470 MHz
Vertical omnidirectional ground-plane antenna or half-wave dipole for30-50 MHz.
The antennae used have a gain of about 2 dB over a half-wave dipole at
150 MHz, 6 dB at 450 MHz and a slight loss at 30 MHz.
The VHF and U H F converters are designed to minimize spurious responses and addi­
tionally are preceded by high and low-pass filters to guard against strong local signals out­side the swept band.

6.

Doc. VHI/86 (F.S.R. of Yugoslavia), 1963-1966
This refers to an apparatus for the automatic monitoring of operation and occupancy
in time of a given frequency. The apparatus is used to monitor occupancy of specific fre­quencies (ascertaining the number of stations working on the same frequency andthe occupancy rate), for making automatic tape-recordings of the monitored transmissions
for the duration of the working signal, subsequently to identify transmissions, if necessary,
to warn the monitoring cabin of an expected transmission, to make time-signal recordingson the same tape of the end of the transmission, using the talking clock of the telephoneexchange.
The apparatus is started and stopped by a working signal produced by the monitored
frequency.
Any receiver and a standard tape recorder, or other transmission recording instruments,
can be connected to the apparatus. It can operate either as a permanent monitor or forthe period of the watch, scheduled in advance, on the frequency concerned.
The working signal of the receiver from the intermediate-frequency terminal, the audio­
frequency terminal or the d.c. terminal of the automatic gain control is used as triggeringRep. 278-1— 360 —

signal. After amplification, amplitude limitation and signal detection, a polarized relay
is used and its sensitivity can be regulated.
To prevent unwanted triggering of the apparatus by atmospherics, variable time-constantelements are incorporated in the detector stage to obtain a delay effect.
The criterion adopted to avoid mis-triggering is the duration of the control signal.
At the end of the transmission, the polarized relay clears after a slight delay, which isnecessary to avoid an unwanted break in the recording due to the pause between theletters or words in the case of an A l emission.
A stage, with a time constant of 20—30 s, after the end of the transmission ensurescontinued operation of the apparatus while the telephone number of the talking clock isbeing dialled to record its time signals on the same tape. The telephone line is occupied
only while the time is being recorded..
An automatic process comprising a “ mechanical finger ” and the standard telephone
dial is used for dialling this number.
In case this number is busy, a special selective stage is provided which uses the charac­
teristics of the busy signal and sets the whole switching process in motion again.
Recording of the working time with this apparatus is very accurate, with a toleranceof ± 10 s.

7.

Doc. VIH/19 (Japan), 1963-1966: Mobile equipment for the automatic monitoring ofoccupancy of the radio-frequency spectrum and its performance

7.1 Principal characteristics o f the equipment
7.1.1 The recording system is of disruptive-discharge type, so that records can be examinedin the course of recording. Moreover, the recorded lines are very thin and the strengthof signals can be indicated by the thickness of the lines.
7.1.2 The sweep rate (120 per hour) being taken into account, the filter in the recording
unit has a passband less than 1 kHz wide, and so it resolves the frequencies very well.
This enables one to identify the class of certain emissions from the recorded diagrams.
7.1.3 The frequency stability of the receiver unit is better than 1 part in 104 and the frequency
scale can be marked at 200 kHz intervals. This scale can be calibrated by means of abuilt-in frequency standard.
7.1.4 The frequency range is approximately between 40 MHz and 200 MHz (the upper
limit may be extended to 500 MHz).
7.1.5 The swept range is 3 MHz.

7.2 Facilities for analysis o f the records
7.2.1 Accuracy o f reading the frequency
At the beginning of the recording, the frequency scale can be marked by a calibrat­ing crystal oscillator. The frequency can be read, by interpolation, from the recordedlines of received signals against the calibrated frequency scale. The accuracy ofreading is determined by the difference between the frequency measured in the field
and that read from the records (the centre of the band for frequency-modulation signals
and the recorded line corresponding to the carrier for amplitude-modulation signals),
and is given as follows:
for amplitude-modulation signals: ± 5 kHz;for frequency-modulation signals: ± 7-5 kHz.
The accuracy for frequency-modulation signals with constant bandwidth is approx­
imately the same as for amplitude-modulation signals.

361 —

Rep. 278-1, 279

7.2.2 Identification o f the class o f emission
The class of certain emissions can be easily identified from the shape and fre­quency spacings of the recorded lines.
7.2.3 Accuracy o f determining the bandwidthThis equipment is to record the relative distribution of the spectra of signals
above a certain level, but it is not intended that the occupied bandwidth, as laid downin the Radio Regulations, Geneva, 1959, should be read from the recorded lines; there­
fore, the width of the spectrum of each signal at a certain level is considered as the
bandwidth for our purpose and studies were carried out to determine the accuracy
with which the bandwidth might be estimated. The width of the recorded lines ofthe signals of various classes of emission is read against the calibrated frequency scale
and the precision of reading is about 3 kHz.
7.2.4 Frequency resolving power
The result of the test gives a resolving power as fine as 6 kHz.
7.2.5 The lowest field-strength
This equipment consists of a receiver unit with a variable attenuator; therefore
the lowest field strength that this equipment is capable of recording is determinedby the field strength measured when the recorded line disappears, as the signal is grad­ually reduced by means of the variable attenuator.
The test was conducted in the 150 MHz band and an antenna gain of zero dB wasused and gave the following results:
for amplitude-modulation signals: — 5 dB rel. 1 jrV/m;
for frequency-modulation signals: + 5 dB rel. 1 pV/m.

R EPORT 279 *VISUAL M ONITORING OF THE RADIO-FREQUENCY SPECTRUM(Question 10/VIII)(1963)
Question 10/VIII seeks information on preferred equipment and preferred methods
for visual monitoring of broad ranges of the radio-frequency spectrum. The following is areport o f progress to date, as summarized from the responses to this Question (Docs. VIII/9(U.S.A.), V III/19 (Belgium), and VIII/26 (United Kingdom), Washington, 1962).
Except for the use of spectrum analysers for signal analysis, and use of panoramictype receivers or adapters for observation of limited widths of the radio spectrum, stationsof the international monitoring system have reported little actual experience in visual moni­
toring operations. Further development of methods and procedures must await actual
experience in the use of broadband spectroscopes at monitoring stations.
Spectrum analysers are- valuable in the recognition and classification of emissions, especiallycomplex emissions. The spectrum analyser is a scanning type of instrument arranged
to display, on a cathode-ray tube, the spectral contents of the frequency band under exam­
ination. Spectrum analysers of various types are under development or in operationaluse.
* This Report was adopted unanimously.

Rep. 279

— 362 —

1.1 A spectrum analyser, described in Doc. VIII/26, can be used as a panoramic receiver cover­ing the frequency range of 25 MHz to 140 MHz and employing a wide sweep. The widthof the sweep can be varied continuously between 1 % and 55 % of the tuned frequency. Two
output filters are incorporated, one with 7 kHz bandwidth for sweeps up to 5 MHz, theother with 35 kHz bandwidth for sweeps of over 5 MHz. Resolution varies from 8 kHz
for a 250 kHz sweep to 100 kHz for a 70 MHz sweep. Sensitivity varies between + 48 dB
and + 54 dB relative to 1 pV across 75 ohms, for frequencies of 25 MHz and 40 MHz res­pectively, to give full deflection on the screen. Frequency markers at 10 MHz intervals
and at 2 MHz intervals can be applied at will, appearing as a bright (or dark) spot on the
trace, the 10 MHz markers being distinguished by double spots.
1.2 The principle of design of a spectroscope is described in Doc. VIII/9. The first of theseunits is expected to cover frequency range 100 MHz to 1000 MHz. The ultimate rangeof the equipment is expected to be 14 kHz to 10 GHz. The principle involved is that ofheterodyning the incoming signals by means of a local sweeping oscillator to produce anintermediate-frequency. Increased selectivity is obtained by further conversion to a second
lower intermediate-frequency. Selective filter bandwidths of 5 MHz, 1 MHz and 400 kHz
are obtained at 775 MHz. The first intermediate-frequency of 775 MHz is converted down
to 30 MHz where, using crystal filters, bandwidths of 25 kHz and 5 kHz are obtainable,
enabling relatively fine spectral details to be observed. This allows selection of the desired
bandwidth and resolution commensurate with the sweep rate selected which should be con­tinuously variable over a wide range. Read-out may be either linear or logarithmic. In
the latter instance, a separate amplifier is provided to give a dynamic range of 140 dB for
display of relative signal strengths. A large 43 cm (17 inch) cathode-ray tube is used for
displaying the spectrum, the vertical displacement being a function of the signal strengthand the horizontal sweep being synchronized with the sweep of the local radio-frequency
heterodyning oscillator. The average overall sensitivity of the equipment at 5 MHz band­
width should be approximately — 90 dBmW. Tests have indicated that 100 to 1000 MHz
wide band radio-frequency amplifiers for use with a radio-frequency spectroscope arecapable of a 6-9 dB noise figure, a gain of 25-40 dB, a sensitivity of — 105 dBmW and an
image rejection of better than 60 dB.
1.3 A wide-band spectrum analyser is available commercially which can be used by monitoring
stations for visual observation of a band 70 MHz wide in the range 10 MHz to 44 GHz.
With two dispersion ranges, 0 to 70 MHz and 0 to 5 MHz, it can be used for broadband
observations of up to 70 MHz. The analyser is normally equipped with a 13 cm (5 inch)
display oscilloscope; however, a 43 cm (17 inch) oscilloscope is available for comprehensivefrequency monitoring.

2.

It has been found that a panoramic view of a broad portion of the radio-frequency spectrum
can be presented on a cathode-ray tube, by the use of suitable sweep circuits in the radio
receiver or in an associated panoramic adapter. Panoramic receivers or panoramic adapters
are under development or in operational use.

2.1 A panoramic receiver is described in Doc. VIII/26, which consists of an HF communica­
tions receiver and a panoramic adapter in a single cabinet, to provide a visual oscilloscope
display in any selected band between 1 and 30 MHz. Scanning is limited to a band lying
between two adjacent multiples of 1 MHz. Sweep width can be varied continuously bet­
ween 60 kHz and 104 MHz. The frequency of the sweep can be either 1 or 10 per second.
Output filters 1-2 kHz, 3 kHz, and 8 kHz are provided. Either linear or logarithmic pres­entations are available. 100 kHz frequency markers can be applied at will.
2.2 Panoramic equipment, designed for visual supervision of mobile services operating in the
VHF bands, is described in Doc. VIII/19. A panoramic adapter used with a VHF receiver

— 363 —Rep. 279

covers the bands 30 to 180 MHz or 85 to 300 MHz with an intermediate-frequencyof 21-4 MHz. Spectrum width is 1-2 MHz. The selective filters consist of three fairly low
frequency (2 MHz) amplification stages, in the form of three double-tuned transformers
adjusted below the critical coupling. Visual display is made on a 13 cm (5 inch) oscilloscope.
2.3 A second type is not associated with an external receiver and does not include sound. The
radio-frequency spectrum from 70 to 190 MHz is examined in small sub-bands of 10 MHz,harmonics from a 1 MHz crystal oscillator are introduced into the pre-amplifiers; reference
markers at 1 MHz intervals are thereby obtained on the oscilloscope. Visuai display ismade on a 13 cm (5 inch) oscilloscope (Doc. VIII/19).
3.

Cathode-ray tubes of various size are employed for visual observation. A 43 cm (17 inch)tube with a P-7 screen and amber filter is suggested on the basis of studies to date. Further
development may make practical the use of larger tubes, or multiple-trace tubes, to extend
the frequency axis of the display (Doc. VIII/9).

4.

To provide'a uniform response in amplitude read out on the broadband spectroscope dis­play, it is of course necessary to employ wideband antennae. In using the spectroscopefor simultaneous observation of a large part of the spectrum, it is necessary to compromiseon the selection of the antennae. The antennae giving the best results with spectroscopes
are: rhombics, log-periodic types, and vertical antennae which are shorter than a quarter
wavelength at the highest frequency under observation (Doc. VIII/9).

5.

Recent developments in the design of broadband amplifiers, and their availability, leave
few, if any difficulties regarding the broadband radio-frequency amplifier units for spectro­
scopes. One wideband amplifier has a frequency response flat within ± 1-5 dB from 1 kHz
to 200 MHz, a voltage gain of 20 dB, a noise figure of 9 dB and a rise time ofless than 0 0026 ps (Doc. VIII/9).

6.

Conclusions
Within the next few years, it is expected that various types of “ broadband ” spectro­
scopes for visual monitoring will become available for use at monitoring stations. The
trend in design and construction of spectrum analysers is towards an increasing value of
total scanning excursion (sweep width).
Several units will probably be required to cover the spectrum simultaneously from
10 kHz to 1000 MHz; however, at the present time no need has been shown for such simul­
taneous coverage. Rather, a monitoring station will probably find it more convenient toobserve only one broad segment of the spectrum at a time.
Actual experience is needed in developing operating methods and techniques in theuse of “ broadband ” spectroscopes for monitoring purposes. Therefore, it is advisablethat studies under Question 10/VIII be continued.

— 364 —Rep. 280-1

REPORT 280-1 *IDENTIFICATION OF RADIO STATIONS(Question 14/VIII)(1956- 1959- 1963 - 1966)
1.

This Report summarizes the contributions and discussions in response to Question 14/VIII.
It also retains that material from Report 280-1 which was considered to have an applica­tion to the adoption by Administrations and operating agencies either of the provisionsof Recommendation 379-1 or of other methods of identification and operating procedures
relating thereto, as discussed in this Report.

2.

Since the IXth Plenary Assembly, some progress has been made, particularly with respect
to phase-modulation of multichannel FSK systems, whereby the identifying signal can besent simultaneously into all circuits using the same sub-carrier. This results in centraliza­tion of identifying signals (Doc. VIII/14 (Japan), Washington, 1962).

2.1 The sub-carrier is directly phase-modulated by the modulator circuit added to the trans­mitting terminal equipment, and the identifying signal can be supplied simultaneously to
all circuits using the same sub-carrier, by means of a distribution amplifier.
Because of the small modulation index required, a simple device consisting of a single
transistor is sufficient for the purpose. The modulated signal is keyed in Morse codeand its amplitude adjusted so that, whatever the class of amplification, the specified modula­tion index is independent of the frequency of the emission, type of emission, etc. The
modulation index can be measured accurately during the operation time of the circuit
regardless of traffic in progress.
The intelligibility of the identifying signal is affected by the modulation index and themodulating frequency. In FI or F6 emission, the modulation index is suitable at 0-05 andno great difference in intelligibility occurs for modulating frequencies between 500 to 1000 Hz.
In a composite circuit of FI and F6 emissions, it is desirable to have the modulation index
greater than 0-05 and the modulating frequency no less than 600 Hz.
3.

Two additional methods have been used for identifying FI emissions simultaneously withtraffic:

3.1 One method (Doc. 468, Warsaw, 1956), is to superimpose an audio-frequency modulation
which produces a phase-modulation at the transmitter output. A low-level amplitudemodulation is applied to the exciter and this ultimately produces phase-modulation throughthe limiting action of the following class C amplifier. The audio tone is keyed and applied
across the common cathode resistor of the balanced modulator. This results in the pro­duction of additional sidebands on either side of the main carrier with a displacement depend­ing on the frequency of the audio tone employed.
It has been found that satisfactory identification is obtained without interference to traffic,
if the amplitude of the sidebands is about 32 dB below that of the carrier. Continuous
repetition of the identifying signal at a rate of 8 w.p.m. is used. The keying device consistsof a notched “ keying wheel ” through which a beam of light is projected thereby operatinga photo-electric cell. An ordinary communications receiver, with the beat-frequency oscil­
lator turned off, is used for reception of the keyed identifying signal.
3.2 Another method has been developed which superimposes'on the carrier an additional fre­quency-modulation at small index and at 400 Hz, keyed by the identifying signal. The con­ditions under which the method is used and the results obtained are described in Doc. 183,
Los Angeles, 1959.
* This Report was adopted unanimously.

— 365 —4.

Rep. 280-1, 281-1

Keyed amplitude-modulation, which is superimposed on frequency-modulation for identifying
signals has, for economic reasons, not been generally applied because the method used
employed high-level modulation.
A method for identifying single-sideband multi-channel systems by the insertion of akeyed audio tone on one of the channels was found to be unsatisfactory due, particularly,
to the difficulties encountered by monitoring observers.

5.

Since the Xth Plenary Assembly, tests made in the United States of America indicated thatkeying of a superimposed pilot-frequency is a satisfactory method of identifying suppressed
carrier single-sideband and independent-sideband emissions. The tests consisted of keying
a pilot frequency of 250 Hz and superimposing the signal upon a 12A9J emission at a levelof 18 dB below peak power. The lowest frequency of the emitted intelligence was 375 Hz.
No difficulty was experienced in using standard communication receivers to receive the iden­
tifying signals. Studies are continuing to determine if the same technique can be applied
to ionospheric scatter circuits.
Note. - With reduced-carrier emissions the above-mentioned method can only be applied if
receivers without automatic frequency control are used.

REPORT 281-1 *IDENTIFICATION OF SOURCES OF INTERFERENCE TO RADIO RECEPTION(Question 15/VIII)(1963 - 1966)
This Report shows the progress made, the methods used, and suggests future procedure,
as noted in Docs. VIII/7, VIII/23 and VIII/30, Washington, 1962.
At the date of this Report, one can only give a partial answer to Question 15/VIII.
Much work has been done, but the ultimate production of a chapter of the Handbook andits Annexes is complex (see Resolution 16-1. Chapter 14 and its Annexes should containa collection of information such as photographs, magnetic-tape recordings, written des­criptions, drawings, etc., describing the interference.) Uniform standards of measurement
between the various countries have not yet been developed, and such standards are essential
to make such information of international value.
The preparation of a chapter and its annexes of the Handbook should proceed in thefollowing order of importance:- information primarily for use at monitoring stations to aid in solving cases of internationallyharmful interference;- information to aid in identifying the sources of industrial interference.
The replies to Question 15/VIII, relating to television interference, have been quite
adequate, although uniform standards of measurement and portrayal have not beendeveloped.
Information on interference to television, obtained so far, has embraced interference
caused by, or due to, the following:- faulty adjustment of the television receiver,- defects in television receivers,- inherent design defects in the television receiver,* This Report was adopted unanimously.

Rep. 281-1— 366 —

- ignition interference,- communication equipment,- domestic electrical apparatus,- devices with “ break ” contacts,- Radar,- receiver radiation,- high voltage power lines,- neon signs,- fighting equipment,- electro-medical devices,- calculating machines and cash registers,- multipath reception,- video interference from aural emissions,- high-frequency generators for industrial use.
There are many other specific cases that may be included in some of the broad categories
above.
It has been pointed out, in some of the replies to Question 15/VIII, that the degreeof distortion of the television picture resulting from the interference will vary slightly withthe class or characteristic of the receiver, but the main features of the distortion are main­tained. From this it may be assumed that the standards for the information collected on
television interference need not be as rigid as the standards for information collected on inter­
ference to other services, such as those using the HF portion of the spectrum (3 to 30 MHz).
This is because H F measuring equipment varies over wide limits in such characteristics as:- bandwidth,- selectivity characteristic,- characteristics of oscilloscopes, spectroscopes and others.
The reply to Question 15/VIII, regarding information collected on interference in the
H F range (3 to 30 MHz), that would be of use to monitoring stations, is not complete.
The procedures for preparing this information involve search of the literature and publica­
tions relating to interference, principally for the purpose of determining how the charac­
teristics are described or illustrated (see Bibliography).
Reviews have been made of fisted descriptions, illustrations, magnetic-tape recordings
and films used by Administrations and private industry. Information from many pro­fessional engineering groups is being used in the study.
Some of the monitoring stations have made aural tape recordings, oscilloscope photo­graphs, and written descriptions of individual characteristics of interference.
Account should be taken of C.I.S.P.R. work.
The need for such information of interference characteristics of radiations and uniform
standards of measurement is urgent and is particularly desirable as aids to personnel at moni­
toring stations. Means must be found to publish such a catalogue.
To accelerate the assembly and publication of other information, Resolution 16-1 has
been adopted.
The magnetic tape recording [18] already issued by the C.C.I.R. will form a complement
to Chapter 14 of the Handbook (see Resolution 16-1).
B ibliography

1. Radio interference suppression techniques (A guide for manufacturers). Signal Corps Engineering
Laboratories, Fort Monmouth, New Jersey.
2. M erriman, H. O. Radio interference from electrical apparatus and systems. Department of Transport,
Telecommunication Division, Canada.

Rep. 281-1, 282-1— 367 —

H ale A. P. Electrical interference. Philosophical Library, Inc., New York, and the Orpington
Press, Ltd, Orpington, Kent.
4. S tephens, G. L. Radio interference suppression (as applied to radio and television reception). Published
for Wireless World by Iliffe and Sons, Ltd, London.
5. R ow e, F. D. H ow to locate and eliminate radio and television interference, John F. Rider Publisher,Inc., New York.
6. D arr , J. Eliminating man-made interference. Howard W. Sons and Co., Inc. The BobbsMerrill Company, Inc., Indianapolis and New York.
7. R and , P. S. Television interference. Remington Rand, Inc., New York.
8. R and , P. S. Television interference handbook. The Nelson Publishing Co., Redding Ridge, Connecticut.
9. A general review of TVI causes, effects and solutions. (WTVIC Interference Aids). Cannon & Sullivan
Technical Publications, Los Angeles, California. ,10. Stoker, W. C. and Siefert, W. W. Shielding for diathermy. Bulletin No. 59, Renselaer Polytechnic
Institute, Troy, New York.
• 11. For shielding of radiated interference from fluorescent lamps. Corning Glass Works, Corning, NewYork.
12. TVI Committee Operation (Suggestions kit for interference elimination). American Radio Relay
League, West Hartford, Connecticut.
13. Location of radio interference on rural power systems. Bulletin of Technical Standards Division,
U.S. Department of Agriculture, U.S. Government Printing Office, Washington, D.C.
14. A practical handbook for location and prevention of radio interference from overhead power lines. U.S.
Naval Civil Engineering Research and Evaluation Laboratory, Port Hueneme, California.
15. K lause, R. G. Radio interference aspects of high frequency stabilized welding transformers. (Paper
presented at district meeting of A.I.E.E., October 4, 1950).
16. Bibliography on radio-frequency interference, Trans IRE, RFI-4, 1 (February, 1962).
17. K neller, K rookovets and F etter. Interference from industrial equipment to television reception.
Moscow (1962).
18. C.C.I.R. Tape recording of different classes of emission and of the procedure for dealing with inter­
ference problems. Issued by the International Telecommunication Union, Geneva (1965).
3.

R E P O R T 282-1 *INTERNATIONAL M ONITORING FACILITIES
Reply to Recommendation No. 5 of the Administrative Radio Conference,
Geneva, 1959
(R esolution 15)'(1963-1966)

With reference to Recommendation No. 5, adopted by the Administrative Radio Confer­ence, Geneva, 1959, the I.F.R.B. has prepared a map (see Fig. 1), showing the distribution ofmonitoring stations throughout the world notified to the I.T.U. and participating in the inter­national monitoring system, in the bands below 28 MHz.
For this purpose the world has been divided into 10 main areas, each divided into a numberof sub-areas; the boundaries of the main areas are printed in heavy lines, while those of the subareas are shown by thinner lines, and correspond to the Geographical Zones for broadcasting
given in the Annex to Appendix 1 of the Radio Regulations, Geneva, 1959. The numbers shown* This Report was adopted unanim ously.

F igure 1

— 369 —Rep. 281-1, 367

inside circles on the map are the code numbers assigned to the various main areas, while the code
numbering for the sub-areas is that used in the said Annex to Appendix 1 to the Radio Regula­tions, Geneva, 1959.
The numbers appearing between brackets on the map represent the number of monitoring
stations notified to the I.T.U. for the sub-areas concerned, by the end of 1965.
Considering the practicality of establishing new monitoring stations, experience has indicatedthat Administrations will continue to locate and operate monitoring stations primarily to serve
their own domestic needs and to fulfil their obligations under Nos. 675 and 676 of the Radio
Regulations, Geneva, 1959. Cooperating Administrations will use part of the time of suchstations, to make monitoring observations at the request of the I.F.R.B. and to furnish dataon spectrum-occupancy for use by the I.F.R.B. Thus, from a practical viewpoint, it would
appear that expansion of the international monitoring system to close present gaps in the world
coverage depends almost entirely upon:- establishment of monitoring facilities by countries having none at present but having thedesire and domestic need for such facilities;- expansion of the number of stations where a country has at present a system inadequate
to meet its own needs;- expansion of monitoring positions or other facilities at existing stations, or readjustmentof work effort, to provide more data for the I.F.R.B.;- co-operation in the international monitoring effort by Administrations having monitor­
ing stations, but not yet furnishing spectrum-occupancy or other monitoring data tosatisfy the requirements of the I.F.R.B.
Accordingly, it is suggested that the best approach to obtain expansion of international
monitoring facilities to secure the desired results which prompted Recommendation No. 5, isfor the Union and the I.F.R.B. to follow up §§ 1 and 2 of this Recommendation relating, to therequired efforts of Administrations, as envisaged in Article 13 of the Radio Regulations, Geneva,
1959.

R E P O R T 367 *M ONITORING OF SWEEPING-TYPE PULSE EM ISSIONS(Q uestion 7/VIII)(1966)
Question 7/VIII seeks information concerning the extent of interference caused bysweeping-type pulse transmissions, the preferred facilities and techniques for monitoringsuch emissions, and the method of identifying the source. Such transmissions are being
used to sound the ionosphere:- for purely scientific purposes;- to determine existing propagation conditions, at times in connection with operational
handling of communication traffic;- to assist in the prediction of future conditions.
* This Report was adopted unanimously.
24

Rep. 367

1.

— 370 —

In evaluating the potentialities for interference of the various types of ionospheric sounder,
it is convenient to divide them into two main categories, vertical and oblique, dependingon the directional characteristics of the transmitting antenna.

1.1 Radiating systems of vertical-incidence sounders are normally designed to direct the energy
vertically; however, scattering due to inhomogeneity of the reflecting media, plus radia­
tion from the antenna at other than a vertical angle, may result in reception of the trans­mitted pulses at a considerable distance from the transmitter site.
1.2 Oblique sounders are often used in evaluating a transmission path at various frequencies,
utilizing transmitting and receiving antennae the radiation patterns of which are essentially
identical to the antennae used for handling communications over the path being studied(e.g. rhombic or log-periodic types). Since such antennae typically radiate an appreciable
portion of the available energy at both horizontal and vertical angles which differ consider­ably from the desired direction, reception may take place over a wide area. Ionosphericscattering also contributes to the dispersion of the main beam, further increasing the inter­
ference potential of the emission.
1.3 One method of varying the frequency of the transmitter involves a continuous sweep in which
the frequency is varied continually in repeated sweeps over a predetermined band of fre­quencies. The interference potential of the continuous-sweeping systems using high powertransmitters has been found to be generally greater than for the more modern stepping sys­tems, especially where the sweep rate is such that the emission is in the passband of thereceiver for an appreciable period of time. Use of high-power systems of this type should
be discouraged. An improvement over the continuous sweep technique is a method ofgating a continuously variable oscillator to create a series of output pulses. This technique
is currently being phased-out in the U.S.A. A third method involves a stepping techniquein which one or more short pulses are transmitted on each of a series of frequencies spaced
at appropriate intervals throughout the frequency range being studied. Research is continu­
ing on new methods to accomplish ionospheric sounding.
1.4 Among the various types of sounder which use the stepping principle are those having thefollowing emission characteristics:
System A
Frequency range: 1 to 49 MHz at 100 kHz intervals,
Total time per sweep: 8 min,Pulse width: 25 gs,
Pulse repetition rate: 30 per second,
Number of pulses at each frequency: 30.
System B (The following is only one of a wide variety of operating modes of which
this equipment is capable)
Frequency range: 4 to 64 MHz at intervals varying from 100 kHz at the lower endof the sweep to 400 kHz at the higher frequencies.
Total time per sweep: 16 s,
Pulse width: 1 gs,
Pulse repetition rate: 20 per second,
Number of pulses at each frequency: 2,
Scan rate: 1 sweep each 10 to 20 min.
1.5 A research institute in the United States, which has operated a large network of oblique
sounders during the past three years, reports that interference resulting from its iono­
spheric sounders has a negligible effect on radiotelegraphy or facsimile services, provided
that the receiving terminals for these services are beyond the limits of the ground-wave
transmission from the sounder transmitter. For those receivers within range of the groundwave, it is necessary to consider the characteristics of the receivers to determine the degreeof interference which may result. Sky-wave interference to radiotelephony is also reported

— 371 —Rep. 367, 368

to be negligible except when the sounder transmitters radiate a significant number of pulses
on the same frequency during one scan.
2.

The best technique for monitoring transmissions from the various types of sounder would
be by making use of the appropriate sounder receiver. However, to provide one of eachtype at a monitoring station would entail a large expenditure of money. Therefore, it isevident that other methods of monitoring these transmissions by stations in the international
monitoring system must be used.
Some limited success has been achieved by monitoring stations in the U.S.A. in identifying
oblique ionospheric sounders when provided with information concerning the emission
characteristics and the transmission schedule or programme. Equipment used includes asuitable receiver, an oscilloscope and an accurate time source. Since it is common practiceto programme the sounder operation so that the sweep is started on the hour and at regularintervals thereafter (5, 10, 15 etc. min), transmissions from more than one sounder may
be observed at a particular frequency at approximately the same time. It is therefore neces­sary to be able to measure the time of reception of the pulses quite precisely. This can bedone by comparing the received pulses with local timing pulses on an oscilloscope. The
pulse repetition rate may likewise be determined by oscilloscope observations, provided two
or more pulses are radiated at each frequency. A spectrum analyser may also be a usefulaid in determining the emission characteristics. Measurement of the pulse length, especiallywhere short pulses are involved, presents a problem because of the need to use a relatively
selective receiver, resulting in considerable pulse distortion, as observed on the monitoring
equipment. Although direction-finders or rotable directional antennae may be useful inobtaining an approximation of the azimuth of arrival of the transmission, by observing several
consecutive sweeps with the direction-finder or antenna adjusted for a different direction foreach sweep, this is a time-consuming procedure, especially where the signal is subject tofading.

3.

As is mentioned in § 2, identification of sounder transmissions as a source of interference
depends upon availability of information concerning the emission characteristics and thetransmission schedule or programme of the particular sounder concerned. However, ifsome means could be devised whereby an identifying signal could be incorporated into thetransmissions without increasing the interference potential, the problem of positive andprompt identification would be greatly alleviated. Such identification would in many cases
be a definite aid in monitoring of swept emissions, but it would not eliminate the need for
information concerning the characteristics and location of all sweeping-type transmittersand their transmission schedules. Publication of this information should be on aninternational basis.

R E P O R T 368 *EXPEDITIOUS M ETHOD OF DETERM INING FIELD STRENGTH
AT M ONITORING STATIONS(Q uestion 4/V III)
(1966)
Question 4/VIII seeks information on an expeditious method for determining fieldstrength in the International Monitoring system, details of equipment for suitable applica­tion, and details of operation and accuracy of measurement.
* This Report was adopted unanimously.

— 372 —Rep. 368

Information on this subject is contained in Docs. VIII/12 (U.S.A.), VIII/15 (United
Kingdom), VIII/16 (Portugal) and VIII/18 (Japan), 1963-1966. The information may besummarized as follows:

1.

GeneralA given field strength will produce different levels of signal at the output of the receiver,depending upon the characteristics of the antenna and the receiver. For example, a signal
rated by the observer as QSA-1, because it is “ scarcely perceptible ” (Appendix 13, Radio
Regulations, Geneva, 1959) as received on a non-directional antenna of short effective lengthand a receiver of poor sensitivity and high noise figure, might produce a “ fairly good ”
signal with a highly-directional, high-gain antenna and a better receiver. It could appear
misleading on the basis of the QSA scale and SINPO, SINPFEMO-codes to rate the signal
as received in the latter case as less than QSA-3.
The degree of accuracy obtainable depends upon several factors, including freedom of
the antenna site from local conditions which disturb the arriving wavefront (e.g., local reflec­tion or reradiation), the care taken in calibrating the systems and the skill of the operator
in evaluating the results. Since, in the interest of expeditious measurements, some com­
promise with optimum accuracy may be required, the ± 2 dB accuracy given in Recommenda­
tion 378-1 may not readily be achievable. Under conditions typical of the installations used
at monitoring stations, the instant field strength will usually be within ± 6 dB of the actual
field strength of the vertically polarized component (see the Annex to Recommendation 378-1,§ 1.1.1). Where greater accuracy is required, information contained in Report 227 and
the Annex to Recommendation 378-1 should be taken into consideration.

2. System and accuracy of measurement
2.1 One suitable system, described in Doc. VIII/18 (Japan) is shown in Fig. 1 and consists ofan antenna with a known antenna gain, a receiver with a detection output meter, a noise
generator and a variable H F attenuator.
2.2 An output from the noise generator at a known level N dB is applied to the receiver, andthe gain in the receiver is regulated so as to keep the detection output meter at a certain
value. Then the signals to be measured are received by the antenna of known antennagain K dB and are applied to the receiver through the attenuator in the same condition as
mentioned above. The attenuator is adjusted so that the detection output is equal to theprevious value; the value is read A dB, and then the field-strength E dB is calculated from:
E = N + A - K(dB)

If the scale of the attenuator is graduated directly in units of (N + A — K) dB, therelative gain difference of the antenna used is within 5 dB over the frequency range 2 MHz
to 20 MHz. Therefore, taking into account errors due to other causes, the field-strength
can be read directly on the scale of the attenuator with an accuracy within ± 5 dB. For
other frequencies, calibration curves may be used, and the field-strength can be determinedfrom the above equation, the error being maintained within ± 5 dB.
2.3 For determining the field strength of keyed telegraph signals, it is preferable that an oscillo­
scope be used instead of a meter; this is because the readings of a meter in response to keyedsignals are inaccurate and are dependent on the time characteristics of the particular meter
used.

3.

Features of the system

3.1 The output of the noise generator used as a calibrating source is constant and independentof frequency for the stated frequency range. Therefore, over this frequency band there
is no need to re-tune the receiver each time, thus enabling calibration of the receiver withease.

— 373 —Rep. 368\

3.2 If the receiver has enough sensitivity for the output of the noise generator, no account needbe taken of linearity, or the frequency characteristic, etc. (however, the receiver should
be used below the saturation point, and a detection output meter is needed).
3.3 As the antenna used has a high gain, the minimum field-strength which can be measured
is low.

4.

Desired characteristics of elements used

4.1 Receiver
A receiver as generally used for monitoring will serve for the purpose.
to use a detection output meter and the best possible noise figure.

It is desirable

4.2 Noise generator
It uses a diode-generating circuit and its output is independent of the frequency. If
the output is low, some amplification is needed, and the amplification characteristic mustbe broadband.

4.3 Antenna
The requirements of the antenna are: non-directivity, broadband, high gain and sim­
plicity of construction. In general, a vertical non-directional loaded antenna is consideredmost desirable.
By using an inverted cone antenna as described in Doc. VIII/15, the equipment may
be used over a very wide frequency band, say 12 kHz to 27-5 MHz. The initial calibration,
to give an overall accuracy of measurement of field strength of ± 6 dB, might be done bycalculation from the geometry of the antenna (see Report 373, Figs. 4 to 8).

4.4 Attenuator
It must have a good frequency characteristic over the frequency band in use.
5.

A more rapid method is described in Doc. V III/16 (Portugal) as follows:
If a lesser degree of accuracy could be accepted, a short vertical omnidirectional antenna
could be installed near the antenna system of the station. This antenna would certainly
be affected by the proximity of directional and other antennae at the monitoring station,
but it should be placed sufficiently near to the station, building to be connected to the receivers
by coaxial cable.
The antenna, about 5 m high, is installed with an earthing system consisting of star­
shaped conductors buried in the ground and connected by a transformer to a coaxial cable,
which in turn can be connected to any of the operators’ positions.
Each working position, with its receiver or receivers, is equipped with a coaxial switch,by means of which the operator can select the most appropriate antenna in the normal sys­tem (directional or otherwise) for monitoring. One position of the switch permits his receiver
to be connected to the vertical antenna.
The vertical antenna-receiver unit is so calibrated that it can be used, in conjunction
with the receiver measuring apparatus, as a secondary system for measuring field-strength.
Thus, if an operator listening to an emission on one of the normal antennae wishes toknow the approximate field-strength, he simply operates the coaxial switch to connect his
receiver to the vertical antenna. The reading on the receiver measuring apparatus andthe frequency calibration curve of the receiver immediately give the approximate field-strength.

— 374 —Rep. 368,369

If a more accurate figure is required, the d.c. voltage can be recorded after detectionin the receiver and the mean value determined.
With this kind of equipment, an accuracy of about ± 6 dB is possible.
Antenna

Noise generator
F igure 1

Arrangements for test

R E P O R T 369 *M EASUREM ENT OF FREQUENCIES OF SINGLE-SIDEBAND,
INDEPENDENT-SIDEBAND AND OTHER COM PLEX EM ISSIONS(Q uestion 2/V III)
(1966)
This Report summarizes the contributions and discussions in response to Question 2/VIII
which provide only partial solution to the problems encountered in the measurement of
frequencies of transmissions of certain complex classes of emission:
1.

Determination of the centre frequency of complex emissions, where the spectrum of theemission is unknown, presents a difficult problem, particularly when a signal is encounteredwhich has no discrete carrier and where all the tones of the system (in the case of a multitone system) are not being transmitted. From the point of view of the monitoring stations,the measurement of independent-sideband (ISB) and single-sideband (SSB) emissions would
be facilitated if a carrier were transmitted, but this is often not practicable when consider­ing the requirements of many present-day systems.
In many ISB emissions a prior knowledge of the system can give guidance in locating
the carrier frequency, so facilitating assessment of the centre frequency. This emphasizes
the need for all transmissions to be clearly described when notifying assignments. Parti­
cularly difficult cases are ISB emissions employing two-tone or frequency-shift sub-carriers,
since they may be indistinguishable from pure FI emissions. To facilitate the measure­ment of the more complex classes of emission, some operating organizations have adopted
designation systems which identify separately the sidebands and sub-carriers. Similarly,* This Report was adopted unanimously.

— 375 —Rep. 369, 370

a system of designation may be used to indicate the position of the centre frequency withrespect to the assigned frequency.

2.

In those instances where a characteristic frequency (defined in No. 86, of the Radio Regula­tions, Geneva, 1959) has been established, e.g. a reduced or incompletely suppressed carrier
or a pilot frequency (see § 2.2.2 of Recommendation 379-1), it is often convenient to measure
the characteristic frequency by adjusting the frequency of a stable variable radio-frequency
oscillator to coincide as exactly as possible with the characteristic frequency as observed
on a spectrum analyser of high resolving power. The precise frequency of the radiofrequency oscillator may then be determined by the usual methods and the deviation from theassigned frequency calculated. Using this procedure for measurements in band 7 (3-30 MHz),
it is desirable that the spectrum analyser have a maximum resolving power (see Recommen­
dation 182-1, § 2), at reduced sweeps, of 10 Hz and that the short-time (10 s) stability ofthe variable radio-frequency oscillator be 5 parts in 107 or better.

3.

Doc. VIII/78 (Japan), 1963-1966, describes a method of determining the approximate
frequency of the suppressed carrier of A3J emissions, by measuring the frequency of thereceiver demodulating oscillator when the oscillator is adjusted for optimum speech articula­tion and understandability. According to tests conducted under varying conditions ofsignal level and noise, the accuracy of this method in the H F band in many cases may be
within 30 Hz.

4.

In multi-tone transmissions, where the characteristics of the emission are known,
determination of the relationships between the various components of the emission witha spectrum analyser and a variable frequency oscillator to serve as a reference frequency,
may permit a reasonably accurate determination of the centre frequency. Another similar
method is to photograph the spectrum display, together with known frequency markers.

R E P O R T 370 *TYPES AND M ETHOD S OF ASSISTANCE BY M ONITORING STATIONS TO
THE OPERATION OF VARIOUS RADIO SERVICES
Exchange of technical information between receiving and measuring
stations by means of exchanges of staff(Study Program m e 13A/VIII)(1966)
This Report takes account of Doc. VIII/79 (E.B.U.), 1963-1966, submitted to the
X lth Plenary Assembly of the C.C.I.R., Oslo, 1966.
To provide for liaison between the various receiving and measuring stations exploitedby its members, the European Broadcasting Union arranges periodical meetings of theengineers-in-charge of those stations. The engineers-in-charge have expressed the opinion
that, to improve the cooperation between the receiving stations and to keep each otherinformed of the methods and equipment used in the other stations, it would be useful toarrange exchanges of staff between them. Such exchanges were therefore arranged in 1963
and 1964 under the auspices of the E.B.U., between three receiving stations. The six
operators who took part in this scheme were all qualified technicians having a considerable
number of years of experience.
'
After these exchanges, the engineers-in-charge of the three stations in question sub­mitted reports on the project, indicating the benefits that had accrued. They also discussed* This Report was adopted unanimously.

I

Rep. 370, 371

—

376 —

the project at a meeting of the engineers-in-charge of receiving stations exploited by the
E.B.U. and its members, in January, 1966.
The detached operators in each case took over the work of operators on the staff ofthe station to which they were attached. Consequently, they were fully integrated in the“ life ” of that station and worked under exactly the same conditions as the other operators
there. They very quickly became accustomed to their new work and although language
difficulties were occasionally encountered, they were never particularly serious.
The engineers-in-charge concerned are of the opinion that a substantial benefit was
gained by these exchanges, because:- the detached operators had the time to inform themselves thoroughly regarding the organiza­tion and equipment of the other station, and to compare them with those of theirown stations. Each of the three stations now has at its disposal more complete
information about the equipment used at the other stations and it is therefore possible
for a valid comparison to be made with its own corresponding apparatus. The operators
were also able to appreciate certain technical operations which would lead to a higher
efficiency and to exchange practical suggestions;- an atmosphere of reciprocal confidence was created between the staff of each station andtheir foreign colleagues who were attached, which has led to much closer collaboration
between the stations. There has resulted an improvement in the regularity and rapidityof the exchange of information, which has improved the efficacity of the monitoring effectedby the three stations. This, in turn, has proved beneficial when difficulties have been
experienced in identifying transmission;- these exchanges encouraged personal contacts between operators from different countries
having different customs and they have also given them a greater interest in their work.
The attached operators certainly showed a great deal of interest and put many questions
to their colleagues regarding the work, working conditions and methods, training andthe like.
It would seem that the optimum duration for such exchanges is two or three weeks.
In effect, the attached operators must be given time to accustom themselves to new appa­
ratus and methods, and about ten days seems to be the absolute minimum for participating
in all the operational duties which are included in a shift, as this implies working at all thevarious operating positions.
It would seem also that the staff which draws the greatest profit from the exchanges
are those of the greatest seniority and experience, but the younger operators neverthelessshow much interest in them. In order that an operator may draw the greatest benefit fromthe attachment, it is necessary that he be assigned tasks which are not too different fromthose that he undertakes in his own station.
The engineers-in-charge of the stations taking part in this project organized by the
E.B.U. deem that it should be repeated at intervals.

R E P O R T 371 *M ONITORING SERVICES IN THE NEW AND
DEVELOPING COUNTRIES(Q uestion 12/V III)
(1966)

1.

Introduction
Question 12/VIII seeks to discover what kind of monitoring services should be started
by new and developing countries, the guidance that can be given in the establishment andorganization of such services and the facilities to be provided by monitoring equipment,
including suitable characteristics.
* This Report was adopted unanimously.

— 377 —Rep. 371

2.. Tasks which a monitoring station should be able to perform
0

2.1 Selection o f frequencies for new communication channels
Studies should be made over a sufficiently long period, of the use of the radio-frequency
spectrum in the selected band with a view to choosing frequencies which can be used with­out causing interference to other already authorized services.
This operation is most important for Administrations and private operating agencies,
since the quality of the circuit and the extent to which it is free from operational incidents
depend to a large degree on the care with which the operating frequencies have been chosen.
2.2 Monitoring o f emissions
By this is meant the monitoring, either periodically or whenever a check seems required,of the country’s own transmitters, and, if necessary, of those of their correspondents. This
monitoring consists in:- measuring the frequencies and bandwidths of the emissions;- checking the quality of the modulation;- checking for freedom from spurious emissions and, in some cases, measuring the strengthof the radiated field.
2.3 Measures relating to interference
In all cases of interference affecting a circuit, measures should be taken promptly to:- determine the cause of interference,- identify the interfering emission,- determine the technical characteristics of the interfering emission,- propose steps for eliminating the interference.
2.4 Participation in the international monitoring system ♦In addition to the help which it should be able to give to another country or anothermonitoring station within the framework of §§ 2.1, 2.2 and 2.3, a monitoring station mustalso be able to participate in the international monitoring system under the conditions
specified in Article 13 of the Radio Regulations, Geneva, 1959.
Such participation consists in carrying out all the monitoring of operations requestedby the International Frequency Registration Board (I.F.R.B.).

3.

Organization and operation of a monitoring station

3.1 General
As regards the organization of a monitoring service, there is no existing plan to meet
all needs. A service might, for instance, be envisaged consisting of a number of organic
sections each playing a specific part. This is why, when planning the structure of a moni­
toring service the nature of the duty or duties to be provided should first be determined.
Among the relevant factors, one might mention the frequency bands to be monitored, thegeographical extent of the area covered, the advisability of installing long-range direction­finders and the need to provide mobile monitoring facilities to supplement the fixed installa­
tions. All these factors should be taken into account when determining the number ofstations required and to obtain an idea of the areas where they should be set up. It goes
without saying that these planning tasks entail budgetary considerations, both as regards
staff and equipment, and it is often these considerations, rather than the requirements them­selves, that determine the scope of the future service. In such cases, thorough preliminary
study of all the factors involved will enable the best use to be made of available funds.

Rep. 371

— 378 —

3.2 The choice o f site for the monitoring station
The site of a monitoring station must be easily accessible by road, easily connected toessential public services such as power and water supplies, as well as telephone communica­
tions and should be near to a residential area where the staff can live. At the same time,
the site selected must be far enough away from built-up areas to avoid industrial interfer­ence. The interference range of a residential area is approximately 400 m and that of anindustrial zone approximately 5 km. For H F monitoring, the height of the terrain is [ofno importance, but since most monitoring stations operate also in the VHF and U H F bands,
it is better to choose a site higher than the surrounding ground. As a general rule, it is also
better to site the station on flat-land covering an area of approximately 100 000 m 2, withgood conductivity and with no obstacles within a radius of approximately 5 km. Whenplanning the establishment of M F and H F direction-finders, a larger area should be envisaged.
Assuming that the developing country in question starts off with the very minimumof communication equipment, and probably no monitoring facilities at all, the monitoring
installations might quite easily be combined with the receiving station of the communica­
tions installations, at least during the initial period of operation. Each transmitting station
should be capable of measuring its own frequencies, to be able to operate correctly. Each
receiving station might be likewise equipped, so as to be, able, if necessary, to render assistanceto its counterpart transmitting station, in measuring the interfering signals and to carryout reciprocal monitoring of the frequencies of its correspondents. Besides resulting ina saving of staff (the same engineers and technicians being available for both communica­
tions and monitoring operations), performance of these various functions in conjunction
would save the expense of establishing the monitoring station on separate ground and in
separate premises. Moreover, the various antennae of the receiving station would be of
the greatest assistance to monitoring operations.
Obviously, in countries where the receiving stations are operated by private operating
agencies other than the national Administration, the question of establishing a monitoring
station in a receiving station should be examined jointly by the Administration of the country
and the private agency operating the receiving station.
3.3 Buildings and power supply
The group of installations of a self-sufficient monitoring station must be housed in premises
with a floor space of at least 70 m 2 consisting chiefly of an equipment room, a power room
and an office.
The centre’s power consumption can be estimated from a few to several kilowatts,
depending on the equipment used.
It is useful to have a stand-by generating set, although some of the equipment may operatefrom batteries.
In the proximity of the station, connection to the power supply must be by undergroundcable, as an overhead line is likely to cause interference and may be an awkward obstaclein the neighbourhood of the station’s antennae.
3.4 Antennae
The question of the antennae for the equipment of monitoring stations is dealt within Report 373.
'
3.5 Sta ff.

.

3.5.1 Establishment
The following staff is absolutely essential for proper working of the monitoring
station:- a specialist in charge of the station,

— 379 —Rep. 371- four operators, capable of performing the more common operations and working
shifts so that one of them is always on duty,- a good all-round technician, responsible for new developments, maintenance andfault clearance and also capable of working as an operator.
3.5.2 Recruitment and training
Although no precise rules can be laid down here on these points, the problem isworth mentioning, as it is undoubtedly the most difficult to solve.
The staff of a monitoring station must be fully familiar with both the techniqueand the operation of the various services which use the frequencies monitored.
Its members must therefore be young enough to be able to keep abreast of thelatest developments in radio technique, but nevertheless have a sound experience of
the work done in transmitting or receiving centres or the radio-operating centres ofthe fixed, mobile and broadcasting services. Such experience would seem to be obtain­
able only through long periods of practical work in these various services.
The assistance and guidance to be given to Administrations for the purpose of
establishing and organizing a monitoring service may take various forms, such as:- consultation with officials of successfully-operating monitoring services;- training periods in operative monitoring services;- vocational training programmes, conducted under technical assistance procedures,for the key personnel of Administrations proposing to establish a monitoring service;- review o f the many technical documents dealing with monitoring rules and standards
published by the I.T.U., engineering or trade organizations and Administrations;study of textbooks and equipment instruction-manuals and any other relevant
explanatory material.

4.

Technical equipment

4.1 Basic requirements
Although some degree of monitoring coverage would be possible with even the sim­plest and most inexpensive installation (e.g., a receiver and a suitable antenna), the following
might be considered as a basic monitoring installation which will satisfy the requirements
for the more important monitoring functions.
4.1.1 Receivers
Receivers covering a minimum frequency range from 200 kHz to 30 MHz withadditional coverage are required. In selecting the receivers, the various classes ofemission to be monitored (for example, single-sideband telephony) should be taken
into account and provision made for the reception of such emissions. A numberof degrees of selectivity, from 1 kHz or even a much smaller bandwidth to at least
12 kHz at the 40 dB points on the receiver selectivity curve, are also desirable.
At frequencies up to 30 MHz, all the qualities expected of receivers for main receiv­
ing stations are required of monitoring receivers, with the addition of good frequency
setting accuracy (better than 500 Hz for communication receivers and better than 1 kHz
for broadcast receivers), rapid tuning and a minimum of waveband switching. Special
attention needs to be given to the suppression of receiver oscillator radiation and to
the suppression of spurious responses of the receiver. A panoramic adaptor unit
may be used with a receiver to provide a visual display of spectrum occupancy. Thereis also considerable advantage in using single-or independent-sideband receivers when
receiving double-sideband signals in the presence of interference.

Rep. 371

— 380 —

Above 30 MHz, receivers capable of accepting amplitude- and frequency-modula­tion emissions are essential and it is important to ensure that adequate'bandwidth
is available.
All receivers should be provided with outputs of the intermediate frequency at
low impedance and with radio-frequency injection inputs. If the latter are locatedbetween the radio-frequency and frequency-changer stages, test and reference signals
injected into receivers, usually at low level, will not radiate from the receiving
antenna. Again, all radio-frequency and intermediate-frequency access points shouldhave a common value of impedance, ideally the same as that of the antenna input
impedance.

4.1.2 Frequency measuring equipment
As stated in the considerings of Recommendation 377-1, it is desirable that theerror of frequency measurement shall not exceed one-tenth of the frequency tolerances
specified in Appendix 3 to the Radio Regulations, Geneva, 1959. The most stringent
internationally agreed tolerances refer to broadcasting stations and fixed stations
operating in the band 4 to 29-7 MHz. This tolerance is 30 parts in 106, reducing to
15 parts in 106 for new transmitters after 1 January 1964, and for all transmittersafter 1 January 1966. The corresponding measuring equipment therefore need todetermine frequency to an accuracy of 3 parts in 106 and 1-5 parts in 106 respectively,or better.
Crystal oscillator frequency standards, with stabilities better than 1 part in 109
per day, are available and, to maintain this order of stability, continuity of power supplies
must be assured. This can be facilitated by using transistorized frequency standards
which can be operated by a battery or by a mains power supply. Frequency standards
are usually calibrated by reference to standard time and/or frequency transmissions,
now available in a number of countries. Many of these transmissions have stabilities
at the transmitter of better than 5 parts in 109, and calibration errors of less than 1 partin 108 are easily realized by the use of a chronograph or frequency comparison appa­
ratus (see § 4.1.6). Where these transmissions are not available, the cooperation ofanother monitoring station could be sought to make simultaneous measurements on
one or more known stable H F transmissions.
Two basic systems of frequency measurement are described below. The firstsystem uses a direct-reading decade oscillator or synthesizer, which may be locked
to the nearest multiple of, for instance, 100 Hz by the local frequency standard, set
to give any output frequency between 20 Hz and 30 MHz, frequencies between 100 Hz
points being generated by a variable-frequency oscillator. Harmonic amplifiers may
be used to extend the range up to 1000 MHz or higher. In measuring AM signals,
or any signal having discrete components, the receiver is first tuned to the wanted signal.
The decade oscillator or synthesizer output is then adjusted so that the beat between
the signal and synthesizer frequencies is exactly 1 kHz. This difference frequency
is determined by a Lissajous figure on a cathode-ray tube. The frequency of the signal
can be read off the decade dials of the synthesizer plus or minus 1 kHz, dependingon whether the reference signal is set below or above the signal frequency. In the second
system, developed for use principally in the H F band, the principle involved is to lockthe first oscillator of a receiver incorporating automatic frequency control, to the signal
component to be measured and then to measure the first oscillator frequency on a
decade counter. The frequency of the signal is then the count frequency, plus or minus
the intermediate-frequency of the receiver, depending on whether the oscillator isabove or below signal frequency. The first system has the advantage of higher accuracy

— 381 —Rep. 371

while the second system is less useful for weak signals but has the advantage of speedof measurement.
When measuring frequency-modulation signals, a difficulty arises owing to the
reduction in carrier level during modulation. By using a mid-frequency indicator
to show differences between the mid-frequency of the frequency-modulation spectrum
and the reference frequency, signals with deviations up to ± 100 kHz or even higher
can be measured. For additional details on frequency measurements see Recommenda­
tion 377-1 and Report 272-1.
4.1.3 Bandwidth or spectrum measuring equipment
Bandwidth or spectrum measurements may be made using a spectrum analyser.
The performance of all types of instrument for bandwidth measurements is limited
by fading and interference especially for observations on long-distance transmissions.
With a spectrum analyser it is possible, by photographically superimposing the resultsof several successive sweeps, to obtain very useful information on the bandspread of
most transmissions received at monitoring stations. Report 275-1 describes typical
spectrum analyses. For bandwidth measurements see Recommendation 443 andReport 275-1.
4.1.4 Field-strength*measuring equipment
Many equipments for field-strength measurements in the frequency range 150 kHz
to 30 MHz incorporate loop antennae connected to the input of a receiver. Suchequipment is usually capable of an accuracy of ± 2 dB, but does not necessarily
have sufficient sensitivity. An alternative arrangement giving greater sensitivity is
to use a vertical rod antenna shorter than 1/4 wavelength for the highest frequency
to be measured, feeding directly into a low-noise amplifier. The system is calibrated
by injecting a known voltage in series with the antenna. It is necessary to erect theantenna clear of large buildings and possible sources of interference. If the fieldstrength measuring equipment is not situated close to the antenna, the low-noise ampli­
fier may be located in a watertight box at the base of the antenna, the output of theamplifier and the antenna calibrating signals being sent over two coaxial cables.
Field-strength measurements in the VHF band may be made by erecting dipole
antennae, of dimensions appropriate for the frequency to be measured, at a height ofabout 10 m above ground. The receiver input voltage may then be determined bysubstitution, the field strength for the matched condition being calculated by theequation:
Field strength = n/X (source e.m.f.)
For details of field-strength measurement techniques, see Recommendation 377—1
and Report 273-1, for details of simple and expeditious methods of measuring fieldstrength, see Report 368 and Recommendation 442.
4.1.5 Identification equipment
The identification of radio signals is one of the most difficult tasks laid upon amonitoring station. This difficulty is partly due to the infrequent transmission ofidentifying signals and partly to the use of abbreviated call signs. In the case of complex
telegraph systems there is difficulty both in radiation and in monitoring and decoding
identifying signals.
The facilities referred to above, namely direction-finding, frequency measurement,
spectrum analysis and field-strength measurement, may all be used as contributory
factors in the identification of the emission, particularly when their precise frequency
and emission characteristics have been notified internationally. It is also desirable

— 382 —Rep. 371

that a monitoring station be equipped for the reception of ISB and FSK signals, inaddition to receivers for classes of emission A l, A2 and A3, together with means ofrecovering from radiotelephony privacy systems, and with some of the simpler tele­graph instruments such as undulators and variable speed teleprinters. A magnetic
tape recorder is also valuable for recording the more abstruse emissions for reference
and subsequent examination by an authority familiar with more complex types oftransmission system (see also Recommendation 379-1 and Report 280-1).

4.1.6 Cathode-ray oscilloscope
A cathode-ray oscilloscope having a vertical amplifier with adequate frequency
response to permit direct display of the intermediate-frequency output of the H F recei­
ver normally used for observations of A3 emissions. This oscilloscope will provide
a convenient means of observing broadcast station modulation levels as well as forfrequency matching (see § 4.1.2 above) and for observing the waveform of keyed emis­
sions (A l, F I, etc).

4.2 Additional equipment
Although equipment mentioned in § 4.1 will perform many of the monitoring functions,certain additional instruments will permit more effective operation of a monitoring station
and will expand its capabilities. These facilities include:
4.2.1 Direction finders for localizing sources of interference to a particular area and as an
aid in identifying emission sources based upon knowledge of their location. Gene­
rally, only the larger monitoring systems, having a minimum of three direction-finding
stations, will benefit greatly from fixed direction-finders, since a minimum of three
bearings are needed to obtain a reasonably accurate fix. However, even one or two
direction finders will provide some useful information. Where the direction-finder
networks of two or more Administrations can be coordinated so that the bearing dataobtained may be shared, improved fix accuracy should result in many instances. For
detailed information concerning the characteristics and relative merits of various
types of direction finder, see Report 372.
4.2.2 Automatic monitoring equipment for unattended surveillance of selected portions of
the radio-frequency spectrum to provide a permanent record of channel occupancy
in terms of time, approximate signal level and bandwidth, and other useful information.
For additional details, see Report 278-1.
4.2.3 Visual monitoring equipment. Although spectrum analysers will provide displaysof limited areas of the radio-frequency spectrum, their design is directed primarily
toward permitting a detailed analysis of an emission, rather than to display a wide
area of the radio-frequency spectrum in terms of presence or absence of emission.
Instruments designed especially for visual monitoring purposes usually make use oflarge cathode-ray tubes, to give a reasonably detailed display even where alarge area of the radio-frequency spectrum is under observation. Sweep rates areusually sufficiently fast so that an essentially continuous display is achieved, as con­trasted to the slower sweeps which are employed in spectrum analysers to obtain opti­
mum trace resolution. Visual monitoring equipment and techniques are discussed
in greater detail in Report 279.
4.2.4 With the aid of a suitable device, frequencies below 3 MHz can be transposed within
the frequency range covered by the H F equipment described. In this way, the possi­
bilities which this equipment offers and with which we have already dealt, can be exploi­
ted to the full.

— 383 —Rep. 371

4.2.5 Adapters are available to enable double-sideband receivers to be used for the receptionof single-sideband and independent-sideband transmissions.
4.2.6 Apparatus is available for the automatic comparison and control of a frequency source,
relative to a VLF standard-frequency transmission. (A list of standard-frequency trans­missions is contained in Report 267-1).
4.2.7 Monitoring of frequencies above 30 MHz generally calls for mobile equipment on
motor vehicles. This could comprise:- a suitable receiver (possibly of the panoramic analysistype),- a frequency measuring device, capable of acting as a calibrated generator with anaccuracy appropriate for the emission to be measured (see Recommendation 377-1),- a field-strength measurer, covering up to 1000 MHz,- a spectrum analyser, with which a single emission or several adjacent emissions withfrequency shift may be observed, while a calibration, based on the calibrated gene­rator, offers the possibility of measuring the nominal frequency, actual occupied
bandwidth, frequency variation, etc.
- an array of antennae, suitable for the type of monitoring to be effected.

5.

Doc. VIII/80 (E.B.U.), period 1963-1966
The European Broadcasting Union has published a Technical Monograph (No. 3102)*
entitled: “ Receiving and measuring stations for broadcasting purposes ”, which describes
the various measuring methods and apparatus used in several European monitoring stations.
In this monograph, a number of passages describe the techniques and equipment likely to
be of particular interest to new and developing countries; in particular, the following para­graphs should be mentioned:
Chapter III: Measuring methods
1. The verification and comparison of the frequencies of the standards
2.2 Frequency measurement by the double-beat method
2.3 Frequency measurement by the interpolation method
2.6 Special cases of frequency measurement
3. The determination of the occupation of the frequency spectrum
4.1 Field-strength measurement procedure
6. Measurement of the depth of modulation
Chapter IV : Apparatus required
1. Antennae
2. Receivers
3. Frequency standards
4.1 Constitution of a frequency-measuring position
5.1 Constitution of the automatic recorders of the occupation of the spectrum
6.1 Constitution of the field-strength measuring equipment
6.2 Essential characteristics of field-strength measuring sets
8.1 Device for measuring the average depth of modulation.

* This monograph can be obtained from: Centre technique de l ’U .E .R ., 32 Avenue Albert-Lancaster,
Bruxelles 18.
’

\Rep. 372— 384 —REPORT 372 *DIRECTION-FINDING AT M ONITORING STATIONS(Question 8/VIII)(1966)
Study Group VIII, taking account of Doc. VIII/34 (U.S.A.) and VIII/87 (India) 19631966, furnishes:- information concerning fixed monitoring stations;- information concerning mobile monitoring stations;- a summary of information contained in the various documents, which, without being
new, will be useful, when grouped, to the monitoring stations;- this information concerns the accuracy of bearings and positions.

1.

Fixed direction-finders (see Annex)
Methods of direction finding and procedures for improving the accuracy of bearings
at fixed monitoring stations are generally directed towards producing an acceptable degreeof accuracy on waves propagated via the ionosphere. Ionospheric propagation exerts
pronounced effects on the characteristics of radio waves which seriously affect the results
obtainable with the different methods of direction finding. The simple rotatable or crossed
loop method of direction finding on ionospheric waves fails at the outset to meet the require­ments of accuracy and consequently need not be considered. Since sky-waves throughout
the entire H F range are of primary importance in direction finding associated with inter­national monitoring, we may also disregard methods that are limited to either very narrow
ranges of frequencies or to frequencies lying above the H F spectrum. Considering alsothat it may often be necessary to locate unidentified sources of interference or unauthorizedtransmitters, we may dismiss from discussion those methods of direction finding which
depend upon the control or cooperation of the transmitter whose location we are trying todetermine. The methods that have proved useful for long-range H F direction finding are
discussed briefly below:

1.1 Spaced-loop system
Spaced loops have proved useful in producing bearings, particularly over the shorter
distance ranges of up to about 650 km (400 miles). The usual construction consists basi­cally of two vertical, parallel loops rigidly mounted coaxially at the ends of a horizontal,
rotatable boom. Another type consists of two such pairs perpendicular to each other in
fixed position, with transmission fines feeding a goniometer at the centre.
In the fixed, four-element system there is an octantal error (in addition to any residual
error in the goniometer), due to the spacing of the elements being an appreciable fractionof a wavelength at the high-frequency end of its working range. However, allowance canbe made for this error in a calibration chart.
In a coaxial spaced-loop direction-finder the pickup elements (antennae) are closed
loops and their individual e.m.f.’s do not vary with the angle of incidence in the verticalplane. Thus, the proportion of wanted (vertically polarized components) pickup to unwanted* This Report was adopted unanimously.

— 385 —Rep. 372(horizontally polarized components) remains high. Since the loops are connected in op­
position, the net polarization error is at a minimum, and this system is superior to the Adcock
up to about 650 km (400 miles). Performance is very good even where the vertical angleof the received wave exceeds 45°. The sensitivity is almost 20 dB poorer than a single loopof the same size as one of the spaced loops.

1.2 Adcock
The Adcock is characterized, basically, by the use of spaced vertical elements. The
vertical elements may be used as a rotating pair or in a fixed four-element system feeding agoniometer at the centre. The latter method begins to exhibit octantal error at frequencies
where element spacing exceeds about one-tenth of a wavelength. In the fixed element system,
particularly, both grounded monopole and elevated dipole systems have been used success­fully. The Adcock is generally more sensitive than spaced-loop systems of reasonable size.
Although the Adcock system is theoretically immune to polarization error where perfectbalance is maintained and pickup on the horizontal lines is eliminated, such an ideal conditionis never achieved in actual practice. An important disadvantage is an inherent limitationin vertical elements— pickup of the wanted vertical component of the received wave falls off
rapidly as the vertical angle of arrival increases. At angles greater than about 45°, the Adcock
not only has reduced pickup but is inferior to the spaced-loop system in accuracy, since thewanted pickup is greatly reduced and the unwanted pickup remains constant. As with any
null method, the introduction of small unwanted signals is damaging. However, although
there is reduced pickup by vertical elements at high angles of wave arrival, over the longer
distance paths, the stronger component will usually be one arriving at low angles. Conse­
quently, the Adcock is quite generally regarded as superior to spaced loops, where bearings
are taken over distances greater than about 650 km (400 miles).

1.3 Doppler system
The Doppler method of direction finding utilizes a rotating antenna rotated either phy­sically or electrically, which causes the received emission to be raised in frequency as theantenna moves toward the source and to be lowered in frequency as it moves away from thesource. At two points, half-way between, the instantaneous frequency of the received signal
is unchanged.
In actual practice the system usually consists of a large number of vertical antennae,each connected through a transmission line to one terminal of a rotating capacity switch.
The receiver is connected to the switch rotor and is thus connected to successive antennae.
The received frequency is phase-modulated at the rate of rotation of the rotor, and is usuallymultiplied in the receiver to produce frequency-modulation. After heterodying the signal
to a suitable intermediate frequency and feeding it into a discriminator, an audio-frequency
is produced, the phase of which can be compared with a reference signal derived from therotation of the rotor.
The radius of the antenna circle is limited to one-half wavelength at the highest fre­quency of operation to avoid ambiguities. This system is relatively immune to moderatefading or other amplitude variations since limiters effectively remove amplitude variations.
It can be expected that there would be some complications, if not severe difficulties, in using
this system on those types of waves where all of the components vary continually in fre­quency, such as single-sideband voice emissions or frequency-modulated emissions. A serious
practical disadvantage in the Doppler system is an extremely critical requirement for pre­cisely equal electrical lengths of transmission lines. This method of direction finding has,
up to the present, found limited use.

Rep. 372

— 386 —

1.4 Wullenweber system
The Wullenweber method of direction finding utilizes a large number of vertical antennae
symmetrically mounted in a circle equidistant from a circular screen. Each antenna isconnected through a transmission line to a capacity stator segment of a rotating switch.
Several rotor segments are used simultaneously and are connected to the receiver throughindividual delay lines which cause the signals from the coupled antennae to arrive at thereceiver in phase, thus producing the sharp beam of a broadside array. Maximum gain
is on the axis of symmetry, but the side-lobe level is down only about 12 dB. However,the pattern can be sharpened by introduction of loss into the off-centre antenna circuits.
Since this is a wide-aperture antenna wherein a relatively large portion of the wave front
is received, distortion of irregularities in the wave front do not result in the degree of errorthat appears in narrow-aperture systems. Also, since several antennae are feeding the receiver
simultaneously, a slight irregularity introduced by or from any one antenna is not nearlyso serious as where each antenna is swept singly and in succession. Hence, transmissionline lengths are not considered quite so critical as in the Doppler system.

1.5 Doc. VIII 187 (India), 1963-1966
1.5.1 Direction-finding equipment with 8 element Adcock antennae, rotating goniometer andautomatic visual indicator is being used at the monitoring stations of the Indian Admin­
istration. By the use of a suitable pre-amplifier after the goniometer at the centreof the antenna system and using simple remote control technique, it is possible tolocate the antenna system at a distance of 300 m from the main reception/indicatorequipment.
1.5.2 For the type of direction-finding equipment indicated, it is possible to have the remotecontrol facility at a moderate extra cost. The availability of the direction-finding
equipment alongside other monitoring equipment has proved to be most convenientin the monitoring work. The same operator who is working on a monitoring channel
can quickly take bearings of any station he desires. Selection of site with respect
to the main monitoring building does not become very critical, as the antennae canbe located up to a distance of 300 m from the main building. The effect of otherantennae in the field also can be thus reduced.
1.5.3 The commercial direction-finding equipment has been modified to use a monitoring
receiver which has better frequency stability (calibration at every 1 kHz interval
right up to the highest frequency of 30 MHz). This again provides a great facility
in tuning quickly and correctly the wanted station for the direction-finding bearing.
1.5.4 The above direction-finding system provides the bearing accuracy between ± 1° forstable signals exceeding 50 pV/m and ± 2° for stable signals exceeding 3 pV/m.
Considering that, in the H F spectrum, the bearing inaccuracies contributed by fading
and instability of the signals and other factors could be of this order, it is felt thatthe basic accuracy of the equipment as mentioned above should be adequate for moni­
toring purposes.
1.5.5 The direction-finding system employing a rotating goniometer has certain disadvantages
as compared with one using phase/amplitude balanced amplifiers etc. With the rotat­
ing goniometer type, bearings are difficult to take in the presence of interference.
Separate calibrations are required when selectivity of the receiver is changed and it
is not always possible to choose the optimum selectivity to avoid interference. Most
systems can, therefore, offer either one or two selectivities such as 1-2 kHz or 3 kHz.
Proper adjustments of tuning, gain control, settings, etc., are required for taking goodbearings. However, usually trained operators are employed at monitoring stations,

— 387 —hence these drawbacks can be overcome to some extent.
ing equipment is fairly cheap.

Rep. 372

This type of direction-find­

1.5.6 It is the experience of the Indian Administration that operational personnel for taking
bearings in the H F bands require considerable training. This involves training inproper adjustments of various controls as also training in taking bearings speciallywhen the signals are fading or the bearings are swinging. Untrained operators tend
to read bearings with certain bias towards one particular value, thus tending to givea false indication of class of bearings.

2. Mobile direction-finder
Because of the requirements of portability, mobile-unit direction-finders normallyused in automobiles are necessarily limited to types that are small physically and easily
manipulated. For the H F range, the most practical choice is a rotating loop. Since mobile
units operate primarily within a pre-determined fix area and generally within the groundwave of the unknown target transmitter, quite satisfactory results have been obtained witha simple rotating loop. In general, the requirement of a boom for either spaced loops orspaced vertical elements practically eliminates these types from consideration for mobile
units.
2.1 The accuracy of single-loop direction finders depends greatly on the polarization and angleof arrival of the wave-front. On ground-wave signals, where there is no sky-wave component
present, and where there is little or no local distortion of the wave-front, due to local reflec­tion or re-radiation of the signal, accuracies approaching ± 2° are possible. Under field
conditions usually encountered, an accuracy of about dr 5° may be expected. However,in areas where local conditions distort the wave-front or where a significant sky-wave com­ponent is present the expected error may increase to several times this value.
The accuracy of mobile-unit loop bearings on ground-wave emissions can be improvedby averaging multiple bearings, as with long-range direction finders. The advantage ofa calibration curve, covering the full 360° of azimuth, when the direction finder is mounted
on an automobile, should not be overlooked. Check bearings should be taken on known
transmitters to confirm the proper operation of the equipment.

3.

Accuracy of bearings and positions

3.1 Classification o f bearings
Appendix 23 of the Radio Regulations stipulates that, to estimate the accuracy anddetermine the corresponding class of a bearing, the operator should use the observational
characteristics shown in Table I. It adds that the operator may, when time permits, take
into account the probability of error in the bearing.
A bearing is considered to belong to a particular class if there is a probability of lessthan one in twenty that the bearing error exceeds the numerical values specified for thatclass in Table I.
The Appendix adds that this probability should be determined from an analysis of thefive components that make up the total variance of the bearing (instrumental, site, propaga­tion, random-sampling and observational components).
This description gives no more than very general guidance without going at all deeply
into the subject.
The following represents an attempt, to group together the existing data in technicalliterature on the operation of direction-finding systems.

Rep. 372

— 388 —The bearings are classified for accuracy, into the four classes defined in Table I, i.e.:
T ableI

Classification of bearings
Observational characteristics
Class

Bearing error(degrees)

Signal strength

Bearing
indication

FadingInterference

Bearing swing(degrees)

Duration ofobservationA±2very goodor gooddefinite(sharp null)

negligible

negligible

less than3adequateB±5

fairly good

blurredslightslightmore than3
less than
5'

short

more than
5
less than
10very short

more than
10

inadequate

C

±10

weak

severely
blurredsevereD

more than
±10

Class
Class
Class
Class

A : probability o f less than 5 %thatthe error exceeds 2°.
B : probability o f less than 5 %thatthe error exceeds 5°.
C : probability o f less than 5 %thatthe error exceeds 10°.
D : bearing with an error greater than those in Class C.

scarcely
perceptible

ill-definedveryseverestrongvery
strongTaking Table I as the reference, a bearing will be a Class A (i.e., a good) bearing when,
during the assessment, all the conditions enumerated in line A of the Table are fulfilled.
A bearing will belong to Class B, that is, it may be regarded as satisfactory, when atleast one of the conditions in line B of the Table is fulfilled.
Similarly, a bearing will fall into Class C and be regarded as fair only, when at least
one of the conditions specified in Line C of the Table is present.
A Class D bearing will merely give an idea of the sector in which the transmitter islocated.

3.2 Errors in bearings
Bearings obtained with a direction-finder are subject to errors due to:- equipment- site of the direction-finder- propagation- operator.
Errors due to the equipment result from its design, as in the case of the octantal error
for example. These errors are taken into account by the calibration arrangement of theapparatus.
Errors due to the site arise from irregularities in the configuration or composition of
the terrain in the vicinity of the direction-finder. These errors vary with direction andfrequency. They may thus be regarded as variable errors.

— 389 —Rep. 372

The third type of error is due to irregularities in propagation. These may give rise
to side deviations in the propagation direction relative to the direction of the arc of the great
circle between the transmitter and the direction-finder.
Moreover, irregularities in propagation give rise to errors due to polarization, whichchanges from one moment to the other in the case of ionospheric propagation.
Changes of direction due to irregularities in propagation may be either slow or rapid.
Consequently, it is not possible to be sure of the real value of a bearing of a transmitter whenobservations are confined to a period of a few minutes, because the effect of slow changes
in the propagation direction is then overlooked. To take this variable factor into account,
it is generally necessary to extend the observations over several hours.
This means that, to improve accuracy, there is no point in making more than ten con­secutive measurements, but these measurements should be repeated at intervals of one
hour or more.
Operator errors, with the exception of those made accidentally, arise from a tendency,
when making a series of measurements on the same transmitter, to take figures close to one
another. This tendency is more marked with manually operated radiogoniometers thanwith automatic ones.
The conclusion may be drawn, therefore, that, when determining an azimuth, in addi­
tion to the systematic error of the equipment, which will be allowed for during calibration,other errors exist.
This raises the following questions among others:- how should the measurements be carried out,
- what value should be taken for the bearing,- how should the bearing be classified.
Since the measured values of a given transmitter change from one moment to another,it may be assumed that their distribution follows the Gaussian law.
The series of measurements obtained may, therefore, be defined by the following twovalues:- the median value of the series, namely that taken from the series for which there are as
many greater as smaller values. In other words, the value exceeded in 50% of the cases;- the variance, measuring the scatter of the series. If vi is the variance, its value will be:Vl=(ai—am)2 + (az—am)2 +(an—am)2(1)

n- 1
ai, ai,an, are the values measured, am the arithmetic mean of these values andn the number of values in the series.
3.2.1 Measurement procedure
If the figure shown by the direction-finder remains unchanged (as in the case ofground-wave transmission), only this figure need be taken.
However, if the figure shown changes from one moment to another, 10 to 15 read­ings should be taken over a period of something like 5 minutes. The readings should
be made at regular intervals and the tendency to take figures close to one anothershould be avoided.
With these figures, one can see from Table I to which class the bearing belongs.
3.2.2 Figure to be taken
The figure to be taken for the bearing is the most probable value in the series,
namely, the arithmetic mean of the values obtained.
3.2.3 Classification o f bearings
The method of classifying the bearing indicated above is somewhat subjective.
Let us consider a more objective way.

Rep. 372

— 390 —To classify a bearing, the total variance of the arithmetical mean of the resultsmust be known, since these are influenced, as shown above, by several sources oferror.
Allowance must also be made for another source of error, namely the limited
number of measurements.
If, instead of making only 10 to 15 measurements during 5 minutes, a greaternumber of measurements was taken over a longer period, a different mean value
would be obtained, which would be closer to the actual value.
This means that, when several groups of measurements are taken on the sametransmitter, each group will have a mean value different from the others. The com­plete set of these mean values will constitute a series, likewise distributed in accordancewith Gussian law, and with a variance of va.
It is known that in this case,va — vi/(n — 1) is obtained.

.

(2)

The calculation of va is a very lengthy operation,
Va = r2l(n — 1)d may be taken,(3)

where r is the difference between the maximum and the minimum values of a seriesof 10 to 15 measurements and d the value deduced from the curve in Fig. 1.

0

5

10

15

20

n
F igure 1

d = r2jvi

The expression can thus be easily applied.
With3^«^12
one need merely takeva = r2/n2(4)

Let us now examine errors due to a long-term change in the propagation direc­
tion.
Without any correction of the bearings on the same transmitter, taken with theaid of two conveniently sited direction finders, a very good idea is obtained of the dis­
tance at which the transmitter is situated. With this distance value and provided
that the measurements have been made over a period of 5 minutes, the experimental
curve in Fig. 2 gives the value v& of the variance due to this source of error.
As regards errors due to the siting of the direction finder, no expression can begiven for determining the value vc of the corresponding variance.

— 391 —Rep. 372

Distance (km)F igure 2

A: dayB: night:

The only way to ascertain vc is through the study of the average errors obtained overperiods of several months on known transmitters with stable propagation.
As a general rule, values of vc are taken for different frequency bands. For example,
a rounded-off value for the 3-5 MHz band ,another for the 5-10 MHz band, yet anotherfor the 10-15 MHz band, and so forth.
The operator error resulting from the tendency to narrow down the spread of the mea­
sured values, corresponds to a variance va which may be ignored with an automatic direction­finder, provided the operator is duly forewarned and which, with a manual one used in thesame circumstances, may be taken as:- equal to zero, if the total width of the minimum is less than 10°, which represents a 5°
uncertainty on either side of the middle point of the sector;- equal to 1, if the total width of the minimum is comprised between 10° and 20°;- equal to 4, if the total width is comprised between 20° and 40°;
- equal to 25 if the total width is over 40°.
The total variance will be
V = Va + Vb + Vc + Vd

(5)With a known v, Fig. 3 gives the error in the bearing with a .probability of 95 %.
is the error shown in Table I. Thus it may be said that:This- a bearing will fall into Class A, if the total variance is less than 1;- into Class B, if the variance is comprised between 1and 6-5;
- into Class C, if the variance is between 6-5 and 25;- into Class D, if the variance is over 25.

Rep. 372

— 392 —

Total variance, v
F igure 3

3.3 Classification o f positions
The Radio Regulations give the following classification of positions:- Class A: positions which the operator may reasonably expect to be accurate to within
5 nautical miles;- Class B: to within 20 nautical miles;- Class C: to within 50 nautical miles;- Class D : positions which the operator may not expect to be accurate to within 50 nau­
tical miles.
3.4 Determination o f position
Let us consider how a position can be determined, using two direction finders. The
cross-bearing of the two bearings obtained gives a point, but because of errors, one cannot
be sure that this point is the site of the transmitter.
Similarly, using three direction finders, a triangle is obtained with the three bearings(see Fig. 4, triangle DFH). In this case too, one cannot be sure that the transmitter is locatedwithin this triangle.
Let us suppose that the median error of two of these direction finders (for example,
A and B) is nil; that is, that there is an equal probability that the two azimuths obtained
are located to the right or to the left of the transmitter.
On whatever side the bearing obtained with the third direction finder C is located(for instance, side CCi, Fig. 5), there are four possibilities (shown in the following Table II).

— 393 —Rep. 372

T a b l e II
Azimuths

Triangle

Site o f the transmitter

CCi
AA i
BB i

DEF

outside the triangle

CCi
AA 2
BB 2

ELM

outside the triangle

CCi
AA i
BB 2

IFP

outside the triangle

CC i
AA 2
BB 2

MOP

within the triangle

Consequently, where the median values of the errors of two of the direction finders areboth nil, the probability that the transmitter is situated outside the triangle is 75%.
It may be concluded that, if the triangle is small (with the median value of the error
approaching zero), the transmitter is probably outside this triangle.

— 394 —Rep. 372

The practical problem to be solved is as follows: how to determine the probable locationof the transmitter, with given bearings and their attendant errors.
The problem should be solved in two stages:- plot on the map the most likely point corresponding to the bearings obtained;- plot the contour, with this point as a centre, corresponding to a given probability thatthe transmitter is sited within it.

3.4.1 The most likely point
With two bearings, the most likely point for plotting on the map is their intersection.
With three direction finders,(the most current practice), the azimuths obtained
will be, for example, those shown in Fig. 4, where A, B and C are the sites of thedirection finders.
Let us designate by D a , D b and D c the distances from the goniometers to themost likely point. Since the location of this point is not yet known, these three dis­
tances can only be given somewhat approximately, it being understood that the siting
is provisional.
Let us designate by v a , v b and vc the variances for the three direction finders,
calculated as shown in § 3.2.3.
The most likely point, P, is the point of intersection of the straight lines drawn
from the apices of the triangle to points E, G and / these points being determined fromthe following equations:
GH/FG = ( v c / v a ) ( D c sin H F D ) 2/ ( D a sin FHD)2(6)

EF/DE = ( v b / v c ) ( D b sin FD H )2/(D C sin HFD)2(7)

D I/H I = ( v a / v b ) ( D a sin FHD)2/(D B sin FDH)2(8)

The position of point P will thus be a function of the distances from the trans­mitter to the direction finders and of the errors of each instrument. The smaller
the error of one direction finder, the closer point P will be to the bearing obtainedwith that instrument.
Taking, for example, a network of three direction finders, forming an equilateraltriangle, and the errors for the three being equal, Fig. 6 will give the position of themost likely point for different cases.

3.4.2 Determination o f the contour
The contour* corresponding to a given probability that the transmitter is locatedwithin it, is an ellipse with the most likely point as its centre.
Let the reference be a set of rectangular axes, with the most likely point as theorigin; the axis will be oriented in accordance with the meridian of this point.
With p as the probability, the ellipse will be defined by(9)in a set of axes having the most likely point as their origin, but shifted in relation to
the preceding set, by an angle cp, measured from the North, and given bytan 2 (p = 2 sj(t — u)(10

— 395 —Rep. 372

F igure 6

this givess —2 (sin ^ cos0j)/Dj2 Vi
i= i

(ID

t =

2 sin2 0*/A 2 v*
*= i

(12)

U =

n
2 COs2

(13)

Vi

i= l
0; is the bearing obtained with direction-finder j ( j = 1, 2 , . . . ) ,Dj the distance from the most likely point to direction-finder j,V] the variance corresponding to direction-finder j;a and b are given byt — s tancp = 1/a2

(14)

M+ -ytan(p= 1/62

(15)

The values ai and bi of the semi-axes of the ellipse corresponding to a probability
p will be (see equation (9)):
2 l 0 g e( l ~ P )a\ = — 2a2 loge(l — p) — —b\2b2 10ge( l — p ) = —t — s tancp
2 lo g e(l ~ p )u + s tancp

(16)

I
(17)

Rep. 372

— 396 —
0,01 ■

0S2©

y 0,03 0,04 ■0 ,05-

0,1 *
0 ,2*
0,3 ■

0,01

0,02

0,03

^ 0,05

c2

0^1

0,2

0 ,5 12 ■0,5 1 2 5 1

5 2 1 0>5

0,2

0,1

0,05

0,03

0,02

j:

0,01
C 2

0,5 ■
0 ,3 .
0 ,2 0,1 ■0,05 ■
0,04 -----o0,02 ■

0.01 ■

s2

F igure 7

As, in general, the ellipse corresponding to p — 0-5 is adopted,
a\ = 1-39/(t-s tancp)(18)

b\ — 1-39/(u + s tancp)

(19)

and

will be obtained.
3.4.2.1 Determination o f the ellipse, by the Hopkins method
The earlier method,devised by Stansfield, is a fairly lengthy operation.
Let us take a set of axes (Fig. 7) plotted on tracing paper,approximately
25 cm long.
The scales of these axes give the inverse square of the distance to theorigin, measured in centimetres.
The arithmetical signs shown in the figures are allocated to each sector
defined by the axes.
The tracing paper is superimposed on the map, making the origin of theaxes coincide with the most likely point and with the axis s2 oriented according
to the meridian of this point.
The straight line which, on the map, links the site of the direction finder
to the most likely point, is then turned clockwise at an angle equal to the squareroot of the variance corresponding to the direction finder.
The straight line thus turned intersects the axes s2 and c2 and the corres­
ponding points can be read thereon. These values (h and mi) are then entered— 397 —Rep. 372

T a b l e III

Scale readings
Values o f se

Sign

Direction finder

*2

C2

1

h

m1

Yhmi

2

/a

m2

J//2W23/3

m3

J//3W3

Total

L

M

Algebraical sum = N

in the second and third columns of Table III. The sign of the sector within
the two semi-axes thus intersected is entered in the fourth column.
The same procedure is used for the other direction finders and the corres­
ponding values (h and m 2 , h and m 3 . . . ) , together with the arithmetical signs,
are entered in Table III
The values for Yh, mi, Vh, m 2 . . . . are calculated and entered in the fifth
colum of the Table.
The sum is then calculated o f the values of the second and third columns
and the algebraical sum of the fifth column (using the signs in the fourth column).
The angle of rotation (p of the axes of the ellipse, in relation to the axes
having the most likely point as their origin and constituted by the meridian
and a straight line perpendicular thereto, is given bytan 2cp = 2N/(L - M )(20)

The values a\ and bi of the semi-axes of the ellipse,oriented respectively,in accordance with the y-axis (northward axisthrough cp°) and the jc-axis are
a\ = — 2 loge (1 —p)l(L + N tan <p)(21)b\ = — 2 loge (1 - p)KM - N tan <p)(22)

Where p — 0-5,
a\ = l-39/(L + TVtan (p)(23)

b\ = 1-39/ ( M - N tan q>)

(24)

and

will be obtained.
The values of ai and bi will be given in centimetres.
3.4.3

Classification o f position
The procedure described in § 3 is used; in addition, the value of the semi­
major axis of the ellipse may be taken.

INevertheless, it is better to take the value
p =1/a \ + b\

(25)
B ib l io g r a p h y

Ross, W. The estimation of the probable accuracy of high-frequency radio direction-finding bear­ings. J.I.E.E., 94, Part IIIA, 15, 722 (1947).
S t a n s f ie l d , R. G. Statistical theory of D.F. fixing. J.I.E.E., 94, Part IIIA, 15, 762 (1947).
B a r f ie l d , R. H. Statistical plotting methods for radio direction-finding. J I.E.E., 94, Part IIIA, 15,673 (1947).
H opk ins , H . G . D .F . p lottin g aid. Wireless Engineer, 33, 7, 173 (July, 1956).

ANNEX
Comments concerning hf long range direction finder
USED AT MONITORING STATIONS IN THE U.S.A.
Description

An Adcock direction finder in use in the U.S.A., having a useful frequency range of
2 to 40 MHz, utilizes two vertical dipoles each about 6 m (20 feet) long and spaced about
6 m (20 feet) apart. The centre line of the dipoles is approximately 6 m (20 feet) above theground. Provision is made for manually or automatically controlled rotation with amaximum rotational speed in the latter condition of 20 to 30 revolutions per minute.
Provision is made for aural or visual readout of the bearing; also for automatic averagingof the bearings over a period of up to 20 or more rotations of the array with a visualdisplay of the averaged bearing.
Bearing accuracy• In a series of tests over a period of several months in 1962, Adcock bearings were takenon 60 W transmitters in locations unknown to the observers. The distances involved wererandom to simulate the conditions of actual problems and varied from a few hundred tomore than 1600 km (1000 miles) in the various tests. Thirteen Adcocks in widely separated
locations produced bearings having an accuracy of 2° or better in 82% of the tests. For
further information on this subject of bearing accuracy, see Report 93.

— 399 —Rep. 373

REPORT 373 *ANTENNAE FO R M ONITORING STATIONS(Question 11/VIII)(1966)
This Report takes account of the documents presented during the period 1963-1966
and of Report 278-1.

1.

Doc. VIII/6 (U.S.A.), 1963-1966

1.1 In considering the extent to which currently available antennae fulfil the requirements ofmonitoring stations, it must be realised that requirements may differ according to the typeof monitoring functions being performed. For general surveillance of the spectrum forexample, it is often desirable to use an antenna with essentially omnidirectional character­istics, whereas for detailed study or analysis of a particular emission, a directional array
may be needed to attenuate unwanted emissions. Therefore, the comments contained
herein will take into account the need for both omnidirectional and directional antennae.
The wide frequency range which monitoring stations are required to cover, precludes any
single type of antenna from giving satisfactory results over the entire range. Therefore,
the following discussion will devote itself to separate comments on bands 4 to 10.
1.1.1 VLF antennae
Because of the tremendous wavelengths involved in band 4, it is generally imprac­
tical at monitoring stations to use an antenna having a physical length exceeding morethan a very small percentage of a quarter wavelength. Commonly used antennae inthis range include simple verticals, top-loaded or umbrella-loaded verticals, flat-tops
and loops. A relatively recent innovation is a loop designed for reception of VLF
standard-frequency transmissions, which makes use of ferrite materials to increase
the signal pickup and to provide directivity. Complete antenna systems, consistingof either a vertical antenna or a large fixed loop with an integral matching network,
bandpass filter and solid-state pre-amplifier, are also being used to increase the signalto-noise ratio and signal input level to the receiver. Ability to change polarizationof the receiving antenna is not important in the VLF range, since in most instances
the polarization of the incoming signal is predominantly vertical.
1.1.2 L F antennae
The situation in band 5 is in some ways similar to that in band 4, except that, as
the frequency is increased, useful antennae can be made somewhat smaller. Beverageantennae are useful where adequate space is available and where advantage canbe taken of the relatively good horizontal directivity obtainable from such antennae.
1.1.3 M F antennae
In many areas of the earth, high directivity of a receiving antenna is, at least,
equally as important as affective length, in view of the congested nature of band 6
especially in the MF broadcast band. Beverage antennae for this range are quite* This Report was adopted unanimously.

Rep. 373

— 400 —
useful, as are loops, either air wound or on ferrite cores. However, more sharply direc­
tional antennae of moderate size would permit more effective monitoring of the MF
range than can presently be accomplished except with expensive or space-consuming
arrays.

1.1.4 H F antennae
Most monitoring stations participating in the international monitoring system
will probably need both non-directional and directional antennae for use in the
H F range (band 7), the former for general spectrum surveillance and the latter for
observation or study of specific signals or azimuth segments. Broadband antennae,with essentially equal signal response at all azimuths, are available from several
sources. These are typically vertical arrays consisting of several elements in parallelto obtain broadband response. Another method of obtaining broadband frequency
response from a vertical antenna is described in Report 278-1.
Although widespread use has been made of rhombic antennae for monitoringin band 7, their large dimensions, together with rather erratic frequency/directivitygain characteristics and a tendency toward unwanted side and back reception lobes,
make them less than ideal in this application. Development during the past few
years of log-periodic and other wideband directive antenna systems represents a majoradvance in antennae with characteristics which suit them for monitoring use. However,
log-periodic antennae likewise have shortcomings. They have generally lower gain
than a rhombic antenna covering the same frequency range, although the response
is generally more constant over its design range. Likewise, although land-space require­ments are generally moderate, the construction costs tend to be greater than for acomparable rhombic array. One desirable characteristic of the log-periodic arrayis the relative absence of reception lobes from the sides and back, along with good
front-to-back reception ratio, an important feature for monitoring in the crowded
band 7.
For coverage of limited frequency ranges, there are numerous types of antenna
arrays which satisfy most directivity and gain requirements. However, few moni­
toring systems are likely to find that their antenna needs are met by such narrow-bandcoverage. Although it may at times be desirable to be able to change the polariza­tion of the receiving antenna to conform to that of the transmitting antenna, it has
been found that, in general, especially over long sky-wave paths, the wave front pola­
rization is considerably distorted so that both horizontal and vertical components
will be present in the received signal regardless of the initial polarization. However,further study in this connection might well be undertaken.

1.1.5 VHF antennae
Extensive experimentation in band 8 has resulted in the development of many
types of antennae having desirable characteristics for monitoring use. Broadband
log-periodic antennae are available, which respond to various wave polarizations,either simultaneously or by means of simple switching techniques; both broadband
and narrowband Yagi-type arrays are available in abundance to meet almost any
conceivable monitoring need. Other useful antennae for the upper VHF range include
corner-reflector arrays and broadside arrays of dipoles with plane reflectors.

1.1.6 UHF-SHF antennae
As in band 8, monitoring observers desiring to operate in bands 9 and 10 may
select from many excellent types of antenna, ranging from scaled-down versions

— 401 —Rep. 373

of VHF antennae in the lower portion of band 9, to elements mounted in parabolicreflectors starting around 1 GHz. It is fortunately true that, although the effective
length of a simple resonant antenna becomes shorter with increasing frequency, theuse of signal concentrators, such as parabolic reflectors, permits a higher effective gain
than is reasonably possible at lower frequencies. Recent developments in log-periodic
and horn antennae designed for mounting in parabolic reflectors, have provided needed
improvements in achieving broadband directive response in the microwave regions.
At least one manufacturer offers a log-periodic and parabolic reflector combination
providing coverage from 1 to 10 GHz with quite respectable gain. Where greater
gain is required, a series of four horns may be used interchangeably with the logperiodic element, and additional horns are available to extend the range to 21 GHz.
The reflector is small enough to permit ready mounting on the roof of an automobile
where mobile observations are needed. A signal gain of 25 dB or more over a halfwave dipole is possible with the horns at frequencies above about 5 GHz with some­what less gain at the lower frequencies, primarily because of the small size of the para­
bolic reflector. For fixed operation, the log-periodic and horn units may be installedin large parabolic reflectors to obtain greater gain, for activities such as space moni­
toring (see Question 6/VIII and responses thereto).

1.2 Desirable characteristics o f antennae
Although the characteristics desired of an antenna will depend upon the intended use,
in most instances the fundamental requirement is to obtain the greatest possible signal input
to the receiver from the wanted signal and at the same time to attenuate unwanted signals
and noise to levels which do not cause interference. There are, of course, exceptions tothis rule where general spectrum surveillance is being performed or where it is desired toobserve relative signal levels of two or more emissions on the same or adjacent channels.
Rejection of unwanted signals can be accomplished by providing horizontal or verticaldirectivity, or both. The use of antennae with very narrow bandwidth or having limited
response at certain frequencies may also be desirable in some instances, especially wherestrong unwanted signals are present which might overload or desensitize the receiver. How­ever, attenuation of such signals by means of resonant filters inserted between the antenna
and the receiver is usually more effective than attempting to eliminate the signal within theantenna itself. At the higher frequencies, certainly in the VHF and higher ranges, consider­able attenuation of unwanted signals can often be accomplished by using antennae whichhave optimum response to the mode of polarization of the wanted signal and which are
relatively insensitive to other propagation modes. Where two or more modes of polariza­tion are commonplace, it may be desirable to be able to alter the antenna polarization
response, either by a simple switching arrangement or by actual rotation of the antenna about
its major horizontal axis. For example, a single Yagi or log-periodic array can readily bedesigned for alternate reception of either vertical or horizontal polarization by either ofthese two methods. Where it is desired to receive both horizontally and vertically polarized
signals simultaneously, two separate antennae may be used, or the elements of a single antenna
may be so arranged as to permit pickup of both polarization modes. Reception of signals
having other types of polarization (e.g. circular, elliptical, etc.) can usually be accomplishedwith general purpose antennae, although specially designed antennae may be more effective.

1.3 Needed improvements in the characteristics o f the monitoring antennae
1.3.1 In the VLF and L F ranges (bands 4 and 5 ), greater signal pickup from relatively small
antennae would be desirable; equally important is the matter of improving the signal26

Rep. 373

— 402 —
to-atmospheric noise ratio, since atmospheric noise is often the limiting factor in weaksignal reception at the lower frequencies. One area which might well be exploredwould be the improvement of the directional characteristics of VLF-LF antennae
not only to eliminate unwanted signals but also to reduce the atmospheric noise input
to the receiver, by minimizing noise pickup from all directions, except the path of arrival,of the wanted signal.

1.3.2 In the MF.and H F ranges (bands 6 and 7), more highly directional antennae of moderatesize, preferably adjustable in azimuth, would be helpful. Although Beverage andrhombic antennae and other currently used directional arrays are reasonably satis­
factory for reception over about 20° of horizontal arc, a considerable number of suchantennae must be used to accomplish reception from all directions. Similarly, althoughbroadband directional arrays such, as log-periodics, have been made rotatable, theirdimensions are such that they must be solidly constructed to withstand wind and weather
and the rotating mechanism adds considerably to their cost. Smaller antennae withcomparable gain would undoubtedly be welcomed by monitoring station operators.
1.3.3 In the VHF and higher ranges (bands 8, 9 and 10), the monitoring specialist probably
has more to choose from in the way of desirable monitoring antennae than at thelower frequencies, largely because the dimensions are smaller and the physical problems
of weight and size become less important. Even so, where very high gain is required(e.g. for monitoring weak signals from spacecraft), the large arrays presently being usedbecome quite cumbersome. In such applications greater gain in more compact arrays
would be desirable. The arrays should be readily adjustable both in azimuth and inelevation, should be capable of reception of emissions having a variety of polarization
modes and should have a frequency response commensurate with the band or bands
to be covered. To keep to a minimum the number of arrays required, when continuous
coverage of bands 8, 9 and 10 (VHF, U H F and SHF ranges) is needed, each antenna
array should preferably be capable of covering at least a frequency range of 2 to 1.

ANNEX
E xamples of antenna systems suitable for stations participating
IN THE INTERNATIONAL MONITORING SYSTEM

1.

A basic antenna system with frequency coverage limited to the frequency range 500 kHz to
30 MHz

1.1 One or more broadband vertical antennae to provide coverage with a single array over afrequency range of 5 to 1 or more. Two or three such arrays will give complete coverageof the ranges of interest. For example, see Figs. 1 to 7 of the present Report.
1.2 Single-frequency or narrow-band monitoring and communication antennae as required tomeet special needs.

2.

A more elaborate antenna system for the range 500 kHz to 30 MHz

2.1 The antennae described in § 1, together with those described below.
2.2 To provide broadband directional-antenna facilities which are lacking in the basic systemdescribed above, either one or more rotatable log-periodic arrays or a series of rhombic anten­
nae will permit greater flexibility of operation, especially on emissions having low signal
levels at the monitoring site or where directional interference rejection is needed.

— 403 —Rep. 373

Coverage from about 6 to 30 MHz can be obtained with a log-periodic array of moderate
size which can be installed to permit rotation for omni-azimuth use.
2.3 An Adcock direction finder may be used to advantage at a monitoring station for purposes
other than the usual one of direction-finding. The directional characteristics are usefulin nulling out unwanted signals while monitoring a co-channel station arriving from a different
direction. Adcocks also have relatively good signal pickup for general monitoring at fre­quencies in the upper portion of their design range.

3.

An antenna system providing wide spectrum coverage at a completely equipped monitoring
station

3.1 All the antennae described in § 2 together with:
3.2 For use below 500 kHz, one or more rotatable loop antennae covering the frequencies ofinterest and one or more vertical or flat-top (multi-wire “ T ”) antennae.
3.3 For use in the VHF range, a rotatable log-periodic array, designed for reception of bothhorizontally and vertically polarized emissions, and other special purpose antennae to meetthe particular needs of the station in this range.
3.4 For UHF-SHF use, special purpose high-gain antennae are usually preferable to broadband
antennae with lower gain. For monitoring emissions from spacecraft, parabolic reflectors
or other signal concentrators are recommended. For this purpose, it is important thatthe antenna array be moveable both in azimuth and elevation from the control positionor that provision be made for automatic positioning control by the incoming signal.
Note. - At a completely equipped monitoring station, coupling between the multiplicity
of antennae and between transmission lines may present a problem. This condition
may be minimized by using multi-purpose antennae, including rotatable arrays, to reduce
the number of antennae required and by making optimum use of coaxial cables in lieu of
open-wire transmission lines. Installation of tuned pre-amplifiers at the antenna ends ofthe transmission lines will help to offset line losses where long lines must be used to achieveadequate spacing between antennae.

4.

Document VIH/17 (United Kingdom), 1963-1966

4.1 Antennae
For monitoring up to 30 MHz, antenna requirements can be met largely by the provisionof the following types:
4.1.1 Wideband omnidirectional antennae for rapid exploration o f the spectrum
For the MF band, a vertical wire or mast and cage antennae are usually adequate.
In the H F band, vertical cage antennae can provide omnidirectional facilities over
a 2% to 1 frequency range. Alternatively, an inverted cone antenna may be used
to provide coverage over the range 12 kHz to 30 MHz (see § 8).
4.1.2 Wideband directional antennae to aid identification and to provide maximum signal tonoise and/or interference ratios
In the H F band, a group of sloping wire antennae has the advantage of simple
construction and reasonable directivity combined with all round coverage. Hence,twelve sloping wires, 150 m long, with a 1 in 5 slope, some 40 m high at the centre
mast and 10 m high at the outer ends, would be satisfactory. Rhombic antennae
also have the advantage of simple construction and reasonable directivity over a 4

Rep. 373

— 404 —
to 1 frequency range. However, a number of such antennae is needed for complete
coverage involving a considerable site area. Consideration may also be given to arotatable log-periodic antenna, particularly for use above 10 MHz.

4.1.3 Direction-finding installations to obtain bearings
An Adcock system may be used to provide these facilities.
For monitoring between 30 and 300 MHz, it is generally desirable to provide
rotatable directive wideband antennae installed at the top of a fairly high mast (45 m).
By this means, it is possible to reduce the number of antennae required to cover thelarge frequency range involved and yet retain reasonable gain and directivity with suffi­
cient resolution for coarse direction-finding purposes. Yagi and log-periodic antennae,both horizontal and vertical, are very suitable.
4.2 Antenna feeders
As far as possible, coaxial cables should be used for antenna feeders; where open-wirefeeders are used it is necessary to pay careful attention to their balancing.
4.3 Earth connections
4.3.1 Earth connections at monitoring station
It is essential that a radio monitoring station should be provided with an adequate
earth system. Such an arrangement might consist of four ungalvanized mild steelrods, about 2 m long and 20 mm in diameter, spaced some 2 m apart. One end ofeach rod could conveniently have a hardened tip and the other end could have a screw
thread, to facilitate a good comiection of the earthing lead. Alternatively, copper
earth plates, for example 1 m square, might be used. In ground of poor conductivity,
it may be necessary to increase the number of spikes or plates. Connections fromthe earth spikes or plates to the earth bar in the monitoring station may be made withcable with a conductor of large diameter.
4.3.2 Earth connections at antennae
Where earth connections are required for certain antennae, i.e. inverted-cone or
sloping-wire antennae, these may be provided by laying, for example, 60 radials ofcopper wire, with a radius of 30 or 40 m.

5.

Doc. VIII/26 (France), 1963-1966

5.1 Land and antennae
A monitoring centre must be installed on land which is as flat as possible and well awayfrom any obstruction, metal obstacle or large clumps of vegetation. It should have an arealarge enough for the centre to be able to erect one or more non-directional antennae, cover­ing the range of monitored frequencies and an array of directional antennae (rhombic), withthe highest possible gain with which the direction of arrival of the waves received can be
determined to a sufficient degree of accuracy.
5.2 Non-directional antenna
In practice, a single antenna may be used for the entire range of frequencies below
30 MHz.
It may consist of a vertical metal mast, about 8 m high, with a terminal capacity at the
top and its base an earthing system of buried conductors in the shape of a star.

— 405

Rep. 373

For greater safety and convenience, however, it is preferable to have several antennaeof this type, especially if some of them are to be assigned to cover a specific frequency band.
5.3 Directional antennae
The possibility of using a radio direction-finder to determine the direction of wave arrival
is not to be ruled out a priori.
However, apart from its high cost, this solution presents particularly difficult problems.
The method of comparing the level of signals received on different directional antennae
is advocated. While this system cannot claim the accuracy obtainable with a direction
finder, it is, on the other hand, much less costly and more quickly set up.
Finally, it is to be noted that high-gain directional antennae are also most valuable for
identifying emissions received with low fields.
The number, type and direction of the antennae to be erected must be determined after
studying the conditions peculiar to the monitoring centre in question.

6.

Doc. Vni/23 (Italy), 1963-1966
In the Monza monitoring centre of Radiotelevision Italiana, an antenna system hasrecently been installed for the VHF and UHF frequency ranges, that has given satisfactory
results.
This antenna system was installed on an iron tower 50 m high, the position of which,at a distance of 200 m from the centre, was chosen so as to avoid interfering with the existing
antennae for the other frequency bands or affecting the field-strength measurements taken
at the centre itself.
The antenna system consists of a rotatable supporting unit with variable speed, tele­commanded from the centre. To this unit, which has a square section of two metres
and a height of six metres, the following antennae are fixed:

6.1 for broadcasting band IV, two antennae, one for the reception of vertical-polarization emis­
sions and one for horizontal-polarization emissions; each of them consists of four arraysof eight dipoles; each antenna has a gain of 17 dB in the 470-790 MHz range;
6.2 for broadcasting band III, two antennae, one for the reception of vertical-polarization emis­
sions and one for horizontal-polarization emissions; the first consists of an 8-dipole arrayand the second of two adjacent 4-dipole arrays; each antenna has a gain of 12 dB in the
174-223 MHz range;
6.3 for broadcasting band II, one antenna for horizontal-polarization only, consisting of six
Yagi three-unit antennae, arranged on two levels, with three antennae at each level; thegain of the system is 14 dB in the 87-108 MHz range;
6.4 for broadcasting band I, two antennae, one for the reception of vertical-polarization emis­
sions and one for horizontal-polarization; each of them consists of two Yagi three-unit
antennae, each antenna having a gain of 9 dB in the 52-68 MHz band.
All the antennae are connected to switching units located on the tower and remotely
controlled from the centre, which enables a single transmission cable to be used for the various
antennae.
The transmission cables between the antennae and the coaxial switching units are of
the flexible type; the 260 m long cable between the antenna switching unit and the measuringapparatus is a 50 £7 cable of a diameter of 80 mm (3 1/8"), having an attenuation of 3-8 dB
at 800 MHz.
It has not proved necessary to use antenna amplifiers.

7.

Doc. VIII/2 (Japan), Washington, 1962
Figs. 1, 2 and 3 describe a vertical omnidirectional loaded antenna that has beenused in Japan for the measurement of the relative field-strength (see also Report 278-1,§ 4).

Rep. 373

— 406 —

Top-loading resistor

Coaxial cable

Vertical omnidirectional loaded antenna

Loading resistor : 250 ohms
Length of radial conductor: 8 m
Length of vertical conductor: 8 m

Rep. 373

— 407 —

200 R
F ig u r e 2

Impedance characteristics of a vertical omnidirectional loaded antenna(see Fig. 1)

Effective height, he/f (m)SWR: 2 0 (except at 2 MHz)(The points on the curve represent the frequency in MHz)

Frequency (MHz)F ig u r e 3

Effective height of a vertical omnidirectional loaded antenna(see Fig. 1)

Rep. 373

8.

— 408 —

Doc. VHI/15 (United Kingdom), 1963-1966
Cone antenna
The inverted cone antenna is shown in Figs. 4 to 7. It consists of 16 equally spaced
wires, 7-6 m high, terminating in a soldered connection at the apex. An associated buried
radial earth consisting of 16 wires, each 10 m long, is necessary. A coaxial cable feeds theantenna to the receiving room, the centre conductor being connected to the apex and the outerconductor to the radial earth system. A property of such an inverted cone antenna is thatthe impedance, nominally 75 Q, shows little variation over the frequency band and directconnection to a coaxial cable having a characteristic impedance of 75 Q. can be effected with­out serious mis-match.
The calibration curves shown in Fig. 8 have been derived from an installation similar
to the one described. Curve B represents the correction factor without cable loss. Curve
A has been calculated assuming a 400 m length of 75 Cl coaxial cable between antenna andreceiver. A further calibration curve would need to be derived from curve B if a significantly
different length or type of cable is employed. Measurements on 48 similar cone antennae
in different locations, showed variations in the correction factor of less than ± 2 dB in 90 %of the measurements.

Plan— 409 —Front elevation

F ig u r e 6

View in the direction AB (see Fig. 4)

Rep. 373

Rep. 373

— 410 —

Relative output of antenne when used
for reception (dB)General view of antenna

Calibration curve of inverted-cone antenna
Note - Scale for use when measuring field strength by the substitution method (see Report 368).
A: including a specified type of cable feeder, 400 m long
B : without cable attenuation

— 411 —9.

Rep. 373

Doc. VHI/70 (O.I.R.T.), 1963-1966
Radio monitoring requires antennae that, for the smallest possible dimensions, are as
wide-band as possible. Non-directional antennae (e.g. for survey observations), as well as
directional antennae (e.g. to eliminate interference, to increase received voltage, to determine
direction), are involved.
In the following, two types of directional antennae that have been developed and applied
for radio-monitoring in the frequency range 30 to 1000 MHz will be described. One typecovers the range from 30 to 180 MHz and the other from 165 to 1000 MHz. In theirdevelopment the fact that such antennae must be suitable both for horizontal as well as
vertical polarization was respected.

9.1 Antenna for the 30 to 180 M H z range
This antenna is illustrated in Fig. 9. Two identical, logarithmically periodic dipole
antennae are so inter-built that their polarization directions are perpendicular to each other.
Each part of the antenna is fed by means of a separate cable, so that the polarization, forexample, can be altered by means of simple switching.
The antenna is mounted on a suitable rotating system, so that transmissions from any
direction can be received. In the following review the most important electrical propertiesare listed:
Frequency range:
Input impedance:
Standing wave ratio:
Antenna gain (relative to elementary dipole) :Polarization:
Antenna length:

30 to 180 MHz
60 fi, asymmetrical
S = UmaxjUmin
2*5
on the average about 5 dB
horizontal and vertical (selected byswitching)
about 4-6 m

9.2 Antenna for the 165 to 1000 M H z range
For this frequency range a new extremely wide-range antenna was developed. Its
design is based on a departure from the logarithmic-periodicity principle. As with logarithmically-periodic dipole antennae, a relatively large number of dipoles fed by means of asymmetrical two-wire cable (Fig. 10) is used. The extreme ends of the dipoles lie on a monotonically rising limiting curve in contrast to the straight line in the logarithmically-periodic
antenna.
A definite dependence of antenna gain on frequency is given by choice of the limiting
curve. The spacing of the dipoles, the diameter as well as the characteristic impedance ofthe symmetrical two-wire feed-line can be so chosen, that the input impedance of the antenna
has the desired value and is approximately independent of frequency.
Fig. 11 shows the antenna for the frequency range 165 to 1000 MHz. The feed-line
system is covered by an epoxy-resin coat strengthened with glass-fibres. By this means theantenna is given sufficient strength and at the same time is well protected against the influencesof weather.
The antenna has the following characteristics:
Frequency range:
Input impedance:
Standing wave ratio:
Antenna gain:
Polarization:
Radiation pattern:
Width at half-power value:

165 to 1000 MHz
60 fi, asymmetrical
S — UmaxI Umin ^see Fig. 12
as desired
see Fig. 13
see Fig. 14

2

IRep. 373

— 412 —

Front-back ratio- over the range of 165 to 400 MHz:X 15 dB- over the range of 400 to 1000 MHz: X 20 dB
Length:about 1-6 m
Width:
about 0-9 m
Weight:about 3-6 kg
The antenna gain rises with the frequency while the radiation angle in the H-plane issmaller.
By this means, the general decrease in both receiver sensitivity, as well as in the powerobtainable from an antenna with rising frequency, can be compensated. The advantagesof the described antenna are evident when one considers that with a logarithmically-periodic
dipole antenna system of the same length in the given frequency range a constant gain of
about 7 dB (relative to an elementary dipole) is barely obtainable.
This antenna is as readily transportable as it is quickly mountable and is therefore also
suitable for mobile applications, e.g. for field-strength measurements or propagation research.
With suitable rotation equipment, it can also be readily used in stationary radio monitoring
stations. The antenna can be mounted both in a horizontal (Fig. 11) as well as in a vertical
position. In stationary installations, in general, signals of arbitrary polarization from any
direction can be received.
Two antennae with mutually perpendicular polarization are fixed on a rotatable mast.
Each antenna has a separate lead-in cable which is led down to the receiver through thehollow mast. The polarization can be selected by means of manually operated switches
or a coaxial relay.

F ig u r e 9Radio monitoring antenna for the 30 to 180 MHz frequency range

— 413 —Directionof mainbeam

Principle of an extremely wideband dipole antenna

F i g u r e 11

Antenna gain, G ed (dB)Radio monitoring antenna for the 165 to 1000 MHz frequency range

Frequency, / (MHz)F i g u r e 12

Antenna gain (relative to an elementary dipole) as a function o f frequency

Rep. 373

Rep. 373

— 414 —

170 MHz

350 MHz

900 MHzF ig u r e 13

Typical directivity diagrams for the antenna shown in Figure 11

— 415 —Rep. 373

Frequency, / (MHz)F ig u r e

14

Half-width-power values for the antenna shown in Figure 11
A: H - plane
B: E - plane
B ib l io g r a p h y

1.
2.
3.
4.
5.
6.
7.

8.
9.

H a r p e r , E. A. Rhombic antenna design. D. Van Nostrand Co., Inc., Princeton, New Jersey (1941).
J a s ik , H. Antenna engineering handbook. McGraw-Hill Book Co., New York (1961).
I s b e l l , D. E. Log-periodic dipole arrays. IRE Transactions, Vol. AP-8, 3 (May, 1960).
K r a u s,

J. D. Antennas, McGraw-Hill Book Co., New York (1950).

L a p o r t , E. A. Radio antenna engineering. McGraw-Hill Book Co., New York (1952).
S c h e l k u n o f , S. A. and F r ii s , H. T. Antennas, theory and practice. John Wiley and Sons, Inc., NewYork (1952).
W il l ia m s , H. Paul. Antenna theory and design. Vol. 2, Sir Isaac Pitman and Sons, Ltd., London(1952).
Antennas and radio propagation. Dept, of the Army Technical Manual TM-11-666 (1953), U.S.A.
Government Printing Office, Washington, D.C.
Antenna handbook, American Radio Relay League Inc., Newington, Conn., 06111.
C.C.I.R. Handbook of directional antennae, published by the International Telecommunication
Union (1966).
Experimentally determined radiation characteristics of conical and triangular antennae. RCA Review,Vol. 13, 4, 425 (December, 1952).

I

PAGE INTENTIONALLY LEFT BLANKPAGE LAISSEE EN BLANC INTENTIONNELLEMENTSTUDY GROUP VIII

(International monitoring)Terms o f reference:
To study technical and operating problems, the solution of which depends principallyon considerations of a technical character relating to monitoring stations participating in
the international monitoring system with regard to:in collaboration with the I.F.R.B., ways in which harmful interference can be verified andreported, in accordance with the International Telecommunications Convention and theRadio Regulations;the development of methods and procedures to be used by monitoring stations in determin­
ing occupancy of the radio-frequency spectrum and the characteristics of emissions and inlocating the source of an emission by direction-finding techniques;
specifications regarding the selection of sites, antennae and other equipment and instru­
mentation.

Chairman:Vice-Chairman:

Mr. M. A m a r o V i e i r a (Portugal)
Mr. P. B o u c h i e r (Belgium)

INTRODUCTION BY THE CHAIRM AN, STUDY G R O U P

VIIIFrequency measurement
Recommendation 377-1 shows the accuracies required in the measurement of frequencies
by monitoring stations.
Attention is drawn to the need to revise these accuracies should the frequency toler­
ances permitted by the Radio Regulations become more severe.
Report 272-1 gives details concerning certain frequency measurements.
No satisfactory procedure has yet been evolved for the measurement of frequencies
in SSB, ISB and other complex types of emission (see Report 369). Question 2/VIII and
Question 1/VIII therefore remain under study. The assessment of the accuracy ofmeasurements is the subject of Study Programme 1A/VIII.

Field-strength measurement
Recommendation 378-1 retains the accuracies to be observed. It includes a paragraphon the calibration of equipment.
The operating requirements of monitoring stations have shown the advantage of an
expeditious method of measuring field strength even if the accuracy mentioned in Recom­
mendation 378-1 has to be waived. Recommendation 442 and Report 368 give details on
the methods and equipment that should be used. Question 4/VIII on this problem, how­ever, has been retained.

— 418 —3.

Bandwidth measurement
A satisfactory method has not yet been found for the measurement of occupied band­
width by a monitoring station. The study of thisproblem is proposed in both Question
5/VIII and Study Programme 6A/1.
To enable monitoring stations to furnish the IFRB with bandwidth estimate, the pro­cedure described in Recommendation 443 has been adopted provisionally in agreementwith Study Group I. The relevant Report (Report 275-1) has been brought up to dateaccordingly.
In the study of bandwidth problems, reference should be made also to the pertinent
documents of Study Group I.

4. Automatic monitoring of occupancy of the spectrum
Question 9/VIII, which remains under study, is partly
tion 182-1 and Report 278-1.

answered in Recommenda­

5. Visual monitoring of the spectrum
In the absence of further replies to Question 10/ VIII, Report 279 was retained unchanged.

6. Measurements at mobile monitoring stations
Report 277-1 was brought up to date.

7. Monitoring of transmissions from spacecraft
Question 6/VIII was retained.
was added to Report 276-1.

A paragraph on the measurement of power flux-density

8. Monitoring of sweeping-type pulse emissions
Question 7/VIII closely resembles former Question 226.
Report 367 gives a part reply to this Question. In view of the level of the interference
which may be caused by this type of emission, Study Group I was asked to propose thatthe specifications of the necessary equipment should be examined.

9. Direction-finding at monitoring stations
Question 8/VIII was retained.
To assist monitoring station personnel, the major part of Report 372 was devoted tothe question of the accuracy of bearings and positions.

10. Antennae for monitoring stations
Report 373 gives part replies to Question 11/VIII. This Report may prove extremely
useful to Administrations wishing to establish new monitoring stations.

11. Monitoring in the new and developing countries
Report 371 contains detailed information on Question 12/VIII and will certainly be ofgreat service to countries intending to establish a monitoring service.

12. Assistance to various services
This problem is the subject of Question 13/VIII and Study Programme 13A/VIII.
Report 370 describes the benefits obtained from a programme for the exchange of moni­
toring personnel of different countries.

Opinion 30 draws attention to the contribution which monitoring stations could maketo the rational use of the spectrum.

13. Identification of stations
Recommendation 379-1 and Report 280-1 contain replies to Question 14/VIII. For
certain complex types of emission no suitable method of transmitting the identification signal
has yet been found. Question 14/VIII has therefore been retained.
Opinion 29 asks that the Radio Regulations provision on the transmission of identifica­tion signals be followed more strictly.
The IFRJB was asked to undertake publication of the list referred to in Opinion 11, using
the information in its possession. This list, brought up to date by information provided
by Administrations, would be extremely useful in solving certain cases of interference.

14. Expansion of the monitoring system
Report 282-1 shows the world distribution of monitoring stations which participate
in the international monitoring system and, in conjunction with Resolution 15, draws atten­
tion to the advantages of extending the coverage of the system.

15. Identification of sources of interference
Question 15/VIII and Report 281 led to the preparation by the C.C.I.R. Secretariat ofa magnetic tape giving information on various classes of emission and on a number of casesof interference.
Following the adoption of Resolution 16-1, mentioned in the section below, Question
15/VIII and Report 281-1 were amended to facilitate the drafting of a handbook dealing
with all aspects of concern to monitoring stations.

16. Handbook for monitoring stations
The expansion on a world-wide scale of the international monitoring system and the
problems raised by such Questions as 11/VIII, 12/VIII and 15/VIII showed the need to pre­pare a handbook for monitoring stations which would assist Administrations, particularly
those of the new and developing countries, in the establishment and operation of thesestations.
Resolution 16-1, under which a number of Administrations undertook to prepare thishandbook in collaboration with the C.C.I.R. Secretariat and which lists the various chaptersof the handbook, was therefore adopted.

17. Problem of concern to the new and developing countries
This new section of § 2.2.2 in Resolution 33 will deal with questions and problems ofconcern to the new and developing countries.
Some aspects of this matter are mentioned above. It is extremely difficult, if
not impossible, to deal with these aspects separately, as certain questions of concern to somecountries may, for various reasons, be of less interest to others.
With this proviso, we would draw attention to the following:
Recommendations: 182-1, 378-1, 379-1, 442, 443;
Reports: 272-1, 275-1, 280-1, 368, 370, 371, 372, 373;
Question: 2/VIII;
Opinions: 29, 30.

Res. 15— 420 —RESOLUTION 15
EXTENSION OF THE INTERNATIONAL MONITORINGSYSTEM TO A WORLD-WIDE SCALEThe C.C.I.R.,.

(1963)CONSIDERING(a) that Recommendation No. 5 of the Administrative Radio Conference, Geneva, 1959,
stresses the urgent need for improvement in the international monitoring system and invites
Administrations to make every effort to develop monitoring facilities;(b) that there are still wide areas of the world where the facilities available to the international
monitoring system are inadequate or non-existent;(c) that it is of utmost importance, to satisfy the needs of the I.F.R.B. laid down by the Radio
Regulations, that all countries having domestic monitoring facilities make them available
for international monitoring to the maximum possible extent;(d) that it is recognized that certain stations may participate in only a limited part of the whole
field of monitoring;(e) the importance, for the safety of life at sea and in the air, of the international monitoring
system in ensuring the correct use of the radio-frequency spectrum by the mobile services;
UNANIMOUSLY DECIDES

1. that all Administrations now participating in the international monitoring system should beurged to continue to do so to the maximum extent possible;

2. that Administrations, who do not at present participate in the international monitoring
system, should be urged to make monitoring facilities available to that system, in accordancewith Article 13 of the Radio Regulations, Geneva, 1959;
3.

that Administrations, located in those areas of the world where monitoring facilities are
inadequate (as indicated by Report 282-1), should be urged to promote the establishment ofmonitoring stations for their own use and make them available for international moni­
toring, in accordance with Article 13 of the Radio Regulations, Geneva, 1959;

4. that Administrations should monitor radio stations in the mobile services systematically,in particular those stations serving maritime and aeronautical needs.

— 421 —Res. 16-1

RESOLUTION 16-1

HANDBOOK FOR MONITORING STATIONS(Q uestions 12/VIII and 15/VIII)
The C.C.I.R.,(1966)CONSIDERING(a) the ever-growing importance of monitoring stations, both for the needs of the international
monitoring system and for the Administrations’ own requirements;(b) the ever-increasing difficulties encountered by Administrations in collecting theinforma­tion required for the establishment or modernization of monitoring stations;(c) Question 12/VIII and, in particular, the importance of compiling useful data to enable new
and developing countries to set up their own stations and to take an active part in the inter­national monitoring system;(d) Question 15/VIII and the urgent need for the collection of visual and/or aural records ofthe typical characteristics of various classes of interfering radiations as an aid to personnel
at stations in the international monitoring system;
UNANIMOUSLY DECIDES

1. that the C.C.I.R. Secretariat should:
1.1 publish a handbook for monitoring stations, containing detailed information on the differ­ent chapters indicated in Annex I ;1.2 publish any complementarly information (for example, magnetic tape recordings), whichcannot be included in the volumes of the handbook;2.

that drafting groups be set up to prepare the various chapters of the handbook, in coopera­tion with the C.C.I.R. Secretariat and, if necessary, the I.F.R.B., following the procedure
mentioned in Annex II;

3.

that Administrations, Private Operating Agencies and International Organizations be asked
to supply to the C.C.I.R. Secretariat any useful information required for the accomplishmentof the task specified in § 1.
ANNEX ICHAPTERS OF THE HANDBOOK

1.

Purpose of monitoring and its field of activity

2.

Siting of monitoring stations

3. Buildings and auxiliary installations
3.1 Buildings
3.2 Power supplies and other installations .

4.
4.1
4.2
4.3
5.
5.1

Antennae
Different types of antennae
Layout of antennae
Transmission lines and distribution equipment
Receivers
Monitoring receivers

Res. 16-1

— 422 —

5.2 Special purpose receivers
6. Frequency measurement
6.1 Standards
6.1.1 standards comparisons
6.2 Methods of measurement
6.3 Precision of measurements
6.4 Measuring equipment
7. Field strength and power flux-density measurements
7.1 Choice of measurement sites for fixed installations
7.2 Measurement cubicles
7.3 Measurement methods
7.3.1 normal methods
7.3.2 expeditious methods
7.4 Calibration of measuring instruments
7.5 Precision of measurements
7.6 Long-term measurements (including field-strength recording and its analysis)
8. Monitoring of spectrum occupancy
8.1 Manual monitoring
8.2 Automatic monitoring
9.

Measurement of the bandwidth of emissions

10. Measurement of modulation (according to the class of emission)
10.1 Measurement of the depth of modulation
10.2 Measurement of the frequency-deviation

11. Special measurements for television emissions
12. Radio direction-finding
12.1 Site characteristics
12.2 Types of equipment
12.3 Precision of bearings

13. Identification
13.1 Identification of transmitters13.2 Identification of classes of emission

14. Identification and location of sources of interference
14.1 Interference caused by radio stations
14.2 Interference from other sources

15. Mobile monitoring stations
15.1 Field of activity
15.2 General characteristics of equipment
15.3 Specifications for the different types of measurement
15.3.1 choice of sites for field-strength measurements

16. Minimum essential equipment for a monitoring station
17. Organization of operation in monitoring stations
17.1 Examples of organization
17.2 Examples of preparation of monitoring reports and compilation of monitoring data— 423 —Res. 16-1

18. Staff
18.1 Recruitment
18.2 Training
19. Participation in the international monitoring system
19.1 Cooperation with the I.F.R.B
19.2 Cooperation between the monitoring stations of different countries
19.3 Service documents of the I.T.U
ANNEX IIARRANGEMENTS FOR PREPA RING THE HANDBOOK

1. To expedite publication of the Handbook, it will be divided into several volumes (one foreach chapter) and these volumes will be issued as and when they are ready, even though
this may sometimes mean departing from the order indicated in Annex I. Each volume
will be in loose-leaf form, so that the Handbook may easily be brought up to date.
2. The C.C.I.R. Secretariat is requested to write to Administrations, Private Operating Agen­cies and International Organizations, asking them to submit relevant information and thenames of the persons capable of participating in the drafting of the various chapters.
3. The drafting group for each chapter, or group of chapters, will consist of a coordinatorresponsible for the draft, assisted, so far as possible, by collaborators belonging to diffferent
Administrations, Private Operating Agencies or International Organizations.
4. For each chapter of the Handbook, the C.C.I.R. Secretariat will assemble the information
received and prepare an outline on the basis of this documentation and that already published.
5. This outline and the relevant documentation will be sent by the C.C.I.R. Secretariat to thecoordinator of the chapter and his assistant authors.
6. The coordinator and his assistant authors will prepare, in collaboration with the C.C.I.R.
Secretariat, a final text for publication.
7. Each drafting group will work to the maximum extent possible by correspondence.
8. The following Administrations, the I.F.R.B. and International Organizations shall desi­
gnate, within three months after the X lth Plenary Assembly of the C.C.I.R.,the individuals
responsible for the drafting of the various chapters:
Chapter 1: Portugal
Chapter 2: U.S.A.
Chapter 3: U.S.A.
Chapter 4: Canada
Chapter 5: Canada
Chapter 6: Federal Republic of Germany
Chapter 7: U.S.A.
Chapter 8: France
Chapter 9: Japan
Chapter 10: Portugal
Chapter 11: E.B.U.
Chapter 12: Portugal
Chapter 13: U.S.A.
Chapter 14: United Kingdom
Chapter 15: Italy

Res. 16-1, Op. 11, Q. 1/Vffl— 424 —

Chapter 16: Federal Republic of Germany
Chapter 17: France
Chapter 18: Canada
Chapter 19: I.F.R.B.
9.

The C.C.I.R. Secretariat will attempt to obtain from Administrations, Recognized Private
Operating Agencies and International Organizations, the designation of the collaborators
indicated in § 2 for the various chapters.

O P IN IO N 11
L IS T O F ST A T IO N S U S IN G SP E C IA L M EA N S O F ID E N T IFIC A T IO N
(Q uestion 14/VIII)
The C.C.I.R.,(1963)CONSIDERING(a) that the Radio Regulations, Geneva, 1959, set forth requirements for transmission of iden­
tifying signals by radio stations;(b) that certain types of radio stations are exempted from the necessity of having a call signfrom the international series, for example, stations which are identified by other means;(c) that many stations, using complex or special types of emission, cannot be identified by ordi­
nary means;(d) that the monitoring stations participating in the international monitoring system need tobe supplied with all the available information on means of identification used by radio stations;
IS UNANIMOUSLY OF THE O PINION

1.

that the I.F.R.B. should be asked to prepare, on the basis of information received from
Administrations, the list of stations which use special identification means; this list to containthe identifying signal, frequency, method of identification used, time of identification, andother pertinent information;

2.

that this list should be kept up-to-date by appropriate supplements.

Q U E ST IO N 1/VIII *F R E Q U E N C Y M E A S U R E M E N T S AT M O N IT O R IN G STA TIO N S
The C.C.I.R.,(1956 - 1963)CONSIDERING

that it is desirable to improve the accuracy, speed and convenience of frequency measure­ments, particularly under conditions of fading, interference, carrier instability, etc., includ­ing the case of suppressed or keyed carriers;* Formerly Question 252(VIII).

— 425 —u n a n im o u s ly

1.

d e c id e s

Q. l/V ffl, S.P. 1A/VHI

that the follow ing question should be studied:what are the accuracy and speed of frequency measurements which can be accomplishedat monitoring stations, especially under the conditions set forth above;2.

what are the difficulties in meeting the required accuracy (Recommendation 377-1), due tolimitations set by:
2.1 the measuring equipment;
2.2 propagation effects such as fading;
2.3 interference due to other transmissions;
2.4 the type of modulation, particularly for wideband transmissions in the frequency range
500 MHz to 10 GHz;3.

to what extent can errors be usefully reduced in practice by statistical processing of the meas­
urement data when measurements are taken at successive times or under different con­ditions ?

STUDY PRO G RA M M E 1A/VIII *M ETHOD OF DETERM INING THE AVERAGE ACCURACY OF FREQUENCYMEASUREMENTS AT M ONITORING STATIONSThe C.C.I.R.,(1965)CONSIDERING(a) that Recommendation 377-1 establishes the accuracy with which monitoring equipment
and frequency measurement procedures should be capable of carrying out such measurements;(b) that in the course of normal operation of a monitoring station, it is impracticable to deter­mine the accuracy with which each measurement has been effected;(c) that the accuracy of the measurement depends, not only on the accuracy of the standard
used, but also on the measurement equipment, the method used and the stability of thesignal level;(d) that it would be most useful to have uniform methods for determining the average accuracyof the measurements made with a given equipment during normal operation of a monitor­
ing station;u n a n im o u s l y d e c id e sthat the following studies should be carried o u t:

1.

determination of practical methods for assessing the highest and the average accuracy of
frequency measurements in the course of routine operation of a monitoring station;2.

determination of the parameters to be borne in mind when evaluating this accuracy, tak­ing into account both stable signals and signals subject to fading.

* Formerly Study Programme 252A(VIII).

q . 2/vm, 3/vm

426 —QUESTION 2/VIII *MEASUREMENT OF FREQUENCIES OF SINGLE-SIDEBAND,
INDEPENDENT-SIDEBAND AND OTHER COM PLEX EM ISSIONSThe C.C.I.R.,(1965 - 1966)CONSIDERING(a) that the growing use of single-sideband, independent-sideband and other types of complex
emission makes it increasingly difficult for monitoring stations to measure emission fre­quencies;(b) that, consequently, there is an ever more urgent need to find methods and equipment capableof performing these tasks,
unanimously decides that the following question should be studied:1.

what are the methods recommended for determining, at monitoring stations, the centre
frequency of the different classes of complex emission;2.

what are the most suitable specifications for the equipment required?

QUESTION 3/V III**
FIELD-STRENGTH MEASUREM ENTS AT M ONITORING STATIONSThe C.C.I.R.,'(1965)CONSIDERING(a) that Recommendation 378-1 -A ccuracy of field-strength measurements by monitoring sta­tions - does not cover all aspects of the problem, and that it recommends that studies, relat­
ing to methods and equipment for use at monitoring stations, should be continued;(b) that the importance o f collecting comparable field-strength data for the purpose o f making
propagation studies is increasing;unanimously decides that the following question should be studied:1.

taking into account the previous work of the C.C.I.R. in this field, what are the preferred
equipment and the preferred methods for measuring the field-strength of emissions for
propagations studies at monitoring stations;among other factors the following should be studied:- the methods for measuring the field strength,- the measuring and recording equipment,- the total frequency range,- the calibrating equipment,* This Question replaces Question 295.
** Formerly Question 293(VIII).

— 426 a —Q U E ST IO N 2-1/VIIIPROCEDURES FOR DETERMINATION OF THE CENTRE FREQUENCY
OF AN EMISSION *(1968)The C.C.I.R.,'

CONSIDERING(a) the growing use of single-sideband, independent-sideband and, in particular, complex andmulti-channel frequency-division emissions;s(b) the difficulty in assessing the corresponding centre frequency for these emissions;( c) that the knowledge of this centre frequency is fundamental in solving problems of harmfulinterference, in determining occupancy of the spectrum and in verifying compliance with thefrequency tolerances prescribed in the Radio Regulations;(d) that, consequently, there is an ever more urgent need to find procedures to solve the various
problems involved;d e c id e sthat the following question should be studied:1.

what are the procedures to be recommended to enable the determination of the centre fre­quency for the different classes of emission;2.

what are the most suitable procedures to be adopted and what are the specifications for the
additional equipment required at transmitting stations and at monitoring stations?

ST U D Y P R O G R A M M E 2-1 A /V III

PROCEDURE CONCERNING FREQUENCY MEASUREMENTS,
CHANNEL IDENTIFICATION AND NOTIFICATION OF FREQUENCYASSIGNMENTS OF SINGLE-SIDEBAND, INDEPENDENT-SIDEBAND, COMPLEXEMISSIONS AND MULTI-CHANNEL EMISSIONS USING FREQUENCYDIVISION MULTIPLEX(1968)The C.C.I.R.,
CONSIDERING(a) the problem in assessing the centre frequency * in relation to a characteristic frequency which
can be measured, to permit comparison between the centre frequency and the assigned fre­quency;* The centre frequency o f the bandwidth occupied by a complete emission (e.g., when all the channels areoperating).

426 b —(b) that the centre frequency of the occupied band is, in many cases, not a characteristic frequency
and consequently the centre frequency is not directly measurable;(c) that in the case of multi-channel emissions, difficulties occur in relating the channels in opera­tion with a given emission and their position in the spectrum with respect to the corresponding
centre frequency, especially when some channels are idle;(d) that the problem cannot be solved solely by new methods at monitoring stations but must be
solved primarily by procedures to be implemented at the transmitting stations;d e c id e s

1.

that the following studies should be carried o u t:

definition of basic procedures to be adopted at transmitting stations to enable:

1.1 determination of the centre frequency in relation to a characteristic frequency which can bemeasured (for instance, transmission at given periods of a characteristic frequency in eachchannel);
1.2 identification of each operating channel and its position in relation to the assigned frequency(for instance, by the use of a code transmitted during the period for station identification);2.

determination of methods to be recommended for finding the centre frequency at monitoring
stations, by measuring a characteristic frequency of the emission in conformity with pro­cedures that could be adopted in response to § 1, to permit comparison with the assigned
frequency;

2.1 specification of the most suitable equipment required;3.

formulation, as a consequence of the above studies, of the necessary modification to be recom­
mended for the procedure for the notification of frequency assignments as prescribed in theRadio Regulations.

— 427 —Q. 3/yni, 4/Vffl- the methods for analysing the records,- the most effective form of presentation and distribution of these data for the benefit ofvarious bodies, for example the I.F.R.B.,
2.

what are the most useful programmes of propagation studies in the different frequency ranges
that can be carried out at monitoring stations, bearing in mind:- the needs o f the I.F.R.B., Study Groups of the C.C.I.R. and other bodies,- the various distances and the particular paths over which propagation data are required;

3. what are the equipment and methods to be preferred for measuring the field-strength ofemissions:- with interrupted carrier,■- with reduced carrier,- with other types of signal, including television signals;

4. whatare the equipment and methods to be preferred for measuring the field-strength ofemissions of the types given in § 3, in the presence of noise and interference?

QUESTION 4/VIII *.
EXPEDITIOUS M ETHOD OF DETERM INING FIELD STRENGTH AT
M ONITORING STATIONSThe C.C.I.R.,(1963 - 1966)CONSIDERING(a) that the accuracies prescribed in Recommendation 378-1 are not always necessary in monitor­
ing observations, an accuracy better than ± 6 dB being sufficient for such a purpose, in thefrequency band 12 kHz to 30 MHz;(b) that, according to studies made to date (see Recommendation 442 and Report 368), equip­
ment answering this purpose can be obtained;(c) that it would be desirable to improve the existing methods for the expeditious measurementof field strength;u n a n im o u s l y d e c id e sthat the following questions should be studied:1.

what type of equipment, including those types described in Report 368, is the most suitable
for the expeditious measurement of field strength at monitoring stations;2.

what specifications should be adopted for the performance of the equipment (antenna, trans­mission line, receiver and calibrating source) ?

* Formerly Question 291 (VIII).

— 428 —Q. 5/V m , 6/VIIIQUESTION 5/VIII *BANDWIDTH M EASUREMENTS AT M ONITORING STATIONSThe C.C.I.R.,(1965 - 1966)CONSIDERING(a) that determination of the occupied bandwidth of an emission, by the method of measuring
total power and out-of-band power, in accordance with the present definition of occupied
bandwidth (see No. 90 of the Radio Regulations, Geneva, 1959), is not generally applicable
to measurements made at a distance from the transmitter;(b) that the I.F.R.B. requires practical optimum standards concerning bandwidth measurements
at monitoring stations;'u n a n im o u s l yd e c id e sthat the following question should be studied:1.

what are the most suitable equipment and methods for bandwidth measurement at moni­
toring stations of the various classes of emission, both on stable signals and signals subject
to fading and in the presence of noise and interference;2.

while awaiting the development of such a suitable method, what is the accuracy obtainable
at monitoring stations when using the bandwidth estimation procedure described in Recom­
mendation 443, when compared to measurements made at or near the transmitter by themethods described in Recommendation 327-1 ?

QUESTION 6 /V III* *M ONITORING AT FIXED M ONITORING STATIONSOF RADIO EM ISSIONS FRO M SPACECRAFTThe C.C.I.R.,(1965)CONSIDERING(a) that the rapid advances in recent years in space technology, including the successful launchingof earth satellites, portend greatly expanded activity in outer space, including the probableestablishment of “ space platforms ” ;(b) that radio will play a major part in these space activities as regards communication, naviga­

tion and data collection and transmission;(c) that “ space platforms” might find a variety of uses in the telecommunication field;* This Question replaces Question 294.
** Formerly Question 290(VIII).

— 429 —q . 6/v m , 7 /v m(d) that the accurate measurement at a fixed monitoring station of frequency, spectrum occu­
pancy, power flux-density at the earth’s surface and certain other technical characteristics
of emissions from transmitters on the spacecraft and platforms, will tend to be more diffi­
cult than on fixed or relatively slow moving sources of emission on or near the earth,u n a n im o u s l yd e c id e sthat the following question should be studied:1.

to what extent will the techniques of measurement, from fixed monitoring stations on theearth, of emissions from spacecraft, differ from those for emissions originating from or near
the earth;2.

what are the requirements for specialized equipment or associated facilities for performing
frequency, spectrum occupancy, power flux-density at the surface of the earth and othermeasurements of emissions from spacecraft;3.

what practical means can be devised for identification, by monitoring stations, of emissions
from specific spacecraft ?

Note. - It would be most desirable that results of measurements of field strength or power fluxdensity made by monitoring stations be assembled by the respective Administrations,to assist in propagation studies made by other Study Groups of the C.C.I.R.

Q U E S T IO N 7/V III *M ONITORING OF SW EEPING-TYPE PULSE EM ISSIONSThe C.C.I.R.,(1962- 1966)CONSIDERING(a) the increasing use being made of very short-duration pulse emissions, which may be modulated
in various ways and which are frequency-swept over wide ranges of the radio-frequency spec­trum;(b) that these emissions may, in some instances, be sources of interference to other transmissions,requiring identification and measurement by monitoring stations to assist in resolving suchinterference;(c) that special facilities and techniques are required by monitoring stations to receive, measureand identify signals of this type;u n a n im o u s l yd e c id e sthat the following question should be studied:

1. what is the extent of interference caused by sweeping-type pulse transmissions as they passthrough, or temporarily rest on or near, the frequency of other transmissions;2. what are the preferred facilities and techniques to permit reception and measurement bymonitoring stations of these sweeping-type pulse emissions;
3. how may these sweeping-type pulse transmissions be identified by monitoring stations ?

* Formerly Question 226(VIII).
28

Q. 8/V n i, 9/VIII— 430 —Q U E S T IO N 8/V III *DIRECTION-FINDING AT M ONITORING STATIONSThe C.C.I.R.,(1963)CONSIDERING(a) that direction-finding measurements in some cases have very great significance for Admin­
istrations and the I.F.R.B. in the investigation of harmful interference and in their concern
with efficient use of the radio-frequency spectrum;(b) that, while the techniques of direction-finding are well known, the methods and procedures
best suited to the international monitoring system are not established;(c) that the accuracy of bearings may be improved by certain procedures, e.g., by the statisticaltreatment of multiple bearings or by taking reference bearings on known stations;
unanimously decides that the following question should be studied:what methods of direction-finding and what procedures for improving the accuracy of bear­ings can be recommended for:- fixed monitoring stations;- mobile monitoring stations ?

QUESTION 9/V III**
AUTOMATIC M ONITORING OF OCCUPANCY OF
THE RADIO-FREQUENCY SPECTRUM
The C.C.I.R.,(1956- 1963)CONSIDERING(a) that the rapidly increasing demand for radio services continues to require the most efficientuse of the radio-frequency spectrum;(b) that the most efficient use of the spectrum can be made only when its occupancy is known;(c) that automatic monitoring is recommended as a valuable aid to determining the occupancyof the spectrum; and the desirable characteristics of such equipment have been alreadyrecommended in Recommendation 182-1;(d.) that it is desirable to make further studies of equipment characteristics and to determine
the means whereby the greatest benefit may be derived from automatic monitoring records;
unanimously decides that1.

the following question should be studied:what is the accuracy of automatic monitoring equipment in determining frequency, band­
width and field strength;* Formerly Question 254(VIII).
** Formerly Question 255(VIII).

— 431 —Q. 9/VIII, 10/VIII

2.

what is the capability of automatic monitoring equipment in determining signal-tonoise ratios;

3.

what are the best means of analysing and evaluating automatic monitoring records, both
singly and collectively;

4.

is it possible to analyse present records by automatic means and, if not, what modifications
are necessary to enable this to be done ?

QUESTION 10/VIII *VISUAL M ONITORING OF THE RADIO-FREQUENCY SPECTRUM
The C.C.I.R.,(1959)CONSIDERING(a) that every useful means of monitoring observation and measurement should be employedat monitoring stations, including visual methods employing a radio-frequency spectro­
scope;(b) that a panoramic view of a portion of the radio-frequency spectrum can be presented ona cathode-ray tube by the employment of suitable sweep circuits in the radio receiver orin an associated panoramic adapter;( c) that the simultaneous presentation o f broad ranges of the spectrum on one or more cathoderay tubes would provide for a rapid determination of spectrum occupancy, frequency, ampli­
tude and harmonic content (if one or more octaves are presented) of individual signals
and broadband coverage characteristics o f signals, including interference;(d) that, although panoramic adapters have been employed to some extent in monitoring
stations as an adjunct to aural monitoring, it appears that more information can be obtained
visually by monitoring observers, particularly in broadband visual presentation of thespectrum;
unanimously decides that1.

the following question should be studied:what are the preferred equipment and the preferred methods for visual monitoring of broad
ranges of the radio-frequency spectrum with regard to:

1.1 receivers and associated frequency-sweep circuits;
1.2 cathode-ray tubes (including practicable size);
1.3 antennae and associated broadband amplifiers and impedance-matching circuits;2.

what radio-frequency ranges can be presented simultaneously on one or more cathode-ray
tubes of a spectroscope, taking into consideration the frequency characteristics o f the antennae,
amplifiers'and receivers to allow relative comparisons throughout the portion of the spectrum
under visual observation;

3.

what adaptation o f circuitry of the equipment specified in § 1 would be required for a tem­porary increase in the resolution of the spectroscope;4.

what are the desirable operating methods and techniques to obtain maximum benefit fromvisual monitoring with a radio-frequency spectroscope, either when used alone or whenused as an adjunct to aural monitoring ?
* Formerly Question 191(VIII).

I

— 432 —Q. l l / v n i , 12/VIIIQ U E S T IO N 11/VIII *ANTENNAE FO R M ONITORING STATIONSThe C.C.I.R.,(1965)CONSIDERING(a) that the effectiveness of a monitoring station, in providing adequate surveillance over the radio-frequency spectrum, is determined to a major extent by the electrical characteristicsof the available monitoring antennae;(b) that substantial progress has been made in recent years in the development of broadband
antennae having improved characteristics as regards frequency coverage, directivity andgain;(c) that the anticipated future need for providing monitoring station facilities to permit observa­
tions and measurements of transmissions from spacecraft will require specialized antennae,taking into account the relatively weak signals involved and the high antenna directivity
required;u n a n im o u s l y d e c id e sthat the following question should be studied:1.

to what extent do currently available antennae fulfil the requirements of the monitoring
stations, taking into account such aspects as: means of varying both horizontal and ver­tical directivity, gain, space limitations;2.

what are the desirable characteristics of antenna systems for monitoring in the various fre­quency bands of interest and for various propagation modes;

3.

in which areas should further antenna development work be directed in an effort to improvemonitoring antenna characteristics (for instance: directivity, bandwidth, dimensions, possibil­
ities of orientation) ?

QUESTION 12/VIII **M ONITORING SERVICES IN THE NEW AND
DEVELOPING COUNTRIES(Question No. 2 of the Plan Sub-committee for Asia, Geneva, 1963)
The Regional Plan Committee for Asia,(1963)CONSIDERING(a) the importance of radio-frequency monitoring in the improvement of general operation of
the expanding radio services;* Formerly Question 292(VIII).
** Formerly Question 275(VIII).

— 433 —Q. 12/Vni, Op. 29, Q. 13/VIII(b) the need for establishing more radio monitoring stations in the various parts of the world,which up to now have had very little or no radio monitoring services capable of participatingin the international monitoring services;
requests the C.C.I.R. to study the following question:1.

which radio monitoring services should be started by the new and developing countries inthis field;2.

what guidance can be given in the establishment and organization of a radio monitoring
service;3.

what facilities should the monitoring equipment provide and what are the suitable charac­
teristics for such equipment?

Explanatory note: There is a great need for starting some radio monitoring service for conser­
vation of spectrum space, for the avoidance of harmful interference and for finding new
frequencies which the new countries need for their radio services. Guidance in these matterswould be helpful.

O PINION 29
TYPES AND M ETHODS OF ASSISTANCE BY M ONITORING STATIONSTO THE OPERATION OF VARIOUS RADIO SERVICES
The C.C.I.R.,(1966)CONSIDERING

the assistance that the international monitoring system can render in promoting rationaluse of the radio-frequency spectrum;
IS UNANIMOUSLY OF THE O PINION that

the Administrations, C.C.I.R. Study Groups concerned and the I.F.R.B. should be asked
to suggest any technical studies to be initiated and those which should be expanded,
to provide improved assistance by the international monitoring system to Administrations
and to the I.F.R.B.

QUESTION 13/VIII *TYPES AND M ETHODS OF ASSISTANCE BY M ONITORING STATIONSTO THE OPERATION OF VARIOUS RADIO SERVICES
The C.C.I.R.,(1963)CONSIDERING(a) that monitoring stations in the international monitoring system exist for the purpose ofincreasing the effectiveness of radiocommunications throughout the various radio services;* Formerly Question 259(VIII).

— 434 —Q. 13/Vin, S.P. 13A/Vin(b) that techniques progress so rapidly, particularly in new fields such as space telecommuni­

cations, that conditions may exist whereby neither the Administration concerned nor theinternational monitoring system may be aware of the full potentialities of monitoring func­
tions for rendering assistance to radio services;(c) that the attention of all C.C .I.R. Study Groups and all Administrations should be called toavailable monitoring functions, for the purpose that they be alerted to keep the international
monitoring system advised of types and methods of assistance that could be initiated or
expanded to use full potentialities of that system;u n a n im o u s l y d e c id e sthat the following question should be studied:what monitoring functions, not now being performed, or not being rendered to full capability,
could be initiated or expanded to provide improved assistance to Administrations or to
the I.F.R.B. ?

STUDY PRO G R A M M E 13A/VIII *TYPES AND M ETHODS OF ASSISTANCE" BY M ONITORING STATIONSTO THE OPERATION OF VARIOUS RADIO SERVICES
The C.C.I.R.,(1965)CONSIDERING(a) that monitoring stations of various Administrations work towards a common end;(b) that it is desirable for monitoring stations to benefit from one another's experience;(c) that it would be useful, both for the needs of Administrations and those of the I.F.R.B.,

to find a practical way of keeping monitoring stations of each Administratipn informedof the methods and new equipment adopted by monitoring stations of other Administrations;(d) Question 12/VIII and the value of enabling the new and developing countries to obtainpromptly the technical information they require in connection with installing and improving
a monitoring station;'u n a n im o u s l yd e c id e sthat the following studies should be carried out;1.

the best means of expediting the exchange of technical information among monitoring
stations;2.

improvement in the cooperation among monitoring stations;

3.

means of fostering the exchange of bibliographical material among monitoring stations.

* Formerly Study Programme 259A(V1II).

435 —

Op. 30, Q. 14/Vni

OPINION 30
IDENTIFICATION OF RADIO STATIONSThe C.C.I.R.,(1966)CONSIDERING(a) that, by Article 19, Section I, of the Radio Regulations, Geneva, 1959, transmissions without

identification or with false identification are prohibited;(b) that monitoring stations report that many transmissions are made without identification;
IS UNANIMOUSLY QF THE OPIN IO N that

Administrations should follow more strictly the provisions referred'to under § (a).

QUESTION 14/VIII *IDENTIFICATION OF RADIO STATIONSThe C.C.I.R.,(1953 - 1959- 1963)CONSIDERING(a) that Article 19, Section I of the Radio Regulations, Geneva, 1959, requires that the identifying

signal be transmitted, by methods which, in accordance with C.C.I.R. Recommendations,do not need special terminal equipment for reception;(b) that special methods for identifying certain complex classes of emission have been evolved(Recommendation 379—1 and Report 280-1);(c) that, however, there may be now, or in the future, some classes of emission to which thepresently recommended methods of identification cannot be applied satisfactorily;u n a n im o u s l yd e c id e sthat the following question should be studied:

1. which are the classes of emission that cannot be identified by the methods of identification
recommended by the C.C.I.R. or set forth in the Radio Regulations, Geneva, 1959;
2. what satisfactory methods can be evolved for the identification of such emissions?

* Formerly Question 256(VIII).

Q. 15/VIH— 436 —Q U E S T IO N 15/VIII *IDENTIFICATION OF SOURCES OF INTERFERENCE TO RADIO RECEPTION
The C.C.I.R.,(1959 - 1963 - 1966)CONSIDERING(a) that interference-causing radiations have individual characteristics which, when observed

aurally or visually, often enable an experienced monitoring observer to identify the type ofequipment producing the radiations;(b) that a list of all electrical and electronic equipment, which might at times cause radio inter­
ference, would include practically every device that uses electricity;(c) that it would be helpful in the solution of interference problems, for both monitoring obser­vers and radio station operators to compare interfering signals with reference informationof individual signal characteristics to permit rapid identification of those signals;(d) that the individual characteristics mentioned in § (c) might include, but not be limited to :frequency range, distance range, on-olf cycles, time of occurrence, characteristic note or tone,
frequency stability, normal bandwidth, type of signal as viewed on oscilloscope or pano­ramic receiver, type of source equipment and cause of the radiation;u n a n im o u s l y d e c id e sthat the following question should be studied:1.

what are the preferred methods and forms of listing, by written description, magnetic taperecording or pictorial presentation, as appropriate, information on the individual charac­
teristics of all observed types of interfering radiations, produced by radio emissions or byelectrical equipment;2.

what uniform standards of measurement should be adopted for the collection of data to besent to the C.C.I.R. Secretariat for the preparation of Chapter 14 (and its Annexes) of the
Handbook referred to in Resolution 16-1.

* This Question replaces Question 257.

LIST OF DOCUMENTS CONCERNING STUDY GROUP VIII
(Period 1963-1966)
Origin

Doc.

Title

Reference

VIII/1

United Statesof America

Types and methods of assistance by monitor­
ing stations to the operation of various radio
services

Q. 259

VIII/2

United Statesof America

Revision of S.P. 207(VIII). Bandwidth
measurements by monitoring stations

S.P. 207

VIII/3

United Statesof America

Draft Report. Monitoring services in the
new and developing countries

Q. 275

VIII/4

PortugalTypes and methods of assistance by monitor­
ing stations to the operation of various radio
services

Q. 259

VIII/5

United Statesof America

Direction-finding at monitoring stations

Q. 254

VIII/6

United Statesof America

Antennae for monitoring stations

Q. 258

VIII/7

United Statesof America

Proposed modification to Rec. 377. Accu­
racy of frequency measurements at monitor­
ing stations

Rec. 377

VIII/8

United Statesof America

Proposed modification to Rec. 379. Iden­
tification of radio stations

Rec. 379

VIII/9and Corr.l

United Statesof America

Proposed modification to Report 272.
Frequency measurements at monitoring
stations

Rep. 272

VIII/10

United Statesof America

Proposed modification to Report 276.
Monitoring of emissions from spacecraft at
fixed stations

Rep. 276

VIII/11

United Statesof America

Proposed modification to Report
Identification of radio stations

Rep. 280

VIII/12

United Statesof America

An expeditious method of determining fieldstrength in the international monitoring
system

Q. 253

VIII/13

United Kingdom

Proposed modification to Report 275.
Bandwidth measurement by monitoring
stations

Rep. 275

VIII/14

United Kingdom

Identification of sources of interference to Res. 16
radio reception. “ Catalogue ” of charac­
teristics of interfering emissions

VIII/15

United Kingdom

Expeditious method of determining fieldstrength in the international monitoring
system

Q. 253

VIII/16

Portugal

Expeditious method of determining fieldstrength in the international monitoring
system

Q. 253

VIII/17

United Kingdom

Monitoring services in the new and develop­
ing countries

Q. 275

VIII/18

Japan

An expeditious method for the determinationof field strength in the international monitor­
ing system

Q. 253280.

— 438 —Origin

Doc.

Title

Reference

VIII/19Japan

VIII/20

Japan

VIII/21
VIII/22Chairman,
Study Group VIII
Italy

VIII/23
VIII/24

Italy
Italy

VIII/25

U.S.S.R.

VIII/26

FranceAutomatic monitoring of occupancy of theradio-frequency spectrum. Equipment for
the automatic monitoring of occupancy of
the radio-frequency spectrum and its
performance
Types and methods of assistance given bymonitoring stations to the operation ofvarious radio services
Interim report by the Chairman, Study
Group VIII - International monitoring
Proposed revision of Recommendation 182(Geneva, 1963). Automatic monitoring ofoccupancy of the radio-frequency spectrum
Antennae for monitoring stations
Proposed revision of Report 277. Measure­ments at mobile monitoring stations
Draft opinion on the regulation of out-ofband emissions
Monitoring in new and developing countries

VIII/27(TV/89)and Corr.l
VIII/28

Study Group VIII

Summary Record - Joint opening session

I.F.R.B.

VIII/29

Study Group VIII

Proposed modifications to Report 282 International monitoring facilities
Summary record of the first meeting

VIII/30

Working Group
VIII-A

Monitoring of emissions from spacecraftat fixed monitoring stations

Draft mod.
toRep. 276

VIII/31

Working Group
VIII-C ‘

Identification of radio stations (Question
256(VIII)),

Draft mod.
toRep. 280

VIII/32

Working Group
VIII-A

Accuracy of frequency measurements atmonitoring stations (Question 252(VIII))

Draft mod.
toRec. '377

VIII/33

Working Group
VIII-A

Frequency measurements at monitoring sta­tions (Question 252(VIII))

VIII/34
and Corr.l
VIII/35

Working Group
VIII-B
Working Group
VIII-B
Working Group
VIII-B

Direction finding at monitoring stations(Question 254(VIII))
Question 258

Draft mod.
toRep. 272 ■Draft Rep.

VIII/36

Q. 255

Q. 259Rec. 182
Q. 258
Rep. 277
Draft Op.
Draft Rep.

■

Automatic monitoring of occupancy of
the radio-frequency spectrum (Question
255(VIII))

Draft
Rec.

VIII/37

Working Group
VIII-B

Addition to Report 278

Draft
Rep.

VIII/38

Working Group
VIII-B

Draft
Rep.

VIII/39

Working Group
VIII-A

VIII/40

Working Group
VIII-A

Antennae for monitoring stations (Ques­
tion 258(VIII))
Method of determining average accuracy of
frequency measurements at monitoring
stationsExpeditious method of determining fieldstrength at monitoring stations

Draft S.P.
Draft Q.

— 439 —Doc.

OriginTitle

Reference

VIII/41

Working Group
VIII-A

Expeditious method of determining fieldstrength at monitoring stations (Ques­
tion 253(VIII))

Draft
Rep.

VIII/42

Working Group
VIII-A

Measurement of frequencies of single-side
band, independent side-band and othercomplex emissions

Draft Q.

VIII/43

Working Group
VIII-A

Expeditious method of determining fieldstrength at monitoring stations

Draft Rec.

VIII/44

Working Group
VIII-C

Identification of radio emissions from space­
craft

Draft Rep.

VIII/45

Working Group*
VIII-C

Identification of radio stations (Question, 256(VIII))

VIII/46

Working Group
VIII-A

Measurements at mobile monitoring sta­tions

VIII/47

Working Group
VIII-A

Proposal to cancel Report 274

Draft mod.
toRec. 379
Draft mod.
toRep. 277
Rep. 274

VIII/48

Working Group
VIII-A

VIII/49

Working Group
VIII-A
C.C.I.R. Secretariat
Working Group
VIII-A
Working Group
VIII-A
Working Group
VIII-A, B and C
Working Group
VIII-C

Draft letter to the Chairman of Study
Group I - Bandwidth measurements bymonitoring stations
Bandwidth measurements by monitoring
stations
List of documents issued (VIII/1 to VIII/50)
Bandwidth measurements by monitoring
stations
Proposed modification to Question 188(VIII)

VIII/50
VIII/51
VIII/52
VIII/53
VIII/54
VIII/55
VIII/56

Working Group
VIII-B
Working Group
VIII-B

VIII/57

Working Group
VIII-B

VIII/58

Working Group
VIII-B
Working Group
VIII-A
Working Group
VIII-A
Working Group
VIII-B

VIII/59
VIII/60
VIII/61
VIII/62
VIII/63

Working Group... VIII-B
Study Group VIII

Draft Rec.

Draft Q.
Q. 188

Handbook for monitoring stations

Draft Res.

Proposed modification to Res. 16. Identifica­tion of sources of interference to radio
reception
First report to Study Group VIII

Res. 16

Types and methods of assistance by monitor­
ing stations to the operation of various radio
services
Types and methods of assistance by monitor­
ing stations to the operation of various radio
services
Proposed modifications to Report 282.
International monitoring facilities
Field-strength measurements at monitoring
stations
Report by W.P. VIII-A to Study Group VIII

Draft S.P.

Types and methods of assistance by monitor­
ing stations to the operation of various radio
services
Monitoring services in the new and develop­
ing countries
Summary record of the second meeting

Draft Op.
Rep. 282
Draft Q.

Draft Op.
Draft Rep.

— 440 —Doc.

OriginTitle

VIII/64

Working Group
VIII-C

Guidance for the I.F.R.B. on the matter ofOpinion 11

Op. 11

VIII/65

Working Group
VIII-C

Identification of sources of interference toradio-reception

Res. 16

VIII/66

Study Group VIII

Summary record of the third and last
meeting

VIII/67(IV/166)(VII/57)(IX/159)
VIII/68

C.C.I.R. Secretariat

List of participants (Monte-Carlo, 1965)

C.C.I.R. Secretariat

List of documents issued (VIII/51 to VIII/68)

VIII/69

C.C.I.R.
Secretariat

Comments by the Administration of theUnited Kingdom on Question 291(VIII)

Q. 291

VIII/70

O.I.R.T.

Antennae for radio-monitoring centres

S.P. 182(1)VIII/71

United Statesof America

Monitoring of sweeping-type pulse emissions\

Q. 226

VIII/72

United States. of America

List of stations using sweeping-type pulse
emissionsQ. 266

VIII/73

United Statesof America

Proposed modification to Report 278 Automatic monitoring of occupancy of theradio-frequency spectrum

Q. 255

VIII/74

United Statesof America

Measurement of frequencies of single-side­band, independent-sideband and other complex
emissionsQ. 295

VIII/75

Japan

Proposed revision of Report 275 - Band­width measurement by monitoring stations

Rep. 275,
Q. 294

VIII/76

Japan

Bandwidth
stationsmeasurements

bymonitoring

Q. 294

VIII/77

Japan

Bandwidth
stationsmeasurements

bymonitoring

Q. 294

VIII/78Japan

Measurement of frequencies of single-side­band, independent-sideband and other complex
emissionsQ. 295(VII

VIII/79

E.B.U.

Exchange of technical information between
receiving and measuring stations by meansof exchanges of staff

S.P. 259A(VIII)

VIII/80

E.B.U.

Monograph on receiving and measuring sta­tions for broadcasting purposes

Draft Res.

VIII/81

E.B.U.

Measuring methods and apparatus suitable
for new and developing countries

Q. 275

VIII/82

I.F.R.B.

Memorandum by the International Frequency
Registration Board to C.C.I.R. Study
Group VIII concerning a list of stations
using special means of identification

Op. 11

VIII/83,
Corr.l,and Add.l

Chairman,
Study Group VIII

Report by the Chairman, Study Group VIII

VIII/84

I.F.R.B.

Extension of the international monitoring
system to a world-wide scale

Res. 15

VIII/85

I.F.R.B.

Proposed modifications to Report 282 International monitoring facilities

Rep. 282

Reference

Interim meetings

— 441 —Title

Reference

VIII/86

F.S.R. of
Yugoslavia

Automatic monitoring of occupancy of afrequency and of operations on that frequency

Rec. 182,
Q. 255,
Rep. 277

VIII/87

India

Direction finding at monitoring stations

Q. 254

YIII/88

Study Group VIII

Summary record of the first meeting

VIII/89

Working Group

Proposed modifications to Recommenda­
tion 278 - Accuracy of field strength measure­ments by monitoring stations

VIII/90

Working Group
VIII-A

Attention of the Chairman, Study Group I Equipment for ionospheric sounding

VIII/91

Working Group
VIII-A

Draft Report - Monitoring of sweepingtype pulse emissions

VIII/92

Working Group
VIII-A

Draft Question - Measurement of frequenciesof single-sideband, independent-sideband
and other complex emissions

VIII/93

Study Group
VIII

Draft modification to Report J.f(VIII) Frequency measurements at monitoring
stations

Q. 252

VIII/94

Working Group
VIII-AQ. 295

VIII/95

Working Group
VIII-A

Draft Report - Measurement of frequenciesof single-sideband, independent sideband
and other complex emissions
Draft Recommendation - Bandwidth measure­ments by monitoring stations

VIII/96

Working Group
VIII-C
Working Group
VIII-C

Draft Report - Identification of sources ofinterference to radio reception
Draft Question - Identification of sourcesof interference to radio reception

Q. 257

YIII/98

Working Group
VIII-A

Draft modification to Report 275 - Band­width measurement by monitoring stations

Q. 294

VIII/99

Study Group VIII

Summary record of the second meeting

Doc.

VIII/97

OriginQ. 293Q. 226

Q. 294

VIII/100

C.C.I.R. Secretariat

List of documents issued (VIII/69 to VIII/108)

VIII/101

Working Group
VIII-B

Report by the Chairman

VIII/102Working Group
VIII-C

Draft Resolution - Handbook for monitor­
ing stations

Q. 257,
Q. 275

VIII/103
d/70)

Study Group I

Draft Report - Approximate methods forthe determination of bandwidth

S.P. 180(1),S.P. 181(1)VIII/104(1/74)

Study Group I

Letter to the Chairman, Study Group
VIII - Bandwidth measurements by monitorstations

VII/105
d/75)
VIII/106

Study Group I

Draft Study Programme - Methods ofmeasuring emitted spectra in actual traffic

Study Group VIII

Summary record of the third meeting

VIII/107

Study Group VIII

Summary record of the fourth meeting

VIII/108

Study Group VIII

Status of texts

ILIST OF DOCUMENTS OF THE Xlth PLENARY ASSEMBLYESTABLISHED BY STUDY GROUP VIII
Title

Doc.

Final text

VIII/1001

Types and methods of assistance by monitoring stations Op. 30
to the operation of various services

VIII/1002

Identification of radio stations

Rec. 379-1

VIII/1003

Measurement of frequencies ofsingle-sideband,independent-sideband and other complex emissions

Q. 2/VIII

VIII/1004

Accuracy of field-strength measurements by monitoring
stations

Rec. 378-1

VIII/1005

Expeditious method of determining
monitoring stations

Rec. 442

VIII/1006

Monitoring of sweeping-type pulse emissions

Q. 7/VIII

VIII/1007

Accuracy of frequency measurements atmonitoring
stations

Rec. 377-1

VIII/1008

Expeditious method of determining
monitoring stations

Q. 4/VIII

field strength atfield strength at

VIII/1009

Monitoring of sweeping-type pulse emissions

Rep. 367

VIII/1010

Expeditious method of determining
monitoring stations

Rep. 368

VIII/1011

Measurements at mobile monitoring stations

Rep. 277-1

VIII/1012

Identification of radio stations

Rep. 280-1

VIII/1013

Monitoring of radio emissions from spacecraft at fixedmonitoring stations

Rep. 276-1

VIII/1014

Modification proposed to Report 273

Rep. 273-1

VIII/1015

Bandwidth measurements by monitoring stations

Q. 5/VIII

VIII/1016

Measurement of frequencies of single-sideband, independentsideband and other complex emissions

Rep. 369

VIII/1017

Types and methods of assistance by monitoring stations
to the operation of various radio services - Exchangeof technical information between receiving and measur­ing stations by means of exchanges of staff

Rep. 370

VIII/1018

Bandwidth measurements by monitoring stations

Rep. 275-1

field strength at

VIII/1019

Frequency measurements at monitoring stations

VIII/1020

Identification of sources
reception

VIII/1021

Handbook for monitoring stations

Res. 16-1

VIII/1022

Automatic monitoring of occupancy of the radio-frequency
spectrum

Rec. 182-1

VIII/1023

Bandwidth measurements by monitoring stations

Rec. 443

VIII/1024

Types and methods of assistance by monitoring stations
to the operation of various radio services

Op. 29

VIII/1025

Identification
reception

Rep. 281-1

ofsources

Rep. 272-1

of interference toofinterference

radio

to radioQ. 15/VIII

— 443 —Title

Final text

VIII/1026

International monitoring facilities - Reply to Recommendation No. 5 of the Administrative Radio Conference,
Geneva, 1959

Rep. 282-1

VIII/1027

Monitoring services in the new and developing countries

Rep. 371

VIII/1028

Automatic monitoring of occupancy of the radio-frequency
spectrum

Rep. 278-1

VIII/1029

Direction finding at monitoring stations

Rep. 372

VIII./1030

Antennae for monitoring stations

Rep. 373

VIII/1031

List of documents issued (VIII/1001 to VIII/1031)

I