1 UNITED STATES 5PARTMENT OF OMMERCE

UBLICATION

Y v \

NBS TECHNICAL NOTE 611

U.S.

PARTMENT

OF

FOMMERCE

National

Bureau

of

NBS Frequency-Time

Broadcast Station WWV,

Fort Collins, Colorado
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and

technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and

Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates

that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac

Radiation2—Nuclear Radiation 2—Applied Radiation2-—Quantum Electronics3 —

Electromagnetics3—Time and Frequency3—Laboratory Astrophysics3—Cryogenics3

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of

well-characterized materials needed by industry, commerce, educational institutions, and

Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor

Radiation—Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute also monitors NBS engineering standards activities and

provides liaison between NBS and national and international engineering standards

bodies. The Institute consists of the following technical divisions and offices: Engineering Standards Services—Weights and Measures—Flammable Fabrics

Invention and Innovation—Vehicle Systems^ Research—Product Evaluation Technology—Building Research—Electronic Technology—Technical Analysis

Measurement Engineering.

THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center

consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of

the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader

aspects of the National Measurement System; provides appropriate services to ensure

that the NBS staff has optimum accessibility to the scientific information of the world, and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and

Publications—Library—Office of Public Information-—Office of International

Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

- Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.
ional Bureau f Standard! MAY 16 i972 [V^ QCC

Git too UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

Ti

NBS TECHNICAL NOTE 611

ISSUED OCTOBER 1971

Nat. Bur. Stand. (U.S.), Tech. Note 61 1, 29 pages (Oct. 1971) CODEN: NBTNA

NBS Frequency-Time Broadcast Station WWV,

Fort Collins, Colorado

Peter P. Viezbicke

Time and Frequency Division

Institute for Basic Standards

National Bureau of Standards

Boulder, Colorado 80302

rf*i »f c,

<">cau ot

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide

a means for making available scientific data that are

of transient or limited interest. Technical Notes may

be listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

(Order by SD Catalog No. C 13.46:6 11), Price 35 cents

CONTENTS

Page

1. INTRODUCTION 1

Z. SITE DESCRIPTION AND SURVEY Z

3. BUILDING DESIGN Z

4. SYSTEM DESIGN . . . . 11

4. 1 Antenna Design 11

4. Z Frequency- Time Code and Control Systems 14

4. 3 Transmitters Z3

4. 4 Monitoring System Z4

5. SUMMARY Z4

6. ACKNOWLEDGMENTS . . Z5

7. REFERENCES Z5
LIST OF FIGURES

Page

Figure 1. Map showing location of site with respect to Fort Collins,

Boulder, and Denver,. „ 3

Figure 2. Contour map of WWV and WWVB/WWVL showing location

of transmitter buildings and antennas. 4

Figure 3. Photograph of the NBS Fort Collins field stations 5

Figure 4. Photograph of the WWV transmitter building 7

Figure 5. Floor plan of the WWV transmitter building 8

Figure 6. View of the transmitters along the south corridor of the

building . 9

Figure 7. The south corridor of the building behind the transmitters,

showing overhead cable trays, power line disconnect

switch, and air ducts to the transmitters 10

Figure 8. Graph showing theoretical coverage of WWV for the

Western Hemisphere during the summer at high solar

activity. 12

Figure 9- Measured radiation pattern of the 15 MHz WWV vertical

dipole. Deflection proportional to field strength

normalized to a distance of 1 mile (1. 6 km) from

the antenna. 13

Figure 10. Vertical radiation pattern of a vertical half-wave dipole

located 3/8 ^ above good ground. The frequency is

10 MHz. 15

Figure 11. Design details of the WWV antennas 16

Figure 12. Photograph of the 25 MHz dipole antenna 17

Figure 13. A view of one of the 2.5 - 25 MHz standby antennas. .... 18

Figure 14. Block diagram of control equipment. 19

Figure 15. Photograph of control equipment. 20

Figure 16. Block diagram of the 10 kW transmitter. • ° 21

Figure 17. Block diagram of the 40 kW transmitter. 22

iv
NBS FREQUENCY- TIME BROADCAST STATION WWV,

FORT COLLINS, COLORADO

Peter P. Viezbicke

This report describes the design and construction of

the National Bureau of Standards frequency-time broadcast

station located at Fort Collins, Colorado. The principal

function of the station is to broadcast basic. standards of

frequency and time signals on frequencies of 2.5, 5, 10,

15, 20, and 25 MHz. These high frequency transmissions,

which can be received on the simplest of equipment, provide the necessary accuracy required to fulfill some of the

needs of industry, Government, and the public. The technical and administrative supervision of the station is under

the Time and Frequency Division, Frequency- Time

Broadcast Services Section, National Bureau of Standards,

Boulder, Colorado.

Key words: High frequency; standard radio frequencies;

time-frequency broadcasts; time signals; WWV.

1. INTRODUCTION

At 0000 hours GMT December 1, 1966, WWV transmissions

were transferred to and placed into operation at Fort Collins,

Colorado. The old and obsolescent Greenbelt, Maryland facility was

replaced in its entirety at the Fort Collins site. Since its rebuilding

in 1943, WWV-Greenbelt had made the basic standard of frequencytime service available continuously to its users through HF broadcast

transmissions on frequencies in the 2.5 to 25 MHz range [l, 2].

Throughout the years, however, equipment became old, faulty, and

continually in need of repair. In order to continue this most essential

and widely-used service, Congress appropriated $970, 000 in 1962 to relocate the station in the west-central part of the continental United

States. Funds became available the latter part of fiscal year 1964,

the relocation program commenced in 1965, and WWV began initial

broadcasts in December 1966. The new facility, located on a site near the present WWVB/WWVL station, not only provides a more

reliable service throughout most of the country, but it is also in close
proximity to the Boulder Laboratories, which provides its technical

and administrative supervision.

This report describes the new WWV Fort Collins HF broadcast

installation. Its scope includes site description, building design,

system design, antenna design, frequency-time code and control

systems, transmitter characteristics, and monitoring system.

2. SITE DESCRIPTION AND SURVEY

The NBS transmitter site is located approximately seven miles

(11.3 km) north of Fort Collins on Highway No. 1 enroute to Wellington,

Colorado. It covers an area of appi oximately 380 acres (1 . 537 x 10 m ) and is located in Section 7, Township 8 North, Range 68 W of the South

P.M., Larimer County, Colorado. Figure 1 gives a map of the site

detailing the locations of WWVB/WWVL and WWV facilities and arrangement of the antennas is presented in figure 2. An aerial view of the

Fort Collins site is shown in figure 3. WWV operates with six antennas which are arranged and located

in an arc of a circle on the ridge of a hill. The terrain in all but the

southerly direction of propagation slopes downward in the immediate

vicinity of the antennas. Although declivity in the southerly direction

is not as pronounced as in the other directions, omnidirectional lowangle radiation does result and is used advantageously due to these

natural terrain features as well as the electrical soil properties of the area. The relatively high soil conductivity of 29 millimhos/meter at the site is attributed in part to the high saline content of the soil. This

region has been under irrigation for a number of years which probably

explains the high concentration of salt deposits and the resulting high

conductivity.

The building, constructed into the side of a hill, is located at a lower elevation than the antennas. This location was selected to prevent objectionable reflections that might cause deleterious effects on

the radiation characteristics of the antennas.

3. BUILDING DESIGN

The tee- shaped transmitter building is of cement block construction, air cooled, and has a total area of 6880 ft^ (639 m.2); it consists

of the following specific areas: The transmitter room occupies an
DENVER MOUNTAIN AREA O -"— O

Figure 1. Map showing location of site with respect to Fort Collins, Boulder, and Denver. (To convert

to kilometers, multiply by 1.6.)

3
Figure 2. Contour map of WWV and WWVB/WWVL

showing location of transmitter buildings

and antennas.
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area of 3067 ft 2 (285 m^); the laboratory and shielded room 1206 ft^ (112 m^); and the office, galley, shops, and restrooms the remaining

952 ft 2 (88 m2 ). The building is located approximately 1250 ft (381 m)

in a northeasterly direction from the WWVB/WWVL facility. The

entire complex was designed specifically to provide a nearly dust-free

environment for the six operational and two standby transmitters.

However, it affords, in addition, ample laboratory space to carry out

experimental measurements and tests relative to the frequency and

time broadcast services and other NBS activities. Figure 4 is a photograph of the building; a drawing of the floor plan is shown in figure 5.

The transmitter room is so designed that only the front of each

transmitter is accessible from an operating corridor. A view of the

south operating corridor is shown in figure 6. This design not only

reduces blower noise in the laboratory area, but permits more uniform

and regulatory temperatures in the operating and laboratory areas and

also discourages the presence of unauthorized personnel behind the

transmitters.

The transmitters operate in a nearly dust-free environment.

Initially, the outside air is washed, then dried by passing through

evaporation filters, and finally blown and distributed through insulated

ducts to each transmitter. The air-flow through the transmitters is

then exhausted into a ceiling plenum chamber located around the periphery of the building above the equipment area. When the static

pressure in the plenum reaches a particular level, four large fans,

located on the roof, exhaust the air to the outside. Standby backup

fans located in the ceiling on each side of the building are used should

failure occur in the regular operating units. Figure 7 gives a photograph of the corridor behind the transmitters detailing overhead cable

trays, power line disconnects, and air ducts to the transmitters.

Frequency standards, time code generators, and associated control and monitoring equipment are located in a shielded enclosure. A

second shielded room is provided as part of the laboratory to carry

out interference-free measurements. Both rooms are air conditioned

and are temperature-controlled to ± 1.1° C.

The standby generator room accommodates power panels and

service entrance line disconnect switches and distribution circuit

breaker panels. Space is provided to locate and mount two standby

generators. Although a commercial power utility provides 500 kVA

of three-phase Y connected power from two separate sources to the

building, additional standby power is available from a 250 kW diesel
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NOTE: ALL MAIN BLOC. WALLS 8" THICK

ALL INSIDE DIN. ARE t TO t

TOTAL ENCLOSED BUILDING AREA 6880 SO FT.

• FLOOR PLAN • To convert: Ft to meters «' mult, by 0. 305.

In to meters: mult, by 0. 025.

Figure 5. Floor plan of the WWV transmitter building.
Figure 6 . View of the transmitters alonj

the south corridor of the

building.
Figure 7. The south corridor of the building behind the transmitters,

showing overhead cable trays, power line disconnect switch,

and air ducts to the transmitters.

10
generator. Power, delivered to both WWVB/WWVL and WWV, is

provided through electronically controlled switch gear. In the event

failure occurs in the operating power source, the electronic equipment

senses the failure and instantly switches to the other line. After a limited period of time it resets and switches back to the original source

providing the malfunction has been corrected.

4. SYSTEM DESIGN

The WWV Fort Collins system design was based, in part, upon

predicted coverage carried out by Hayden, Lucas, and Kirby [3]. The

computations and analyses were made of expected geographical coverage, reliability, and noise ratio in the Western Hemisphere. These

data, taking into account the seasons., solar activity, and daytime and

nighttime conditions, were obtained assuming transmitter power levels

of 10 kW using half-wave vertical dipole antennas and operating at frequencies of 2.5, 5, 10, 15, 20, and 25 MHz. Figure 8 gives a theoretical coverage graph of WWV for the Western Hemisphere during

the summer at high solar activity using a simple antenna and a receiver

with a noise figure of 10 db or less.

4. 1 Antenna Design

The half-wave vertically polarized antennas employ tower sections

of commercial manufacture and are designed to withstand winds up to 112 mph (180 km/h). The center-fed guyed antennas are mounted on

hinged bases and fastened to concrete foundations.

The antenna is basically a modified sleeve design with the feed

point located X./4 above ground. The upper \/4 section of the mast,

appropriately insulated from the lower section, constitutes one-half

of the radiating element. The lower half consists of nine sloping wires,

X./4 long, equally spaced and connected to the center mast. The wires

slope downwards to the ground at an angle of 45°. The skirt, each

wire appropriately insulated, not only functions as the lower \/4 radiating section of the dipole, but also serves as mid-tower guy lines.

With this arrangement, the driving point impedance is approximately

50 ohms and the current developed at the mast base-ground junction is

minimized. This allows the tower to be connected directly to ground.

Measurements carried out on the antennas indicated that the radial

ground system did not affect antenna input impedance; the ground

system was nevertheless incorporated to enhance radiation at grazing

angles. Figure 9 gives the measured radiation pattern at grazing

11
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12
13
angles of the 15-MHz WWV vertical dipole in the horizontal plane. The

theoretical vertical pattern of a vertical dipole fed 3/8 X above ground

is shown in figure 10 from the report by Berry, et al [4].

The antenna design is readily adaptable to a coaxial feed line and

provides low-angle omnidirectional radiation. It yields a gain of

approximately 1 . 7 db over its quarter-wave counterpart, and is easily

matched through a double stub tuner. The adjustable shorting stubs, one located at the base of the tower, the other spaced 3/8 X in the

direction of the transmitter, not only match the antenna precisely to 50 ohms but also provide an effective dc ground for the system. This

protects the transmitters from possible lightning damage. A drawing

of the dipole antenna including design details is presented in figure 11.

Figure 12 gives a photograph of the 25 MHz antenna.

Two wideband standby antennas are also fed with rigid coaxial

line. These are series excited, base-fed, vertically polarized omnidirectional X/4 monopoles. The commercially manufactured antennas

are located at the center of a 36 radial wire ground screen and operate over a frequency range of 2.5 to 25 MHz. The antennas are capable

of handling 50 kW average power with a nominal standing wave ratio of

less than 2 to 1 when terminated in a 50-ohm load. Continuous coverage is accomplished without switching at either the antenna or transmitters. Figure 13 is a photograph of one of the antennas.

4.2 Frequency- Time Code and Control Systems

Frequency generators, multipliers, time-code generators and

programming equipment are located in a lOx 18 ft (3x5.5 m) shielded

enclosure. A block diagram of one of three identical systems is presented in figure 14. A photograph of the equipment is shown in

figure 15.

The frequency control equipment consists essentially of three

complete and independent frequency generating systems. Each unit

contains a cesium beam atomic frequency standard; a set of amplifiers

and dividers providing 5.0, 1. 0, and 0. 1 MHz output frequency at the

non-offset atomic frequency; a fail-safe motor-driven resolver acting

as frequency offset generator; a second set of amplifiers and dividers

providing 5.0, 1.0, and 0.1 MHz offset (-300 parts in 1010); 1 a time

code generator-programmer and an rf driver unit which provides 2 W

PEP (Peak Envelope Power) excitation for each of the transmitters.

Frequency offset to be discontinued commencing 1 January 1972.

14
90- Frequency = 10 MHz

Vertical Halfwave Dipole

Feed Point Height = 1 1. 25 Meters Good Land

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Figure 10. Vertical radiation pattern of a vertical half- wave dipole

located 3/8 X above good ground. The frequency is 10 MHz,

15
To convert ft to meters, mult, by

0. 305. To convert in to meters,

mult, by 0. 025.

'/2

" diameter mylar guys support

the 10-15-20-25 MHz antennas -

5

/\e steel cable-insulators support

the 2.5 and 5.0 MHz masts.

ANTENNA DIHENSIONS

FRED. (MHz) Hi Ht L« La- 1 L. L, L2 R

2.5 93'-0- 98'-6 - 100-0- 150-0" 147-5" 55-4" 81-2- 162'

5.0 46'-0" 49-3

_ 49'-0 - eo'-o- T3'-8- 9-4- I4--7" 81'

10.0 22'-9 - 24'-7" 24'-0" — 36'-IO- 4

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- 6'-?V 40'

15.0 l5'-0

- 16'- 5" l5'-6- 24'-6 - 2'-3V 4'-2V 27'

20.0 1

1 "- 3- 12'- 3" l?-0" 18- 5" 4'-llV 7-8V 20' 250 9'-r 9'- 10" 10- 6" !4'-9

- 3-2V 5-7 V

16'

All tower sections constructed on l8!/2

" equilateral

triangle pattern using lli," x '/8

" side roils • Cross

bracing formed by continuous 7

^6

" solid rod fashioned into a zig-zag shape joining side rails every 15V and electrically welded • Hot dip

galvanized finish.

WAdjustable shorted stubs - spaced ^6 X at operating frequency - matches antenna

to 50 ohms.

-Precast trans,

line support posts.

Additional sets of guys and an additional

set of three guy anchors are used to support

the 2.5 and 5.0 MHz antennas. (See Dim. LA - I

)

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" Rigid line connects

to the 5-10-15 MHz antennas. \%" Rigid line connects

to the 2.5-20-25 MHz antennas.

( L, a L 2 - Distance to short circuit in line)

Figure 11. Design details of the WWV antennas.

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The driver is capable of either upper or lower sideband transmission

with any degree of carrier insertion along with the capability of

conventional double sideband amplitude modulation as currently used.

A fourth rack of equipment, used in conjunction with the three

generating systems, contains the UT2 and Geoalert keyer, the coaxial

switching equipment, phase-error multipliers, and phase detectors

used for monitoring the output signals of the generating units.

In an adjacent area of the shielded room is a fifth rack that contains a six-channel recorder that continuously displays the phase

relationships between the 1 -MHz outputs of the cesium standards and

the phase relationships between the 100-kHz outputs of the amplifier

and divider units operating at the offset frequency. The full scale

chart width on all channels is 1 /us. Located in this same area are two commercial pre-recorded units used for voice announcements.

Milton describes the relationship of the transmitted signals to the NBS

frequency standard and the intercomparison controls in great detail [5].

4. 3 Transmitters

A total of eight transmitters, six operational and two standbys, are used to broadcast frequency-time information at the station [2],

Four of the eight are rated at 40 kW PEP and are normally operated

at 10 kW average power. The remaining four are rated at 10 kW PEP

and operate at 2. 5 kW average power. Three of the 10-kW amplifiers are connected to dipole antennas via 3-1/8" (7.93 cm) rigid transmission line and transmit on assigned frequencies of 5, 10 and 15 MHz.

The fourth amplifier is connected to a standby antenna via similar line

and operates in the 2. 5 - 25 MHz frequency range. Three of the 2. 5-

kW amplifiers are connected to the other three operational dipoles via

1-5/8" (4. 12 cm) rigid transmission line and transmit on frequencies

of 2. 5, 20 and 25 MHz. The fourth lower power amplifier is connected

to a standby antenna similar to the one mentioned above. The 10- and

40-kW amplifiers are identical in design with all component parts interchangeable with one another. Figures 16 and 17 give block diagrams

of the two amplifiers.

The amplifiers operate in a linear mode and connect into a 50 ohm

unbalanced transmission line. The 10-kW amplifier consists of three

stages of amplification, associated power supplies, and control circuits.

A 6CL6, class A amplifier, couples to a 6146 linear driver that drives

a class AB1 PL172 amplifier stage. This unit, capable of 1 kW rf PEP,

drives a 4CX5000A tetrode. The 40-kW amplifier consists of the 10-kW

23
amplifier and an additional stage of amplification. The final amplifier uses an ML-6697 grounded grid triode and its associated power

supplies, control, and overload circuitry.

The different transmitters, frequency and time code generator,

and other functions of the two stations are monitored from two control

points. One is located at WWV, the other at WWVB/WWVL. The

system is designed to allow monitoring both stations from either

location.

4.4 Monitoring System

Monitoring essential electronic functions at the station employs

graphic recorders, visual indicators and associated audible alarms.

Graphic recorders display atomic and offset atomic time on a sixchannel recorder. Three channels are used to readout frequency

comparisons among the three cesium beam standards. The other three

channels readout the comparison among the three cesium-beam-generated offset frequencies. Similarly, functions associated with the

generation of frequency, time code information, and voltages required

to operate equipment located in the shielded room and those associated

with the rf amplifiers are connected to visual and audible alarms.

These aids are designed into console units centrally located at the two

stations.

5. SUMMARY

Radio station WWV at Fort Collins, Colorado, broadcasts

frequency-time information on 2.5, 5, 10, 15, 20, and 25 MHz. The

station is located approximately 7 miles (11.26 km) north of Fort

Collins on Highway 1 and is readily accessible by automobile from

Denver and Boulder via Interstate Highway 25 or U. S. Highway 287.

Average rf power of 10 kW is transmitted on 5, 10, and 15 MHz;

2.5 kW is transmitted on 2.5, 20, and 25 MHz. Each transmitter is

connected to a vertical half-wave dipole via rigid coaxial cable. Double

stub tuners, located at the base of each tower, are used to adjust the

antennas precisely to 50 ohms. Two additional transmitters and

associated antennas are used for standby purposes.

Frequency and time are generated by cesium beam standards

that are kept within ± 1 part in 10 12 of the NBS frequency standard in

Boulder, Colorado [2, 5]. Associated time code generators, offset generator,

audichrons, Geoalert keyers, frequency multipliers, recording and

24
monitoring equipment function integrally to provide a worldwide

frequency-time broadcast service with transmitted accuracies up to

5 parts in 10 12 .

6. ACKNOWLEDGMENTS

Appreciation is extended to R. S. Gray for his valuable assist- ance in fabrication of antenna transmission lines, antennas, and

measurements of antenna parameters in the early stages of building

construction; to J. B. Milton and E. Rogers for the design and

development of frequency control and other electronic equipment;

and to G. Hicks for her untiring and diligent secretarial services.

7. REFERENCES

[l] NBS, Standard frequency and time signals WWV and WWVH,

Proc. IRE (Corresp.), 44, No. 10, 1470-1473 (Oct. 1956).

[2] Viezbicke, P. (Editor), NBS frequency and time broadcast

services --radio stations WWV, WWVH, WWVB, WWVL,

Nat. Bur. Stand. (U. S. ), Spec. Publ. 236, 1971 edition,

13 pages (July 1971).

[3] Haydon, G. W. , Lucas, D. L. , and Kirby, R. C. , Predicted

coverage of WWV Fort Collins for 10 and 100 kilowatts

(Unpublished report).

[4] Berry, L. A. , and Chrisman, M. E. , Linear high frequency

antennas over a finitely conducting spherical earth, ESSA Tech.

Report IER 8-ITSA 8, 1 17 pages (Sept. 1966).

[5] Milton, J. B., Standard time and frequency: its generation,

control, and dissemination from the National Bureau of Standards

Time and Frequency Division, Nat. Bur. Stand. (U. S. ), Tech.

Note 379, 27 pages (Aug. 1969).

25

form NBS-114A (1-711 U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS-TN-611

2. Gov t Accession No.3. Recipient's Accession No.

4. TITLE AND SUBTITLE NBS Frequency- Time Broadcast Station WWV,

Fort Collins, Colorado

5. Publication Date October 1971

6. Performing Organization Code

7. AUTHOR(S) Peter P. Viezbicke

8. Performing Organization

10. Project/Task/Work Unit No. 2730121

9. PERFORMING ORGANIZATION NAME AND ADDRESS NATIONAL BUREAU OF STANDARDS, Boulder Labs DEPARTMENT OF COMMERCE

Boulder, Colorado 80302

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

Same as #9.

13. Type of Report & Period Covered Final 1965-1966

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.)

This report describes the design and construction of the National Bureau of Standards frequency-time broadcast station located at Fort Collins, Colorado.

The principal function of the station is to broadcast basic standards of frequency

and time signals on frequencies of 2.5, 5, 10, 15, 20, and 25 MHz. These high

frequency transmissions, which can be received on the simplest of equipment,

provide the necessary accuracy required to fulfill some of the needs of industry,

Government, and the public. The technical and administrative supervision of the station is under the Time and Frequency Division, Frequency- Time

Broadcast Services Section, National Bureau of Standards,. Boulder, Colorado

17. KEY WORDS (Alphabetical order, separated by semicolons) High frequency; standard radio frequencies; time -frequency broadcasts;

time signals; WWV.

18. AVAILABILITY STATEMENT

\Xi UNLIMITED.

Z2 FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

29

22. Price

35 cents

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