Rational Bureau of Standards

Library, B.W. Bldg

APR 5 1965

^ecltnical v2ote 9Jo. 302

IBUOGRAPHY OF

ADING ON MICROWAVE LINE OF SIGHT

TROPOSPHERIC PROPAGATION PATHS

AND ASSOCIATED SUBJECTS

H. T. Dougherty

I. S. DEPARTMENT OF COMMERCE

IATIONAL BUREAU OF STANDARDS
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listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials. Central Radio Propagation Laboratory.** Ionosphere Research and Propagation. Troposphere

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NATIONAL BUREAU OF STANDARDS

technical ^ote 302

Issued August 31, 1964

BIBLIOGRAPHY

OF

FADING ON MICROWAVE LINE OF SIGHT

TROPOSPHERIC PROPAGATION PATHS

AND ASSOCIATED SUBJECTS

H. T. Dougherty

Central Radio Propagation Laboratory

National Bureau of Standards

Boulder, Colorado

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

Price: 60 cents

TABLE OF CONTENTS

Page No.

Introduction 1

Subject Index 3

Author Index 9

Titles and Abstracts 15

1933 15

1940 16

1941 16

1946 17

1947 23

1948 28

1949 30

1950 35

1951 38

1952 39

1953 41

1954 45

1955 48

1956 54

1957 57

1958 60

1959 64

1960 74

1961 79

1962 87

1963 97

1964 106

Addendum Ill

iii

Bibliography of Fading on Microwave Line of Sight

Tropospheric Propagation Paths and Associated Subjects

H. T. Dougherty

A collection of titles and abstracts is presented for articles dealing with the microwave fading that has been observed on tropospheric

line of sight paths. Selections are included for related subjects such as:

measurement of meteorological factors; spatial, frequency and time

diversity reception; and attenuation due to trees and buildings. Also

included is a subject index and an author index.

Introduction

This bibliography contains over 200 titles and abstracts from the

open literature published between 1933 and the first half of 1964. Although

most are taken from English language publications, several selections

are also included from French, German, Russian, Italian, and Japanese

language publications. In general, selections from "in house" publications or reports of limited distribution were avoided. This course was

followed not only because such reports are not readily available to all

interested parties but also because they generally appear later in a more

concise published version.

To properly cover the subject "Fading on Microwave Line of Sight

Tropospheric Propagation Paths," it is necessary to also include at least

representative selections from associated subjects such as microwave

antennas, reflection coefficients, measurement of meteorological factors,

attenuation due to trees, etc. The frequency range of phenomena covered

here is roughly several hundreds of MHz to several tens of GHz, the

region of decimeter and centimeter wavelengths.

The titles and abstracts are grouped by their year of publication

and arranged alphabetically (by authors) within each year. Identification

numbers are assigned in the same manner; the first two digits indicate
the year followed by a hyphen and the number indicating its alphabetically

ordered position within that year. The letter "A" preceeds addendum

entries.

Special acknowledgement is due Mrs. B. J. Gibson and Mrs.

M. A. Molta who typed and proofread the manuscript.
Subject Index

Angle of Arrival:

46-3, 46-10, 48-5, 52-3, 55-8

Antennas, Anti-Reflective:

46-1, 59-13

Antennas, Microwave:

47-6, 61-8

Atmospheric Absorption:

46-7, 49-6, 52-6, 53-11

Atmospheric Refraction:

50-1, 51-1, 51-3, 59-3, 59-4, 59-5, 59-23, 60-1, 60-2, 61-6,

62-4, 63-13, A 49-1

Attenuation Due to Rain:

46-9, 47-7, 49-6, 55-14, 59-10, 60-8, 62-7, 63-9, 63-18, 64-7

Attenuation Due to Trees, Buildings:

46-4, 46-7, 55-10, 61-12, 63-11

Bibliographies

:

53-4, 55-2, 64-6

Combiners, Diversity:

54-5, 55-1, 58-3, 59-9, 60-9, 61-4, 61-9, 62-11, 62-17

Correlation of Refractive Index and Fading:

49-7, 50-3, 54-1, 57-1, 59-22, 61-17, 62-2, 62-7, 63-4

Correlation of Refractive Index and Phase Variation:

59-21, 60-11, 61-14

Diffraction by a Sperical Earth:

41-1, 47-1, 47-2, 64-10, A 49-1
Diffraction by Terrain Features:

47-1, 48-3, 48-6, 50-3, 61-12, 62-18, 63-11, 64-3

Divergence Factor:

41-1, 46-7, 46-8, 51-2, 57-5, 62-19, 63-5, A 48-1, A 49-1

Diversity Reception:

47-4, 56-8, 58-4, 60-5, 61-15, 62-9, 63-2, 63-5

Diversity Reception Frequency:

46-5, 47-4, 53-7, 56-6, 63-5

Diversity Reception, Spatial:

47-4, 53-3, 54-3, 55-3, 55-7, 56-6, 57-4, 59-16, 60-7, 61-4

61-9, 62-3, 62-11, 63-5

Diversity Reception, Time:

62-10

Ducts, Atmospheric:

49-1, 49-7, 50-1, 50-3, 56-7, 59-11, 61-3, 64-2, A 49-1

Ducts, Ground Based:

48-5, 59-3, 61-5

Ducts, Oceanic:

47-5, 48-5, 49-7

Effective Earth's Radius:

33-1, 47-6, 53-1, 53-8, 57-5, 59-4, 61-3, 63-13, A49-1

Elevated Layers:

47-8, 49-1, 49-3, 49-4, 58-2, 62-6, 62-8, 64-2, 64-9, 64-11

Fading, Characteristics of:

46-5, 46-7, 53-9, 54-3, 58-6, 61-16, 61-17, 63-3, 63-5

Fading, Depth of:

52-6, 56-2, 58-4, 61-1, 62-3

Fading, Due to Diffraction:

52-2, 55-3, 59-10, 60113, 61-16, 62-3

4
Fading, Due to Ducts

:

53-9, 54-1, 55-3, 58-7, 58-10, 59-11, 61-16, 63-5

Fading, Due to Elevated Layers:

40-1, 60-6, 63-4

Fading, Due to Multipath:

33-1, 40-1, 46-1, 46-3, 48-2, 50-3, 51-2, 52-3, 52-5, 53-7,

53-9, 55-3, 56-5, 56-6, 58-7, 59-13, 59-19, 59-20, 61-11,

61-16, 62-11, 62-9, 63-15, A49-1

Fading Duration:

52-3, 52-6, 53-3, 54-1, 57-4, 58-4, 61-1, 61-7, 62-3, 63-3,

A63-1, A64-2

Fading, Frequency Selectivity of:

53-7, 56-3, 59-19, 62-3, 63-3, 63-5

Fading, Mechanisms:

59-2, 49-3, 52-1, 52-3, 58-4, 61-16, 62-1, 62-9, 63-5

Fading, Range:

47-6, 48-1, 50-4, 52-6, 53-7, 53-9, 57-1, 62-7

Fading, Reduction of Effects of:

46-1, 48-6, 53-3, 53-7, 54-3, 55-7, 56-6, 57-4, 57-6, 59-19,

61-4, 61-9, 62-9

Fading, Variation of:

48-1, 50-3, 50-4, 51-3, 52-2, 52-6, 56-2, 57-4, 58-4, 58-6,

60-6, 61-1, 61-16, 61017, 62-9

Fresnel Zone Clearance:

46-7, 52-2, 53-3, 53-8, 54-3, 55-12, 63-5, 64-3

Frequency Variations:

62-15

History:

46-7, 46-11, 48-4, 58-4, 59-2, 60-10

Meteorological Factors Affecting Propagation:

40-1, 47-9, 48-4, 48-5, 49-1, 49-4, 49-7, 50-5, 50-7, 51-1,

56-5, 59-4, 59-6, 62-4, 63-5, 63-6, 63-12, 64-4
Meteorological Measuring Instruments:

50-5, 53-2, 59-1, 62-13, 64-4, A60-1

Meteorological Profiles:

47-5, 48-2, 49-1, 49-2, 56-7, 59-9, 64-7

Path Length Difference:

41-1, 46-8, 47-2, 49-1, 51-1, 57-5, 58-1, 61-4

Phase Combining:

61-4, 61-9, 62-11

Phase Variation of Received Signal:

55-5, 55-6, 55-13, 49-15, 59-16, 59-17, 59-21, 60-11, 60-12,

61-13, 61-14, 62-14, 63-10

Pulse Measurement of Multipath:

52-5

Propagation Paths, Over Land;

33-1, 40-1, 46-4, 46-6, 46-7, 46-11, 47-9, 48-1, 48-2, 48-3,

48-6, 49-2, 49-6, 50-3, 50-4, 52-2, 53-3, 53-7, 53-8, 53-9,

54-1, 54-3, 55-5, 55-6, 55-11, 57-1, 58-9, 59-14, 59-21

59-22, 60-6, 60-11, 61-1, 62-9, 63-5, 64-5

Propagation Paths, Over Water:

33-1, 41-1, 46-4, 46-7, 46-11, 47-5, 49-7, 52-1, 52-6, 54-3,

54-6, 55-3, 55-4, 55-7, 55-11, 56-1, 56-3, 57-2, 57-4, 59-13,

59-16, 61-1, 61-2, 61-11, 62-1, 63-5, 64-5

Propagation Phenomena:

41-1, 47-1, 47-7, 49-1, 49-6, 50-1, 51-2, 53-10, 57-3, 58-1,

59-18, 63-5, A49-1

Prolonged Space Wave Fadeouts:

54-1, 57-1, 61-1, 62-3, 63-3

Ray Theory:

49-2, 55-8, 61-6, 63-15, A49-1

Ray Tracing:

58-10, 59-1, 59-5, 59-H, 60-1, 60-2, 61-6, 63-13, 63-15
Reflection Coefficients:

41-1, 46-7, 47-3, 58-4, 60-4, 62-9, 63-5, 63-8, A49-1

Reflection Coefficients, Elevated Layers:

49-4, 49-8, 58-2, 62-8, 63-8, 64-9, 64-11

Reflection Coefficients, Over Ice and Snow:

50-6, 52-4, 56-9

Reflection Coefficients, Over Land:

46-4, 48-2, 49-1, 54-2, 55-11, 58-9, 59-2, 59-7, 59-14, 59-22,

63-14

Reflection Coefficients, Over Water:

46-4, 46-7, 54-4, 55-4, 55-11, 56-1, 56-3, 59-2, 59-8, 61-2, 62-12

Refractive Index Measurements:

53-2, 59-1, 59-9

Refractive Index Maps:

59-4, 59-6, 60-3, 64-2

Refractive Index Modified:

47-5, 48-2, 49-7, 59-11, 62-4, A49-1

Refractive Index Profiles:

49-5, 53-5, 57-1, 59-4, 60-1, 61-11, 62-4, 62-6, 63-4

Refractive Index Statistics:

59-23, 63-4

Refractive Index Structure

:

59-1, 59-5, 59-23, 63-3, 64-5

Site Selection:

49-2, 61-10, 62-18, 63-19

Statistics of Fading Models:

46-2, 47-4, 55-9, 55-12, 56-4, 58-3, 58-5, 58-6, 58-8, 59-10

62-5, 62-16, 63-2, 63-3, 63-5, 63-16, 64-1, A 47-1, A60-2, A63-1,

A64-1, A64-2

I

Spectra, Power:

55-5, 55-6, 55-7, 57-2, 59-21, 60-6, 60-11, 61-2, 61-14,

62-15, 63-10
Texts:

51-2, 58-1, 60-4, 61-8, 63-5, A 49-1, A63-1, A 64-2

Zonal Screens (Fresnel):

47-3, 50-2, 58-4, 63-17, 64-8
Author Index

Akita, K. 62-6

Anastassiades, M. A. 62-1

Anderson, E. W. 63-1

Anderson, N. L. 59-1

Aoyagi, S. 63-17

Arsen'ian, T. I. 62-2

Bachynski, M. P. 59-2

Barghausen, A. F. 61-14, 63-3

Barker, C. B. A48-1

Barrow, B. B. 63-2

Barrows, E. C. 62-15

Barsis, A. P. 56-2, 57-1, 61-1, 62-3, 63-3

Bateman, R. 46-1

Bauchman, R. W. 47-5

Bean, B. R. 53-1, 54-1, 59-3, 59-4, 59-5, 59-6, 60-1

60-2, 60-3, 62-4, 63-4, 63-12, 64-4

Beard, C. I. 56-1, 57,2, 61-2

Beckmann, P. 62-5, 63-5, A 64-1

Bergmann, P. G. 46-2

Beyers, N. J. 59-1

Binnian, W. 47-5

Birnbaum, G. 53-2

Blassel, P. 54-4

Bogle, A. G. 52-1

Boithais, L. 54-4

Braaten, A. M. 47-9

Braude, S. Ya. 59-7, 59-8, 59-15, 59-16, 59-17, 61-3

Brekhovskikh, L. W. 60-4

Bremmer, H. 50-1, 58-1, A49-1

Brennan, D. G. 55-1, 59-9

Brocks, K. 51-1

Brilliant, M. 60-5

Bullington, K. 47-1, 54-2, 57-3

Burns, W. R. 64-1

Burrows, C. R. 33-1

Bussey, H. E. 50-2, 53-2

Byam, L. A. 50-4, 53-3

Cabessa, R. 55-3

Cahoon, B. A. 59-5, 60-1, 64-2

Capps, F. M. 57-1

Carter, W. R. 52-6

9
Chapman, C. W. 61-12,, 63-11

Chavance, P. 52-2, 54*3

Clarke, K. K. 58-3

Conn, J. 58-3

Cornford, E. C. 49-5

Court, G. W. G. 55-4

Cox, C. 54-4

Crain, C. M. 53-5, 53-6

Crawford, A. B. 40-1, 46-3, 52-3

Cumming, W. A. 52-4

Davies, H. 49-1

Dawson, G. 61-4

Day, J. P. 50-3

Deam, A. P. 53-5, 55-5

De Lange, O. E. 52-5

Domb, C. 47-2

Dougherty, H. T. 64-3

du Castel, F. 58-2

Durkee, A. L. 48-1

Dutton, E. J. 60-2, 61-5, 61-6

Englund, C. R. 40-1

Evans, H. W. 59-10

Fannin, B. M. 55-5, 59-1

Fanaki, F. M. 63-8

Ferrell, E. B. 33-1

Fitch, E. 47-4

Flock, W. L. 60-6

Ford, L. H. 46-4, 46-6

Forsgren, K. H. 51-3

Franceschetti, G. 63-6

Frank, V. R. 63-4

Freethey, F. E. 60-12

Fukushima, M. 62-6

Funakawa, K. 62-7

Gerhardt, J. R. 48-5, 53-5

Gerlach, G. G. 46-5

Gilmer, R. O. 64-4

Ginzton, E. L. 55-11

Glaser, W. 63-7

Gorbach, V. I. 59-15 , 59-16, 59-17

Gordon, W. E.

Gossard, E. E.

48-2

62-8

10
Gough, M. W. 49-2, 58-4, 62-9

Gray, D. A. 63-9

Griin, A. 49-3

Gudmandsen, P. 57-4

Hamlin, E. W. 48-2

Hammerton, T. G. 47-6

Hartman, W. J. A 60-1

Hathaway, S. D. 59-10 • Hay, D. R. 63-8

Herbstreit, J. W. 55-6, 61-14

Hershberger, W. D. 60-6

Hey, J. S. 47-3

Hogg, D. C. 63-9

Horn, J. D. 59-6, 60-3

Hornberg, K. O. 61-14

Hoyt, R. S. A 47-1

Ike garni, F. 53-9, 59-H, 61-7, 64-5

Iriye, H. 62-6

Israel, H. 49-4

Jackson, F. 47-3

Jakes, W. C. 52-3

Janes, H. B. 59-21, 60-11, 60-12, 61-14, 62-15, 63-10

Jarkowski, H. 49-7

Jasik, H. 61-8

Jelonek, Z. 47-4

Johler, J. R. 59-12

Johnson, M. E. 61-1, 62-3

Johnson, W. E. 61-14

Jones, F. E. 49-5

Joy, W. R. R. 61-11

Kahn, L. R. 54-5, 62-10

Kakita, K. 53-9, 58-6, 61-9

Kane da, Y. 63-18

Karapiperis, L. N. 62-1

Kariambas, N. K. 62-1

Karpeiev, G. A. 59-20

Kato, J. 62-7

Kato, S. 59-13

Katz, I. 56-1, 57-2

Katzin, M. 47-5

Kawazu, S. 59-13

Kaylor, R. L. 53-7

11
Kerr, D. E. 51 2

Kiely, D. G. 52-6, 54-6, 56-3

King, A. P. 46-9

Kirby, R. S. 61-10, 63-3

Kirkpatrick, A. W. 60-11, 61-14

Kitchen, F. A. 61-11

Klein, W. 53-8

Kleinsteuber, W. 49-3

Kono, Y. 53-9

Komarov, N. N. 59-8

KUhn, U. 60-7

LaGrone, A. H. 55-7, 61-12, 63-11

Lamont, H. R. L. 47-6

Lane, J. A. 55-10, 63-4, 63-12, 64-9

Larsen, B. F. 57-4

Lehfeldt, W. 49-6

Lewin, L. 62-11

Libois, Li. J. 53-8

Mackey, R. C. 60-6

Maloney, L. J. 59-14, 61-10, 64-3

Mansfield, W. V. 55-9

Martin, F. L. 63-13

Martin, P. E. 63-11

Marukawa, T. 62-12

Mathwich, H. R. 55-12

Matsuo, S. 53-9

Matthews, P. A. 64-9

McFadden, J. A. 56-4, 58-5

McGavin, R. E. 59-14, 62-13, 64-4

McPetrie, J. S. 46-6, 49-7

Meadows, R. W. 64-9

Megaw, E. C. S. 46-7, 48-3

Men", A. V. 59-15, 59-16, 59-17, 61-13, 62-14

Micheletta, C. 63-14

Millar, J. Z. 50-4, 53-3

Millington, G. 46-8, 49-8, 57-5

Misme, P. 56-5, 58-2

Montgomery, G. F. 57-6

Morita, K. 58-6, 59-13

Muchmore, R. B. 55-8, 55-14

Mumford, W. W. 40-1

Munk, W. 54-5

12
Nakagami, M. A 60-2

Nakahara, S. 63-17

Norton, K. A. 41-1, 47-7, 53-10, 55-9, 59-18, 61-14,

62-15

Nupen, W. 64-6

Oguchi, T. 60-8, 64-7

Oliver, R. 46-4

Omberg, A. C. 47-7

Omori, T. 58-7

Ostrovsky, I. E. 59-8, 61-3

Oxehufwud, A

.

59-19

Ozanich, A. M. , Jr. 60-3

Paraskevopoulous, P.G. 62-1

Parsons, S. J. 47-3

Peters, O. F. 51-3

Perlat, A. 53-11

Peterson, C. F. 61-14

Phillips, W. E. 50-5

Pierce, J. N. 60-9

Preikschat, F. K. 64-8

Pryce, M. H. L. 47-2

Rainey, R. J. , Jr. 63-15

Riblet, H. J. A48-1

Rice, P. L. 61-10

Rice, S. O. 58-8

Richards, E. G. 61-11

Riggs, L. P. 64-2

Rivet, P. 56-6

Robertshaw, R. G. 47-6

Robertson, S. D. 46-9

Sanin, F. S. 61-3

Sato, R. 58-7

Saxton, J. A. 50-6, 55-10, 60J-10, 64-9

Schelleng, J. C. 33-1

Schmelovsky, K. H. 56-7

Semenov, A. A. 59-20- 62-2

Semplak, R. A. 63-9

Sharpie ss, W. M. 46-3, 46-10

Sherwood, E. M. 55-11

Short, P. J. 55-9

Sicinski, L. 49-7

Siddiqui, M. M. 62-16, 63-16

13
Smith, H. W. 55-7

Smith-Rose, R. L. 46-11, 48-4, 50-7

Smyth, J. B. 47-8

Sommermeyer, K. 49-4

Spetner, L. M. 56-1

Spizzichino, A. 63-5

Staras, H. 56-8

Starnecki, B. 49-7

Stein, S. 60-9

Stjernberg, Bo. K. E. 51-3

Straiton, A. W. 48-5, 53-6, 55-7, 59-22

Stratonovich, R. L. A 63-1, A 64-2

Suzuki, M. 56-9, 58-9

Thayer, G. D. 59-4, 60-1, 61-6

Thompson, L. E. 46-12, 48-6

Thompson, M. C, Jr. 55-6, 59-21, 60-11, 60-12, 61-14, 62-15

Thorn, D. C. 63-15

Tomlinson, H. T. 59-22

Troitskii, V. N. 60-13

Trolese, L. G. 47-8, 50-3

Turin, G. L. 61-15, 62-17

Ugai, S. 53-9, 59-23, 61-16, 61-17, 63-17, 63-18

Vetter, M. J. 61-14

Voge, J. 53*11, 58-2

Vogler, L. E. 55-9, 64-10

Von Rosenberg, C. E. 53-6

Wait, J. R. 64-11

Walters, L. C. 59-12

Weihrauch, H. 62-18, 63-19

Weiss, G. H. 63-16

Wells, P. I. 61-14

Wheeler, B. F. 55-12

Wheelon, A. D. 55-8, 55-13, 55-14

Wickizer, G. S. 47-9

Wilkerson, R. E. 62-19

Wong, M. S. 58-10

Wright, F. E. 63-13

14
Schelleng, J. C. , C. R. Burrows and E. B. Ferrell (March 1933)

Ultra-short-wave propagation, Proc. IRE 21, 3, p. 427- 463.

33-1 Abstract: Part I of this paper first describes a method of measuring attenuation and field strength in the ultra-short-wave range.

A resume of some of the quantitative experiments carried out in

the range between 17 megacycles (17 meters) and 80 megacycles

(3.75 meters) and with distances up to 100 kilometers is then

given. Two cases are included: (1) "Optical" paths over sea

water and (2) "Nonoptical" paths over level and hilly country. An

outstanding result is that the absolute values of the fields measured

were always less than the inverse distance value. Over sea water,

the fields decreased as the frequency increased from 34 megacycles (8. 7 meters) to 80 megacycles (3. 75 meters), while the

opposite trend was found over land. As a rule, the signals

received were very steady, but some evidence of slow fading was

obtained for certain cases when the attenuation was much greater

than that for free space.

Part II gives a discussion of reflection, diffraction, and

refraction as applied to ultra-short-wave transmission. It is

shown, (1) that regular reflection is of importance even in the case

of fairly rough terrain, (2) that diffraction considerations are of

prime importance in the case of nonoptical paths, and (3) that refraction by the lower atmosphere can be taken into account by

assuming a fictitious radius of the earth. This radius is ordinarily equal to about four thirds the actual radius.

The experiments over sea water are found to be consistent

with the simple assumption of a direct and a reflected wave except for distances so great that the curvature of the earth requires

a more fundamental solution. It is shown that the trend with frequency to be expected in the results for a nonoptical path over

land is the same as that actually observed, and that in one specific case, which is particularly amenable to calculation, the absolute values also check reasonably well. It is found both from

experimental and from theory that nonoptical paths do not suffer

from so great a disadvantage as has usually been supposed.

15
Englund, C. R. , A. B. Crawford and W. W. Mumford (Aug. 1940)

Ultra-short-wave transmission over a 39-mile "optical"

path, Proc. IRE, 28, 360-369.

40-1 Abstract: Continuous records of ultra-short-wave transmis - sion on wavelengths of 2 and 4 meters, over a good "optical"

path, have shown variations in the received signal strength.

These variations can be explained as being due to wave interference; an interference which varies with the changes in the

composition of the troposphere.

Some of the variations are due to changes in the

dielectric -constant gradient of the atmosphere near the earth.

Other variations are explicable in terms of reflections from

the discontinuities at the boundaries of different air masses.

The diurnal and annual meteorological factors which affect

the transmission are discussed.

Norton, K. A. (Dec. 1941) The calculation of ground -wave field

intensity over a finitely conducting spherical earth, Proc.

IRE 29^_ 623-639.

41-1 Abstract: Equations and curves are presented which simplify

the calculation of ground -wave field intensity over a finitely

conducting spherical earth for transmitting and receiving

antennas of arbitrary heights and polarization.

16
Bateman, R. (May 1946) Elimination of interference type fading at micro^

wave frequencies with spaced antennas, Proc. IRE, 34, 662-676.

46-1 Abstract: The element spacing of an antenna array is described

which will provide a null in the direction of the ground reflected

ray patho

Bergmann, P. G. (Oct. 1946) Propagation of radiation in a medium with

random inhomogeneities, Phys. Rev. 70, 486-492.

46-2 Abstract: Approximate formulas, derived from geometrical optics,

are shown to correlate the statistical properties of inhomogeneities

with fluctuations in signal level. Further, simplification of the

formulas permits the prediction of signal fluctuations dependent

upon range. --W.N.

Crawford, A. B. , and William M. Sharpless (Nov. 1946) Further

observations of the angle of arrival of microwaves, Proc.

IRE, 34^ 845-848.

46-3 Abstract: Microwave propagation measurements made in the

summer of 1945 are described. This work, a continuation of

the 1944 work reported elsewhere in this issue of the Proceedings of the I. R. E. and Waves and Electrons, was characterized

by the use of an antenna with a beam width of 0. 12 degree for

angle -of-ar rival measurements and by observations of multiplepath transmission.

17
Ford, L. H. , and R. Oliver (May 1946) An experimental investigation

of the reflection and absorption of radiation of 9 cm wavelength,

Proc. Phys. Soc„ (London), 58, 265-280.

46-4 Abstract: The paper, which was circulated as a confidential

report to the Radio Research Board in October 1944, describes

measurements on the reflecting power of various surfaces at a wavelength of 9 cm and angles of incidence ranging from 80 to

45°; these included level and uneven bare ground, vegetationcovered ground, tap water and a 4% salt solution approximating

to sea water. Specular reflection was found to occur only from

very level surfaces; the absorptions of these surface media were

measured, and from the combined measurements of reflection

and absorption their electrical constants were derived.

Rough surfaces, either of bare ground or vegetation-covered

ground, gave values of reflection coefficient in general agreement

with the optical rule that regular reflection is only observed from

an uneven surface if the product of the depth of the surface irregularities and the cosine of the angle of incidence is a small fraction

of the wavelength.

The calculated values of reflection coefficient corresponding

to dry soil, wet soil and sea water for angles of incidence varying

from 0° to 85° are given in an appendix to the paper.

Gerlach, G. G. (Dec. 1946) A microwave relay communication system,

RCA Rev., 7, 576-600.

46-5 Abstract: This paper reviews the experimental results obtained

with a 4000 megacycle multichannel relay system connecting New

York and Philadelphia. The system employs a frequencymodulated subcarrier which in turn is used to frequency-modulate

the final carrier. Demodulation to the subcarrier frequency is

effected at relay stations. The microwave relay equipment, which

resulted from this experimental work and which will be installed

by the Western Union Telegraph Company in a circuit connecting

New York, Washington, and Pittsburgh, is described.

18
M'cPetrie, J. S„ , and h. H. Ford ( 1946) Some experiments on the propagation over land of radiation of 9. 2 cm wavelength, especially on

the effect of obstacles, J. IEE Part III- A, 93_, 531-538.

46-6 Abstract: The salient results are brought together of a number of

experiments on the propagation of radiation of a wavelength of

9. 2 cm, carried out during 1943-44. All the measurements described were made over land, some over open country and some

over transmission paths which were obstructed by various obstacles.

The obstacles included trees, both leafless and in full leaf, brick

walls, windows, and other parts of buildings.

Many of the obstacles caused such large attenuations that

they should generally be regarded as opaque objects round which

diffraction takes place Stone buildings, groups of trees so dense

that the sky cannot be seen through them, and the trunks of trees

come into this category. Semi-transparent obstacles (causing a loss of signal of 10 db or less), include windows, tile or slate roofs,

the sides of a light wooden hut, and thin screens of trees when the

transmission path goes through the branches.

Megaw, E. C. S. (1946) Experimental studies of the propagation of

very short. radio waves , J. IEE Part 3A 93, 79-97.

46_7 Abstract: The paper presents a survey of the experimental

work on the propagation of very short waves, and especially

of centimetre waves, carried out in this country during the

war. Although much of the paper is necessarily descriptive,

and by no means all the problems are solved, it has been

written with the aim of providing the radio engineer with

applicable results where they have been established.

After referring to the main differences in propagation

characteristics between these waves and longer radio groundwaves, the state of the art at the beginning of the war is

briefly noted and the development of the war-time experimental

work is outlined. Some simple theoretical characteristics

are then described to provide a background for the experimental results which follow.

19
Preliminary experimental studies over land and sea

paths are described, with a summary of the tentative conclusions to which they led.

The main experimental programme consisted of measurements of 3 -cm, 9-cm, and 3yz-m waves over sea paths 57

miles and 200 miles in length; and of 9-cm waves over a single

38-mile land path. The measurements were continuous over

some of these paths for periods between two and three years;

and, particularly as regards detailed correlation with meteorological measurements, the work is still in progress.

In a concluding Section some investigations into special

aspects of very -short-wave propagation are described; data on

reflection from sea and land, and on the effect of obstacles,

are included in this Section.

Millington, G„ (Jan. 1946) Curved earth geometrical optics, Marconi

Rev., 9, 1-12.

46-8 Abstract: In this paper the effect of the earths curvature in the

geometric -optical treatment of propagation within the visual range

is presented as a correction to the flat earth geometry. Factors to be

applied to the flat earth values of the angle of elevation at the point

of reflection and of the path difference between the direct and reflected

waves are derived by a simple graphical process, and also the divergence factor arising from the increased divergence on reflection

from the convex surface of the earth is obtained. Asymptotic values

are given for points very near to the horizon.

20
Robertson, S. D. , and A. P. King (April 1946) The effect of rain upon

the propagation of waves in the 1- and 3- centimeter regions, Proc.

IRE, 34, 178P-180P.

46-9 Abstract: This paper presents some experimental results which

show the effect of rain upon the transmission of electromagnetic

waves in the region between 1 and 4 centimeters.

At a wavelength of 1. 09 centimeters, the waves are appreciably attenuated, even by a moderate rain. Attenuations in excess

of 25 decibels per mile have been observed in rain of cloudburst

proportions.

The attenuation of waves somewhat longer than 3 centimeters

is slight for moderate and light rainfall. During a cloudburst,

however, the attenuation may approach a value of 5 decibels per

mile.

Sharpies s, William M. (Nov. 1946) Measurement of the angle of

arrival of microwaves, Proc. IRE 34, 83 7-845.

46-10 Abstract: This paper describes a method of measuring the

direction from which microwaves arrive at a given receiving

site. Data which have been collected on two short optical

paths using a wavelength of 3 1/4 centimeters are presented

to illustrate the use of the method. Angles of arrival as large

as 1/2 degree above the true angle of elevation have been observed in the vertical plane, while no variations greater than

±1/10 degree have been found in the horizontal plane. These

results indicate that radar directions for low angles of elevation may be in error by several tenths of a degree during times

when anomalous propagation conditions are present. Possible

solutions to the problems introduced by variations in the angle

of arrival are suggested.

21
Smith-Rose, R. L (1946) A preliminary investigation of radio

transmission conditions over land and sea on centimetre wavelengths, J. IEE Part III A 93^ 98-100.

46-11 Abstract: Papers already presented at this Convention have

surveyed both the circumstances that gave rise to, and the

steps that were taken to implement, a detailed and systematic

investigation of the mode of propagation of radio waves within

the centimetre wavelength band. The present contribution

surveys the analysis of the data obtained in some of the investigations described by Megaw. The results of this analysis

provide some of the essential basic information which the

engineer designing either a radiolocation system or a communication link requires in order that he may assess in advance the performance and reliability of the service to be

expected under a variety of conditions.

Thompson, L. E. (Dec. 1946) A microwave relay system, Proc. IRE,

34, 936-942.

46-12 Abstract: A method of double -frequency modulation suitable for

long-distance transmission of multichannel signals by means of

radio -relay stations is described. Propagation, radio-frequency

bandwidth, and radio-frequency power are discussed briefly. The

signal-to-noise ratio and distortion of the system are shown by

theory and experiment. An experimental circuit between Philadelphia

and New York is described and the results are given.

22
Bullington, K„ (Oct. 1947) Radio propagation at frequencies above

30 megacycles, Proc. IRE, 35, 1122-1136.

47-1 Abstract: Radio propagation is affected by many factors, including

the frequency, distance, antenna heights, curvature of the earth,

atmospheric conditions, and the presence of hills and buildings.

The influence of each of these factors at frequencies above about

30 megacycles is discussed, with most of the quantitative data

being presented in a series of nomograms. By means of three or

four of these charts, an estimate of the received power and the

received field intensity for a given point-to-point radio transmission

path ordinarily can be obtained in a minute or less.

The theory of propagation over a smooth spherical earth is

presented in a simplified form that is made possible by restricting

the frequency range to above about 30 megacycles, where variations

in the electrical constants of the earth have only a secondary effect.

The empirical methods used in estimating the effects of hills and

buildings and of atmospheric refraction are' compared with experimental data on shadow losses and on fading ranges.

Domb, C„ , and M. H. L. Pryce (July 1947) The calculation of field

strengths over a spherical earth, J. IEE, Part III, 94, 32 5-339.

47-2 Abstract: Curves and formulae are given for the calculation of

field strength at any height and distance from the transmitter for

the case of horizontally-polarized electromagnetic waves over a curved earth or sea. Sufficiently within the optical range the field

is calculated by ray theory, and appropriate quantities for calculating path difference and divergence of reflected ray are given.

At exact optical cut-off the field is calculated by an approximate

method believed to be accurate to 1 db, and is presented in the form

of contour curves of equal field strength on a plot of receiver height

against transmitter height. Sufficiently far beyond optical cut-off

the field is given by the first term in the diffraction-formula series.

To calculate the field near optical cut-off, a curve should be drawn

of field against distance for the heights of transmitter and receiver

in question which joins smoothly the ray-theory curve for inside

optical range to the one-term curve for the region beyond and passes

through the point determined for the actual cut-off distance. The

case of vertically polarized waves is also briefly discussed, and

curves and formulae are given for the reflection coefficient (including

23
surface -wave term) where ray theory is applicable, and for one

term of the diffraction formula in the region well beyond optical

cut-off.

Hey, J. S. , S. J. Parsons, and F. Jackson (Sept. 1947) Reflexion of

centimetric electromagnetic waves over ground, and diffraction

effects with wire -netting screens, Proc. Phys. Soc. , 59, 847-857.

47-3 Abstract: Difficulties in the operation of centimetric wavelength

radar equipment at low angles of elevation (less than 10°) have led

to a detailed consideration of the influence of ground reflexion. A

technique is described for the determination of the relation between

the signal strength of the echo from an isotropic reflector and the

angle of elevation of the reflector. Measurements obtained over

natural ground sites are shown to be in accordance with simple

theoretical considerations. The effect of wire-netting artificial

screening has been examined, the experimental results being in

general agreement with those derived by theoretical treatment of

diffraction using Sommerfeld's formula.

Jelonek, Z. , E. Fitch, and J. H. H. Chalk (Feb. 1947) Diversity

reception, Wireless Eng. , 24, 54-62.

47-4 Abstract: The diversity gain is defined as the reduction of transmitter power permissible on the introduction of a diversity system

for the same proportion of time loss of signal.

Curves and formulae are obtained for this gain, which is shown

to depend on the proportion of time loss allowed for the service, the

number of received signals used, the correlation between fading in

these signals and a parameter characterizing the propagation conditions. This parameter is discussed; in order to obtain a better

estimate of its value, it is suggested that more data on propagation

conditions should be accumulated for links on which diversity reception is contemplated.

24
Katzin, Martin, Robert W. Bauchman and William Binnian (Sept.

1947) Three -and nine-centimeter propagation in low ocean

ducts, Proc. IRE, 35, 891-905.

47_5 Abstract: One-way radio propagation measurements on 9 and

3 centimeters between ship and shore, coupled with meteorological measurements on ship and ashore, were made in the

Atlantic tradewind area off the east coast of Antigua, British

West Indies, early in 1945. Persistent low-level ducts, aver-*

aging 20 to 50 feet in height, within effective strength of 5 to

10 M units, were found to exist all the time. The height and

strength of the duct appears to depend on the wind speed, low

winds producing low ducts of moderate strength while higher

winds result in higher but weaker ducts.

Various antenna-height combinations were explored to

determine the optimum heights for utilization of the duct. Very

effective trapping was found on 3 centimeters, the optimum

height being between 6 and 15 feet, depending on duct conditions. On 9 centimeters the degree of trapping was only

partial, and the strongest signals were obtained with the

highest heights available (46 feet transmitting and 94 feet

receiving). Rates of decrease of signal averaged 0.85 decibel

per nautical mile on 9 centimeters up to about 80 miles, and

0.45 decibel per nautical mile on 3 centimeters for all ranges.

Beyond 80 miles the rate of decrease of signal on 9 centimeters

was much less, about 0.2 decibel per nautical mile. Rain

squalls had no observable effect on the strength of received

signals.

Measurements inland from the shore site showed that

the duct is destroyed within one -quarter mile from the water's

edge, but that effective radio transmission can be obtained with

installations up to at least a mile inland if the terrain is flat

and low-lying. The duct reforms the leeward side within a distance of 2 miles offshore.

Radar measurements of 3 centimeters gave results

substantiating the one-way measurements. Ranges up to 47

miles on a small vessel were obtained with the antenna at 6

feet, lower maximum ranges being obtained with higher

heights of radar antenna, in agreement with the findings of

the one-way measurements.

25
Lamont , Ho R. E. , R G. Robertshaw, and T„ G. Hammerton (Nov.

1947) Microwave communication link, Wireless Eng. , 24, 323-332,,

47-6 Abstract: A description is given of a single-channel duplex radiotelephone on a wavelength of 3. 2 cm, A single parabolic mirror is

used as aerial for both transmitted and received signals which are

separated in a waveguide system,, The transmitter is a klystron

oscillator of about 75 m W output. The superheterodyne receiver

is fitted with automatic -frequency control and automatic -gain control.

Operation over optical paths up to 70 miles long is described. A

signal-to-noise ratio of about 55 db is obtained over a 57-mile path.

Norton, Kenneth A. and Arthur C. Omberg (Jan. 1947) The maximum

range of a radar set, Proc. IRE 35, 4-24.

47_7 Abstract: Formulas are derived which may be used to calculate the maximum range of a radar set. It is shown that the

maximum range obtainable with a given radar set depends

upon (1) the energy in the pulse, i. e. , the peak power times

the time duration of the pulse or the average power divided by

the pulse-recurrence frequency; (2) the transmitting and receiving antenna gains; (3) the transmission line, antenna, and

transmit-receive-box losses; (4) the "effective width" or time duration of the transmitted pulses; (5) the "effective

bandwidth" of the receiver; (6) the radio frequency of the transmitted waves; (7) the recurrence frequency of the transmitted

pulses; (8) the "noise figure" of the receiver; (9) the cosmic,

atmospheric, and man-made noise picked up by the antenna;

(10) the attenuation during passage of the radio waves through

the atmosphere due to the absorption by the atmospheric gases

and rain drops; (11) the "effective echoing area" of the target;

(12) the directivity of the transmitting and receiving antenna

in elevation and azimuth, and (13) the effect of the ground,

which, in turn, is inextricably associated with the particular

site used, the height of the target above the ground, and the

polarization of the transmitted radiowaves.

26
Smyth, J. Bo, and L. G. Trolese (Nov. 1947) Propagation of radio waves

in the lower troposphere, Proc. IRE, 3_5, 1198-1202.

47-8 Abstract: The effect of tropospheric layers on the propagation of

high-frequency radio waves has been experimentally investigated.

A theory is proposed which is in agreement with the salient propagation characteristics observed on a nonoptical link. Fields beyond

the optical horizon are governed by the layer height and the refractive index change through the layer. For low layers the higher

frequencies have the advantage because of height gain, whereas for

higher layers the lower frequencies have the advantage of higher

reflection coefficients.

Wickizer, G. S. , and A. M. Braaten (July 1947) Propagation studies on

45.1, 474, and 2800 megacycles within and beyond the horizon, Proc.

IRE, 3_5, 670-680.

47-9 Abstract: Continuous recordings of field strength on 474 and 2800

megacycles, over a period of 13 months, revealed maximum values

three to four times the free-space field at distances of 42. 5 and 70.

1

miles from the transmitting site atop the Empire State Building, New

York City. Recordings on 45. 1 megacycles during the same period,

on a reduced schedule, did not exhibit the large variation found on

the higher frequencies. Refraction was found to be greater in the

summertime, the strongest periods occurring at night or in the

early morning. Refraction greater than normal was not evident when

the average wind velocity was above 13 miles per hour. A study of

weather conditions during the periods of strongest refraction indicated

that roughly 60 per cent of the gradients were of the frontal type,

involving different air masses, and approximately 60 per cent of

the gradients were higher than 100 feet above the earth's surface.

27
Durkee, A. L. (Feb. 1948) Results of microwave propagation tests

on a 40 -mile overland path, Proc. IRE 36, 197-2 05.

48-1 Abstract: This paper gives the results of a series of microwave radio propagation tests over an unobstructed 40 -mile

overland path. The purpose of the tests was to investigate

the transmission characteristics of such a path at centimeter

wavelengths over a long period of time. Statistics on the

transmission results at wavelengths ranging from 1.25 to 42

cm are given. The tests extended over a period of about

two years.

Hamlin, E. W. and W. E. Gordon (Oct. 1948) Comparison of calculat

ed and measured phase difference at 3.2 centimeters wavelength, Proc. IRE 36, 1218-1223.

48-2 Abstract: Radio propagation and associated meteorological

measurements, made by the Electrical Engineering Research

Laboratory of the University of Texas during April, 1946, on

a path from Gila Bend to Sentinel in the. Arizona desert, show

that, for meteorological conditions that could be represented

by a linear M curve, the magnitude and phase of the field

resulting from propagation over a 27 -mile path on 3 cm could

be calculated on the basis of a direct wave, and one reflected

from a surface tangent to the actual profile at the point of

reflection. Apparent reflection coefficients between 0.3 and

0. 8 were found for desert sand on 3 cm for this path.

Megaw, E. C. S. (Jan. 1948) Some effects of obstacles on the propagation

of very short radio waves, J. IEE, Part III, 95, 97-105.

48-3 Abstract: The paper deals with effects of localized obstacles,

including reflection as well as shadowing, which are of practical

importance in radio communication and radar, particularly on

decimetre and centimetre wavelengths. In a digest of available

theoretical results, later compared with the experimental findings,

attention is drawn to some unresolved difficulties. In most of the

practical problems discussed, prediction to a useful approximation

is, however, shown to be possible.

The experimental work described has been carried out by or

for the Admiralty, and much of it had its origin in the special problems of naval communications and radar. It has, however, wider

applications at almost every point; applications to radar navigation

are specifically discussed.

28
Smith - Rose, R. L. (Jan. 1948) Meteorology and the propagation of

radio waves, Nature, 161 , 145-146.

48-4 Abstract: Provides a review of experimental investigation of the

meteorological factors affecting propagation. - HTD.

Straiton, A. W. , and J. R. Gerhardt (July 1948) Results of horizontal

microwave angle -of -arrival measurements by the phase-differenqe

method, Proc. IRE, 36_, 916-922.

48-5 Abstract: This paper gives the results of horizontal microwave

angle -of -arrival measurements made at a location on the King

Ranch, a few miles south of the Naval Air Station at Corpus Christi,

Texas. Small deviations of the angle of arrival in a landward direction from the geometric path were noticed at nearly all times. Sixty

per cent of the measurements showed angular deviations less than

0. 015°, and 90 per cent showed deviation less than 0. 03°. The

angular deviation is directly proportional to path length if constant

gradient persists over the path. Under this condition, deviations

greater than 0. 10° will be expected, 10 per cent of the time, on a path 23 miles long. The measured angular deviations show a general correlation with the measured horizontal gradient of index of

refraction. Meteorological soundings showed overwater ducts

present nearly all of the time, with a maximum difference of

approximately 50 M units between the surface of the water and the

3 8 -foot level.

Thompson, Leland E. (1948) Microwave propagation experiments,

Proc. IRE 36, 671-676.

48-6 Abstract: Propagation tests at frequencies between 3000 and

4000 Mc. are described. The effect on the received signal

of changes in the index of refraction of the atmosphere are

discussed, and means are suggested for minimizing signal

variations with particular regard to the application of microwave-relay communication systems. Theoretical data is

given on diffraction at these frequencies.

29
Davies, H. (Nov. 1949) A preliminary study of some results from the

radio-meteorological investigation conducted in Canterbury, Trans.

Royal Soc. of New Zealand, 77, 78-85.

49-1 Abstract: The mechanics of orthodox propagation of cm waves in a well mixed atmosphere are discussed, including lobe distribution

above the horizon due to interference of direct and reflected rays.

Anomalous propagation in a duct is considered and the effect of a

land- sea transition on the vertical structure of potential temperature,

specific humidity, modified refractive index and duct shape in a typical NW advective duct are illustrated. These cause considerable

superrefraction of wavelengths of 3 and 10 cm.

(Met. Abs. 81-57)-- C. E, P B.

Gough, M. W. (1949) VHF and UHF propagation within the optical

range, Marconi Review No. 95, 121-139.

49-2 Abstract: The mechanism of VHF and UHF propagation can

be explained in terms of five major factors, namely;—

(1) Atmospheric refraction;

(2) Ionospheric reflections;

(3) Tropospheric reflections;

(4) Diffraction;

(5) Ground reflections.

(5) is the dominant influence on propagation within the optical

range, and it is with this aspect of the problem that this article

is concerned.

From the ray concept of propagation, a technique has

been evolved using simple microwave field strength measurements to forecast the behavior of VHF and UHF transmissions

over a specific optical path. In particular the method predicts,

without further measurement, the best height for the receiving

aerial on any frequency in the VHF or UHF band.

The process is based on the assumption that ground

reflection is confined to a point. This assumption becomes

increasingly invalid with increasing wavelength and may lead

to errors. However, these can be corrected to a large extent

by invoking Fresnel's zone theory, which defines what region

of the path is involved in reflection. Furthermore, by examining the ground irregularities in this region the reflecting

power of the ground can be assessed.

30
This article develops the theory of the microwave survey technique and describes and interprets a survey made over

a test path, from which the behavior of specific longer waves

is predicted. It concludes with a description of confirmatory

experiments made over the same path which verify the predictions . The "calibration" of optical paths by the use of microwaves eliminates the necessity for tests on operational wavelengths, and coupled with the lightness and compactness of

microwave equipment, saves experimental labour, particularly

if the path is to carry transmissions on more than one wavelength.

Grun, A., and W. Kleinsteuber (Sept. 1949) Der durch den Feuchtigkeitsund Temperaturgang der unteren atmosphSrischen Schichten

verursachte Interferenzschwund im Dez imetergebiet, Archiv der

Elektrischen Ubertragung, 3_, 209-219. (The interfering fading in

the decimeter band, caused by the temperature and humidity

variation of the lower layers of the atmosphere. )

49-3 Abstract: Since the changeable curvature of a ray is due to the

weather dependent gradient of the index of refraction, the difference

in variation of both rays (i. e. , the direct and the earth reflected)

gives simple formulas for calculation of the field strength. Observational results evaluated by this method were found in good agreement with available meteorological observations.

(Met. Abs. 81-60)-- W.N. (Bibliog, 64-6)

31
Israel, H. , and K. Sommermeyer (Jan. 1949) Uber partielle Reflexion

elektromagnetischer Wellen in der Troposphere, Z. Meteorologie

3, 32-39. (Partial reflection of electromagnetic waves in the

troposphere.

)

49-4 Abstract: A marked partial reflection of electromagnetic waves

by atmospheric formations can only occur if the dielectric constant

at the reflecting surface changes considerably in a distance shorter

than or at the most, of the same order as the wavelength. Most

reflections at inversions, etc. , are limited to waves of a few hundred

meters or more. Decimeter waves can be reflected by water vapor

discontinuities in transient turbulent eddies, mostly over the sea,

and in thunderclouds and the space above them. Uniform ionization

density in a thundercloud cannot explain reflection, and authors

suggest ionization in discharge channels.

(Met. Abs.l.ll-175)--C.E.P. B.

Jones, F. E. , and E. C„ Cornford (Sept. 1949) The measurement of the

velocity of propagation of centimetre rad-io waves as a function of

height above the earth, Part 2, Proc. IEE, Pt. 3, %, 447-452.

49-5 Abstract: Part I of the paper gave an account of the measurement of the velocity of propagation of centimetre waves over a sea path at low level, and concluded that the velocity is 186 217

± 16 miles/sec. Part 2 gives the results of experimental flights

observed from two Oboe ground stations in order to measure the

velocity of propagation as a function of height above the earth.

The results indicate higher velocities than those previously

calculated. The most probable values for the mean velocity of

propagation between ground and aircraft at 10 000, 20 000, and

30 000 ft. are 186 233, 186 246, and 186 256 miles/sec respectively, the metric equivalents being 299 713, 299 733, and

299 750 km/sec respectively.

32
Lehfeldt, Wilhelm (1949) Die Ausbreitung der Ultrakurzen (quasioptischen)

Wellen, Archiv der Elektrischen Ubertragung, 3, 137-142, 183-

186, 221-228, 265-269, 305-312, 339- 346 (July-Dec. ) (Propagation of ultrashort ( quasi- optical) waves. )

49-6 Abstract: This detailed study contains two main parts. The first

part discusses such problems as: (1) refraction of the ray in a homogeneous atmosphere, (2) refraction and reflection in an

inhomogeneous atmosphere, (3) reflections and blurred boundaries,

(4) influence of ions upon reflection and refraction, (5) suppression

by scattering and absorption. Influence of the earth's surface . In the second part, devoted to discussion of the results obtained

by measurement, the following topics are highlited: (1) the technique of measurements, (2) measurements of over-land propagation, (3) statistical over-land results, (4) measurements over

the sea, and at 9 cm wavelength over plain lowland, (5) ranges.

(Met. Abs. 81-67) -- W.N. (Bibliog., 64-6).

McPetrie, J. S. , B. Starnecki, H. Jarkowski and L. Sicinski

(March 1949) Oversea propagation on wavelengths of 3 and 9

centimeters, Proc. IRE 37, 243-257.

49_7 Abstract: This paper summarizes the results obtained from

tests extending from 1943 to 1946 which were made to determine the meteorological factors controlling the propagation

of centimeter waves. Oversea paths of 60 and 200 miles off

the West Coast of Great Britain were used for the experiments

Continuous records of radio field strengths and frequent

measurements of the meteorological conditions along the paths

were made. The correlation between the radio results and

the various meteorological parameters is studied in the

light of current theories of microwave propagation.

33
Millington, G. (Oct - Dec 1949) The reflection coefficient of a linearlygraded layer, Marconi Rev. 1 2, 140-151.

49-8 Abstract: The curves given in this paper refer to the specific

problem of the reflection of a horizontally polarized plane

wave incident obliquely on a layer in which there is a linear

variation of dielectric constant, and hence of the square of the

refractive index, from some constant value on one side of the

layer to some other constant value on the other side of the

layer. They have a particular application to the propagation

of ultra high frequency radio waves in the troposphere, and

should, therefore, be a useful contribution to our knowledge

of long distance transmission on these frequencies.

It is to be noted that the curves refer only to the case

of horizontal polarization. The analysis for vertical polarisation has been worked out, but it is different in form from

that for horizontal polarisation. It is well known, for instance,

that in the case of reflection at a sharp boundary there is a zero or minimum reflected wave at the Brewster angle that

does not occur with horizontal polarisation. It does, however,

happen that when the changes in refractive index is very small

and the wave is incident at a nearly glancing angle, the reflection coefficient for vertical polarisation is numerically almost

the same as for horizontal polarisation, though its analytical

form is different.

Under these strictly limited conditions, the curves for

horizontal polarisation give also the numerical value of the

reflection coefficient for vertical polarisation to the accuracy

to which they can be used. When the change of refractive index

is small, this may mean that the two cases are practically equivalent over the range for which the reflection coefficient is

appreciable, but as this equivalence is solely a matter of

numerical approximation, while analytically the two cases remain fundamentally distinct, it is perhaps best to limit the use

of the curves to the case of horizontal polarisation to which

alone they strictly refer, even where they may happen to give

an approximate numerical value for vertical polarization.

34
Bremmer, H. (Nov. 1950) Voortplanting van radiogolven in de troposfeer,

Nederlandsch Tijdschrift voor Natuurkunde, 16, 275-280 (Propagation of radio waves in the troposphere)

50-1 Abstract: A discussion of superrefraction, radio ducts and other

aspects of radio wave reflection and propagation in the troposphere

is illustrated by schematic diagrams and examples. - M.R.

Bussey, H. E. (Dec. 1950) Reflected ray suppression, Proc. IRE, 38,

1453.

50-2 Abstract: The use of Fresnel zone screens is described as a means of suppressing ground reflections on line of sight microwave paths

.

Day, J. P., and L. G. Trolese (Feb. 1950) Propagation of short

radio waves over desert terrain, Proc. IRE 38, 165-175.

50-3 Abstract: Results are given of an experimental investigation

of the effect of relatively simple topography and meteorology

upon the propagation of short radio waves over an optical

26.7-mile path and a nonoptical 46. 3 -mile path. Two types

of meteorological conditions were encountered during the

course of the experiments performed in the Arizona desert.

In the daytime the atmosphere was well mixed with the index

of refraction distribution nearly standard. At night a small

scale duct was formed, due to a temperature inversion

arising from the cooling of the ground by radiation. Measurements of the vertical distribution of field strength over a 190-foot interval were made under these two meteorological

conditions for frequencies of 25, 63, 170, 520, 1,000, 3,300 5 9, 375 and 24, 000 Mc. The effect of the diurnal meteorological

cycle on the field strength is discussed for both the optical

and nonoptical path. Diffraction effects on the short path

due to small scale irregularities of the terrain are also

discussed.

35
Millar, J. Z. , and L. A. Byam (June 1950) A microwave propagation

test, Proc. IRE 3_8, 619-626.

50-4 Abstract: A description is given of a microwave propagation

test which was conducted over a period of a year with simultaneous transmission on wavelengths of 16.2, 7.2, 4.7, and

3. 1 cm over an unobstructed 42 -mile overland path. Comparative charts depict variations in daily fading range, illustrate

diurnal and seasonal characteristics of fading, and reveal the

marked disparagement between winter and summer fading.

Curves are presented showing relative field-strength distribution for both winter and summer periods, and also the

distribution of hourly minima. These curves may be useful

in considerations bearing on continuity of service that may be

expected with relation to wavelength and to time of day,

winter or summer.

Phillips, W. E. (July 1950) The permittivity of air at a wavelength of

10 centimeters, Proc. IRE, _38, 786-790.

50-5 Abstract: This paper reports measurements of the permittivity

of moist air under different conditions of pressure, temperature,

and water-vapor content taken at a frequency of 3, 036 Mc. The

method and apparatus used are described. Results of observations

made are given, and their probable accuracy is discussed.

Saxton, J. A. (Jan. 1950) Reflection coefficient of snow and ice at

V.H.F., Wireless Eng., 27, 17-25.

50-6 Abstract: A review is given of the nature and composition of

snow, and of the experimental knowledge of the dielectric properties of ice at very high radio frequencies. From this information an estimate has been made of the dielectric properties of

snow. The presence of a layer of ice or snow on the earth' s surface will produce a modification in the resultant reflection

coefficient of the surface as a consequence of multiple reflections

within the layer. A general formula is given in the paper by means

of which the resultant reflection coefficient for plane waves in the

presence of such a layer may be calculated. The formula is in

36
terms of several basic parameters which have been determined

for frequencies of 30, 300, 3,000, and 30, 000 Mc/s . To illustrate

the effect of these layers, the resultant reflection coefficients of a stratum of ice on sea water and of one of snow on land have been

calculated for frequencies of 300 and 3000 Mc/s, at angles of

incidence of (normal incidence), 45 , and 80 , and for radiation

polarized with the electric vector either parallel to or in the plane

of incidence. It thus appears, for example, that the verticalcoverage diagram of a very high frequency radio transmitter may

be appreciably modified by the presence of layers of ice or snow

in depths likely to occur in practice.

Smith-Rose, R. L. (Jan. 1950) The speed of radio waves and its importance in some applications, Proc. IRE, 38, 16-20.

50-7 Abstract: This paper comprises a review of the present state of

knowledge of the speed of transmission of radio waves under the

practical conditions of certain applications in which such knowledge is important. It is shown first that, for radio waves in a vacuum, their speed of transmission is equal to the velocity of

light (299,755 km/s), to within the limits of experimental error.

When waves of frequencies in the neighborhood of 100 kc/s are

propagated at a height of a fraction of a wavelength above the

earth's surface, their speed is reduced by an amount dependent

upon the electrical conductivity of the earth. For overland transmission, the speed is about 299,250 km/s. For higher frequencies propagated at a height of several wavelengths, the speed of

the waves is determined by the refractive index of the air, rather

than by the properties of the ground. Since the refractive index

decreases with the height of transmission, so does the speed of

the waves increase toward the velocity of light. For example,

centimeter waves propagated at heights of a few hundred feet have

been observed to travel at a speed of about 299, 260 km/s. When

the waves are transmitted between ground and aircraft flying at a height of 30,000 feet (9,800 meters) this speed is increased to

about 299, 750 km/s.

37
Brocks, K. (1951) Probleme der "Radiometeorologie", Ann. der

Meteorologie, 4, 78-86 (Problems of radio-meteorology).

51-1 Abstract: A discussion of the effect of the atmosphere on radio

waves 1 cm to 10 m. The equations of the "relative beamcurvature" (negative gradient of refractive index times earth's

radius) are set out and constants of pressure and vertical gradients of temperature and humidity tabulated. Other measures of

refraction in use are defined. Diurnal variations at Quickborn

are discussed.

(Met. Abs. 81-106)-- C.E.P.B.

Kerr, D. E. (1951) Propagation of short radio waves, McGraw-Hill,

51-2 N.Y. [Text]

Peters, O. F. , Bo. K. E. Stjernberg, and K. H. For sgren ( 1951

)

Microwave propagation in the optical range, Chalmers Tekniska

Hogskola, Handelinger, Goteborg, Sweden, No. 108, 19 pp.

51-3 Abstract: In 1946 when these propagation tests began in the

vicinity of Goteborg, Sweden, access to reports on similar

works by foreign scientists was not possible. The results

presented are nevertheless valuable for studying the influence

of local weather and consist of: transmission field strength,

attenuation, refraction, fading and diurnal variation of 10, 3,

and 1 cm wavelengths. Equipment, sites of installations and

records are shown in photographs.

(Met. Abs. 81-124)-- W.N.

38
Bogle, A. G. (1952) Some aspects of microwave fading on an optical

path over sea, Proc. IEE Part B, 99, 236

52_1 Abstract: Long-term measurements of microwave transmission over a 3 9-mile optical path have shown fading too

deep to be easily accounted for by simple theory.

It is concluded from experimental evidence that both

scattering from turbulence and movements of the interference

pattern contribute to the fading.

Chavance, P. (1954) Etude de propagation des ondes centimetriques

dans le Nord de la France, Annales des Telecomm. 7,

254-261. (The study of centimeter wave propagation in

the north of France.

52_2 Abstract: An investigation of 3.2 and 9.5 cm wave propagation is described which was undertaken essentially for the

purpose of obtaining statistical data for a path with insufficient

clearance. Markedly apparent are the diurnal and seasonal

effects. Finally an effort is made to analyze a few typical

examples of fading and to draw certain information from

recordings made at high speed.—H. T.D.

Crawford, A. B. , and W. C. Jakes, Jr. (Jan. 1952) Selective fading of microwaves , Bell Sys. Tech. J. 3 1

,

68-90.

52-3 Abstract: The results of an extended survey of microwave

propagation over two line -of-sight paths in New Jersey are

described. Angle -of -arrival measurements at 1.25 -cm

wavelength and selective fading observations in a 450-mc

frequency band centered at 3950-mc show that the severe

fading can be explained in terms of multiple-path transmission. A computer of the analogue type was built to simulate

the more complicated selective fading patterns.

Cumming, W. A. (July 1952) The dielectric properties of ice and snow

at 3.2 centimeters, J. App. Phys., 23, 768-

52-4 Abstract: A knowledge of the permittivity and loss tangent of

snow and ice is essential in studying both radar echoes from

39
snow- covered terrain and the attenuation of microwave energythrough snowstorms. To provide this information, a program

was carried out at. the National Research Council of Canada to

measure the permittivity and loss tangent of ice and snow, and

also to determine the reflection coefficients of snow- covered

surfaces, at a wavelength of 3.2 centimeters.

As a result of these investigations values have been obtained

for the permittivity and loss tangent of snow of varying density,

temperature, and water content. Theoretical values of the reflection coefficients of snow- covered surfaces, calculated from these

data, are compared with the values obtained from the direct

measurement of reflections from natural snow surfaces.

De Lange, O. E. (Jan. 1952) Propagation studies at microwave

frequencies by means of very short pulses, Bell Sys. Tech.

J. 31_j_ 91-103.

52- 5 Abstract: Microwave pulses with a duration of about 0.003

microseconds were transmitted over a 22 -mile path from

Murray Hill, N. J. to Holmdel, N. J. , in order to determine

the effects of the transmission medium upon such pulses.

During "fading'* periods multi-path transmission effects with

path differences as great as 7 feet were observed, as well as some other effects. A microwave frequency of 4000 megacycles was employed.

Kiley, D. G. , and W . R. Carter (1952) An experimental study of

fading in propagation at 3-cm wavelength over a sea path,

Proc. IEE Part III, 99, 53 .

52-6 Abstract: The paper describes an experimental study of fading in propagation over a sea path within the radio horizon at a wavelength of 3 cm carried out between July 1950 and January

1951. Horizontal polarization was used. The object of the

investigation was to record the general fading characteristics

(i.e. depth, duration and frequency of occurrence) for summer,

autumn and winter and to present the results in such a form

that the effects of fading on the operational ranges of radar

experiments would be readily appreciated. An initial assessment of the transmitter power required for reliable operation

of a beacon under given conditions has also been made.

40
Bean, B. R. (April 1953) The geographical and height distribution of the

gradient of refractive index, Proc. IRE, 41, 549-550.

53-1 Abstract: Charts are presented of the Feb. and August distribution

of effective earth radius factor over the United States.

Bussey, H. E. , and G. Birnbaum (Oct. 1953) Measurement of variations

in atmospheric refractive index with an airborne microwave

refractometer, NBS J. Res., 51, 171-178.

53-2 Abstract: A microwave refractometer for aircraft use is described, and some of the sources of error in the measurement

of variations of atmospheric refractive index with this instrument are discussed. Observations were made up to 10,000 feet

on 2 days near Washington, D. C. Two refractive-index soundings taken 1 % hours apart showed changes that, in the coarser

aspects, resembled changes shown by radiosonde data. The

fluctuation intensity changed erratically with time and place, but

was usually greatest where the vertical gradient was changing.

A rough analysis of the data showed that the larger fluctuations

occurred over distances of several hundred meters, whereas

over distances less than 5 meters the fluctuations were negligible

(the response of the instrument would have allowed the detection

of fluctuations occurring within 0.5 meter). Large increases

in index were observed on entering cumulus clouds and intense

fluctuations were noted within the clouds.

Byam, L. A. , and J. Z. Millar (1953) Notes on propagation, IRE Conv.

Rec. Pt. 2 Ant. and Comm. , 68-76.

53-3 Abstract: A brief discussion of the fading which occurred during

an extended microwave propagation experiment, operated at a frequency of 4000 Mc. Attention was directed primarily to those

fades which dropped 15 db or more from the normal signal level.

For each such fade, the essential data were extracted and tabulated, including information with respect to the corresponding

level of the diversity (or main) signal.

E.K. (Bibliog. 64-6)

41
Committee on Wave Propagation (May 1953) Tropospheric propagation:

A selected guide to the literature, Proc. IRE, £1, 588-594.

53-4 Abstract: A subcommittee of the IRE Committee on Wave Propagation selects references designed to direct the non specialist

through the mazes of an extensive literature to information on

certain specific aspects of the propagation of short radio waves

through the troposphere.

Crain, C. M. , A. P Deam, and J. R. Gerhardt (Feb. 1953) Measurement of tropospheric index-of-refraction fluctuations and profiles, Proc. IRE, 4l_, 284-290.

53-5 Abstract: This paper presents measurements of index-ofrefraction fluctuations and profiles made with a direct reading

microwave refractometer over the Atlantic Ocean and coastal

areas near Lakehurst, N. J. , in April 1951 and over the

vicinity of Wright-Patterson Field, Dayton, Ohio, in June 1951.

Crain, C. M. , A. W. Straiton, and C. E. Von Rosenberg (Oct. 1953)

A statistical survey of atmospheric index-of-refraction variation, Trans. IRE, AP-1 , 43-46.

53-6 Abstract: This paper presents a statistical survey of index-ofrefraction variations as recorded by an airborne microwave

refractometer. Scales and intensities of the index variations

are given, as well as the parameter AN 2 /l, for data taken

over southwest Ohio during summer months and over the

Pacific Ocean off the west coast of Washington in August and

of California in October. Heights from 2, 000 to 25, 000 feet,

msl, were considered with most of the data taken between

2, 000 and 12, 000 feet. Approximately 1, 200 samples taken on

34 flights were analysed. The composite of the data gave the

following median values:

Index scale = 130 feet

Index Intensity = 0. 3 N

^=7x 10" 4 NVft

42
Kaylor, R. L. (Sept. 1953) Statistical study of selective fading of

super -high frequency radio signals, Bell Sys. Tech. J. 32,

1187-1202.

53 _7 Abstract: The results of two months of comprehensive

frequency-sweep measurements of selective fading in the

band between 3750 and 4190 mc over a radio relay path in

Iowa are reported. An abridgement of the data, general con'

elusions derived from the data and an example of the use of

the data in connection with frequency diversity measures for

radio relay systems are given.

Klein, W. , and L,„ J. Libois (1953) Essais de transmission par faisceau

hertzien sur un long trajet en visibilite optique entre la France et

la Suizze. L'Onde Electrique, 33, 664 (Communication experiment with radio beams on a long line -of- sight path between France

and Switzerland. )

53-8 Abstract: The results of an experimental investigation of propagation conditions is presented for a long (160 km) line-of -sight

path over mountainous terrain. The propagation path had clearances of several Fresnel zone radii for a k = 4/3 effective

earth's radius factor but had zero clearance for k = 1. Observations of the received field at 3000 MHz over a three month

period provided fairly stable values of attenuation relative to free

space. Some correlation between the recorded fields and the

meteorological conditions was observed. - HTD

Matsuo, Saburo, Shigetaka Ugai, Kiyoshi Kakita, Fumio Ikegami and

Yoshinori Kono (Nov. 1953) Microwave fading, Reports of ECL,

Japan, J^ 38-47.

53-9 Abstract: This paper deals with summary of fading characteristics, evaluation of fading range, and methods of decreasing

fading, taken from the analytical materials obtained from the

propagation tests performed on 4000 Mc microwave during the

period of past 3 years by Electrical Communication Laboratory

of Nippon Telegraph and Telephone Corporation. Since this

43
investigation was made mainly for the purpose of obtaining

necessary materials for design of 4000 Mc FM super multichannel telephone relay network, this paper has been prepared

for discussion along that line.

Microwave fading, depending upon the causes, may be

classified into three types; namely, scintillation fading, re- type fading, and duct -type fading. Of these three types, the

scintillation fading, with its small amplitude of variation, does

not give any practical problem, but the latter two types do give

much effect on propagation, so that the investigation was directed to these two types of fading.

Norton, K. A. (Jan. 1953) Transmission loss in radio propagation,

Proc. IRE, 4J_, 146-152.

53-10 Abstract: The utility of the concept of transmission loss in

radio propagation analysis is explored. The transmission loss

of a radio system is defined to be the ratio of the power radiated

from the transmitting antenna to the resulting signal power

available from a loss -free receiving antenna. After discussing

some methods of measuring transmission loss, its calculation

for representative systems is discussed. It is shown that a measure of transmission loss often adopted, namely the attenuation relative to the free -space value, sometimes leads to

errors and confusion in the presentation of the results of

measurements and in applications to radio systems; the use of

the over -all transmission loss of a system avoids these pitfalls.

A discussion is given of the expected variation with time

(fading) of the transmission loss expected for radio systems

involving ionospheric or tropospheric propagation. This discussion involves the theory of the Rayleigh distribution and its

limitations in such applications.

A definition is then derived for the effective noise figure

of a radio system which includes the external noise picked up

on the receiving antenna. This definition is used to explain the

method of determining the maximum range of a radio system.

Finally a discussion is given of the maximum range of a radio system as limited by interference from other radio

signals plus noise rather than from noise alone.

44
Perlat, A. , and J. Voge (Dec. 1953) Attenuation des ondes centimetriques et millimetriques dans l'atmosphere, Ann, des Telecomm. , 8, 395-405 (Attenuation of centimeter and millimeter waves in

the atmosphere).

53-11 Abstract: The authors delineate the effects of the atmosphere

on very short waves and the importance of atmospheric attenuation. In the first section results obtained by American and

English workers are surveyed in connection with absorption by

rain, snow, hail, fog and clouds. Attenuation by atmospheric

ozone and by water vapor is also considered, taking into consideration the effects of altitude and temperature. The second

section is a statistical study presenting precipitation, fog, water

vapor and temperature data of France and North Africa. In the

third section a method is worked out for calculating atmospheric

attenuation over a given path for specified percentages of given

time periods. --E.K. (WN Bibliog. 64-6)

Bean, Bradford R. (May 1954) Prolonged space-w^ve fadeouts at

1, 046 Mc observed in Cheyenne Mountain propagation program,

Proc. IRE 42, 848-853.

54-1 Abstract: During the first year of continuous operation of the

Cheyenne Mountain propagation program, recordings of

1, 046 -mc fields at receiving locations within the radio horizon

have exhibited 'Ifadeouts" or prolonged periods of attenuation

often in excess of 20 db below the monthly median level and

lasting from a minute up to several hours. The occurrence

of these fadeouts has been found to coincide with widespread

super-refraction as evidenced by enhanced signals beyond

the radio horizon and ground modification of the refractive

index profile.

45
Bullington, K. (Aug. 1954) Reflection coefficients of irregular terrain,

Proco IRE, 42_, 1258-1262

54-2 Abstract: Radio relay paths with strong ground reflections

experience more fading than similar paths with negligible

ground reflections. In order to minimize fading the route

survey for the transcontinental microwave -relay system

included measurements of ground reflection coefficients on

most of the proposed repeater sections. In most cases the

reflection coefficients at 4, 000 mc were in the range from

0. 2-0.4. Attempts to correlate these results with the path

profiles and to obtain a suitable theoretical explanation indicate

that no simple relation exists but that a statistical relationship

can be found to fit the observed data.

Chavance, P. , L. Boithais and P. Blassel (1954) Etude de

propagation d'ondes centimetriques dans le region

Mediterraneenne, Annales des Telecomm. 9> 158-185.

( A study of centimeter wave propagation in the Mediterranean

Region.

)

54-3 Abstract: This paper presents the results obtained to date by

C. N. E. T. in a study of centimeter wave propagation in the

Mediterranean region. The first part, I, constitutes a general description of the investigation. It specifies the

points of interest for the paths investigated; one between

Corsica and the continent and the other along the Mediterranean coast and indicates the different types of experience

encountered on these paths. The second part, II, is devoted

to the equipment employed; transmitters, receivers and

special arrangements. The third part, III, presents the

results obtained during the different experiments: a statistical

study of the Corsica-continent path at 1400 and 3150 Mc/s;

a comparison for horizontal and vertical polarization; the

distribution of the atmospheric index (of refraction) along

the beam; the influence of path's clearance upon its stability;

improvement by vertical space diversity; a study of a short

path high above the sea surface. Although this study is not as yet complete, interesting results from the practical as well as the scientific point of view have already been furnished.

H.T.D.

46
Cox, C. and W. Munk (1954) Statistics of the sea surface derived from

sun glitter, J. Marine Res. 13, 198-227.

54-4 Abstract: Aerial photographs of the sun's flitter on the sea

surface, taken under carefully chosen conditions in the Hawaiian

area, were coordinated with measurements of winds (1-27 knots)

from a vessel. Statistics of the glitter, -interpreted in terms of

the statistics of the slope distribution of the sea surface, gave

the following results: (1) As a first approximation the slope

distribution is found to be Gaussian; this can be accounted for

by an arbitrarily wide continuous spectrum of ocean waves,

but not by a spectrum consisting of a few discrete frequencies.

(2) The ratio of the up/downwind to crosswind components in

mean square slope is less than two; this indicates a directional

"beam width" in excess of 130° for the relatively short waves

that contribute to the slope spectrum. (3) The mean square slope,

regardless of direction, increases linearly with wind speed and

reaches a value of (tan 16°) for a wind speed of 14 m sec" ; this empirical relation follows in form and to an order of magnitude from a spectrum proposed by Neumann on the basis of wave

amplitude observations. A spectrum proposed by Darbyshire

cannot be reconciled with our observations.

Further results which have not been interpreted are: (4) An upand down-wind skewness which increases with increasing wind

speed is such as to make the most probable slope a few degrees

rather than zero, with the azimuth of ascent pointing downwind.

(5) A peakedness, which is barely above the limit of observational

error, is such as to make the probability of very large and very

small slopes greater than Gaussian. (6) Oil slicks laid by the

vessel over an area of one quarter square mile reduce the mean

square slope by a factor of two or three and eliminate skewness

but leave peakedness unchanged.

The distribution of particle acceleration is closely related to

the distribution of slope. Accordingly, the total mean square

acceleration increases linearly with wind speed and reaches

?

— 1 a value (at the surface) of (0. 4 g) c at a wind speed of 14 m sec

47
Kahn, L. R. (1954) Ratio squarer, Proc. IRE, 42, 1704.

54-5 Abstract: An optimal output signal to noise ratio is derived

for the linear adding diversity combiner.

Kiely, D. G. (1954) Some measurements of fading at a wavelength of

8 mm over a very short sea path, J. Brit. IRE, 14, 89-92.

54-6 Abstract: The results of a pilot experiment designed to investigate the magnitude of atmospheric refraction effects in the

8 -mm wavelength band are described. Records of signal fading

on a 1 -mile over-sea path with a low transmitter and a high

receiver indicate that these effects are very large.

Brennan, D. G. (Oct. 1955) On the maximum signal-to-noise ratio

realizable from several noisy signals, Proc. IRE, 43_, 1530.

55-1 Abstract: A derivation is presented of the output signal to noise

ratio for an nth order maximal (S/N) ratio combiner.

British IRE (1955) Abstracts of papers which have appeared in the

Journal over the past 15 years (Vols. 1-15, 1939-1955),

British IRE, 48 pp.

55-2 Abstract: The abstracts cover the principal papers published

in the past 15 years in this journal which, prior to 1939, was

referred to as "The Proceedings". The sections of radio

meteorology including propagation and instrumentation are

listed under Radio Communication (621.396) and subdivided

according to the latest amendments to the U. D. C, system.

(Met. Abs. 14.7-112)-- (W.N. Bibliog. , 64-6).

48
Cabessa, R. (1955) Realization de liasons par faisceaux hertzian

de qualite sur des trojets maritime s en Grece, L'Onde

Electrique 35, 714-727. (The achievement of reliable radio

communication links on over -water paths in Greece.

55-3 Abstract: The successful performance of several communication links, 24 overwater paths and 8 overland paths, is

described. The frequencies of operation ranged from 1.7

to 2.3 Gc/s and space diversity reception was employed.

The choice of terminal sites was determined in the light of

the following sources of fading on line-of-sight microwave

paths: super refraction (ducting); substandard refraction

(earth-bulging); interference between direct and reflected

waves; and interference due to reflections from elevated

layers.—H. T. D.

Court, G.W. G. (1955) Determination of the reflection coefficient of the sea,

for radar -coverage calculation, by an optical analogy method,

Proc. IEE, Pt. B, 102 , 827-830.

55-4 Abstract: An approach to the solution of the problem of the

effect of a rough sea surface on the vertical coverage of a radar set, by means of an optical analogy, is suggested. The

reflection of light waves by a ground-glass surface is considered,

and the results of optical experiments are applied to the case

of radio waves reflected by the surface of the sea. The method

does not yield a precise solution to the problem, but the result

achieved does not conflict seriously with practical results which

have been recorded up to the present.

A typical coverage diagram derived by this method is

given to show the effect on the coverage of the variation of

sea-surface condition as indicated by the sea-state scale.

Deam, A. P., and B. M. Fannin (Oct. 1955) Phase-difference

variations in 9, 350-megacycle radio signals arriving at

spaced antennas, Proc. IRE 43, 1402-1404.

55-5 Abstract: The phase difference between 9, 350 megacyclepersecond radio signals received from a common transmitter

49
at two horizontally spaced antennas was measured by the

Electrical Engineering Research Laboratory of the University

of Texas during March, 1955. The transmitter was located

on Cheyenne Mountain in Colorado and the site of the receiver

was at Fort Carson, 3. 5 miles distant. The elevation angle

of the transmitter as seen from the receivers was 9 degrees.

This paper presents and discusses the results of these measurements .

Herbstreit, J. W., and M. C. Thompson (Oct. 1955) Measurements

of the phase of radio waves received over transmission paths

with electrical lengths varying as a result of atmospheric

turbulence, Proc. IRE, 43j_ 1391-1401.

55-6 Abstract: A system for the measurement of the variations in

electrical lengths of radio propagation paths is described. The

observed path-length instabilities are considered to be caused

by the same atmospheric turbulence responsible for the existence of very high frequency and ultra high frequency fields far

beyond the radio horizon. Results obtained on 172.8 mc and

1,046 mc along 2> l/z- , 10-, and 60-mile paths are reported. It is pointed out that measurements of this type provide a powerful tool for the study of the size and intensity of the refractivity

variations of the atmosphere giving rise to the observed phenomenon.

LaGrone, A. H. , A. W. Straiton and H. W. Smith (April, 1955)

Synthesis of radio signals on overwater paths, Trans. IRE

AP-3, 48-52.

55-7 Abstract: The fluctuations of radio signals at microwave

frequencies on overwater paths are explained on the basis of a periodic rise and fall of the water level. From this study,

it is seen that the variations in the radio signal strength will

contain the frequency of the water-level cycles and also the

second and third harmonics of the water-level cycles.

50
The same model predicts that the cross -correlation

function of the fluctuation of the radio signal at two vertically - spaced antennas will drop from unity to zero as the separation

distance is changed from zero to one -half of a lobe width of a height-gain interference pattern.

Although the model assumes reflection from a plane

surface, the results of the study successfully explain most of

the features of the observed fluctuations of the radio signals

on two overwater paths.

Muchmore, R. B. , and A. D. Wheelon (Oct. 1955) Line-of-sight

propagation phenomena—I. Ray treatment, Proc. IR E 43,

143 7-1449.

55 _8 Abstract: The effect of variations in index of refraction on

line-of-sight propagation of electromagnetic waves in the

troposphere is investigated using, in this paper, a ray theory

approach. Mean-square variations in phase delay and phase

correlation between two paths are calculated. It is shown

that these quantities are relatively insensitive to the form of

space correlation function assumed for the index of refraction.

The mean-square phase is proportional to AN^i where I is scale length and AN the mean-square variation in index of

refraction, whereas in beyond lin e-of- sight propagation the

received power is proportional to AN / i . o Variations in angle of arrival are also calculated and

it is shown that here the assumed space correlation of index

of refraction is critical in determining the angle of arrival

characteristics. It is shown, however, that a certain portion

of the angle -of -arrival spectrum is insensitive to the choice.

51
Norton, K. A., L. E. Vogler, W. V. Mansfield and P. J. Short

(1955) The probability distribution of the amplitude of a constant vector plus a Rayleigh-distributed vector, Proc. IRE

43, 1354-1361.

55_9 Abstract: Formulas, tables, and graphs are given for the

probability distribution of the instantaneous resultant amplitude

of the sum of a constant vector and a Rayleigh-distributed

vector. It is emphasized that two distributions are required

to describe a Rayleigh-distributed vector: the distribution of

its amplitude and the distribution of its phase. A summary is

presented of physical conditions which must be satisfied for a given phenomenon to exhibit statistical properties of a Rayleighdistributed vector. References are made to ways in which these

distributions may be used to describe random variables occurring in ionospheric, tropospheric, and irregular terrain propagation problems. Finally, a discussion is given of amplitude

and phase distributions of two other random vectors encountered in tropospheric propagation studies.

Saxton, J. A., and J. A. Lane (May 1955) VHF and UHF reception effects

of trees and other obstacles, Wireless World, 6l_, 229-232.

55-10 Abstract: Some experiments to determine the attenuation

caused by screens of trees and thick woods at frequencies of

100, 540, and 1, 200 Mc/s are described, and these and other

data are used to estimate the attenuation over the frequency

range 30-3, 000 Mc/s. This work carried out as part of the

programme of the Radio Research Board. The nature of the

diffraction loss and variation of field strength behind opaque

obstacles of various kinds for the same frequency band is

examined on the basis of the Fresnel theory of diffraction.

Sherwood, E. M. , and E. L. Ginzton (July 1955) Reflection coefficients

of irregular terrain at 10 cm, Proc. IRE, 43_, 877-878,

55-11 Abstract: Reflection coefficients measured at 10 cm wavelength are presented as a function of polarization and angle of

incidence for a variety of terrain and water surfaces.

52
Wheeler, B. F. , and H. R. Mathwich (Oct. 1955) Use of distribution

curves in evaluating microwave path clearance, Trans. IRE,

PGI-4, 31.

55-12 Abstract: Distribution curves for the duration of fades as a func

tion of mean fade duration and type of fading are presented and

their application is described.

Wheelon, A. D. (Oct. 1955) Near field corrections to line-of-sight

propagation, Proc. IRE 43_, 1459-1466.

55-13 Abstract: This study considers the line-of-sight propagation

of electromagnetic waves in a turbulent medium. Interest

here centers on the received signal's phase stability. The

field equation describing propagation through a region

characterized by random dielectric fluctuations is first

developed. Solutions of this equation which represent the

scattered field are derived with ordinary perturbation theory.

These solutions are next used to calculate the rms phase

error for an arbitrary path in the troposphere. This approach

includes both a three dimensional and near -field description

for the multipath, scattered amplitudes; thereby overcoming

the limitations of previous treatments. The phase correlation

between signals received on two parallel .transmission paths is

derived last to illustrate the role of overlapping antennae

beams

.

Wheelon, A. D. , and R. B. Muchmore (Oct. 1955) Line-of-sight

propagation phenomena—II. Scattered components,

Proc. IRE43_, 1450-1458.

55-14 Abstract: The foregoing investigation of line-of-sight

propagation through a turbulent atmosphere is continued and

enlarged. Generalizations of the ray calculation to include

scattering contributions by off-axis blobs are given. It is

found that the previous expressions for rms phase errors are

substantially maintained. The dependence of these fluctuations

on receiving antenna beamwidth is adduced. These techniques

are then applied to estimate phase scintillation' for transmission

through a rainstorm. Meteorological data are used to relate

such errors to rainfall intensity and inter scintillation frequency spectra. Numerical values for these effects are given

for representative atmospheric conditions.

53
Beard, C. I. , I. Katz, and L. M. Spetner (April 1956) Phenomenological vector model of microwave reflection from the ocean,

Trans. IRE, AP-4 , 162-167.

56-1 Abstract: A model of one-way transmission of microwave

electromagnetic signals over the ocean surface is developed

from experiment. The received signal is described as a vector

sum of a constant direct signal, a coherent reflected signal,

whose amplitude and phase are fixed by geometry and sea state,

and a fluctuating reflected component of random amplitude and

phase. By interpreting experimental data in the light of this

phenomenological model it has been possible to relate, quantitatively, the coherent and incoherent reflected signal and total

signal to geometry and sea state. The results give support to

the theoretical expression previously derived by Ament and

others relating the coherent reflected signal to "apparent

ocean roughness". In addition, the general shape of the curve

relating the incoherent scattering to "apparent ocean roughness!'

has been established and its asymptotic value found.

Barsis, A. P. (Oct. 1956) Some aspects of tropospheric radio wave

propagation, Trans. IRE, PGBTS-6, 1-10.

56-2 Abstract: The Tropospheric Propagation Research Section of

the Radio Propagation Engineering Division, National Bureau

of Standards, has conducted extensive measurements of programs in the 100-1000 Mc frequency range. A variety of

transmitting and receiving antenna heights were used, and longterm recordings are available over distances ranging from well

within to far beyond the radio horizon.

Some results of this measurement program are evaluated

to provide estimates for power requirements and interference

problems concerning broadcasting services in this frequency

range.

54
Kiely, D. G. (1956) Quelques problemes poses par la propagation des

ondes de 8 mm et de 3 cm, au dessus de la mer et a travers la

pluie, Ann. Telecomm. , 11_, 233-244 Nov. and 267-279 Dec.

(Some problems posed by wave propagation of 8 mm and 3 cm

wavelengths over the sea and through rain).

56-3 Abstract: This article describes the results of a large number

of experimental investigations of the propagation of centimeter

and millimeter waves. The first part, devoted to 8 mm waves,

treats three subjects: investigation of the echoes from rain for

monostatic and bistatic CW radars; measurements of fading for a very short over-sea path; and measurements of the reflection

coefficient of water for various angles of incidence. The second

part deals with 3 cm wave propagation measurements of fading

on a very short over-sea path. The results of these measurements explain the reduction of range of radars. Next, measurements are described of the characteristics of guided waves

propagated along "Goubau" wires; measurements which show

the considerable importance of the effects of rain. --HTD

McFadden, J. A. (Dec. 1956) The axis -cros sing intervals of random

functions, Trans IRE, IT-2, 146-150.

56-4 Abstract: For an arbitrary random process £(t) there exists

a function x(t) which may be obtained by infinite clipping. The

axis crossings of x(t) are identical with those of £(t). This

paper relates the probability density P(t) of axis -crossing

intervals to r( t), the autocorrelation function of x(t), i, e. , the autocorrelation after clipping. It is shown that the expected number of zeros per unit time is proportional to r'(0+),

i.e. , the right-hand derivative of r(-r) at t = 0. Next a theorem is proved, stating that P(t) = over a finite range

< t < T if and only if r(-r) is linear in | t | over the corresponding range of | t | . If r(-r) is nearly linear for small

t, then the initial behavior of P(t) is like r"(-r). These

results are illustrated by some simple, random square -wave

models and by a comparison with Rice's results for Gaussian

noise.

55
Misme, P. (1956) Evanouissements d' interferences causes par des

discontinuity s frontales, L'Onde Electrique 36, 43-47.

(Destructive interference caused by frontal discontinuities.)

5£_5 Abstract: Multipath effects caused by abrupt changes in the

gradients of refractive index are described. Particular

attention is given to the case of cold weather fronts characterized by the localized abrupt drop in temperature and increase

in temperature. Some experimental observations are presented of the resulting destructive and constructive interference effects. —H. T. D.

Rivet, P. (1956) Essais de diversite et etude de l'effect defocalisation

sur les liaisons longues en visibilite, L'Onde Electrique 36,

24-31. (A diversity experiment and study of the effect of

defocusing on long line -of- sight paths.

56-6 Abstract: Both space and frequency diversity effects are

investigated for the fading encountered on long line-of -sight

microwave paths. Both multipath and defocusing are considered as the causative mechanism. —H. T. D.

Schmelovsky, Karl-Heinz (Aug. 1956) Partielle Reflektionen in schwachen

tropospharischen Wellenleitern, Zeitschrift fur Meteorologie,

10, 239-243 (Partial reflections in weak tropospheric wave-ducts),

56-7 Abstract: This work describes an approximation process for

obtaining the propagation constants in weak ducts. A diagram

collects the results for some special height relations of the

modified refraction index. Transl. of author's abstract (Met.

Abs. 8.4-343).

56
Staras, H. (Aug. 1956) The statistics of combiner diversity, Proc. IRE,

44_, 1057-1058.

56-8 Abstract: The distributions are presented for the output signal

to noise ratio of an nth order of diversity linear adding combiner

for input signal voltages whose S/N ratios are Rayleigh distributed.

Suzuki, M. (1956) Problems concerning the variations of p (Equivalent reflection coefficient) in microwave propagation over

snow-covered terrain, ETJ of Japan 2^ 104-107.

56-9 The reflection coefficient of snow covered terrain is evaluated

for a variety of angles of incidence and dielectric constants.

H.T.D.

Barsis, A. P., and F. M. Capps (1957) Effect of super -refractive

layers on tropospheric signal characteristics in the Pacific

Coast region, IRE Wescon Conv. Rec. Part 1, 116-132.

57 _i Abstract: Results of tropospheric radio wave propagation

measurements over two paths between San Nicholas Island and

the California coast near Pt. Mugu are correlated with the

characteristics of refractive index profiles determined at the

path terminals simultaneously with the radio measurements.

The radio paths extend to the vicinity of and slightly beyond

the radio horizon. Specifically, it was found that the existence

of super -refractive layers (either ground-based or elevated)

favors the occurrence of prolonged space -wave fadeouts for

the within -the -horizon path, and increases the short-term

fading range for the beyond -the -horizon path. It was found

that the base and top elevations of a super -refractive layer,

and also the magnitude of the refractive index gradient within

the layer have a noticeable effect on various characteristics

of the received signal for both paths. An example of this

is found if the hourly median basic transmission loss for the

beyond -the -horizon path is plotted as a function of the layer

heights. These results generally agree with earlier observations by Smyth and Trolese.

57
Beard, C. I. , and I. Katz (April, 1957) The dependence of microwave

radio signal spectra on ocean roughness and wave spectra,

Trans. IRE AP-5, 183-191.

57-2 Abstract: This paper is an extension of previous work on

reflection of microwaves from an ocean surface. The present

analysis, dealing with spectra, is based on data obtained in a one-way X-band propagation experiment performed across the

Golden Gate, San Francisco. Two paths of 9, 000 and 15, 000

feet were used. To describe the ocean surface, wave gages

were mounted on a piling driven into the Golden Gate channel.

Radio-signal spectra are found to be broader than the

ocean-wave spectra and the spectral breadth a function of

ocean roughness. The important result of this analysis is the

establishment of a linear relationship between ocean roughness

and the spectral breadth of the radio signals. Ocean roughness

is measured by the product of the standard deviation of the

wave height and the grazing angle divided by the radio-wave

length. Radio spectral breadths are determined by the frequencies at which each spectrum drops to the 0. 9-, 0.8-,

0.7-, 0.5-, 0.25-, and 0. 1 -power points. The breadths are

then expressed as ratios of these frequencies to the frequency

of the peak in the simultaneous ocean-wave spectrum.

The analysis now enables one to predict the approximate

shape of the spectrum of the radio signal received in a oneway transmission path given only a knowledge of the geometry,

radio-wave length, ocean-wave height, and the peak frequency

in the ocean spectrum.

Bullington, K. (May 1957) Radio propagation fundamentals, BSTJ, 36 , 593-626,

57-3 Abstract: The engineering of radio systems requires an estimate of the power loss between the transmitter and the receiver.

Such estimates are affected by many factors, including reflections, fading, refraction in the atmosphere, and diffraction

over the earth's surface.

58
In this paper, radio transmission theory and experiment

in all frequency bands of current interest are summarized.

Ground wave and sky wave transmission are included, and both

line of sight and beyond horizon transmission are considered.

The principal emphasis is placed on quantitative charts that

are useful for engineering purposes.

Gudmandsen, P. and B. F. Larsen (July, 1957) Statistical data for

microwave propagation measurements on two oversea paths

in Denmark, Trans. IRE, AP-5 , 255-259.

57-4 Abstract: Measurements were carried out on 6.4-cm. and 17-

cm wavelength on two optical paths, 54 -km and 82 -km long,

stretching over sea nearly East-West and starting at the

same point. For the greater part of the measurements,

height-spaced receivers were used. The bulk of the statistical data comprises distributions of field strengths for every

day of measurement. Curves for single receivers and

diversity combinations of two receivers have been worked

out. Distributions for every hour of a day as well as distributions of fadurations for a few days with special propagation

conditions were obtained. A study of special fading phenomena

with almost coinciding fades on the receivers in operation has

been made.

The data reveal that the field strength distribution for

single receivers on days with a great number of fades generally approximates the Rayleigh distribution irrespective of

wavelength path, and antenna height within the range of height

considered. The field strength distributions for diversity

systems approximate the diversity Rayleigh distribution,

which is derived from two uncorrelated Rayleigh distributed

signals. Deviations from appropriate Rayleigh distribution

towards more serious fading conditions seem to be more

frequent and more pronounced for diversity systems than for

single receivers. Distributions of fade durations are found

to be log-normal. Measurements on three-height-spaced

receivers on 17 -cm wavelength indicate that the simple tworay theory is insufficient to describe the fadings on a path

over sea.

59
Millington, G. (Jan. 1957) The concept of the equivalent radius of the

earth in tropospheric propagation, Marconi Rev., "20, 79-93.

57-5 Abstract: The concept of the equivalent radius of the earth to

take account of a linear variation of refractive index with height

in tropospheric refraction is re-examined. It is shown that

the transformation is not limited to nearly horizontal rays, but

that essentially it reduces the curvature of the earth by that of a ray traveling horizontally and the curvature of the rays by the

amount required to straighten them at whatever angle to the

horizontal that they may be going. The results obtained geometrically in a previous paper (46-8) for the angle of elevation

at the reflection point, the optical path difference between the

direct and indirect rays and the divergence factor are derived

by simple analysis, affording a useful check on the method.

Montgomery, G. Franklin (Dec. 1957) Intermittent communication

with a fluctuating signal, Proc. IRE 4_5, 1678-1684.

57-6 Abstract: Intermittent transmission is proposed as a method

to combat the effects of signal fading. Message error and

average transmission rate are functions of operating bandwidth and threshold signal-to-noise ratio. The method is

evaluated for Rayleigh -fading signals, using binary frequency

modulation and phase modulation. One variable -bandwidth

system is examined. The theoretical advantage (power

gain > 40 db for a binary error =10 ) is reduced by practical

limitations but should be nearly realized for some systems.

Bremmer, H. (1958) Propagation of electromagnetic waves, Encyclopedia of Physics, XVI, Electric Fields and Waves, Sec. 97,

58-1 596-601 (Handbuch der Physik, Springer-Verlag, Berlin) [Text],

60
du Castel, F. , P. Misme, and J. Voge (March 1958) Reflexion d'une

onde electromagnetique par une couche d'atmosphere presentant

une variation de l'indice de refraction, Acad. Sc. , Comptes

Rendus, 246 , 1838-1840 (Reflection of an electromagnetic wave

from an atmospheric layer with a variable refractive index).

58-2 Abstract: A more general formulation of the reflection coefficient,

which may be interpreted as an increasing function of the atmosphere thickness where great stability prevails, is presented.

(Met. Abs. 10. l-342)--A. V.

Clarke, K. K. , and J. Cohn (May 1958) Carrier-to-noise statistics

for various carrier and interference characteristics, Proc.

IRE 4_6j_ Part I, 889-895.

58-3 Abstract: Techniques are presented for the calculation of the

statistical properties of the resultant carrier-to-noise ratios

of systems subject to both additive and multiplicative noise.

The cases considered are those in which the desired signal is

either steady or exhibits Rayleigh fading while the interference

consists of receiver noise plus an interfering signal which may

be steady, Rayleigh fading, Gaussian fading, or Rayleigh fast

fading with slow Gaussian fading of the median of the Rayleigh

distribution. The results of the indicated calculations are

presented graphically. A simple process is outlined for converting the data presented for use with any other signal strength.

The utility of the data is demonstrated by a sample

calculation the results of which are presented graphically.

This calculation derives threshold data for the system as a function of desired signal power with the percentage of time

that it operates in one of its two possible modes (fading or nonfading) as a parameter.

Attention is called to the technique demonstrated in the

Appendix. This result appears quite useful in many joint or combination probability problems, especially those requiring

numerical solutions.

Although this paper stemmed from work on line-of -sight microwave links, the results may be useful in other applications in

the hf, vhf, and uhf regions.

61
Gough, M. W. (May 1958) Microwave line -of -sight propagation,

Elec. Eng. 30, 237-247.

58-4 Abstract: After sketching the historical and physical background of the subject, this article surveys some fundamental

investigations into microwave line -of -sight propagation made,

mainly since 1939, in Europe and the U.S.A. Theoretical

work, based principally on classical optical concepts, is reviewed in conjunction with related experimental investigations,

statistical processes important in the research and engineering

aspects of the subject are also discussed.

McFadden, J. A. (March 1958) The axis-crossing intervals of

random functions—II, Trans. IRE, IT -4 , 14-24.

58_5 Abstract: This paper considers the intervals between axis

crossings of a random function £(t). Following a previous

paper, continued use is made of the statistical properties of

the function x(t) and the output after £,(t) is infinitely clipped.

Under the assumption that a given axis -crossing interval is

independent of the sum of the previous (2m + 2) intervals,

where m takes on all values, m = 0, 1,2, *

' *

, an integral

equation is derived for the probability density P (t) of axiscrossing intervals. This equation is solved numerically for

several examples of Gaussian noise. The results of this calculation compare favorably with experiment when the highfrequency cutoff is not extremely sharp. Assuming that the

successive axis -crossing intervals form a Markoff chain in

the wide sense, infinite integrals are found which yield the

variance a (t) and the correlation coefficient k between the

lengths of two successive axis -crossing intervals. These

parameters are obtained numerically for several examples

of Gaussian noise. For bandwidths at least as small as the

mean frequency, k is large. For los-pass spectra, k is

small, yet the statistical dependence between successive

intervals may be strong even when the correlation k is

nearly zero.

62
Morita, Kazuo and Kiyoshi Kakita (Sept. 1958) Fading in microwave

relays, Reports of ECL, Japan 6, 3 52-370.

58-6 Abstract: A statistical description is presented for the

fading encountered on microwave line -of- sight paths. The

theoretical distributions are compared with experimentally

observed distributions to provide empirical expressions

for percent occurance of severe fades as a functional path

length; standard deviation of hourly mean signal levels as a function of path length; etc. A statistical description

is also provided for signal-to-noise ratios due to fading.

Omori, Takeo and Rihachi Sato (Jan. 1958) Multipath propagation of

microwaves, Tech. J. of ECL, Japan, 6, 1-11.

58-7 Abstract: The distortion experienced for multichannel FM

transmission over five line -of -sight microwave paths (3.85 to

9.41 Gc/s) is described. The effects of multipath and of

ducting conditions are considered.

Rice, S. O. (May 1958) Distribution of the duration of fades in radio

transmission: Gaussian noise model, Bell Sys. Tech. J. 37,

581-635.

58-8 Abstract: The fluctuations of a received radio signal due to

fading are assumed to behave like the envelope of narrow-band

Gaussian noise. Estimates of the distribution of the fade

lengths for various depths of fades are given, and relations

which may be useful in analyzing fading data are derived. A

similar problem involving the separation of the intercepts of

the noise current itself, instead of its envelope, is also

discus sed.

Suzuki, M. (1958) Experimental analysis of equivalent reflection

coefficient of various reflecting rough surfaces in microwave

propagation, ETJ of Japan, 4, 3-6.

58-9 Abstract: The reflection coefficient is evaluated for various

angles of incidence and types of surfaces and terrain with

crop cover. —H. T. D.

63
Wong, Ming S. (Sept. 1958) Refraction anomalies in airborne

propagation, Proc. IRE, 46, 1628-1638.

58-10 Abstract: Propagation at 250-10, 000 mc often encounters:

1) dense fadings where the radio signal fluctuates spatially

with large amplitudes and small spacing s from maxima to

minima, e.g. amplitudes of up to 40 db and spacings at

3 000 mc of 1 mile; 2) radio holes, where the signal falls

spatially to a level often 15 db or more below the levels

outside; 3) antiholes, where the signal fluctuates spatially

with large amplitudes and irregular spacings; 4) radio ducting, including cases where the transmitter or receiver is far

above a ducting layer in the air.

The anomalies (1-4) are portrayed by ray tracings

using a differential analyzer which solves a simplified ray

equation.

Anderson, W. L. , N. J. Beyers and B. M. Fannin (July, 1959)

Comparison of computed with observed atmospheric

refraction, Trans. IRE, AP-7 , 258-260.

59-1 Abstract: Ray tracing methods have been applied in the

computation of atmospheric refraction for a path at White

Sands Missile Range, N. Mex. , with a range of about 48

miles and an elevation angle of 14.5 milliradians. The

atmosphere was assumed to be horizontally stratified.

Refractive index profiles were derived from meteorological

data obtained from surface observations, wiresondes,

radiosondes, and airborne ref Tactometer soundings. The

profiles were classified "A", "B", or "C", in descending

order of reliability, prior to radar refraction computations.

The classification system considered the variety of data

available, the time lag between radar and weather observations, and the proximity of the sounding to the propagation

path. A good correlation between observed and computed

angles resulted and the correlation was directly related to

the classification.

Radar observations were made in the X-band and

instrumental precision maintained to within 0.25 milliradian.

Total bending ranged between 0. 56 and 2.23 milliradians,

with standard deviation 0.38 milliradian.

64
The rms deviation of computed from observed angles

ranges from 0. 19 to 0.41 milliradian for Class A and Class C

data, respectively. The correlation coefficient ranges from

0.81 to 0. 13. It is concluded that within the limits of this

experiment: a) ray tracing methods are justified, b) horizontal stratification may be assumed and c) the accuracy of

bending predictions is increased by improving the meteorologi'

cal data.

Bachynski, M. P. (June 195 9) Microwave propagation over rough

surfaces, RCA Review 20, 308-335.

59_2 Abstract: The field of propagation of short radio waves over

rough surfaces is surveyed. The results of available experimental measurements are summarized and theories which are

readily amenable to calculation are discussed. The experimental findings may serve as an indication of typical values

to be expected in practical situations. The effects of both

irregular terrain and sea surfaces are considered. The limitations of various theoretical approaches are outlined and aspects

requiring further study are indicated. An extensive bibliography

is also included.

Bean, Bradford R. (1959) Climatology of ground-based radio ducts,

NBS J. Res., 63

D

, 29-34.

59_3 Abstract: An atmospheric duct is defined as occurring when

geometrical optics indicate that a radio ray leaving the transmitter and passing upwards through the atmosphere is sufficiently refracted that it is traveling parallel to the earth's

surface. Maximum observed incidence of ducts was determined

as 13 percent in the tropics, 10 percent in the arctic and 5

percent in the temperate zone by analysis of 3 to 5 years of

radiosonde data for a tropical, temperate, and arctic location.

Annual maximums are observed in the winter for the arctic and

summer for the tropics. The arctic ducts arise from groundbased temperature inversions with the ground temperature less

than -25 C while the tropical ducts are observed to occur

with slight temperature and humidity lapse when the surface

temperature is 30 C and greater.

65
Bean, B. R. , and G. D. Thayer (May 1959) Models of the atmospheric

radio refractive index, Proc. IRE, 47, 740-755.

59 _4 Abstract: Evaluation of atmospheric refraction effects on

UHF-VHF radio propagation has long been accomplished with

the convenient four -thirds earth concept of Schelling, Burrows,

and Ferrell. This method has proven particularly useful in

evaluating performance of point-to-point radio communications

systems. However, relatively new long-range applications

have demanded a model of atmospheric radio refractive index

more representative of observed refractive index profiles

than the simple linear decay inherent in the four -thirds earth

approach.

This paper introduces two models of atmospheric radio

refractive index which can be used to predict refraction effects

from the value of the refractive index at the transmitting point.

Both models offer considerable improvement over the fourthirds earth model, particularly for applications at long distances and high elevations in the atmosphere. Further, both

models may be adjusted to represent mean conditions at different times of year and in different geographical locations.

A new method of predicting radio-ray refraction at very low

initial elevation angles is introduced which utilizes both the

initial value and the initial height-gradient of the refractive

index over roughly the first 100 meters above the earth's

surface. This method, which is dependent only upon the first

two radiosonde reporting levels or simple tower measurements

of the common meteorological elements, results in a considerable improvement of the values of ray -refraction predicted by

the model.

Bean, B. R. , and B. A. Cahoon (Nov-Dec. 1959) Effect of atmospheric horizontal inhomogeneity upon ray tracing, NBS J. Res. , 63 D, 287-292.

59-5 Abstract: The tracing of radio rays is normally carried out

under the assumption that the refractive index varies only in

the vertical direction. Although this assumption appears to be

quite reasonable in the average or climatic sense, it is seldom

66
satisfied under actual conditions and is strongly violated byhorizontal airmass changes occurring near frontal and landsea interfaces. This latter case is investigated by tracing rays

through two instances of observed marked horizontal variation

of the refractive index. The bending for these ray paths was

then compared with values obtained under the normal assumption

of horizontal homogeneity.

Although at 1 kilometer and above these horizontal

changes appear to have little effect, rays emitted at low elevation angles are sensitive to extreme horizontal variations of

the atmosphere near the surface, such as those associated with

ducting conditions. However, since it appears that such conditions occur less than 15 percent of the time at most locations,

the majority of ray-path calculations may be carried out under

the normal assumption of horizontal stratification of the refractive index.

Bean, B. R. , and J. D. Horn (Nov. -Dec. 1959) Radio-refractiveindex climate near the ground, NBS J. Res. , 63 D, 259-271.

59-6 Abstract: The radio refractive index of air is a function of

atmospheric pressure, temperature, and humidity and is found

to vary in a systematic fashion with climate. It was found that

the surface value of the refractive index may be estimated

four to five times more accurately from charts of reduced-tosea-level values than from similar sized charts of surface

index. Worldwide maps of 5-year means of this reduced

value are presented for the months of February and August,

for the minimum monthly mean value of the year and for the

range of monthly mean values. Year-to-year variation of

monthly means is also considered. Applications of these

data to the prediction of radio field strengths indicate a possible 3 0-decibel difference in median level of identically

equipped tropospheric communications systems due to

climate alone.

Braude, S. Ya„ (1959) The Fresnel coefficients for a rough surface,

59-7 (in Russian), Izv. Vyssh. Zav. Radiofiz. 2, 69I-696.

67
Braude, S. Ya. , N. N. Komarov, and I. E. Ostrovsky (1959) On the

statistical character of the scattering of centimeter radio waves

by the rough surface of the sea, (in Russian), Radiotekhnika i. 59-8 Elektr. , 3, 172-179.

Brennan, D. G. (June, 195 9) Linear diversity combining techniques,

Proc. IRE 47, 1075-1102.

59-9 Abstract: This paper provides analyses of three types of

diversity combining systems in practical use. These are:

selection diversity, maximal-ratio diversity, and equal-gain

diversity systems. Quantitative measures of the relative

performance (under realistic conditions) of the three systems

are provided. The effects of various departures from ideal

conditions, such as non-Rayleigh fading and partially coherent

signal or noise voltages, are considered. Some discussion is

also included of the relative merits of predetection and postdetection combining and of the problems in determining and

using long-term distributions. The principal results are

given in graphs and tables, useful in system design. It is

seen that the simplest possible combiner, the equal-gain

system, will generally yield performance essentially equivalent

to the maximum obtainable from any quasi -linear system. The

principal application of the results is to diversity communication

systems and the discussion is set in that context, but many of

the results are also applicable to certain radar and navigation

systems.

Hathaway, S. D. and H. W. Evans (Jan. 1 959) Radio attenuation

of 1 1 kmc and some implications affecting relay system

engineering, Bell Sys . Tech. J. 38, 73-89.

59-10 Abstract: Radio waves at 1 1 kmc are attenuated by rain. In

order to derive rules for engineering radio relay systems at

IT kmc, a one-year experiment was conducted in a region of

frequent heavy rainfall. The attenuation of paths 27 and 12

miles long was measured, together with rainfall at two-mile

intervals along the paths. The instrumentation and the test

results are described, and some implications related to

systems engineering are pointed out.

68
Ikegami, F. (July, 1959) Influence of an atmospheric duct on

microwave fading, Trans. IRE, AP-7, 252-257.

59-11 Abstract: The results of continuous observation of a duct

carried out utilizing a tower 312 meters high are presented

together with those of measurements of microwave fading

conducted simultaneously.

The variation of duct height with time, as well as the

influence of the duct on fading for a horizontal and an oblique

propagation path, are investigated in detail.

A ray-theoretical analysis is given, indicating that

fading may be attributed to the divergence or the convergence

of radio waves and to the interference of two or more rays,

caused by existence of a duct, or, more generally, of nonlinear

M-profile.

A comparison of calculation with experimental results

shows that many of the characteristics of microwave fading

are well explained by means of this interpretation.

Johler, J. Ralph and Lillie C. Walters (May, 1959) Mean absolute

value and standard deviation of the phase of a constant vector

plus a Rayleigh -distributed vector, NBS J. Res. 62, 183-186.

59-12 Abstract: The mean absolute value of the phase and the standard deviation of the phase of a constant vector plus a Rayleigh'

distributed vector are determined by an evaluation of the

first and second moment integrals of the probability distribution for various values of average relative intensity of the

random Rayleigh -distributed component. The results of a quadrature evaluation of the integrals are tabulated over a wide range of values of average relative intensity (k = 0.010

to 1, 000).

69
Kawazu, Sukemoto, Shusuke Kato, and Kazuo Morita (June 1959)

Over-sea-propagation of microwave and anti - reflected- wave

antenna, Reports of E. C. L. , Japan, 7\_ 171-191.

59-13 Abstract: The fading mechanism encountered for microwave

over-sea, line-of-sight paths are described and compared

with experimental observations. Distributions are given for

the sum of a direct wave, a specularly reflected wave and a

diffusely reflected wave for uniformly distributed relative

phases. An anti-reflected wave antenna is described which

consists of a vertical array spaced so as to provide an

antenna pattern null in the direction of the reflection point.

The theoretical and experimental performances of the antennas

are compared.H.T.D.

McGavin, Raymond E. , and Leo J. Maloney (1959) Study at 1, 046

megacycles per second of the reflection coefficient of

irregular terrain at grazing angles, NBS J. Res., 63D,

235-248.

59-14 Abstract: An experimental determination of the reflection

coefficient over rough terrain is reported. The reflected

signal received over rough terrain is considered to be made

up of two components, one that is a specular component and

the other a Rayleigh-distributed component. Where one terminal is low, the Rayleigh component is considered to be

small with respect to the specular component but increases

in relative magnitude as the height of the lower terminal

increases. A terminal height is reached where the specular

component is no longer significant, and the reflected energy

is essentially Rayleigh-distributed. A terminal height is

quickly reached above which the mean value of the reflected

energy is relatively constant, of a low value, and independent

of the grazing angle.

Men', A. V., S. Ya„ Braude, and V. I. Gorback (1959) Fluctuations of

the phase front in the propagation of decimeter waves over the

surface of the sea, (in Russian), Dokl. Akad. Nauk SSSR, 125 , 59-15 1019-1022.

70
Men.', A. V., S. Ya„ Braude, and V. I. Gorbach (June 1959) Experimental investigation of phase fluctuations of centimeter waves

propagated over the sea surface (in Russian) , Izvestia

Vysshikh Uchebnykh Zavedenii, Radiofizika, 2, 848-857.

59-16 Abstract: Report on results of experimental measurement of

the fluctuations of phase fronts during the propagation of vertically polarized radio waves over the sea surface. The frequency employed was 3000 Mc/s and the experiments were

carried out under various meteorological conditions during

July-Sept, and Oct. -Dec. , over a fixed sea route having a length of 33 km. The differential method of measurement was

employed, in which the fluctuations of the phase differences of

the signals received by spaced antennas were employed to

determine the intensity and the decor relation of the pha.se

fluctuations at various points of the wave front. Fixed transmitting and receiving antennas were used. In order to reduce

the effect of the shore refraction, the receiving systems were

situated at 15 to 20 meters from the shore with distances of

2, 5, 10, 30, and 100 meters separating them from the first

(reference) antenna. The error in the measurement of the phase

difference fluctuations was less than ± 1°, even when the amplitude of the received signals varied as much as 60 db. Results

of measurements are shown in 11 figures. -- R.M. (W N Bibliog. 64-6).

Men', A. V., V. I. Gorbach, and S. Ya. Braude (March 1959) Effect

of an interface on the fluctuations of radio waves propagated in

an inhomogeneous medium (in Russian), Izv. Vyss. Ucheb.

Zav. , Radiofizika, 2_, 388-394.

59-17 Abstract: The authors obtain approximate expressions for

determining amplitude and phase fluctuations in the line of sight

and beyond the horizon in connection with propagation in an

inhomogeneous medium over a plane interface. It is shown that

there is substantially no dependence of the intensity of fluctuations on distance, wave length, and altitude in comparison with

the free space case. Computed values are compared with exper

imental data. -- Transl. of authors' abstract. - R.M.

(WN Bibliog. 64-6).

71
Norton, K. A. (June 1959) Transmission loss in radio propagation,

Pt. 2, NBS Tech. Note No. 12, App. I-III.

59-18 Abstract: In an earlier report with this title (53-10) the concept of transmission loss was defined and its advantages

explained. In this report a survey will be made of the transmission losses expected for a wide range of conditions, i. e. , for distances from 10 to 10, 000 statute miles; for radio frequencies from 10 kc to 100,000 Mc; for vertical or horizontal

polarization; for ground waves, ionospheric waves, and tropospheric waves; over sea water or over land which may be

either rough or smooth; and for various geographical and

climatological regions.

Oxehufwud, A. (1959) Tests conducted over highly reflective terrain

at 4, 000, 6,000, and 11, 000 Mc, Trans. Amer. IEE, Parti

78, 265-270.

59-19 The author considers the problem of choosing the optimum

heights of antennas so as to avoid more than one reflecting

surface. Some effects of the variation of atmospheric

refraction are also considered. --HTD.

Semenov, A. A. , and G. A. Karpeiev (Feb. 1959) Investigation of

rapid fading of radio signals at medium distances along the

Earth's surface, Rad. Eng. and Elec. , 4, 43-54.

59-20 Abstract: The results of investigations on the fading of 3 cm

band signals reflected from standard reflectors with surface

propagation in the zone of direct visibility are given. A result

of the investigation is a preliminary estimate of the effect of

the surface on the formation of reflected radio signal amplitude

fluctuations. The result of the work may be useful for passive

retranslation, as well as in radiolocation of ground level targets,

72
Thompson, M. C. , Jr., and H. B„ Janes (July-Aug. 1959) Measurements of phase stability over a low-level tropospheric path,

NBS J. Res., 63D, 45-51.

59-21 Abstract: A knowledge of the statistics of atmosphere -induced

variations in the phase of the received signal (i. e. , variations

in electrical path length) is essential in evaluating the reliability of any system using radio waves for measuring distance

and/or velocity. This paper describes an analysis of phase

variations measured at 9,400 megacycles per second over a 9.4- mile path near Boulder, Colorado, during a 40-hour

period in September 1958. The power spectral density of

these variations is shown to be approximately proportional to

f over a wide range of frequencies throughout the period

of recording. The long-term phase variations are closely

correlated with atmospheric refractivity measurements made

at the path terminals.

Tomlinson, H. T. , and A. W. Straiton (Oct. 1959) Analysis of 3-cm

radio height-gain curves taken over rough terrain, Trans. IRE

AP-7, 405-413.

59-22 Abstract: This report describes the effect of terrain and

meteorological conditions on the height-gain pattern of 3. 2 -cm

radio waves over various short transmission paths. Equivalent

reflection coefficients are obtained and potential reflection areas

are investigated. A study of the time variations in the height

of nulls in the signal strength pattern is made and the relationship between movement of the nulls and the corresponding refractive index distribution is considered.

Ugai, Shigetaka (Aug. 195 9) Statistical consideration of the structure

of atmospheric refractive index, Reports of ECL, Japan, 7,

253-289.

59-23 Abstract: A 300 meter tower is employed to obtain 12 level

samplings of the refractive index gradient on an hourly basis

over a two month period. These are compared with radiosonde data obtained twice a day for the same period. The

resulting distribution of vertical refractive index gradient was

found to be approximately normal. The analysis is then extended to determine the resulting mean and standard deviations

from radiosonde data between 900 and 1000 mb levels on a monthly basis and for 8 geographical locations.—H. T.D.

73
Bean, B. R. , G. D. Thayer and B. A. Cahoon (I960) Methods of

predicting the atmospheric bending of radio rays, NBS J. Res. , 64D, 487-492.

60-1 Abstract: Three methods for predicting the bending of radio

rays when the refractive index profile above the surface layer

is unknown have been developed recently by the authors. These

methods are: a statistical technique for refraction at high

initial elevation angles, estimation of bending from an expoential model of atmospheric refractive index, and a modification

of the exponential model to account for the heavily weighted

effects of anomalous initial refractive index gradients at small

initial elevation angles. Each model is dependent upon the

value of the refractive index at ground level or, in the case of

superrefraction, the additional knowledge of the refractive

index gradient next to the earth's surface. Each method works

best in a particular range of initial elevation angles or meteorological conditions. The height and angular ranges of application of each method are checked by comparison with values

obtained from 77 diverse refractive index profiles representative of wide climatic variation. It is found that the use of

the best of the three methods will always result in a prediction

of the total atmospheric bending within 10 percent for initial

elevation angles from zero to 10 milliradians and to within 4

percent for initial elevation angles greater than 17 milliradians

(~ 1 deg).

Bean, B. R. , and E. J. Dutton (May-June, I960) On the calculation

of the departures of radio wave bending from normal, NBS

J. Res., 64 D, 259-263.

60-2 Abstract: The calculation of nonnormal tropospheric bending

of radio waves is treated in terms of a reduced-to-sea-level

value of the refractive index. This method emphasizes

departures of bending from the average bending for the United

States and consists of visualizing ray bending as consisting of

two parts; an "average" component and a "departure -fromaverage" component. The "average" component comprises

most of the bending and is obtained accurately from refraction

tabulations while the component due to departures is easily

obtained by graphical means.

74
Bean, B. R. , J. D. Horn and A. M. Ozanich, Jr. (Nov. I960)

Climatic charts and data of the radio refractive index for

the United States and the World, NBS Monograph 22, 178 pp.

(Supt. of Doc, U. S. Govt. Print. Off., Washington, D. C.)

60-3 Abstract: The radio refractive index of air, n = 1 + N X 10

is a function of atmospheric pressure, temperature, and

humidity and varies in a systematic fashion with climate.

Included in this Monograph is a compilation of refractive index data. Data listings made up of observations from

45 U. S. surface weather stations for 2 -hour intervals over

an 8 -year period are given. Mean values, maxima, minima,

and standard deviations of the refractive index have been calculated and tabulated for these observations. Additionally,

mean vertical profiles of the refractive index have been prepared for 43 U. S. upper air sounding stations from longterm means of pressure, temperature, and humidity.

Earlier studies of refractive index climate are assimilated and put into perspective. One such study is an extensive

analysis and mapping of the refractive index climate of the

United States. A worldwide radio refractive index climatology

is developed based upon monthly mean observations of pressure,

temperature and humidity.

An important finding of these climatological investigations is the strong correlation of N with height. A reducedto-sea-level value of the index, termed N is used to eliminate this systematic height dependence. The surface value of

N, N may be estimated four to five times more accurately

from c itself.

gcharts of N than from similar -sized charts of N

From climatic charts of NOSN may be estimated at

any given location in the United States Throughout the day

during every season. In addition detailed annual and diurnal

cycles, as well as 8 -year cumulative probability distributions,

are given for 12 representative U. S. stations.

On a worldwide basis, charts of mean N are presented

for both summer and winter season.

Brekhovskikh, L. W. (I960) Waves in layered media, Academic Press,

60-4 New York and London [ Text] .

75
Brilliant, Martin (Sept. I960) Fading loss in diversity systems,

Trans. IRE, CS-8, 173-176.

60-5 Abstract: In a communication system using optimum diversity

combining, the mean signal-to-noise ratio of the combined

signal is the sum of the mean signal-to-noise ratios of the

separate signals. However, the effective signal-to-noise

ratio of the combined signal is less than this. The ratio of

the mean to effective signal-to-noise ratios of the combined

signal is called the fading loss.

The effective signal-to-noise ratio, and hence the fading

loss, depends upon the measure of effectiveness used, which in

turn depends upon the form of information conveyed by the signal.

In a high-quality speech system, the fading loss is shown to

depend principally upon the order of diversity (the number of

signals combined). In a binary communication system, the

fading loss is shown to depend principally upon the mean

signal-to-noise ratio of the separate signals. The system

design considerations in these two cases are therefore different.

Flock, W. L. , R. C. Mackey and W. D. Hershberger (May, i960)

Propagation at 36, 000 Mc in the Los Angeles basin. Trans.

IRE, AP-8, 235-241.

60-6 Abstract: Fading characteristics at 36 kmc over a line -of

sight path in the Los Angeles basin have been shown to be

closely correlated with meteorological conditions, particularly

with the relatively persistent, low-level temperature inversion of the area. No positive evidence of the influence of

atmospheric pollutants has been found, but it has been shown

that suitably located microwave paths can be of value for

locating and monitoring temperature inversions when they

are accompanied by sufficient variation in water -vapor content. The relation of diurnal variations in propagation characteristics to diurnal variations in the temperature inversion

and in atmospheric turbulence indicate that the refraction

mechanism is the predominant one in causing the observed

large fading amplitudes. The view is further strengthened

by the relatively noncritical relation of fading to the proximity

of the inversion layer.

76
Kuhn, U. (Oct. 1960) Space -diversity measurements on a broadcast

link with optical range (in German) Nachrichtentechnik, 10,

430-434.

60-7 Abstract: Measurements of received levels are reported for a period of 21 months, using a 1.3 Gc/s system, an 82 km path

and two aerials with 2 50 \ vertical spacing. Marked reductions

of long and short term variation effects are shown. Measurements of input signals versus aerial height indicate a small

reflection coefficient and show bad agreement with theoretically

predicted values. (EE Abstract 4221, July 1961 -- AR).

Oguchi, Tomohiro (Sept. I960) Attenuation of electromagnetic wave

due to rain with distorted raindrops, J. Radio Res. Labs.

(Tokyo) 7_j_ 467-485.

60-8 Abstract: The total cross-section of a spheroidal particle

of any material with small eccentricity is derived by the

solution of scattered field which is expressed as the firstorder approximation of drop deformation. Then, by the use

of the theoretical value of eccentricity of raindrops falling at

terminal velocity, the total cross -sections of distorted raindrops for vertically and horizontally polarized plane waves are

computed at 8.6 mm wave-length, and the relation between the

attenuation and the rate of precipitation is obtained. From

these curves, greater attenuation is expected theoretically in

case of horizontal polarization.

Pierce, J. N. , and S. Stein (Jan. I960) Multiple diversity with

nonindependent fading, Proc. IEE 48, 89-104 App. III.

50-9 Abstract: Previous analyses of diversity techniques are ex- tended to include the performance of an optimum (maximalratio) combiner in the case of nonindependent signal fading

fluctuations, for an arbitrary number of diversity branches.

The analysis includes the general possibility of correlations

among the quadrature components of the various signals. Some

computational simplifications for certain cases of physical

interest are given, as well as a specific application to two

problems in digital communications.

77
Saxton, J. A. (I960) Propagation a. travers la troposphere, L'Onde

Electrique 40, 505 -514. (Propagation through the troposphere).

60-10 Abstract: A brief histofy of experimental investigations of

tropospheric propagation is presented. The conclusions to

date and the major problems remaining are described. —H. T. D.

Thompson, M. C. , Jr. , H. B. Janes, and A. W. Kirkpatrick

(Jan. I960) An analysis of time variations in tropospheric

refractive index and apparent radio path length, J. Geophys.

Res. , _6_5_L 193-201.

60-11 Abstract: The National Bureau of Standards has been conducting a series of measurements for a study of the characteristics

of the turbulent lower atmosphere and its effect on the accuracy

of radio direction -finding, guidance, and geodetic measurement systems. The results of three experiments are presented, one consisting of recordings of refractive index and

apparent path length variations at 9400 Mc/s over a 15.5-mile

path on Maui, Hawaii and the other two consisting of similar

measurements made over a 9.5-mile path near Boulder,

Colorado. The correlation of refractive index and apparent

path length fluctuations is discussed as well as the power

(variance) density spectra of both variables.

Thompson, Moody C. , Jr., Harris B. Janes, and Frank E. Freethey

(Feb. I960) Atmospheric limitations on electronic distancemeasuring equipment, J. Geophys. Res., 65, 389-393.

60-12 Abstract: In recent years various instruments and techniques

have been developed for measuring distances electronically.

The accuracy of such measurements depends on the accuracy

with which time and the velocity of propagation of radio waves

can be determined.

78
The National Bureau of Standards, under the sponsorship of the Air Force Ballistic Missile Division, has been

studying the effects of atmospheric turbulence on the performance of radio distance- and/or velocity-measuring systems.

Many of the data collected in this study are applicable to the

problem of determining the accuracy of radio surveying

methods, Long-term variations in the apparent length of a 15.5-mile path in Hawaii are shown, along with the effects of

correcting for the atmospheric refractive index observed at

2 to 5 points along the path.

Troitskii, V. N„ (Dec. I960) The propagation of centimetre waves on

long-distance mountain routes, Rad. Eng„ and Elec. , 5, 6l-69o

60-13 Abstract: This article is concerned with the fading of centimetre

and decimetre waves on long-distance mountain routes. Experimental data on the fading on three mountain routes in Central

Asia are givena Conclusions are made concerning the nature

of the fading on mountain routes using the long-distance tropopheric propagation of ultra-short waves.

Barsis, A. P. , and M„ E. Johnson (FebD 1961) Prolonged spacewave

fadeouts in tropospheric propagation, NBS Tech. Note No. 88.

61-1 Abstract: This paper contains the results of studies performed

during the last several years on the short-term variability of

tropospheric signals received over within-the -horizon paths.

Signal variations of this type have been termed "prolonged

space -wave fadeouts, " as they are mainly characterized by

reductions in signal level to many decibels below presumably

constant values determined from geometrical optics methods.

The data described here wereobtained from measurements

over propagation paths in the Pacific Coast region of Southern

California, and the continental region of Eastern Colorado.

Fadeouts are analyzed as a function of carrier frequency, path

characteristics, and meteorological parameters. The study

also includes an evaluation of fadeouts observed over a path

using a mountain peak as a diffracting knife-edge like obstacle

between transmitter and receiver.

79
Beard, C. I. (1961) Coherent and incoherent scattering of microwaves from the ocean, Trans. IRE AP-9 , 470-483.

61 -Z Abstract: This report, the third in a series, summarizes

experimental studies of microwave over -ocean propagation

on line -of- sight paths. Measurements at 5.3, 3.2, and 0.86

cm wavelength in 1955, in the Gulf of Mexico, between two

oil drilling platforms one mile apart are compared with the

results of the phenomenological model developed earlier.

The total field was measured at maxima, and minima of the

interference patterns using a sequence of receiver beam

widths. The scattered field alone was measured by means of a narrow beam. The 1955, Gulf of Mexico data, are consistent with the previous 1953, Golden Gate data, in regions of

overlap of certain parameters, and provide extended coverage

for other values under different conditions.

7 -1

Braude, S. Ya. , I. E. Ostrovskii, and F. S. Sanin (Jan. 1961) Use of

the concept of negative equivalent Earth radius for estimating

strong refraction of radio waves (in Russian), Izvest. Vyssh.

Ucheb. Zaved„ Radiofizika, 4, 67-73.

61-3 Abstract: The concept of the negative equivalent earth's radius

is introduced in the well known rays alignment method to be

applied to the case of the positive refraction: dn/dh - 1, 57. 10 ' m

(n being the refractive index, h - height above earth's surface).

The earth's sfericity is taken into account and Frenels formulas

are used for the field calculations. The problem comes to the

plane boundary one by the introduction of the corresponding

reduced heights. Formulas and curves are given for the heights

of the interference maximums versus the values of the negative

equivalent radius at the given distance from the source of radiation. All calculations are carried out with the assumption

that there exists a constant gradient of the refractive index in a sufficiently thick atmospheric layer. (WN Bibliog. 64-6).

80
Dawson, G. (1961) A space aerial diversity reception technique for

microwave radio relay systems, Proc. Microwave Seminar,

Tokyo, I_, Doc. No. 4, 86-101.

61-4 Abstract: Experience with space diversity reception systems is

recounted. The specification of a dynamic space diversity system

in terms of antenna spacing and combiner operation is described

for microwave paths subject to fading due to multipath or atmospheric ducts. -- HTD.

Dutton, E. J. (June 1961) On the climatology of ground-based radio

ducts and associated fading regions, NBS Tech. Note 96, 38

pp. , (Office of Tech. Serv. , U. S. Dept. of Commerce,

Washington, D. C.)

61 _5 Abstract: An atmospheric duct is defined as occurring when

geometrical optics indicates that a radio ray passing upwards

through the atmosphere is sufficiently refracted that it travels

parallel to the earth's surface. Maximum observed incidence

of ducts was determined to be 13%, 10%, and 5% by analysis

of three to five years of radiosonde data for a tropical,

temperate, and arctic location, respectively. Annual maxima

are observed in the winter for the arctic and summer for the

tropics. Arctic ducts arise from ground based temperature

inversions with the ground temperature less than -25 C;

temperate zone ducts arise from radiation inversions and

accompanying humidity lapse; while tropical ducts occur with

slight temperature and humidity lapses when the surface

temperature is 30 C and greater. The mean initial elevation

angle of a radio ray trapped by these ducts is found to be about

3 mr, with the maximum value about 5.8 mr. The steepest

gradient of N observed is -420 N units /km. Observed ducts

trap radio-waves of frequency > 1 kMc at all locations for at

least 50% of the time.

Fading regions arising from abnormal defocussing

of radio -rays passing from an elevated antenna down through

the duct to a ground-based receiver are analyzed. The horizontal extent of these regions is determined for the same

arctic, tropic, and temperate conditions given above.

81
Dutton, E„ J„ , and G. D. Thayer (Oct. 1961) Techniques for computing

refraction of radio waves in the troposphere, NBS Tech. Note

No. 97.

61-6 Abstract: Eight methods of computing atmospheric refraction

of radio rays are discussed with appropriate theoretical background. These methods are:

(1) The high-angle, or astronomical, refraction case

(2) The statistical method

(3) The low-angle, or terrestrial, refraction case

(Schulkin's method)

(4) The four -thirds earth model

(5) The exponential model

(6) The initial gradient correction method

(7) The departures -from -normal method

(8) A graphical method (Weisbrod's and Anderson's

method).

Sample computations are included for each of the above methods,

Ikegami, F. (1961) Estimation of short interruption due to fading in

microwave relay system, Proc. Microwave Seminar, Tokyo

I, Doc. No. 8, 59-71.

61-7 Abstract: An empirical method is presented for estimating the

duration of deep fades for microwave line of .sight paths. -HTD

Jasik, H. (1961) Antenna Engineering Handbook, McGraw-Hill, New York

61-8 [ Text] .

82
Kakita, K. (1961) Space diversity reception in microwave relay systems,

Proc. Microwave Seminar, Tokyo I, Doc. No. 9, 102-120.

61-9 Abstract: A brief explanation is presented of the equipment

and principles involved for a space diversity system. Phase

combining is employed, requiring both phase detection and

phase shifting circuits. - HTD

Kirby, R. S. , P. L. Rice, and L. J. Maloney (Oct. 1961) Characteristics of point-to-point tropospheric propagation and siting

considerations, NBS Tech. Note 95, 102 pp. (U.S. Dept. of

Commerce, Off. of Tech. Serv. , Washington, D. C. 20234).

61-10 Abstract: This Technical Note presents the fundamental

characteristics of tropospheric propagation, with particular

application to point-to-point telecommunications.

The concept of service probability is introduced, and its

application to the planning of tropospheric circuits is discussed.

This concept provides an objective means for taking into

account the variables and uncertainties connected with a planned

circuit so that a reasonable balance can be made between the

cost of installation and operation, and the probability of success.

Principles of siting based on taking advantage of favorable

technical characteristics of the sites, and on associated considerations such as radiation hazards, are discussed.

Simple methods of making preliminary estimates of performance adequate for field use are presented.

83
Kitchen, F. A., W. R. R. Joy, and E. G. Richards (May, 1961) Some

factors influencing 3 cm radiowave propagation oversea

within and beyond the radio horizon, Proc. IEE, Part B, 108,

257-263o

61-11 Abstract: The results of a number of short term oversea

measurements of the variation of received signal level with

range from a 10 Gc/s transmitter are presented. It is shown

that the variation of signal level within the horizon was rarely

that expected for propagation through an atmosphere having a uniform refractive index gradient. Signal losses of from 5 to

30 db frequently occurred well within the horizon, these losses

being recovered when the range between transmitter and

receiver was sufficiently reduced. A well defined interference

pattern usually occurred in the region of reduced signal level.

Some data on the variation of refractive index with height up to

about 700 ft. above sea level were gathered using a radio sonde

and a captive balloon, but the detail was not sufficiently fine to

enable a direct relationship to be established between signal

losses within the horizon and the occurrence of irregularities

in the refractive index profile at low elevations.

A direct relationship was found to exist between the signal

level within the horizon and that propagated well beyond the

horizon into the extra diffraction region.

LaGrone, A. H. , and C. W. Chapman (Sept. 1961) Some propagation

characteristics of high UHF signals in the immediate vicinity

of trees, Trans. IRE, AP-9, 487-491.

61-12 Abstract: Results are reported of measurements made at very

low angles of 2880 -Mc vertically-polarized signals over wooded

areas, with the elevation angle to the transmitter the principal

variable. The effects of one tree and of many trees on the

apparent location of a signal source, as determined with a narrow-beam antenna, are reported. A hypothetical directionfinding system is assumed and its pointing characteristics

determined.

84
Men', A. V. (Oct. 1961) Time (spectral) characteristics of phasedifference fluctuations occurring in the propagation of radio

waves in the troposphere, Rad. Eng. and Electronic Physics,

6, No. 10, 1451-1459.

61-13 Abstract: Average "statistical" spectral characteristics of

phase- difference fluctuations, obtained from experimental

measurements over sea water, of fluctuations on a wavelength

X = 10 cm and on a fixed path 33 km long, are given for a wide

frequency interval.

The data obtained pertain to the case of "transverse"

correlation with different distances between receiving antennas

(bases) b, ranging from 2 to 100 m, corresponding to different

ratios d/i < 1 (i - characteristic correlation scale). The

measurements were carried out at the illuminated region as well as in the penumbral and shadow regions.

Norton, K. A., J. W. Herbstreit, H. B. Janes, K. O. Hornberg,

C. F. Peterson, A. F. Barghausen, W. E„ Johnson, P. I. Wells, M. C. Thompson, Jr., M. J. Vetter, and A. W.

Kirkpatrick (Nov. 1961) An experimental study of phase

variations in iine-of -sight microwave transmissions, NBS

Monograph 3 3, 90 pp, (Supt. of Doc. U. S. Goy't. Print. Off.

Washington, D. C.)

61-14 Abstract: During 1956 an experiment was conducted at

Maui, Hawaii, to study the time variations in the phase of

arrival of microwave signals propagated over a 15-mile

line-of-sight path and the time variations in the phase difference of signals originating at a common antenna and received at two points on a horizontal baseline normal to the

propagation path. These time variations are analyzed in

terms of their serial correlation functions and power density

spectra for different times of day, and for several baseline

lengths ranging from 2.2 to 4, 800 feet. The slope of the power

spectra and the total variance of phase difference variations

are shown to be dependent upon baseline length. In some

instances there was evidence of a diurnal cycle in total variance of both phase and refractive index, with larger variances

during the day time, but in other instances this diurnal effect

85
was not detectable. The slope of the phase spectra appeared

to be independent of time of day or meteorological conditions.

The long-term variations in single-path phase were well correlated with variations in the mean value of refractive index

measured at 5 points along the path.

Turin, George L. (July 1961) On optimal diversity reception, Trans.

IRE IT -7, 154-166.

61-15 Abstract: The ideal probability- computing M-ary receiver is

derived for a fading, noisy, multidiversity channel, in which

the link fadings may be mutually correlated, as may the link

noises. The results are interpreted in terms of block diagrams

involving various filtering operations. Two special cases,

those of very fast and very slow fading, are considered in

detail.

Ugai, S. (1961) Studies on microwave propagation within line -of- sight distance,

Proc. Microwave Seminar, Tokyo, I, Doc. No. 6, 30-43.

61-16 Abstract: The fading mechanisms for microwave line of sight

paths are classified as k-type and duct type fading. The characteristics of each type are described in terms of the path geometry and transmission frequency. - HTD

Ugai, S. (May-June 1961) Characteristics of fading due to ducts and

quantitative estimation of fading, Rev. of ECL, Japan, % p. 319-

61-17 Abstract: As a result of long-term propagation tests carried

out on four frequencies simultaneously, it has been clarified

that microwave fading due to the irregular distribution of the

refractive index of the air has two modes of variation - longperiod variation and short-period variation. The characteristics

of each have been described.

The quantitative relation between these two variations was

found experimentally. It has been brought to light after considerations by geometrical optics and experimental analysis that

the long -period variation is closely related to the statistics of

the distribution of the refractive index of the air, which can be

obtained by radiosonde data for the method of estimating the

fading ranges in UHF and SHF bands for all seasons and various

places is described.

86

..
Anastassiades, M„ A„ , L, N. Karapiperis, N. K. Kariambas, and P. G.

Paraskevopoulous (May 1962) Prediction of the field strength

fading forms by means of weather situations, Geofisica Pura e Applicata, 52_, 143-152.

62-1 Abstract: In this study the different forms of the electromagnetic

field strength recordings at the Thera-Vrete microwave link are

examined, in comparison with the corresponding weather situations prevailing over that area. According to the amplitude of

fluctuations, the different forms of recordings have been classified in three basic types A, B, C and the annual frequency of

the appearance of these types has been observed. Finally, the

influence of weather situations on radio wave propagation was

examined and it has been found that in most cases a close

relationship exists between weather situations and the different

fading forms of the electromagnetic field so that a prediction

of the fading form may become possible by means of the

weather forcast.

Arsen'ian, T„ I., and A. A. Semenov (Oct. 1962) Comparison of statistical characteristics of fluctuations in direct and reflected

fields of microwave signals in the troposphere, Rad. Eng. and

Elec. Phys., 7, 1573-1576.

62-2 Abstracts The report presents the experimental results of

comparison of the statistical characteristics of fluctuations in

the direct and reflected fields of microwave signals under

identical or similar propagation conditions. It is shown that

the time autocorrelation functions of fluctuations in the direct

and reflected signals coincide. The space autocorrelation

functions (transverse) undergo oscillations which are similar

in nature in the direct and reflected signals^. The experimental

results are compared with the theoretical behavior of the space

correlation for the special case of the correlation function for

fluctuations in the refractive index of the medium in the form

of a Gaussian curve.

87
Barsis, Albrecht P. and Mary Ellen Johnson (1962) Prolonged spacewave fadeouts in tropospheric propagation, NBS J. Res. , 66D,

681-694.

62-3 Abstract: This paper contains the results of studies performed

during the last several years on the short-term variability

of tropospheric signals received over within-the -horizon paths

in Colorado and California. Signal variations of the type observed over such paths have been termed "prolonged space

wave fadeouts." They are analyzed as a function of carrier

frequency, path characteristics, and meteorological parameters,

The study also includes an evaluation of fadeouts observed

over a path using a mountain peak as a diffracting knife-edge

obstacle between transmitter and receiver.

Principal results show a stronger diurnal trend of

fadeout incidence in continental climates than in maritime

climates. A significant dependence of the fadeout characteristics on the refractive index structure has been observed in

maritime climates.

In general, fadeouts tend to be more frequent but of shorter

duration for higher frequencies. There are also indications

that the occurrence of fadeout is well correlated on vertically

spaced antennas. Thus conventional space diversity techniques

may not be effective to increase the reliability of systems

operating over within-the -horizon paths.

Bean, Bradford R. (1962) The radio refractive index of air, Proc.

IRE 50, 260-273.

62-4 Abstract: This is a tutorial paper. The derivation of the

classical Debye expression for the radio refractive index is

reviewed. Recent determinations of the constants in this

expression are reviewed and the conclusion reached that

differences between constants are small compared with the

error in using standard, meteorological data in the formula.

The various transformations of refractive index data are

discussed as a natural result of the model assumed for its

height distribution. The effect of the use of the various units

is illustrated by examples drawn from radio climatology and

the refraction of radio waves.

88
Beckmann, Petr (1962) Statistical distribution of the amplitude and

phase of a multiply scattered field, NBS J. Res., 66D, 23 1-240,

62-5 Abstract: The probability distribution of the amplitude and

phase of the sum of a large number of random two-dimensional

vectors is derived under the following general conditions: Both

the amplitudes and the phases of the component vectors are

random, the distributions being arbitrary within the validity

of the Central Limit Theorem; in particular, the distributions

of the individual vectors need not be identical, the amplitude

and phase of each component vector need not be independent

and the distributions need not be symmetrical. The distributions formerly derived by Rayleigh, Rice, Hoyt, and

Beckmann are shown to be special cases of this distribution.

Fukushima, M. , H. Iriye, and K. Akita (Sept. 1962) Spatial distribution

characteristics of atmospheric refractive index from helicopter

and kytoon observations, J„ Rad„ Res. Lab. (Japan), % 369-383,

62-6 Abstract: Atmospheric refractivity profiles, elevated inversion

layer characteristics and turbulence spectra were observed at

elevations up to 2, 000 m MSL by the use of a helicopter and a kytoon, during August, I960, July to August and November , 1961. It was found that the value of k of the earth's effective

radius ka varied 1.52 (August, I960), 1.59 (July-August, 1961),

to 1.30 (November, 1961). Large-scale elevated inversion

layer characteristics were obtained with the extraordinarily

intense and stable signals in UHF beyond-the -horizon propagation. The turbulence spectra nearly approach a -2 power law

at high wave numbers.

89
Funakawa, Kenji and Joji Kato (Sept 196Z) Experimental studies of

propagational characters of 8.6 mm wave on the 24 km path,

Jo Radio Res. Labs. 9, 351-367.

62-7 Abstract: The propagational experiments of 8.6 mm wave on

the 24 km path have been carried out nearly all the year round.

From the results of the rain attenuation measurement, an empirical method was developed for the estimation of the longterm distribution of rain attenuation. During no-rainfall period, the fading range is large in the morning and about midnight in summer. The estimated value of absorption by water

vapor is somewhat larger than the value measured by Texas

University.

There is fairly noticeable correlation between the fading range and the appearance of temperature inversion in the

atmosphere.

Gossard, E. E. (May 1962) The reflection of microwaves by a refractive

layer perturbed by waves, Trans. IRE, AP-10 , 317-325.

62-8 Abstract: The power spectra of amplitude and slope for several

cases of internal waves on a radio refractive layer are shown

and the implication of these waves for radio and radar coverage

is discussed. The angular reflection patterns are derived for

rough layers and the beamwidths in elevation and azimuth are

obtained. The amplitude, frequency, wavelength and velocity

of atmospheric waves are described, and the possibility of

such waves acting as very rapidly moving reflectors is discussed. It is concluded on the basis of present observations

of wavelength, amplitude, and phase velocity of atmospheric

internal waves that they are not likely to be a source of very

rapidly moving reflections such as were observed by Waterman

at microwave frequencies.

90
Gough, M. W. (July 1962) Propagation influences in microwave link

operation, Brit. J. IRE, 24, 53-72.

62-9 Abstract: Basic characteristics of ground-to-ground propagation in the frequency band 50 - 10 000 Mc/s are discussed,

with emphasis on the operation of point-to-point radio links.

Practical applications of such knowledge are illustrated by

appraisals of the use of flat radio mirrors for circumventing

mountain obstructions on microwave radio links, and of the

capabilities of large-aperture aerials and space-diversity

systems in reducing fading. Ground reflections are shown to

be a key factor in the performance of very short wave radio

links and the influence of inhomogeneities in the lower atmosphere is also stressed. It is pointed out how statistical

analysis' of temporal and spatial signal strength variations

can often reveal the nature of the propagation mechanism at

work, while at the same time pointing the way to improvements

in circuit reliability.

Kahn, L. R. (1962) A time diversity technique for speech transmission

over rapidly fading channels (Echoplex), IRE Int. Conv. Rec„

10 , Part 8, 157-160.

62-10 Abstract: The Echoplex system is restricted to systems having

a high degree of frequency repetition, such as voice or music.

The speech spectrum is split up by bandpass filters and a progressive time delay is applied to each portion of the spectrum before being modulated on to the carrier. At the

receiving end decoding equipment delays the various speech

segments by such amounts as to make the time delay for all

equal. The signals are then fed to a combiner, which may be

a ratio squarer or linear combiner. Advantages are: (1)

effective anti-fade characteristics; (2) peak-to-average ratio

of the Echoplex encoded wave is considerably smaller than a normal speech wave, giving 6 dB improvement in s/n ratio;

and (3) privacy. (--C. Van der N. , EE Abstract 3320, March

1963).

91
Lewin, L. (July 1962) Diversity reception and automatic phase

correction, Proc. IEE Part B, 109 , 295-304.

62-11 Abstract: The interference between the direct ray and a ground -reflected ray gives rise at the receiver of a communication link to a sinusoidal field pattern in the vertical plane

consisting of nodes and maxima. The position and pattern

wavelength of this field depend on the receiver and transmitter

heights and spacing and on propagation conditions in an effective

curvature parameter, C. This parameter varies in time and

is the cause of most fading at a single antenna. Its upper

limit, which may be as high as 2 . 5 for a small percentage

of the time, determines minimum antenna heights for lineof-sight transmission under extreme conditions. C is normally

about 3/4. Its range of variation determines the optimum

spacing of a pair of diversity antennae, and suitable design

formulae are given. Experiments using a pair of mirrors, a varying transmitter frequency, and photographs of oscillograph

traces indicate an extreme lower value of C over water of

-1.5. A moving -film display shows that conditions can vary

rapidly from minute to minute, although at other times the

display is steady for hours at a time.

An automatic phasing junction has been designed for

insertion in the feed from two diversity antennae, the drive

for the phasing element being taken from the receiver. A

combined signal nowhere smaller than the greater of the

received signals is obtained from the combining element, and

when the diversity spacing is chosen with regard to the extreme

values of curvature obtained on the path, an excellent overall

response is ensured. Some preliminary figures are given for

the performance of an improved combining network and phase

control apparatus operating in conjunction with a height -diversity

microwave system over a 69-mile overwater path.

92
Marukawa, T. (Aug. 1962) Surface roughness and effective reflection

coefficients of the sea in 9 Gc/s-band wave propagation, (in

Japanese), J.' Inst. Elec. Comm. Engrs. (Japan), 45, 1071-

1075.

62-12 Abstract: A report of measurements of the surface roughness

and the effective reflection coefficient of the sea for 9 Gc/s - band transmissions over a 5. 75 km path at the entrance to

Tokyo Bay. The values of p , the reflection coefficient,

were obtained by the aerial height gain pattern method. The

measurements of the sea waves were made about 500 m from

the reflection point of the radio waves. The results obtained

show that the bigger the sea waves are, the smaller is the

value of p , and the range of variation of the p g

values

increases with the height of the waves. Short-period fading

may also result from sea-wave height variation.

McGavin, R. E. (May 1962) A survey of the techniques for measuring the radio refractive index, NBS Tech. Note 99, 3 7 pp.

(Supt. of Doc. U. S. Gov't. Print. Off., Washington, D. C. )

62-13 Abstract: The radio refractive index can be measured either

directly or indirectly. The former method is utilized by

radio frequency refractometers ; the latter method involves

measurement of temperature, pressure and humidity and

conversion to refractive index. In terms of convenience and

accuracy the direct method is superior; however, lack of

universal use of refractometers requires the use of weather

service type of data for the bulk of refractive index structures.

Meteorological sensing is limited mainly by the inaccuracy in

measuring humidity which under ideal conditions appears to

limit the accuracy to ± 1.0 N. Gradient measurements utilizing radiosondes reflects an accuracy no better than ± 3 N units.

Radio frequency refractometers are capable of accuracies as much as an order of magnitude better than that achieved by

meteorological sensors. Lightweight refractometers have

been devised for balloon-borne and dropsonde measurements

reflecting accuracies inferior to the conventional refractometer

but superior to the radiosonde.

93
Men', A. V«, (Feb. 1962) The correlation of amplitude and phase

fluctuations of radio waves propagating in the troposphere,

(in Russian), Radiotekhnika i Elektronika (USSR), 7, 232-238.

62-14 Abstract: The correlation between fluctuations in amplitude

and phase at one and the same point in space in the propagation of radio waves in an inhomogeneous turbulent medium is

investigated. It is shown that the theoretical conclusions

concerning the decor relation of these fluctuations in the

distant region, obtained by Chernov [Dokl. Akad. Nauk, SSSR,

Vol. 98, No. 6, 953 (1954)], assuming an unbounded medium,

are correct. The results of experimental measurements of

the correlation of amplitude and phase fluctuations for propagation in the lower regions of the troposphere both in the

irradiated region and in the region hidden by the earth's

curvature are given. (RCG - EE Abstract 1038, Jan. 1963).

Norton, K. A., E. C. Barrows, M. C. Thompson, Jr., and H. B.

Janes (Dec. 1962) Variance of radio frequency caused by

atmospheric turbulence in line-of -sight transmissions,

Trans. IRE I- 11, 153-155.

62-15 Abstract: The frequency stability of a radio signal propagated

over a line -of -sight path is reduced by time variations in phase

velocity along the path. This instability caused by the atmosphere will produce errors in frequency measurements made

by averaging a standard frequency transmission over a period

of time T and also in time interval measurements made by

counting the number of cycles of the standard frequency

received during a period of time T. Recent measurements

of the variations in phase of a received signal at microwave

frequencies permit estimation of both types of error as a function of T.

These atmosphere -induced errors are compared to

the errors inherent in the best currently available crystal

oscillators and it appears that the latter source of error is

dominant for line-of-sight paths through the atmosphere.

94
The level and slope of the frequency spectra have been

observed to vary over wide ranges with_time and geographical

location. The spectral form W(f ) ~ f expected on the

basis of the Obukhov-Kolmogorov theory of atmospheric

turbulence has a slope which lies well within the range of

observed slopes for the range of fluctuation frequencies from

1 cycle/day to 1 cps

.

Siddiqui, M. M. (March-April 1962) Some problems connected with

Rayleigh distributions, NBS J. of Res. , 66D, 167-174.

62-16 Abstract: This is an expository paper presenting the following: (1) the origin, and (2) the properties of the Rayleigh

distribution; (3) the most efficient estimators of its parameters; (4) a test of the hypothesis that a set of observations

is from a Rayleigh distribution; (5) the distribution of the

ratio of two independent Rayleigh variates; and (6) the Rayleigh

process derived from a normal process.

Turin, G. L. (March 1962) On optimal diversity reception, II, Trans.

IRE CS-10, 22-31.

62-17 Abstract: In a previous paper the structure of the optimal

multi- diversity receiver for a fading, noisy diversity channel

was determined under the assumption that the memory of the

receiver does not extend beyond the* time interval of the signal

currently being received. The probability of error for such a receiver is determined herein under the following assumptions:

the channel is binary and symmetric; the (Gaussian) noises

in the various diversity links are white and independent; and

the fadings in the various links are Rayleigh distributed and

slow, but not necessarily independent. Detailed curves of

this probability of error are given for various orders of

diversity in the two cases of independent fadings and

"exponentially correlated'11 fadings.

Since the optimal receiver may be difficult to implement,

a more easily implemented "square -law combining" receiver is

also considered, and it is shown that for all practical purposes

this simpler receiver behaves optimally. Finally the effect

of the assumption that the receiver has a short memory is

considered by comparing its performance with that of a longer

memory receiver studied by Pierce and Stein.

95
Weihrauch, H. (1962) The determination of the location of transmitters

for UHF and microwave communication with the aid of a

relief -map model (in German), Wiss. Z. Hochsch. Elektrotech. , 8, 65-74.

62-18 Abstract: The optimum position of UHF transmitters can be

determined on a relief-map model of the receiving area byusing a miniature light source as "transmitter" and photographing the shadowy and illuminated areas. Measurements

proved that there is a good correlation between illuminated

areas and areas of high field strength whereas the actual

field strength can be still considerable in the shadowy parts.

It is proved that the use of a light source as transmitter is

justified and the sources of errors are mathematically analysed.

The effects of the obstacles and the curvature of the Earth is

taken into consideration and the correction factors are presented in diagrams. Radiation patterns of aerials can be

simulated by a mask on the light source. A* brief survey of

other methods of determining the position of UHF transmittersis given. (LGS - EE Abstract 979, Jan. 1963).

Wilkerson, R. E. (1962) Defocusing of radio rays by the troposphere,

NBS J. Res., 66D, 479-485.

62-19 Abstract: When radio rays pass through the atmosphere, they

are defocused due to its presence. This effect is measured by

the divergence coefficient and general formulas are derived for

D , the divergence coefficient of the direct ray, and D , the

divergence coefficient of the reflected ray assuming a smooth

spherical earth. As examples, D and D are shown for some

typical cases with an "exponential'^atmosphere (troposphere).

96
Anderson, E. W. (Feb. 1963) The S.H. F. radio link comes of age,

Point-to -Point Telecomm. (GB), 7, 4-15.

63-1 Abstract: The history of the development of S.H. F. (3000

to 30, 000 Mc/s) microwave communication links is traced

from the early experiments up to the present day„ The present situation is briefly reviewed and some of the factors which

will influence future developments are discussed.

Barrow, Bruce B. (March 1963) Diversity combination of fading

signals with unequal mean strengths, Trans. IRE, CS-11

,

73-78.

53 _2 Abstract: The paper compares several techniques of diversity

combination without placing the usual restriction requiring the

mean signal-to-noise ratios on the various diversity branches

to be equal.

The probability distribution of the postcombination

SNR is calculated for various cases, and it is shown that the

shape of this distribution curve is not greatly affected either

by the choice of diversity technique or by reasonable unbalance

in the mean SNR's on the various diversity branches. Various

diversity techniques are compared by calculating the number of

decibels by which transmitter power would have to be increased

to achieve performance equivalent to that of the maximal-ratio

combiner, which is the optimum. The same comparison is

shown to hold, at the low SNR's that are of greatest practical

interest, for a number of different types of fading, including

Rayleigh fading of unequal mean strengths on the various

branches, correlated Rayleigh fading, and certain non -Rayleigh

types.

Constant-gain combination, which is a generalization of

equal-gain combination, is discussed. It is shown that the

gains in the different diversity branches should be adjusted to

make the noise powers equal before combination.

97
Barsis, A. P. , A. F. Barghausen and R. S. Kirby (Jan. 1963)

Studies of within -the -horizon propagation at 9300 Mc,

Trans. IEEE AP-11, 24-38.

63-3 Abstract: Propagation characteristics of radio signals in the

9300-Mc frequency range were investigated over a 1 13-km

tropospheric within-the -horizon path in Eastern Colorado.

Special attention was given to the short-term fading characteristics of the received carrier envelopes and to the bandwidth

capability of the medium in this frequency range, which was

studied by the comparison of amplitude variations of two CW

carriers separated by 100 Mc in frequency. For this purpose,

correlation coefficients between carrier envelopes as well as the distributions of carrier amplitude ratios were analyzed.

Although these parameters are related, the amplitude ratio

has some advantages as an indicator of selective fading phenomena for within-the -horizon paths.

By sampling the 9250 and 93 50 Mc instantaneous

carrier amplitudes at the rate of one per second, an over -all

value of 0.91 was obtained for their cross-correlation coefficient. The standard deviation of the amplitude ratios

expressed in db at 9250 and 9350 Mc averaged 0.76 db, with

a maximum hourly value of 1.81 db. These results include

the effect of space diversity, as separate antennas were used

for transmission and reception of the two carriers, but they

support the feasibility of wide -band modulation techniques for

within-the-horizon paths if judged by the statistics of amplitude variations at discrete frequencies at the limits of the

band considered.

Short-term and long-term fading characteristics at

9300 Mc are similar to the ones previously observed on lower

frequencies over this path. An analysis of prolonged spacewave fadeouts in this frequency range resulted in fadeout

depths up to 25 db below weekly transmission loss medians,

approximately log -normal distributions of fadeout durations,

and the expected diurnal variations of fadeout occurrence

typical of a continental climate.

98
Bean, B. R. , V. R. Frank, and J. A. Lane (1963) A radiometeorological study, Part II. An analysis of VHF field strength

variations and refractive index profiles, NBS J. Res. , 67D,

597-604.

63-4 Abstract: This paper discusses the cumulative probability

distributions of field strength for four 200 km VHF paths in

Illinois in terms of a classification of refractive index profiles.

It is shown that extended elevated layers produce signal enhancements of 10 to 25 db above the level observed in unstratified conditions. Assuming the layer characteristics given

by radiosonde data, the best agreement between calculated

and measured values of field strength is obtained using a layer

model with a linear n -profile.

The possible influence of smaller layers is also discussed in relation to the observed results for conditions

judged to be unstratified or well mixed on the basis of sonde

data.

Beckmann, P., and A. Spizzichino (1963) The scattering of electr*omag.

netic waves from rough surfaces, MacMillan Co., New York

63-5 [ Text] .

Franceschetti, Giorgio (Nov. 1963) An approach to tropospheric duct

propagation, Proc. IEEE 51^ 1481-1486.

63-6 Abstract: A modal solution for the em propagation in a spherical stratified troposphere is derived, via the MarcuvitzSchwinger formalism. The approximations due to the small

curvature of the earth are illustrated. The representation of

the sources via the complete set of modal solutions is presented, as well as the excitation factors, computed for the

vertical electric or magnetic dipole. The possible use of

digital and analog computers is highlighted. Future plans for

the work are the computations of a great deal of digital and

analog solutions, and also the study of the influence of the

random variability of the tropospheric refraction index. In

the Appendix, a preliminary case [f (z) = az] is presented.

99
Glasser, W. (April 1963) Present position and development trends of

optical-path radio communication systems, (in German),

Nachrichtentechnik, 13, 123-127„

63-7 Abstract: An account of present-day practice in the field of

optical-path radio communication systems compairing their

performance with that of multi-channel cable systems and

discussing the factors influencing the choice of operating

frequencies, modulation techniques and type of electronic

equipment employed at sender and receiver and at relay points,

The article concludes with a reference to methods of trans - horizon communication without employing fixed relay station

on the earth. (RHB - EE Abstract 12244, Oct. 1963).

Hay, D. R„ , and F. M. Fanaki (March 1963) Experimental technique for

studying reflection coefficients of tropospheric inhomogeneities,

63-8 Canadian J„ of Phys. , 41, 563-567 [ an abstract] .

Hogg, D. C. , R. A. Semplak, and D. A„ Gray (March 1963) Measurement

of microwave interference at 4 Gc due to scatter by rain, Proc.

IEEE, 5J_, p. 500.

63-9 Abstract: An experimental observation is reported of an interference effect caused by rain. The interfering noise signal

arrived at the receiving antenna due to scattering of energy by

a thunder shower. The observed variation with time is presented

for this scatter interference, the associated rainfall rate, and

the noise source. - HTD

Janes , H. B. (Nov. 1963) Correlation of the phase of microwave signals

on the same line of sight path at different frequencies, Trans.

IEEE, AP-11 , .716-717.

63-10 Abstract: The phase and phase difference variations and their

power spectra are presented for 9.2 and 9.4 Gc/s signals received

over a 47 km line e»f sight propagation path.

100
LaGrone, A. H. , P. E. Martin, and C. W. Chapman (Feb. 1963) Height

gain measurements at VHF and UHF behind a grove of trees,

Trans. IEEE, BC-9 , 37-54.

63-11 Abstract: Results are reported of horizontally polarized signal

strength measurements of frequencies of 82, 210, 633, 1280,

and 2950 mcps. The measurements were height gain runs made

behind a grove of trees in full leaf. The site was selected so

that propagation took place over approximately the same path

near the receiver terminal at all frequencies. Measurements

were repeated at several distances. Theoretical analyses are

reported for several assumed cases for comparison with the

field measured data. Exceptionally good agreement was found

in many cases.

Lane, J. A., and B. R. Bean (1963) A radiometeorological study,

Part I. Existing radiometeorological parameters, NBS J.

Res. , 67D, 589-595.

63-12 Abstract: A survey is made of existing radiometeorological

parameters, including those derived from the vertical profile of refractive index, n, and others which involve the concept of thermal stability. Quantitative comparison of radio

and meteorological data confirm the value of N, (the surface

value of [n—l] 10 ) and AN (the difference in value of N and

N at one kilometer) in a wide variety of conditions. For

particular areas, however, it seems desirable to develop

improved prediction techniques using a parameter which is

related to the size, stability, and intensity of elevated layers

in the troposphere.

101
Martin, F„ L. , and F. E. Wright (April 1963) Radar ray refraction

associated with horizontal variations in the refractivity, J. Geophys. Res., 168, 1861-1869.

63-13 Abstract: The relative bending effects on a radio ray of the horizontal and vertical gradient of refractivity are investigated. With

the use of ray-curvature formulae developed by Wong, convenient

differential equations governing the three-dimensional ray path are

derived. It is also shown that the ratio of "horizontal to vertical"

bending effects is a maximum when the ray is propagated in the

vertical plane containing the horizontal gradient of refractivity.

In a two-dimensional example, computations of path height as a function of horizontal distance are obtained by numerical integration. For this purpose, a regional space -time averaged exponential

model drawn from climatological studies of Bean and Thayer is

used. Even though this smoothed model and an extreme version

of it derived synthetically by increasing the horizontal gradient

everywhere by a factor of 10 have comparatively strong horizontal

gradients, the "horizontal bending" effect is virtually negligible.

It is not implied, however, that this conclusion is necessarily

applicable to an atmosphere exhibiting small-scale fluctuations

in the refractivity pattern. The ray paths corresponding to the

nonhomogeneous model are significantly different from those in

a horizontally uniform atmosphere. The problem of replacing a

nonhomogeneous model by an equivalent horizontally uniform one

is also investigated. The choice of the best uniform atmosphere

depends upon minimizing the r.m. s. height error over a designated horizontal path length, and this in turn requires the specification of several ray-propagation parameters in addition to the

distribution of refractivity.

102
Micheletta, C. (Feb, 1963) Radiowave diffraction on limited areas of

ground, Alta Frequenza (Italy), 32_, 127-132

63-14 Abstract: The problem is examined for the purpose of determining

the reradiated field by a portion of homogeneous and smooth ground,

effectively flooded by both antennas of a line -of- sight link and

having a sharply limited contour with respect to the vertical

projection of the axis of the same link.

Rigorous methods being excluded, since they are applicable

with difficulty even to a flat circular figure, there exists no other

possible way but to integrate the field contributions which are

produced by the surface elements of a curved ground, considered

as Huygens sources.

This procedure is only approximate, since it supposes the

diffraction area to be perfectly conductive and neglects the effects

at the countour of such area.

However, if its dimensions are very large with regard to the

wavelength and if the polarization is horizontal, the obtained

results are not far from truth and may be actually useful for

applications in particular link situations.

In the study, performed for the above mentioned practical

purposes, some questions of a theoretical character have acquired

certain prominence, such as the specification of the so called

"essential domain of reflection", that is of the portion of ground

which mainly contributes to the reflected field and the portion of

the half -period zones, respectively, on flat ground (diffraction

ellipse) and on curved ground. Confronting the diffracted fields

by such zones a possible, new definition of the spherical divergence

coefficient of Van der Pol and Bremmer is deduced.

103
Rainey, R. J., Jr., and D. C. Thorn (July, 1963) A refraction

correction technique which includes nonsymmetric index of

refraction, Trans. IEEE AP-11, 446-450.

63-15 Abstract: The problem of predicting refraction errors in a nonsymmetric, inhomogeneous atmospheric refractive index

distribution is examined, utilizing the basic (vector) differential equation of a ray path. The simplifications made in

the basic equation are based on known atmospheric refraction

characteristics in conjunction with the limitations inherent

in obtaining distributions over a wide region which are valid

for a given time. The assumptions made are 1) n = 1,

2) total bending is small, and 3) the gradient of n along the

ray path is approximately the same as the gradient of n along

the straight line in the launch direction. A fourth assumption,

not mathematically necessary but useful in analyzing actual

situations, is that the gradient of n may be described by regions of constant gradient.

The first three assumptions allow the general threedimensional ray path to be computed in terms of its two plane

ray projections; the fourth assumption yields a mathematically

simple solution for each path.

Siddiqui, M. M. and G. H. Weiss (Nov. -Dec. 1963) Families of

distributions for hourly median power and instantaneous

power of received radio signals, NBS J. Res. 67D, 753-762.

63-16 Abstract: In this paper the gamma family of probability

distributions is studied in connection with the distribution

of hourly median received power or transmission loss. By

taking a mixture of Rayleigh distributions with gamma distributions as mixing distributions the long-term distributions

of instanteous signal power are theoretically derived. These

distributions are evaluated in closed form under several

hypotheses. The question of estimating the parameters is

discussed. Graphs and tables are prepared to facilitate the

application of the theory to the data.

104
Ugai, S. , S Aoyagi, and S. Nakahara (May 1963) Microwave transmission

across a mountain by using diffractor gratings, (in Japanese),

Jo Inst. Elec. Comm. Engrs. (Japan), 46 , 653-661.

63-17 Abstract: This is a report on the diffractor grating method, which

is found to considerably improve the various characteristics of

radio waves propagated over a mountain district. The gain by the

diffractor grating, which is usually built over the top of a diffracting

mountain, is theoretically treated according to the Fresnel-Kirchhoff theory, to give the basis of actual design for the net or the

gratings of diffractor.

Also several experimental results using this diffractor method

are presented, which show great improvements as expected in the

various characteristics, and suggest a considerable advantage of

the use of this method, as compared with the reflector plate method

hitherto used. - KF„

Ugai, S„ , and Y„ Kaneda (May 1963) Statistical evaluation of microwave

attenuation due to rain cells, Rev. Elec. Comm. Eab. , 11, 268-

63-18 Abstract: From statistical investigations of the characteristics

of rainfall, the concept of rain cells was obtained. This paper

describes a statistical method of estimating the attenuation due

to rain in radio relay links on the basis of this concept of rain

cells and a method of determining the optimum path length for

radio relay spans.

Weihrauch, H. (March 1963) Site determination for UHF and microwave

link transmitters with the aid of a relief model, II, (in German),

Nachrichtentechnik, 1_3, 111-114.

63-19 Abstract: For Ptc I see Abstract (62-18). This part discusses

some practical points in connection with work on the model,

including the effect of the surface of the model on the results, and

methods for obtaining the correct spatial distribution of light

transmitted from the lamp. Various methods for obtaining an

estimate of service area from a proposed transmitter are compared and finally some of the applications of the method are

pointed out. (E. A. ; EE Abstract 6496, 1964, May).

105
Burns, W. R. (1964) Some statistical parameters related to the

Nakagami-Rice probability distribution, NBS J. Res. , Radio Science, 68D, 429-434.

64-1 Abstract: Formulas and tables are given for the mean and

standard deviation of R=20 log r where the random variable

r has the Nakagami-Rice distribution. This distribution is of

interest in connection with the short-term fading characteristics

of some received radio fields. A particularly simple formula

for the mean of R is obtained in terms of the well-known

exponential integral function —Ei(—x). Additional information concerning the median and interdecile range of R is also

given.

Cahoon, B. A. , and L,. P, Riggs (Sept„ 1964) Climatology of elevated

superrefractive layers arising from atmospheric subsidence,

ProCo 1964 World Conference on Meteorology, Boulder, Colorado.

64-2 Abstract: Some world wide charts are presented of the seasonal

variations of height and persistance of elevated ducting layers in

tropical and subtropical regions. - HTD

Dougherty, H. T. and L. J. Maloney (Feb. 1964) Application of

diffractions by convex surfaces to irregular terrain situations,

NBS J. Res., Radio Science 68D, 239-250.

64-3 Abstract: Previous solutions by Rice and by Wait and Conda

are combined and extended to provide more readily evaluated

formulas for the diffraction of radio waves by the "rounded

obstacles" encountered in irregular terrain situations. A

comparison with experimental data is also provided.

106
Gilmer, R. O. , R. E. McGavin and B. R. Bean (Sept. 1964)

The response of microwave refractometer cavities to

atmospheric variations, Proc. of 1964 World Conference on

Meteorology, NBS Boulder Laboratory.

64-4 Abstract: The microwave refractometer has been used extensively in the study of the refractive index structure of the

atmosphere. Little work has been done evaluating the sampling

cavity of the refractometer as an accurate measuring probe

of the short-term variations of the atmosphere. Wind tunnel,

water flow tunnel > and free atmospheric tests of the microwave sampling cavities currently in use have yielded information on aspect and velocity sensitivity, and on the spatial

resolution of the cavities,

The tests revealed that the air flow through the sampling

cavity undergoes a transition from laminar to turbulent type

flow at wind velocities in excess of 5 mph. The pressure in

the cavity decreases as the wind velocity increases. The

indicated error due to the pressure drop at 15 C is as high

as 1 N unit at 135 mph for a cavity oriented into the wind.

This error appears to be a function of the aspect of the cavity

relative to the direction of the wind, becoming a minimum at

an angle of ZZyz .

Flow tunnel tests gave direct visual indications of the

flushing time versus the aspect angle of the sampling cavities.

A characteristic flushing length of approximately 2. 5 feet for

complete flushing was measured at as compared to 5. 75

feet at 90°.

These tests revealed the limitations imposed on the

measurement of the structure of the index of refraction by

the sampling cavities. The results have suggested new

possible approaches of construction of the cavity to reduce

the errors due to aspect sensitivity and to increasing the

spatial resolution of the sampling probe.

107
Ikegami, F. (May-June 1964) Radiometeorological effects in propagation over the sea and islands, Rev. Electr. Commun. Labor. , NTT, 12, 5-6, 312-324.

64-5 Abstract: The studies on meteorological factors and propagation over the sea and islands are reviewed. For various

modes of propagation such as line-of-sight, beyond the horizon and mountain-diffraction, special phenomena have been

described which are peculiar to oversea propagation.

The differences' are discussed between overland and

oversea paths, on the refractive index structure of the atmosphere, diurnal and seasonal variations in signal strength, and

occurrence of abnormal propagation conditions.

Nupen, Wilhelm (May 1964) Bibliography on propagation of radio waves

through the troposphere, NBS Tech. Note No. 304

64-6 Abstract: A bibliography of over a thousand abstracts or titles

taken from the literature published between 1902 and 1964. The

subject matter is confined to the effects of the earth's atmosphere

on radio frequency radiation from 10 c/s to 100, 000 Mc/s. -HTD

Oguchi, Tomohiro (Jan. 1964) Attenuation of electromagnetic wave due

to rain with distorted raindrops (Part II), J. Radio Res. Labs.

(Tokyo) 1_L_ 19-37.

64-7 Abstract: In the preceding paper, the total cross-section of a spheroidal particle of any material with small eccentricity

was derived in the first -order approximation of drop deformation, and introducing the theoretical value of eccentricity of

raindrops falling at terminal velocity, the total cross -sections

of distorted raindrops for horizontally and vertically polarized

plane waves were computed at 34.8 Gc/s.

By the use of these cros s -sections, the theoretical

relation between attenuation and the rate of precipitation for

horizontally and vertically polarized plane waves was obtained.

108
The present paper is a continuation of the preceding

one. The total cross -section of a spheroidal particle is derived to the second -order approximation of drop deformation.

The numerical computations for the first- order approximation

are extended from 4 Gc/s to 100 Gc/s.

Under the condition of constant rainfall rate, it is concluded that the difference of attenuation between horizontally

and vertically polarized wave divided by that of vertically

polarized one becomes very small as frequency becomes

higher, except some frequency range, where the raindrops

having major contribution to the attenuation are resonant with

the incident field.

Preikschat, F„ K. (Aug. 1964) Screening fences for ground reflection

reduction, Microwave Journal, 7, 46-50.

64-8 Abstract: This article describes the design of Fresnel diffracting

fences which, when placed in the foreground of one antenna, will

provide a specified reduction in the ground reflected wave for line

of sight paths. - HTD

Saxton, J. A., J. A. Lane, R. W. Meadows, and P. A. Matthews,

(Feb. 1964) Layer structure of the troposphere, Proc. IEE,

III, 275-283.

£4_9 Abstract: A discussion is presented of the manner in which

layer-type echoes may arise and be observed using a 10 cm

radar at vertical incidence; such echoes are due to variations

in the gaseous refractive index and not to water droplets in

clouds or precipitation. Specular reflection and scattering

processes are compared and the conditions indicated when an

echo may be due to one or the other process, although the

applicability of the turbulence theories used to relatively thin

layers needs to be established.

The results of the analysis are discussed in relation

to data obtained from simultaneous soundings of the troposphere

by radar and airborne microwave refractometers. Some

comments are made regarding further experimental and

theoretical investigations of the fine structure of elevated

layers

.

109
Voder L E (Julv 1964) Calculation of groundwave attenuation in the

"

far" diffraction region, Radio Sci. J. Res. NBS/USNC-URSI 68D, 819-826.

64-10 Abstract: This paper presents a graphical method of determining

the groundwave attenuation over a spherical homogeneous earth

in the far diffraction region. The curves are applicable to either

vertical or horizontal polarization and to any combination of

effective earth's radius, electromagnetic ground constants, frequency, path distance, and antenna heights. A criterion is given

that indicates the method may be used not only for far beyond

line-of-sight paths but, in many practical situations, at line -of -

sight or even slightly within. Examples illustrating the use of

the formulas and curves are included.

Wait J R (July 1964) A note op VHF reflection from a tropospheric

' layer. Radio Sci. J. Res. NBS/USNC-URSI, 68D, 847-848.

64-11 Abstract: Some remarks concerning reflection from tropospheric

layers are made with special reference to a recent paper by Bean,

Frank, and Lane on the subject. It is indicated that the finite

vertical extent of the layer must be considered in the analysis.

110
ADDENDUM

Hoyt, R. S. (1947) Probability functions for the modulus and angle of

the normal complex variate, BSTJ 26, 318-359.

A 47-1 Abstract: This paper deals mainly with various "distribution

functions" and "cumulative distribution functions" pertaining

to the modulus and to the angle of the "normal" complex

variate, for the case where the mean value of this variate is

zero. Also, for auxiliary uses chiefly, the distirbution function pertaining to the reciprical of the modulus is included.

For all of these various probability functions the paper derives

convenient general formulas, and for four of the functions it supplies comprehensive sets of curves; further, it gives a

table of computed values of the cumulative distribution function for the modulus, serving to verify the values computed

by a different method in an earlier paper by the same author.

Riblet, H. J. and C. B. Barker (1948) A general divergence formula,

J. Appl. Phys. 19, 63-70.

A48-1 Abstract: A divergence expression for the ratio of energy per

steradian reflected from a smooth curved surface to that incident on the surface is derived. It generalizes previous results

in that the 'source and point of observation may both be at finite

distances from the reflecting surface. No restrictions are placed

on the angles of incidence and reflection except that they be equal.

The only limitation placed on the analytic accuracy of the geometrical result is that the surface be sufficiently smooth so that

the principle radii of curvature are defined at the point of

reflection. It is required, of course, that the wave-length of

the energy shall be small compared to the principle radii of

curvature of the surface, in order that the geometrical result

may be interpreted as a divergence formula. All of the previous

results on this problem known to the authors are derived as special cases. Application of the result in connection with the

spreading of radio waves by the curvature of the earth leads to

somewhat simpler formulas than now available.

Ill
Bremmer, H. (1949) Terrestrial Radio Waves, Elsevier Pub. Co. , New

York. (Text).

A49-1

Hartman, W. J. (I960) Limit of Spatial Resolution of Refractometer

Cavities, J. of Res. NBS 64D , 65-72.

A60-1 Abstract: Filtor factors that determine an upper limit for the

wave numbers for which refractometer measurements can be

used to calculate the spectrum of refractivity are derived in

this paper based on the assumption that the refractometer

s

measure a weighted average of the refractive index in a volume

of air surrounding the center of the refractometer cavity. Two

models are used assuming the weighting function has spherical

symmetry around the center and one model is used assuming the

function has cylindrical symmetry. All models result in a simple

mathematical form which should be easy to use in further theoretical developments.

Naka garni, M. (i960) The m-distribution - a general formula of

intensity distribution of rapid fading, Statistical Methods

in Radio Wave Propagation (ed. W. C. Hoffman), Pergamon

A 60-2 Press, Oxford.

Stratonovich, R. L. (1963) Topics in the theory of random noise,

Vol. I, (translated from the Russian by R. A. Silverman),

A 63-1 A Text.

Beckmann, Petr. (Sept. 1964) Rayleigh distribution and its generalizations, Radio Sci. J. Res. NBS 68D , 927-932.

A 64-1 Abstract: The Rayleigh distribution is the distribution of the

sum of a large number of coplanar (or time) vectors with random amplitudes and uniformly distributed phases. As such,

it is the limiting case of distributions associated with more

general vector sums that arise in practical problems. Such

cases are the following: (a) The phase distributions of the vector terms are not uniform, e.g. in the case of scattering from

rough surfaces; (b) One or more vector terms predominate,

112
their mean square value not being negligible compared to the

mean square value of the sum, e.g. in the case of signals

propagated in cities, meteor-scatter, and atmospheric noise;

(c) The number of vector terms is small, e.g. in radar returns

from several close targets; (d) The number of vector terms

is itself random, e.g. in atmospheric turbulence, meteorscatter and atmospheric noise. The resulting distributions

for these cases and their deviations from the Rayleigh distribution will be considered.

Stratonovich, R. L. (1964) Topics in the theory of random noise,

Vol. II (translated from the Russian by R. A. Silverman),

A 64-2 Gordon and Breach, New York.

GPO 846 . 122 113