Title Page
 Table of Contents
 List of Tables
 List of Illustrations
 Historical background
 Planetary atmospheres
 Theory of the propagation of radio...
 Receiving apparatus of the University...
 Observational procedures
 Jupiter during the first appar...
 Jupiter during the second...
 Saturn, Uranus, and Venus
 Biographical sketch

Title: Studies of radio frequency radiations from the planets
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00098008/00001
 Material Information
Title: Studies of radio frequency radiations from the planets
Alternate Title: Radio frequency radiations from the planets
Physical Description: ix, 161, 1 leaves : illus. ; 28 cm.
Language: English
Creator: Carr, Thomas Deaderick, 1917-
Publication Date: 1958
Copyright Date: 1958
Subject: Radio astronomy   ( lcsh )
Planets   ( lcsh )
Physics thesis Ph. D
Dissertations, Academic -- Physics -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
Thesis: Thesis - University of Florida.
Bibliography: Bibliography: leaves 158-160.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
 Record Information
Bibliographic ID: UF00098008
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000546080
oclc - 13170330
notis - ACX0038


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Table of Contents
    Title Page
        Page i
        Page ii
        Page iii
    Table of Contents
        Page iv
        Page v
    List of Tables
        Page vi
    List of Illustrations
        Page vii
        Page viii
        Page ix
    Historical background
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
    Planetary atmospheres
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
    Theory of the propagation of radio waves in ionized gases
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
    Receiving apparatus of the University of Florida observatory
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
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        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
    Observational procedures
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
    Jupiter during the first apparition
        Page 114
        Page 115
        Page 116
        Page 117
        Page 118
        Page 119
        Page 120
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        Page 129
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        Page 131
        Page 132
        Page 133
        Page 134
    Jupiter during the second apparition
        Page 135
        Page 136
        Page 137
        Page 138
        Page 139
        Page 140
        Page 141
        Page 142
        Page 143
        Page 144
        Page 145
        Page 146
        Page 147
        Page 148
    Saturn, Uranus, and Venus
        Page 149
        Page 150
        Page 151
        Page 152
        Page 153
        Page 154
        Page 155
        Page 156
        Page 157
        Page 158
        Page 159
        Page 160
    Biographical sketch
        Page 161
        Page 162
        Page 163
Full Text





June, 1958

Ai;tOr.. LELI&E22 Fil

The writer expresses his most sincere gratitude to the

Chairman of his Graduate Committee, Dr. A. G. Smith, whose assistance,

advice, and encouragement throughout the course of the project played

a very large part in its success. He also wishes to express his

appreciation to Dr. R. C. Williamson, Chairman of the Physics

Department, whose initial support and continued interest made the

work possible and permitted the establishment of radio astronomy as

an active field of research at the University of Florida.

The writer wishes to thank Dr. J. W. Flowers, Dr. G. C. Omer,

and Dr. D. C. Swanson of the Physics Department faculty for their

advice and encouragement. He is greatly indebted to his colleagues,

Mr. R. J. Pepple and Mr. C. H. Barrow, for their assistance in most

of the phases of the research and also in the preparation of the

illustrations for this dissertation. He also wishes to express his

appreciation to Mr. George Harris of the Physics Department Shop for

his assistance in the construction of antennas, to Mr. J. K. Jackson,

Mr. H. L. Register, and Mr. W. H. Perkins for their assistance in the

maintenance of nightly watches and in the construction of equipment,

to Mr. H. W. Schrader, Mr. C. C. Pennell, Mr. A. L. Garris, and Mr.

R. Warren of the Physics Department Shop for the construction of

antenna components and for other aid, to Mr. M. L. Vatsia and Mr. A.

R. Phillips for photographic assistance, and to Mrs. Barbara Jones

for typing this manuscript.

Finally, acknowledgement is due Dr. Roger M. Gallet of the

National Bureau of Standards, whose suggestion it was that the

inaugural project in radio astronomy at the University of Florida

consist of a study of the newly-discovered radio frequency radiation

from Jupiter.

The writer wishes to express his appreciation for the financial

support of the National Science Foundation, which made much of the

work possible.




ACKNOWLEDGEMENTS ....................... ii

LIST OF TABLES. . . . . . . . . .. ... . vi

LIST OF ILLUSTRATIONS . . . . . . . .... ... vii


The Beginnings of Radio Astronomy . . . . 1
Previous Investigations of Radio Radiation from
the Planets. . . . . . . . . 5

II. PLANETARY ATMOSPHERES. . . . . . . ... .18

Jupiter . . . . . . . . . . . 18
Saturn. . . . . . . . . ... . 21
Uranus and Neptune. . . . . . . ... 22
Venus . . . . . . . . . . . 23
Mars . . . . . . . . . . 24
Mercury . . . . . . . . . . . 25
Pluto . . . . . . . . .. . . 26
Earth . . . . . . . . . . . 26

IONIZED GASES .................. 30

Propagation in the Absence of a Magnetic Field. 31
Polarization in the Presence of a Magnetic Field. 32
Polarization in the Longitudinal Case . . .. 33
Polarization in the Transverse Case ..... .33
Polarization in the General Case . . ... .33
Determination of Magnetic Field Intensity by
Means of Polarization Measurements . . . 3A
Simplified Appleton Polarization Formula. ... 35
Conditions for Reflection of Ordinary and
Extraordinary Components . . . . ... .36
Effects of Collisions . . . . . .. 37
Behavior of Transients Origin; ting within an
Ionosphere . . . . . . . ... 38

FLORIDA OBSERVATORY. . . . . . . ... .40

Project Chronology and Participants. . . .. 40
The 18 Mc/s Broadside Array. . . . . ... 42
Receiving, Recording, and Calibration Equipment
used During the First Apparition. . . .. 49
Calculation of Broadside Array Pattern and Gain. 54
The 22.2 Mc/s Corner Reflector Array . . . 69
A Method for the Measurement of the Pattern and
Gain of Large Antennas. . . . . . ... 79
The 18 Mc/s Yagi Array. . . . . . .. 84
The 27.6 Mc/s Yagi Array . . . . . . 87
The 22.2 Mc/s Polarimeter. . . . . . ... 89
Receiving and Recording Equipment used During
the Second Apparition . . . . . .. 100

V. OBSERVATIONAL PROCEDURES. . . . . . . ... 109


Observational Data .. . . . . . . . 114
Rotational Periods . . . . . . . . 118
The Jovian Ionosphere. . . . . . . ... 127
The C-Day Cycle. . . . . . . . ... 130
Radiation Intensity Distribution . . . ... 133
Waveform Studies . . . . . . . .. 133


Flux Intensity Distributions . . . . .. 135
Correlation with System III Longitude. . . ... 137
Polariieter Measurements . . . . . . 138
The Sunrise Effect. . . . . . . 145

VIII. SATURN, URANUS, A;D VENUS . . . . . . .. 149

Saturn During the First Apparition . . . .. 149
Uranus During the Second Apparition. . . .. 151
Saturn During the Second Apparition. . . .. 152
Venus During the Second Apparition. . . . . 152

LX. SUMMARY ....................... 154

LIST OF REFERENCES . . . . . . . . ... . . 158

BIOGRAPHICAL SKETCH . . . . . . . . .. .... 161


1 LFJTH ('F PH.I.Ur CCABLE. .............. .;



4 POLARIMETER DATA ................... 141




Figure Page

1. Periods of occurrence of 18.3 Mc/s radiation from
Jupiter plotted against longitude of the
central meridian at the time of observation. . 9

2. Periods of occurrence of 22.2 Mc/s radiation from
Jupiter plotted against System II longitude;
data of Burke and Franklin . . . . . .. .12

3. Configuration of the 18 Mc/s broadside array. ... 43

4. View of the broadside array from the southwest. 45

5. Block diagram of system used during first apparition. 50

6. Essentials of calibration circuit . . . ... .52

7. Electronic and recording equipment, first apparition. 55

8. Factors making up the pattern of the 18 Mc/s
broadside array in the east-west vertical plane. 57

9. Factors making up the pattern of the 18 Mc/s
broadside array in the north-south vertical
plane . . . . . . . . . . . 58

10. Diagram for Fb(9) derivation. .......... 59

11. Diagram for F (9) derivation. . . . . . ... 61
12. Diagram for Fd(9) derivation. . . . . . . 62

13. East-west pattern of 18 Mc/s broadside array,
calculated from Eq. (15) . . . . . 64

14. North-south pattern of 18 Mc/s broadside array,
calculated from Eq. (17) . . . . . .. 65

15. Configuration of the corner reflector array . .. 70

16. The 22.2 Mc/s corner reflector array as seen from
the east . . . . . . . . ... . 72

fiiure P iC

1,. Jurn:tLorin o:. for Lhe Z"'.2 M.:,/s :orner refl'l.:-to-
Sr r. . . . . . . . 7.

1_. *.-:--Jur-,d : .et-~- t pat teLT, of th 1e '- .2 2 R. /- .:orn.r
reflector r . . . . . . . . 7

19. Measured north-south pattern of the 22.2 Mc/s corner
reflector array. . . . . . . . ... 78

20. Conmutated record comparing a single-dipole corner
reflector array with a standard array ..... . 81

21. Sighting structure for determining direction of the
airplane. . . . . . . . . . . . 82

22. The antenna field. . . . . . . . . . 85

23. The 27.6 Mc/s Yagi array and the polarineter array . 88

24. Polarization diagram . . . . . . .... .95

25. Block diagram of receiving and recording equipment
used during the second apparition . . . .. 101

26. Antenna matching and calibration input circuit . . 103

27. Electronic equipment used during the second
apparition. . . . . . . . .... . 108

28. Typical recordings of Jupiter noise made at 18 Mc/s. 115

29. Periods of occurrence of 18 Mc/s radiation from
Jupiter (first 3ppcrition) plotted against
System II longitude of the central meridian
at the time of observation. . . . . ... 117

30. Probability of occurrence of 18 Mc/s radiation from
Jupiter (first apparition) plotted for 50
intervals of System II longitude. . . . ... 119

31. Long-tern drift lines for radio and visual features
of Jupiter. . . . . . . . .... . 121

32. System III histogram of observations of Jupiter
made between December 31, 1956 and March 6, 1957. 125

33. Histogram of the observations of Shain and of Burke
and Franklin plotted in System III longitudes . 126

Figure Pnge

34. Jupiter activity (in arbitrary units) plotted
as a function of date, showing 8-day cyclic
behavior ... .............. .... 131

35. System III histogram of observations of Jupiter
radiation on 18 and 22.2 Mc/s between December
19, 1957 and March 31, 1958 . . . . . . 139

36. Polarimeter record of a Jupiter burst on 22.2 Mc/s . 140



The Beginnings of Radio Astronomy

Man has always wondered at the stars. Probably since the

very days when the spark of human intelligence first began to glow,

he has yearned for knowledge about them. The planets caught his

attention early. Thousands of years before the dawn of recorded

history the ancients recognized these wanderers in the sky, which

slowly change position with respect to the rest of the firmament.

After the invention of the Arabic number system, the wanderings of

the planets began to be systematized. This marked the beginning of

the science of astronomy, although it was to be a very long time

before the disentanglement of astronomy from astrology was achieved.

About three hundred years before Christ, Aristarchus of

Samos advanced the theory that, contrary to the prevailing idea of

a geocentric universe, the earth actually revolves about the sun

in a circular orbit. This notion seemed so preposterous, however,

that it was disregarded until nearly 2,000 years later. About 1540

the Polish monk Copernicus, reviving and extending the theory of

Aristarchus, presented a qualitatively correct picture of the solar

system in which the planets and the earth, itself a planet, revolve

in orbits about the sun.


Proof of the Copernican theory was provided in the early

seventeenth century by Tycho and Kepler, and by Galileo. The

theoretician Kepler, using the remarkably precise planetary

observations made earlier by the experimentalist Tycho without the

aid of a telescope, deduced his celebrated three laws describing

the elliptical motion of the planets around the sun. Galileo, who

shares with Newton the honor of being the founder of the classical

physics of today, heard about the accidental discovery of the

principle of the telescope by the Dutch optician Lipperhey, and

promptly built himself one at Venice. Using an improved model of

his telescope in 1610, Galileo observed that the planets appear as

luminous discs while the stars remain points of light. He discovered

the more prominent moons of Jupiter, the rings of Saturn, the cres-

ent phases of Venus, sunspots, and the rotation of the sun. After

the discovery by Newton toward the end of the seventeenth century

of the law of gravitation, the formulation of his three laws of

motion, and his advances in optics, steady progress in astronomy

and physics was assured.

So began astronomy. In 1888, at about the start of the epoch

of the great modern American observatories, Heinrich Hertz in Germany

proved experimentally the existence of electromagnetic radiation.

The characteristics of this radiation had previously been worked out

mathematically in great detail by Maxwell. Using microwaves pro-

duced by spark discharges, Hertz demonstrated the rectilinearity of

propagation, shadow production, reflection, refraction, interference,

and polarization. He further showed that the radiation propagates

with the velocity of light and is indeed a manifestation of the same

phenomenon as light, differing only in wavelength and frequency.

Long distance propagation of electromagnetic radiation was first

accomplished by Marconi in 1901, marking the birth of radio. After

the invention of the electron tube by Fleming and de Forest, the

development of radio technology was rapid. An ionized layer in the

high atmosphere capable of reflecting radio waves was postulated by

Kennelly and Heaviside in 1902, but its existence was not proven

experimentally until 1925. By means of the pulse echo method

devised in 1926 by Breit and Tuve (a technique which was the fore-

runner of radar), it was demonstrated that waves of frequencies

below a critical value are reflected by the ionosphere, while those

above this value penetrate it.

In 1931 an electrical engineer working at the Bell Telephone

Laboratories, Karl Jansky (1), using a steerable multi-dipole

antenna array on a frequency of about 20 Mc/s, identified a per-

sistent hissing noise emanating from his radio receiver as of extra-

terrestrial origin. Jansky, after having taught himself the funda-

mentals of astronomy, determined beyond doubt that the radio noise

was arriving from a widely-dispersed source centered approximately

at declination -100, right ascension 18h, corresponding to the

approximate direction of the center of our galaxy, the Milky Way.

Thus did a perceptive engineer with no previous astronomical training

become the father of radio astronomy.

Subsequent to the pioneer work of Jansky, Reber further

investigated the distribution of the galactic noise in direction and

frequency in considerable detail. Southworth and Reber independently

found that the sun itself emits radio noise, which at times fluctuates

radically in intensity. The intensity was found always to be in

excess of that expected from a black body radiator at the temperature

of the surface of the sun.

Following the rapid advance made in radio and radar during

World i'ar II, radio astronomy came of age, with great parabolic

reflectors and multielement antenna arrays springing up in various

parts of the globe. A large number of radio stars were found, only

a few of them coinciding with visible objects detectable with even

the largest optical telescopes. A single radio spectral line was

found, that at a wavelength of 21 centimeters, resulting from the

emission or absorption of the neutral hydrogen gas thinly dispersed

throughout space.

Although most of the post-war activity has been at the

higher radio frequencies where the resolution necessary to separate

radio stars is more easily achieved, some work has continued at

frequencies in the vicinity of 20 Mc/s, which approaches the lowest

frequency capable of penetrating the terrestrial ionosphere. The

radio interferometer, consisting of two widely-separated antennas

connected to produce an interference pattern made up of a set of

fan-shaped lobes, has been widely used to achieve resolution at

these lower frequencies. The radio interferometer is an outgrowth

of the radio direction-finder, and is analogous with the optical

Lnterferometer. It was first applied to ridio ataronoca by Rl.le

Although the interferometer has the disadvantage that its multilobed

pattern is highly ambiguous in the determination of direction, it

remained for some time the only feasible method for obtaining

apertures of several wavelengths when the wavelength is as long as

50 feet. However, Mills of Australia developed an ingenious type of

antenna array which achieved with a reasonable number of dipoles the

same resolution as a rectangular dipole array so large that it would

be impracticable, and which possessed the advantage over the inter-

ferometer of being unambiguous. This array is called the Mills Cross.

Previous Investigations of Radio
Radiation from the Planets

A Mills Cross antenna was constructed at the Carnegie

Institution at Washington in 1954 for the frequency 22.2 Mc/s. Burke

and Franklin (2), while studying the radiation from the Crab Nebula

with this array, frequently noticed a burst of interference which

always occurred at approximately the same sidereal time, and always

lasted about the length of time required for a point source to pass

through the antenna beam. The interference appeared to be coming

from the direction of Jupiter. This was verified when the plot of

the right ascension of the interference over a period of two months

showed the same drift as that of Jupiter. The radiation was

extremely sporadic. Out of a total of 31 records of the passage of

Jupiter through the beam, only 9 showed the bursts of noise, the

intensity of the bursts varying over a wide range. The flux per

unit bandwidth of this radiation often reached 5.2 x 10-23 watts

m-2 (c/s)-1, and occasionally was several times greater. Calculations

by Burke and Franklin indicated that the peak power radiated by the

source was at least 300 watts per c/s of bandwidth. On one occasion

when measurements were made simultaneously on 22.2 Mc/s and on

38.7 Mc/s with an interferometer of higher gain, the radiation from

Jupiter was strong at the lower frequency but was completely absent

at the higher. The conclusion of Burke and Franklin was that the

radio noise is concentrated below 38 Mc/s.

The discovery by Burke and Franklin was also reported in an

editorial note in Nature (3). This brief report suggested that

Jupiter signals night be caused by distrubances in the planetary

atmosphere similar to terrestrial thunderstorms, but on a much larger

scale. The radiation field produced by a single terrestrial lightning

flash, as determined by E. T. Pierce, was given as 15 volts/m at a

distance of 20 km on a frequency of 1 Mc/s and bandwidth of 1 Mc/s.

Making reasonable assumptions about the frequency spectrum, and

making use of the fact that there are on the average about 100

lightning flashes per second in the terrestrial atmosphere, it was

calculated that the terrestrial thunderstorm static would produce at

the distance of Jupiter a power flux of about 5 x 10-21 watts

m-2 (c/s)-'. This is 100 times greater than the value for the Jupiter

radiation given by Burke and Franklin; it was thus concluded that

discharges akin to terrestrial lightning are a possible cause of the

noise from Jupiter. However, it was pointed out that the resultant

ignal from the rrany lightnLng flashes occurring each second on earth

would appE-r at the distance of Jupiter as a steady noise rather than

the irregular bursts actually observed from Jupiter.

Upon learning of the discovery of Burke and Franklin, Shain

(4,5) in Australia made a search of old records, taken in 1950-1951

at a frequency of 18.3 Mc/s, for possible occurrences of noise from

Jupiter. Many such occurrences which had previously been mistaken

for terrestrial interference were indeed found, confirming the work

of Burke and Franklin, and leading to the further conclusion that in

1951 the radiation came from a localized region of the planet.

Two series of records were studied. The first series was

obtained using an antenna array having the relatively narrow beam-

width 170. Radiation from Jupiter appeared on about half of these

records. The radiation appeared as violent fluctuations, often going

off-scale at an intensity greater than 5 x 10-21 watts m-2 (c/s)-1

Fairly accurate direction-finding was possible front some of the records

which were obtained with the use of a split-beam technique, indicating

that the direction of the noise source was the same as that of Jupiter

to within :10. Over the six-month period during which this series of

records was made, the right ascension of the noise source changed in

the same manner as did that of Jupiter, substantiating the indenti-


The other series of records was made using an antenna beam

which was narrow in declination, but which was eight hours wide in

hour angle, almost the length of time required for a full rotation

of Jupiter. This series revealed Jupiter radiation on 27 out of the

30 days on which there were suitable records, although in every case

the bursts of radiation come in groups of only an hour or two in

duration. A close correlation was found to exist between the times of

occurrence of the bursts and the rotation of Jupiter. Figure 1 shows

the longitudes of the central meridian of the luminous disc of Jupiter

during the times when bursts were received. A steady drift is apparent

in the plot using System I longitude, which is based on a rotation

period of 9h 50 30s. However, in the plot using System II longitude,

based on a rotational period of 9h 55m 40s6, the lines indicating times

of occurrence are almost directly under one another. Most of the

occurrences lie between 0 and 1350 longitude (System II), indicating

that the major source of radiation is centered at about 670 longitude

(System II). Actually a slight negative drift can be detected in the

System II diagram of Figure 1. Shain took this as an indication that

the period of rotation of the source was slightly less than that of

the System II longitude coordinates. From the slope of this slight

drift, he calculated the rotation period of the noise source to be

9h 55 13 (+5S). Shain briefly mentioned that he used this rotation

period to extrapolate backward in tine from his second series of

records to the first, si( months earlier, to ascertain at what System

II longitude the noise center should have been when the first series

was made. It turned out that the occurrence bands for the first series

were centered at a longitut .about 00 sLmller than that indicated by

the extrapolation. Shain gave no explanation for this disparity.

o 90 1800 27003600 900 180 27003600
1951 ,
J -- _.
AUG. 20-

30 -



Oc30 -
OCT. 3 . ..5-

18002705B60 90 1800

AUG. 20-

30- -
SEPT 1 -

10- -

20- .-

0- -

Fig. l.--eriods of occurrence of 18.3 Mc/s radiation from
Jupiter plotted against longitude of the central meridian at the
time of observation. [After Shain, Australian Journal of Physics

2, 67 (1956).]

It had been brought to Shaints attention by Fox of the British

Astronomical Association that a small white spot at the boundary

between the South Temperate Zone and the South Temperate Belt, which

had been studied by Reese, possessed a rotational period of 9h 55m 13,

the same as that attributed to the noise center. Shain thus concluded

(erroneously, as will be shown later) that the Reese white spot was

probably the source of the radio noise.

In speculating on possible explanations of the observed fact

that the radiation occurrences are concentrated within a well-defined

band of longitude of the central meridian, Shain suggested that an

ionosphere on Jupiter may be the cause. Such an ionosphere would

restrict the Jupiter rotation angle during which radiation could be

received at the earth. That is, the ionosphere would cut off the

outgoing radiation when the earth is at low altitudes as seen from

the source below the ionosphere. Shain suggested that the radiation

from Jupiter could be used in studying radio propagation in the space

between Jupiter and the earth, particularly through the corona of the

sun. In fact, by comparing some of his records taken at midday when

Jupiter and the sun were near conjunction with other records taken

at night when Jupiter was at opposition, he thought that he could

detect a difference in the average intensity of the signals, caused

by partial absorption of those which had passed through the corona.

He also pointed out that measurement of the refraction of Jupiter

radiation passing through the corona would provide information of

great interest. Finally, Shain stated that observations of radiation

from Jupiter were being made at the time the report was written in

1955, but that the occurrences were less frequent than in 1951.

Shortly after publication of the reports by Burke and Franklin

and by Shain, Smith (6) in England, using antenna arrays of relatively

high gain, attempted unsuccessfully to receive radiation from Jupiter

at 38 Mc/s and at 81 Mc/s. He could have detected 10-2 watts m2

(c/s)-l on 38 Mc/s, and 3 x 10-26 watts m-2 (c/s)-1 on 81.5 Mc/s, the

recorder response time being 6 seconds in both cases. The significance

of these observations would seem to be somewhat doubtful, since the

integrating time exceeded the expected burst duration. He estimated on

the basis of his negative results and the positive results of his pre-

decessors at lower frequencies that the spectrum of the Jupiter radiation

must vary at least as rapidly as the 5.5 power of the wavelength.

The report of Burke and Franklin did not contain enough

detailed data for a study of the correlation of noise occurrences at

22.2 Mc/s with Jupiter longitudes. However, Burke and Franklin sent

some of their later data to Brookes (7), who published it in the form

shown in Figure 2. As in the case of Shain's data obtained at 18.3

Mc/s, the 22.2 Mc/s noise occurrences were grouped in a particular

band of System II longitudes, although the groups in the two cases

were centered at different places. Brookes pointed out that the 22.2

Mc/s noise center, the Red Spot, and certain bright areas in the South

Temperate Zone were all at approximately the same System II longitude.

He suggested that the radio source and these visual features were

closely associated. (It will be shown later that this apparent

1955 ....... ...... a ....... ........ I

Nov. 2-



Dec. 2-


20- ........ ......... ......... ...... ... -

1800 2700 3600 90 1800

Longitude (System II)

Fig. 2.-Periods of occurrence of 22.2 Mc/s
radiation from Jupiter plotted against System II
longitude; data of Burke and Franklin. [After
Brookes. Journal of the Association of Lunar and
Planetary Observers 10, 15 (1956).]

asEociation at the t ti tr he data of Burke and Franklin were obtained

was a coincidence.)

In a paper presented at the March, 1956 meeting of the

American Astronomical Society, Franklin and Burke (8) reported

further progress in their study of radio radiation from Jupiter. They

mentioned the observed correlation of the radio source at 22 Mc/s with

System II longitude, the possible correlation between the Red Spot and

the radio source, and the fact that the white region suggested by Shain

as the source could no longer be so considered. They suggested the

possible significance of the fact that Shain received radiation in

1950-1951 during approximately 1350 of rotation of Jupiter, while their

data in 1955-1956 show a characteristic rotation angle of the order of

500. They reported further that data have been obtained by their

colleague, H. W. Wells, at two other frequencies, 18 Mc/s and 27 Mc/s.

These data indicated that the Jupiter radiation is not part of a

continuum. There was no correlation between the occurrence of bursts

on the three frequencies, and only a general agreement between the times

of prolonged disturbances. It appeared, however, that the sources at

all three frequencies were located predominantly between System II

longitudes 2800 and 600. An interferometer was constructed for the

purpose of determining if the Jupiter radiation is circularly polarized.

Many records were obtained indicating a high degree of right-hand

circular polarization, nearly 100 percent in some cases. One event

exhibited successively right-hand and left-hand circular polarization.

In another paper presented at the March, 1956 meeting of the

American Astronomical Lociety, Kraus (9) of Ohio State University

described some observations of the waveform of the Jupiter distur-

bances at 26.6 Mc/s. He reported that although many of the signals

consist of single pulses, a considerable number occur in pairs or

triplets of pulses. These seemed to fall into two groups, adjacent

pulses in the groups being separated by about 4 second and 1/40

second, respectively. The individual pulses were of the order of

10 milliseconds duration or less. Kraus suggested two possible

mechanisms for these multiple pulses, namely, that they are multiple

electrical discharges on Jupiter, or that they are an echo phenomenon

in which the second and third pulses are echoes of the first. Kraus

estimated the peak radiated power of the Jupiter signals to be of the

order of 10 kilowatts per c/s bandwidth.

At the same meeting, Gallet (10) of the National Bureau of

Standards at Boulder, Colorado, described his simultaneous observations

of the radiation from Jupiter on 18 Mc/s and 20 Mc/s. There was

usually more radiation at 18 Mc/s than at 20. Individual signals

observed at one of these frequencies were absent on the other,

indicating that single pulses contain only a narrow range of fre-

quencies. The signals appeared to be of two types, slow bursts lasting

two or three seconds and sharp clicks, some of which were as short as

0.001 second, like those caused by terrestrial lightning. Gallet

stressed the possibility of a detailed study of the ionosphere of

Jupiter by radio methods. He pointed out that a study of the

polarization of the radiation might indicate whether or not Jupiter

"-,. m"-, n-tic fl- L.I, nd .. h.d 5 ingle -iL which h the r r11 Lion cut off

= 'he plarn't rot- .: -hould giv,: rLaonrm.tion on the propFrt i~s of

it- iono-pr.r:r. (Kr.,,J: il'o ujggE..- ted that. thr falct tn.t tr. r *dJt ion

i- :pp.irntlj cut off b: for.: th,. -ourc,2 re.rch.r thi. lirut or tih'- Fp'ljn.t

is due to total internal reflection from its ionosphere, as had Shain

earlier.) Gallet expressed the belief that the Red Spot is one of the

sources of the radiation. Finally, he suggested that the mechanism

producing the radiation lies in the agitation of an ionized atmosphere

by shock waves originating at the surface of the planet.

Kraus (11, 12, 13) in 1956 reported in a series of three

articles in Nature the discovery of impulsive radio signals from the

planet Venus at a frequency of 26.7 Mc/s. He classified the signals

into two types, one appearing as sharp spikes of duration less than 1

second, and the other more sustained and apparently modulated at an

audio-frequency rate. The peak power flux density of the bursts from

Venus was given as 8.9 x 10-22 watts m-2 (c/s)-1. The signals were

observed many times, always when Venus was within the antenna beam.

The antenna used was actually an interferometer, and the presence of

nulls in the observed data coinciding with expected interferometer

nulls from a source in the direction of Venus was given as the main

evidence that the source was indeed Venus. These nulls were illustrated

in a sample record in one of the reports; however, it must be said that

the nulls in this record are not very well-defined, nor is the agree-

ment with the expected positions particularly striking. Kraus reported

finding several characteristic periodicities in the data, as well as

echoes from the moon of pulses originating on Jenus, but none of the

evidence appears conclusive. All of the observations were made

during daytime or early evening, when the terrestrial ionosphere is

sufficiently dense to permit sky-wave propagation at this frequency,

with the result that terrestrial interference was heavy.

At the spring, 1957 joint meeting of the International

Scientific Radio Union and the Institute for Radio Engineers in

Washington, Gallet (14) presented some conclusions from his invest-

igations of Jupiter radiation at 18 and 20 Mc/s over a two year

period. The antennas used permitted continuous observation of the

planet for longer than the 10-hour rotation period. Several sources

spaced in longitude were resolved by the method originated by Shain.

From a comparison of the data recorded by Shain in 1951 with his own

data recorded in 1956 and 1957, Gallet concluded that the sources do

not move relative to each other and must therefore be fixed to the

solid body of Jupiter. He established the rotation period as about

10 seconds less than that of System II. He stated th-t the ionosphere

of Jupiter is an important controlling factor in the reception of

radiation from Jupiter, and that he has observed a correlation between

the occurrence of the radiation and the solar activity. He further

stated that the total activity at 20 Mc/s is only 0.6 that at 18 Mc/s.

In a private communication received later from Franklin, Gallet's

value of the rotational period of the radio sources (and of the solid

core of Jupiter) was given as 9h 55m 29-4 (-0.1).

In 1957, Smith and Douglas (15) at Yale University made a

search for radiation from JipiteLr and turnjn at the fr-quency 21.1

Mc/s, uuing a pair of four-element Yagi arrays 2.3 -avelengIths apart

connected a. i phas':-:.;itchirg interf-romet.r. NLn:. probably Jupiter

events wer- recorded durLnc March, 1957. Saturrn ias observed durLng

April and May, with the result that on a total of 13 nights radiation

was presumably received from this planet. These 13 events all

satisfied several criteria for Saturnian origin, including fit to the

interferometer pattern and to a possible rotation period of 10 22m.

It was stated, however, that these preliminary results must be

considered inconclusive pending more data, better discrimination

against terrestrial atmospherics and galactic background, and

comparison with work of others.



Uell-established or at least highly plausible information on

planetary atmospheres, which has been gained largely by telescopic

and spectroscopic observations and by theoretical considerations, will

be summarized in this chapter. Major emphasis will be placed on those

planets known or suspected to be sporadic radio emitters. The principal

sources of this information are Jones (16) and Kuiper (17).


The four major planets, Jupiter, Saturn, Uranus, and Neptune,

possess many similarities to each other and many dissimilarities to the

lesser planets. This is due largely to the fact that, unlike the earth

and its smaller neighbors, the major planets are massive enough so that

they have been able to retain vast quantities of the light gases

hydrogen and helium in their atmospheres. They also have in common

relative remotensess from the sun, resulting in low atmospheric

temperatures. The largest of these giant planets is Jupiter.

When observed through a telescope, Jupiter appears as a bright

disk, slightly flattened at the poles, and possessing a number of dark

belts parallel to the equator. The flattening at the poles and cor-

responding equatorial bulge probably result from the relatively high

rotational velocity, the rotational period being less than ten hours.

Th-: dark belt- are protatlt clouds f-,ormed of droopl.t of ccondensed

vapors floating in the atmosphere. The belts may show considerable

internal structure, such detail as light or dark spots, bulges, and

curling wisps being common. Some of the markings last only a few

hours, others weeks or months, and a few, notably the great Red Spot,

for years. The periods of rotation of the various belts differ

slightly. The belts are often colored, with red, brown, and orange


The existence of a number of permanent currents in the

visible material on Jupiter has been established; these currents are

parallel to the equator, and account for differences in rotational

periods of the belts. Velocity differences in adjacent currents may

be sufficient to produce differential speeds of up to two hundred

miles per hour. The atmosphere is in a perpetual state of metero-

logical turmoil. Although the currents are permanent, their positions

and rotational rates may vary from year to year. The broadest is the

equatorial current, which covers a zone 10,000 to 15,000 miles wide

and has an average period of about 9h 50m 30s. This is the rotational

period upon which the central meridian longitude coordinates designated

"System I" are based. These are the coordinates which are usually

employed for specifying positions of equatorial markings. The periods

of rotation of the other currents lie between 9h 55m and 9h 56m, but

bear no apparent relation to the latitude. The central meridian

longitude coordinates designated "System II", corresponding to a

rotational period of 9h 55m 40S6, are usually the ones in which

positions of markings occurring in the non-equatorial currents are


The great Red Spot was observed as far back as 1857, and may

be identical with a marking observed by Hooke in 1664. Its appearance

changes considerably. At times it is very conspicuous and of a brick

red color; at other times it loses its color and disappears. It is

about 30,000 miles long and 7,000 miles wide, the long axis being

parallel to the equator. Its rotational period is subject to large

and irregular variations; it obviously cannot be attached to the

solid surface of the planet. Wildt has suggested that the Red Spot

may be a vast solid body, possibly solid hydrogen, floating in an

ocean of highly compressed atmospheric gases. The observed behavior

of the Red Spot is not inconsistent with such a hypothesis.

Another long-enduring marking is the South Tropical Disturbance,

an elongated dark region lying in the belt just south of the Red Spot.

It was first seen in 1901, was lost in 1940, and reappeared in 1955.

The mean density of Jupiter is 1.34 times that of water.

According to one theory the planet possesses a rocky core of about

22,000 miles radius. Above it is postulated a layer of ice about

16,000 miles thick, and an atmosphere about 6,000 miles thick. However,

only the outer hundred miles (or less) of the atmosphere is in the

gaseous state, that below having been compressed to a liquid or solid.

Jupiter's atmosphere is believed to consist mainly of hydrogen

and helium. However, spectroscopically observable quantities of methane

and ammonia are also present. Gaseous methane and ammonia are estimated

.o be pre-ent Ln the amounts 150 iand 7 mnltr-itmosph-res, req?:ctive:l .

There is no free oxygen nor carbon dioxide, and probably no free

nitrogen. Clouds consisting of droplets of liquid ammonia or small

crystals of frozen ammonia are undoubtedly present.

Jupiter is about 5.2 times farther from the sun than is the

earth, so it receives only 0.037 as much solar radiation. As a con-

sequence, surface temperatures are much lower than on earth. The

measured temperature of the visible part of Jupiter is -1400 C.

Jupiter's orbital period is 11.9 years. Seasonal effects are probably

insignificant, since the inclination of the axis of rotation is only

about 30

Jupiter has twelve known satellites. The largest, designated

J III, possess sufficient mass to retain an atmosphere, as do some of

the others. However, no atmosphere has yet been detected.


Saturn, the second largest of the planets, is noted for its

unique rings. They are composed of myriads of granules of solid matter,

either ice or some other material coated with frost. The surface of .

Saturn is marked by light and dark belts parallel to the equator, as in

the case of Jupiter. Saturn's belts, however, are sparser and contain

less detail than those of Jupiter. Occasionally, white spots appear.

Those occurring near the equator have a rotational period of about

10h 16"; a spot observed at latitude 360 north had a period of 10h 38m.

The rotation of the atmosphere thus appears more rapid at the equator

than elsewhere, the effect being even more pronounced than in the case

of Jupiter. Saturn also shows more flattening at the poles and bulging

at the equator than does Jupiter, an indication of an even more

extensive atmosphere. Saturn is about 9.5 times as far from the sun

as is the earth; it receives only 0.011 the terrestrial intensity

of solar radiation. Its temperature is -1550 C, 150 lower than that

of Jupiter.

Saturn is believed to consist of a rocky core about 14,000

miles in radius, above which is a layer of ice some 6,000 miles thick,

and on top of this an atmosphere 16,000 miles thick. However, the

atmosphere is gaseous only within the outer few hundred miles. The

atmosphere probably consists largely of hydrogen and helium. Observable

quantities of methane and ammonia are also present. The amount of

methane is 350 meter-atmospheres, while that of ammonia is about 2

meter-atmospheres. Condensed ammonia droplets or crystals are probably

present in the form of clouds.

Saturn's orbital period is 29.5 years.

Saturnts largest satellite, Titan, has an atmosphere of its

own. Spectroscopic observations of it indicate the presence of methane,

in the amount of 200 meter-atmospheres.

Uranus and Neptune

Due to their remoteness, less information is available on

Uranus and Neptune. They both appear sea-green in the telescope.

Extremely faint belts have been seen on Uranus. Spectroscopic and

pnotoelectric ob.ervtations give a value of about 10h 4m for the

rotational period of Uranus (which shows a decided oblateness), and

15h 40m for Neptune. Uranus is about 20.0 times as far from the sun

as is the earth, and Neptune about 30.0 times; Uranus receives only

0.0025 the terrestrial intensity of solar radiation, and Neptune only

0.0011. Temperature measurements indicate that Uranus is colder than

-1800 C; Neptune's temperature cannot be measured, but must be lower

than this.

It is postulated that both planets have an ice coating 6,000

miles thick, while the depths of the atmosphere are 3,000 miles for

Uranus and 2,000 miles for Neptune, only the outer portions of which

are gaseous. The atmospheres are largely hydrogen and helium, but

methane is observable spectroscopically; indeed, it is the absorption

due to methane which gives the planets their characteristic green

color. The amount of methane on Uranus is 1,500 meter-atmospheres

and on Neptune 2,500 meter-atmospheres. All the gaseous ammonia has

apparently been frozen out.

The orbital period of Uranus is 84 years; that of Neptune is

165 years.


Venus is the brightest object in the sky, other than the sun

and moon. Since its orbit is inside that of the earth, the illuminated

face of Venus goes through phases similar to those of the moon. The

mass of Venus is 0.82 that of the earth. Its orbital period is 225

days, and the synodic period is about a year and seven months. Since

its surface cannot be observed because of perpetual clouds, its

rotational period is not known. Being about 0.72 times as far from

the sun as is the earth, it receives 1.9 times the solar radiation.

The measured temperature of the bright side is 550 C; that of the dark

side is -200 C. The temperature at the surface of the planet, beneath

the cloud cover, is believed to be well above 1000 C.

The only gas which has been detected with certainty in the

atmosphere of Venus1 is carbon dioxide, but this is present in

abundance. The amount is about 1,000 meter-atmospheres. Oxygen and

water vapor, if present at all, are very scarce.

According to Jones (16) the entire surface of Venus is desert

(although according to another common theory it is covered by oceant.

Jones states that never-ending storms, much more violent than any on

earth, continually stir up yellow dust from the surface and blow it

high into the atmosphere. The whole atmosphere is hazy from dust. It

is this which makes Venus so bright in reflected sunlight, and also

prevents us from seeing its surface. If this picture is correct, one

would surmise that it might be possible to detect radio radiation from

discharges of static electricity occurring in the violent dust storms.


Mars is considerably smaller than the earth. Its orbit being

just outside that of the earth, Mars under favorable conditions

lit has just been learned from Professor Harlow Shapley that an
aurora on Venus showing the presence of nitrogen gas has recently been
detected spectroscopically.

approamres the earth more closely than any other planet e..cept cnar-.

Unlike the other planets, the surface of Mars can be seen in some

detail. Visible features are snowcaps near the poles, a white strip

presumably of frost seen along the east side just after sunrise,

occasional cloudiness and dust storms, the famed and controversial

"canals", and large greenish areas believed to be vegetation. Its

temperature is 200 C in the hottest portions and about -85o C in the


Carbon dioxide has been detected in the atmosphere of Mars,

in the amount of 4.4 meter-atmospheres. Water vapor is undoubtedly

also present in a very small amount. There is probably little free

oxygen. Other possible atmospheric components are unknown, although

the presence of nitrogen is highly probable. The atmosphere is very

thin, rarer apparently than on the highest mountains on earth. Clouds

are seldom seen. There is apparently little meteorological activity

on Mars of the type expected to result in large electrical discharges,

although there is the possibility of lightning in the occasional dust


The rotational period of Mars is about that of the earth; its

orbital period is 1.9 years.


Mercury, the planet with the innermost orbit, is difficult to

observe because of its proximity to the sun. It is so hot and so

small that it has no atmosphere, and is therefore of little interest

in the present study.


Pluto, the most remote of the known planets, is probably

smaller than the earth. Virtually nothing is known about its

atmosphere. Pluto is not considered likely to be an observable

radio emitter.


The atmosphere of the earth near the surface is composed of

78% nitrogen (by volume), 21% oxygen, 0.9% argon, 0.03% carbon dioxide,

0.01% hydrogen, traces of the other noble gases, and variable amounts

of water vapor. Its major divisions are the troposphere, the strato-

sphere, and the ionosphere. The troposphere, the layer nearest the

surface, is characterized by the presence of great clouds of water

droplets, other manifestations of weather, and a decrease of temperature

with height. In the stratosphere the temperature is essentially

constant and there are few clouds. The ionosphere is made up of

sparsely distributed atmospheric molecules, atoms, and ions. If the

temperature of the earth were measured in the same way as that for

the other planets, a value of about U 0 C would be obtained.

The tropospheric phenomenon of greatest interest in the

present study is the thunderstorm. The thunderstorm is of concern

for two reasons. Lightning discharges are the source of atmospheric

radio noise, which is the most serious form of interference to be

combatted in the observation of planetary radio radiation. Further,

the mechanism by means of which lightning is produced may provide a

clue to the origin of the planetary radio radiation. A typical

rhurid-er: .oram origLr-i it-5 rA.ri 3w iill -%r.?j of l.nd bco ~.- hi.-ed t..'

the sun more than its surroundings. The heated, moisture-laden air

in the vicinity rises into levels of lower pressure and temperature.

Adiabatic expansion and cooling cause condensation of a part of the

moisture; the condensation liberates heat. The rising air, warmer

now than its ever-cooler surroundings by virtue of the condensing

moisture, continues its buoyant ascent. In this way a violent updraft

is formed and maintained. The resulting cumulus cloud will billow

a mile upward, stopping only when it runs out of moisture. Water

drops continually forming inside are lifted by the updraft to higher

altitudes, where they freeze to form hail or snow. The hail and

snow may alternately rise and fall within the cloud many times before

it finally reaches the ground as rain. Somehow in this process

positive charge accumulates in the top of the cloud and negative

charge in the bottom. A tremendous potential difference between

top and bottom is thus built up, finally resulting in a lightning

discharge. The discharge may occur between the top and bottom of

the cloud, between the cloud and ground, or between oppositely

charged portions of adjacent clouds.

The mechanism causing the separation of charge within the

cloud is not known, although there are several theories (18). One

ofL the more plausible is the ice-friction theory. It has been shown

that when two insulators of the same material are rubbed together

they become charged, usually negatively, while the air becomes

positively charged. High fields have been observed in Antarctic

blizzards and in dust storms. According to the ice-friction theory,

ice particles forming and being blown violently about in the upper

part of the thundercloud become charged negatively by friction,

leaving the air positively charged. As they grow heavier they settle

to the base of the cloud, where they hang suspended for a time by the

electrostatic attraction between the negative charges they carry and

the positively charged air they left behind in the top of the cloud.

Finally, when the lightning discharge occurs, the potential difference

is neutralized, and the hail and raindrops held in the ominously dark

base of the great cloud fall to the ground in a deluge.

Lightning discharges radiate a large amount of energy in the

radio spectrum. Although the maximum energy occurs at a frequency

of about 15 Kc/s, there is enough in the spectral region 15 to 30

Mc/s to interfere seriously at times with planetary reception.

There are on earth about 100 lightning discharges every

second, on the average. Some of the radio radiation from this

continual activity, at frequencies high enough to penetrate the iono-

sphere, will pass out into space. The terrestrial radiation in the

15-30 Mc/s band, as observed with a radio receiver at a distant point

in the solar system, would appear as a steady noise of random

(gaussian) amplitude distribution, since it is composed of randomly-

occurring, overlapping pulses. It would seem to be of about the same

character as the galactic noise.

The ionosphere of the earth occurs in the outer fringe of the

atmosphere, where the mean free path of the rarified gaseous components

1, very IcnI andI the- r.te- of collision ic reistivel, lo.. Thi

principal daytime ionospheric layers are the D layer at about 35

miles altitude, the E layer at about 60 miles, the Fl layer at

about 120 miles, and the F2 layer at about 180 miles. Generally at

night only the F layer (no longer divided into sub-layers) is present.

These ionized layers are due to the action of ultraviolet

radiation from the sun, the different layers resulting from photo-

dissociation of different atmospheric constituents. In the lower

layers recombination by collision is rapid, and the layer disappears

with the setting of the sun. However, in the F layer collisions are

so infrequent that some ionization persists throughout the night,

although the ion density usually drops until sunrise. The behavior

of the night-time F layer ion density is subject to snomalies resulting

from magnetic disturbances and atmospheric tides. The average maximum

electron number density for the F layer at midnight is 2.5 x 105/cm3.

The electron number density is about four times greater during a

sunspot maximum than during a sunspot minimum. The number density of

neutral particles in the F layer is 2 x 1010/cm The F layer collision

frequency is of the order of 10/s.

The earth is the only planet known to have a magnetic field

(prior to the studies of Jupiter's radio radiation), although it is

possible that every planet has one. The magnetic axis of the earth

is inclined at about 120 to the rotational axis. At Gainesville, the
resultant magnetic field intensity is 0.51 gauss, the dip is 58 ,

and the magnetic declination is 10 E.




Much can be learned about the variable radio radiation from

Jupiter (or other planets) and about environmental conditions at the

source by the application of certain results of the well-established

theory of propagation of radio waves through ionized gases. The

elementary theory for propagation in the absence of a static magnetic

field was provided by Eccles and Larmor. Later, Lorentz laid the

foundations for a theory including the effects of a steady externally

applied magnetic field, known as magneto-ionic theory, by considering

the special cases of propagation directly along the magnetic field

and also at right angles to it. Following this, Appleton in about

1927 generalized the Lorentz theory to include propagation in any

direction with respect to the static magnetic field, and applied it

to explain the observed phenomena related to propagation of radio

waves in the terrestrial ionosphere. Hartree and also Goldstein

independently arrived at the Appleton formula at about the same time.

The general theory is extremely complicated. The discussion

which follows is based largely on material which is found in textbooks

by Mitra (19) and by Pawsey and Bracewell (20). This information will

later be used in attempts to prove from the experimental data that

Jupiter indeed has an ionosphere, and to deduce from the observed


F'CiarizaLior. of Lnh, r."c.ivvd sI-7i.a-i at cuch aZ raoE.ibl about th-

ra -. tc fi!-l or. JLpit-;r, if an-. A theory due to Jaeger and

Westfold (21) concerning the propagation of transient electrana1netic

phenomena oriirnating within an ionized medium will also be summari-ed

brief,:, sin:e i. may shed some Light on the na'.ure of the source of

the radiation from Jupiter.

Propagation in the Absence of a Magnetic Field

Considering first the relatively simple case of propagation

in a horizontally stratified ionosphere without a static magnetic

field (19), let a radio wave be incident on the boundary at an angle i.

The wave will be refracted at the boundary, and also within the medium

if the electron density varies with height. If the electron density

gradually increases with height, a refracted ray which entered the

ionosphere froa below will be bent more and more away from the normal

until it finally becomes horizontal. After having became horizontal,

the ray will continue bending downward and will eventually emerge

from the lower ionospheric boundary. This constitutes total internal

reflection. The refractive index in any layer is

n2 = 1 Ne2/(rmf2 (1)

and from Snell's Law the condition for reflection from a particular

layer is

sin2 i = n2 = 1 Ne2/mf2 (2)

where i = angle of incidence with respect to the normal;

n = refractive index in the layer;

N = number of electrons per uni' volume in -he layer;

f = wave frequency;

e, m are the electronic charge and mass.

If the incidence is vertical, n = 0 at the height of reflection,

in which case

S= Ne2/(m) (2)

where fo is the critical frequency (also called the plasma frequency)

for the layer having electron density N; i.e., it is the highest

frequency which will be reflected at normal incidence.

Eq. (1) can be rewritten,

n2 1 f2 ( )

So long as there is no externally applied static magnetic field,

the ionized medium has no effect on the polarization of the wave.

Polarization in the Presence of a Magnetic Field

If a static magnetic field is present the analysis is greatly

complicated (19). However, in general a single incident wave will

split into two components due to the fact that the medium is now

anisotropic. These two coaponens, or propagation modes, will be

polarized differently and will usually follow different paths in the

medium; they will travel at different velocities, will be reflected

at different layers (if at all), and will experience different amounts

of absorption. In analogy with optical birefringence, the two modes

are referred to as the "ordinary" and "extraordinary" modes.

-o i ..r- _a i Cn i rr: Ltor. tJ% iraia -. s

For the social casr of oronaaation in the same dir.c ion as

.dat of he s atic ma-netic field, i. ., the longitudinal case, the

ordinary mode is circularly polarized in the left-handed sense and the

extraordinary mode is circularly polarized in the right-handed sense,

provided f>fo (implying relatively high frequency or low electron

density). On the other hand, if f
frequency or high electron density), the polarization senses are the

converse. For propagation in the opposite direction to that of the

static magnetic field, the senses of polarization are converse to

those for propagation in the same direction as the magnetic field.

Polarization in the Transverse Case

For the special case of propagation at right angles to the

direction of the static magnetic field, i.e., the transverse case, the

two modes are both plane polarized, at right angles to each other. In

this case the electric vector is parallel (or antiparallel) to the

magnetic field for the ordinary mode, and perpendicular to the magnetic

for the extraordinary mode. In this particular instance the magnetic

field has no effect on the ordinary ray, since the electric vector and

static magnetic field vector lie along the same line.

Polarization in the General Case

For the general case of propagation at any angle with respect

to the static magnetic field (other than 00 or 90) the two modes are

elliptically polarized (19). The polarization ellipses for the

individual modes have the same ratio of major to minor axis. The

major axis orientations for the two are perpendicular, and the senses

of polarization are opposite to each other. The rules for determining

the sense of elliptical polarization are similar to those for circular

polarization in the longitudinal case. If there is a component of the

static magnetic field in the same direction as that of propagation,

then for f > fo, the elliptical polarization is left-handed for the

ordinary mode and right-handed for the extraordinary node; but for

f < fo, the converse is true. If there is a component of the static

magnetic field in the opposite direction to that of propagation, all

the polarization senses are just the converse of corresponding ones

in the previous statement. The major to minor axis ratio of the

polarization ellipses is a function of the direction of the magnetic

field with respect to that of propagation, the magnetic field intensity,

and the ratio fo/f. Transitions from ellipses which become circles

at one extreme to ellipses which become straight lines at the other are

continuous with variations in the above parameters.

Determination of Magnetic Field Intensity
by Means of Polarization Measurement

If in the outer reaches of a planetary ionosphere the electron

density (and hence fo) decreases gradually to zero with increasing

height while an appreciable magnetic field still remains, then the

axial ratio of the ordinary and extraordinary polarization ellipses is

a function only of the direction and magnitude of the magnetic field at

the height at which the electron density became essentially zero (20).

LuLt. suert travel iof r3's through a v.acuumr aftl.r er t fror. the .-p or

the ionosphere will not alter the polarization existing at emergence.

If both the ordinary and extraordinary components penetrate

the ionosphere from below and arrive at a point outside with approxi-

mately equal intensities, the resultant polarization at any instant.

due to the superposition of the two components (which are individually

elliptical) could be elliptical in either sense, depending upon the

phase relationship of the two. The sense of the resultant polarization

would be expected to vary erratically due to the effect of fluctuations

in the polarizing ionosphere. On the other hand, if the polarization

is actually observed to be predominantly of one particular sense,

then it can be assumed that only one of the components is escaping

froa the ionosphere, the other having been reflected internally or

absorbed. In such a case, measurement of the elliptical axial ratio

provides a means of determining the static magnetic field intensity if

the angle between the field and the propagation direction is known.

Simplified Appleton Polarization Formula

If the effect of collisions of electrons and other ions with

neutral molecules and atoms is neglected, the formula derived by

Appleton expressing quantitatively the state of polarization can be

greatly simplified (19), probably without causing too much error for

the cases of in-erest. The simplified polarization formula is

R=-J sI sHe I +I +"f sne I
I -'- -c L W I-'
2fcTs f 72

hhere R = Ez/Ey, E and E. being the complex vector representations
of the electric field components along the z and y
axes, respectively, when the x exis is in the
direction of propagation (imaginary terms signify
phase quadrature with real terms);

2 = Ne2/(nmr), X, e, and m having the same interpretations
as before;

fH = He/(2Tmc), H being the intensity of the static magnetic
field (the quantity fT is called the gyrofre-
quency of the electron);

f = wave frequency, as before;

Q = angle between the direction of propagation and the static
magnetic field.

For f 9 fo, the extraordinary ray is given by the upper

(positive) sign before the radical in Eq. (5), and the ordinary ray is

given by the lower (negative) sign. For f < fo, the converse is true.

When R is a rcal number, 0, or oo, the wave is plane polarized.

'hen R = -j or +j, the polarization is circular in the right-handed or

left-handed sense, respectively. Whcn R is any other negative or

positive imaginary number, the polarization is elliptical in the right-

handed or left-handed sense, respectively. All the rules previously

given for determining the state of polarization can be deduced from

Eq. (2).

Conditions for Reflection of Ordinary
and Extraordinary Components

There pre two different sets of reflection conditions for the

ordinary and ectraordin-ry coriponents (19). The gyrofrequency of the

electron, He/(2TrTc), determines which of the sets of conditions

prevails. The two situations are as follows:

b) .-,ve frequency grel er than gy rofrequency.. If
he > ri/(ia: ), o will reflected wh eflec/ted
-hen ull'-,/IT ru J) = 1; -rdj the E.CtrcrirL-,-r-4;' r;i, a.-ll
tt. l'.ect,.ed 'ter,

IJc. ,/(In -L" = He/(?"l m-cf) or l-HI' /(n,' ic['

i, 'ticr]?evtr E i. 15 ernco.rLtere,- f'irs t).

b) Wave frequency less than gyrofrequency. I1 f the ordinary ray will be reflected when Ne /(Tr mr ) = 1;
and the extraordinary ray will be reflected when

Ne2/(Tr f2) = 1 + He/(2T mcf).

Effects of Collisions

Since the effects of collisions of electrons and other ions

with neutral atoms end molecules have thus far been neglected, it is

now necessary to consider them (19). In general, collisions will

cause absorption. Absorption tends toward a maximum as the refractive

index approaches a minimum. Either the ordinary ray or the extra-

ordinary ray may suffer the greater absorption, depending upon other

parameters. Collisions can also give rise to a state of polarization

different from that indicated by Eq. (5) if the collision frequency

approaches a certain critical value given by

Q= (He cos 9)/(2mc tan 9).

Near the top of a planetary atmosphere, where the polarization

of an escaping ray attains its final state, the collision frequency is

zero and Eq. (5) can obviously be used. However, for a ray traversing

the terrestrial ionosphere from the direction of Jupiter the collision

frequency is not zero, but is of the order of IC/second (i.e., the

value for the F layer just after midnight). The minimum value of

Oc during the period of the polarimeter measurements was about

2.8 x 107, occurring when Jupiter was on the meridian ( at which

time 6 = Yo). Since this value is several orders of magnitude higher

than the collision frequency, Eq. (5) is valid for this case also.

Behavior of Transients Originating
within an Ionosphere

Jaeger and Westfold (21) have studied the mathematical problem

of propagation of transient phenomena originating within an ionized

medium, with a view to accounting for certain observed features of the

solar radio radiation. The assumption was made that a localized

region of the medium is disturbed very suddenly and briefly by an

external force; the theory deals with the resulting transient electro-

magnetic wave. Exact solutions of a number of transient problems of

linear propagation in a homogeneous ionized medium without a static

magnetic field were first obtained, utilizing the Fourier transform.

This was followed by examinations of the effects of a magnetic field,

the possibilities of extension to two- or three-dimensional systems,

and the effects of inhomogeneity in the medium.

Although the theory is exact only for greatly oversimplified

cases, a number of conclusions can be drawn regarding the propagation

of a disturbance originating within the corona of the sun (and, it is

hoped, within the ionosphere of Jupiter). The more interesting of

these conclusions are as follows (21):

c) R.diction will be emitted at -11 frequencies greater
thEn the plsnm, frequency, fo, and there will be no
radiation at frequencies less than fo (neglecting
any static magnetic field).

b) Trc .Lr,~Lt .r : ,' c,f" rje r.i i '.ior. a. a. -r', eTTu.lnc', f
which is greater than fo will normally .3crea3e
with frequency; this dcr'.ase vl1 be ac.orJTirg to
a law such as f-2 or f-4.

c) The intensity of a pulse of radiation sent out will
decay with time, possibly with the time factor e- ,
where is the collision frequency at the point of

d) There will be a time difference in the arrival of
direct waves of various frequencies, higher fre-
quencies arriving first and the frequency fo last.

e) If the source is above the level of maximum electron
density, then the radiation propagated inward will
be reflected at the level for which f equals f;
thus for all frequencies greater than f pulses
leaving the ionosphere will be double, he second
peak being smaller than the first.

There is considerable experimental support for these con-

clusions in the case of solar radiation. However, it must be

emphasized that the effects can be expected only if the source lies

within the ionosphere, and only then in case the original disturbing

force is in the form of a brief but intense pulse, for otherwise a

persisting originating disturbance will mask the transient reaction

produced by the medium.

It should be possible to test sane of the above predictions

experimentally in the case of radiation from Jupiter.




Project Chronology and Participants

A broadside antenna array for operation at 18.0 Mc/s was

designed by the writer in February, 1956. It was constructed by

Mr. C. H. Barrow, Mr. George Harris, and the writer, between March

and September, 1956. The array was used for Jupiter observations

between December, 1956 and April, 1957, being the only antenna in

operation during this period. Observers participating were Prof.

A. G. Smith, Mr. Barrow, the writer and beginning about midway in

the season, Mr. R. J. Pepple.

Observations of Saturn were made with the 18 Mc/s array

between February and April, 1957.

During the period of the Jupiter observations, preliminary

experiments were also performed on the detection of possible

fluctuations of light arriving from the planet coincidentally with

the radio bursts.

In order to increase the probability of detecting radiation

from Saturn, a 22.2 Mc/s corner reflector array was designed, largely

by the writer (but with substantial contributions by Prof. Smith, as

was usual). It was constructed by Prof. Smith, personnel from the


fhy-: ics .partru-rt Srnop, ana ti. writer ui April, 1,57. Observitions

of faturn i na.Je in .I,' with this arr.a w-ere not valid, ELnce it w-a

lt:r diicov'.re- tn.t the :rray ,as not fInr.:tionLng proFprl'y th

time. The defect was locatea and corrected in August, 1957.

Up to this point the work of the Radio Observatory had been

financed entirely from Physics Department funds, made available

through the support of Prof. R. C. Williamson, departmental chairman.

In August of 1957, however, a grant of $20,000 was made to the

Observatory by the National Science Foundation. This generous

assistance made possible a great expansion of the program.

A method for the measurement of directional patterns and gains

of large antenna arrays was developed largely by the writer and applied

between July and November, 1957.

A great deal of effort was also expended throughout this period

on improvements in the corner reflector array, and on innovations aimed

at improving performance, which were not always successful.

A polarimeter for operation at 22.2 Mc/s was designed by Mr.

Pepple and the writer, and was constructed by Mr. Pepple between

November, 1957 and January, 1958.

Two Yagi arrays, for operation at 22.2 Mc/s and 27.6 Mc/s

respectively, were purchased during 1957. Steerable masts to support

them were constructed and the arrays were erected. The Yagi arrays

were operational in January, 1958.

Following the construction or installation of each array,

considerable work was required in the preparation of associated

impedance matching, phasing, receiving, switching, recording, and

calibration equipment inside the observatory.

Five channels were in operation during most of the second

apparitionsI of the planets of interest, from December, 1957 to May,

1958, one of the channels being the polarimeter. The frequencies

employed were 18.0, 22.2, and 27.6 Mc/s. Observers participating

during this season were Prof. Smith, Mr. Barrow, Mr. Pepple, Mr. J.

K. Jackson, Mr. W. H. Perkins, Mr. H. I. Register, and the writer.

Extensive observations were made of Jupiter, Saturn, Uranus, and


In March, 1958, results of the studies of Jupiter during the

first apparition were published in the Astrophysical Journal (22).

The 18 Mc/s Broadside Array

The 18 Mc/s broadside array consists of eight half-wave

dipoles suspended a quarter wavelength above a reflecting plane, as

shown schematically in Figure 3. The dipoles arranged in two east-

west lines of four each, with a spacing of one-half wavelength

between the lines. The reflecting screen is 133 feet long in the

east-west direction, and 82 feet wide in the north-south direction.

It consists of 28 tautly stretched No. 6 aluminum wires, spaced 3

feet apart. This spacing is close enough so that the system of wires

1The term "first apparition" will be used henceforth to
designate observations made during the period December, 1956 to May,
1957, and "second apparition" to designate observations made between
December, 1957 and May, 1958.



Fig. 3.--Configuration of th 18 Mc/s oroadsidc

is almost as efficient a reflector for 18 Mc/s .mvc of east-west

polarization as a continuous sheet of metal. Each line of four dipoles

is itself a center-fed collinear sub-array, the individual dipoles in

it being end fed. Quarter-wavelength shorted phasing stubs between

the adjacent dipoles in each half of the collinear sub-array provide

the 1800 phase shift necessary to maintain the four dipoles in phase

coincidence for a source lying on the main lobe axis. The feed points

of the two collinear sub-arrays are joined by a length of line passing

between them, and the main transmission line is connected to an inter-

mediate point on this bridging line. The position of the junction

point determines the relative phasing of the two collinear sub-arrays,

which in turn determines the declination (i.e., the position in the

north-south vertical plane) of the axis of the main lobe of the

antenna pattern. No east-west directional control of the main lobe

axis was provided; the axis is confined to the meridian plane. A

portion of the array is shown in Figure 4.

The dipole lengths (23), 1, were determined from the formula,

1 = 468/f, (6)

where 1 is in feet and the frequency, f, is in Mc/sec. The value of

1 in this case is 26.0 feet. The height of the dipoles above the

reflecting plane, X/4, and the spacing between collinear sub-arrays,

A/2, were determined from the free space wavelength (23) calculated

by the formula

X= 984/f, (1)

Being in feet and f in Me/sec. The value of N in this case is

Fig. 4.--Vie. of the broadside array from the southwest.

54.7 feet. The lengths of the phasing stubs could be determined

either by calculation (i.e., 0.975 X/4, where 0.975 is the propagation

velocity factor for the line used), or as was actually done, by direct

measurement with the standing wave indicator.

The dipoles were made of No. 14 copper-clad steel wire. The

phasing stubs between dipoles, the bridging line between collinear

sub-arrays, and the main transmission line are all of commercially

available 300-ohm open wire line. The collinear sub-arrays are

supported between 2" x 4" wooden masts (which were coated with pre-

servative where in contact with soil) and are guyed with galvanized

iron wire broken up into non-resonant lengths by small insulators.

For use in matching impedances in the array, an 18 Mc/s

Hartley oscillator, of a few watts power, and a simple standing wave

indicator were built in accordance with instructions given in

references (23) and (24). The standing wave indicator consists

essentially of a pickup coil which could be clamped to the open wire

transmission line, a resonant coil and condenser, a crystal diode

detector, and a 0-100 microampere meter. By obtaining meter readings

at various points along a line in which the current distribution was

known, the standing wave indicator was found to be linear within the

required limits.

As the first step in matching impedances in the array, a

300-ohm feed point at the center of each of the collinear sub-arrays

%was provided. This was accomplished by means of a strategically

placed matching stub. The required length and position of the matching

tuL. :re *-t*r- r..j' I .iLh thl.: ai-j of LI t d in., va ..-.: ~n i. i 0lor irn

Ltj: I'c, lic -n n:i.nn .r. .. Ltc r rci r ir t r.~.3- J- on ci Lr e .3s i.:ru-cr t.eJ
; tie c n L:r s-r .l on-. of .h,- .sit-frry (... .- Jirec(lj L o th-

aJijc-cnt en r: of tn: Lro central dipFlE:). The v.c lltor .: cauplel

to the temporary transmission line. The standing wave ratio in this

line and the distance of the first null from the antenna were determined

with the aid of the indicator. Using these two parameters and a graph

given in reference (24), the proper length and position along the line

for a matching stub (a shorted stub in this case) were determined.

Such a matching stub ias connected, and the portion of the temporary

transmission line beyond it was clipped off. The remaining terminals,

across which the impedance is 300-ohms pure resistance, are the feed

point for the collinear sub-array. In the same manner a 300-ohm feed

point was provided for the other collinear sub-array.

After connecting the 300-ohm bridging line between the feed

'points of the to collinear sub-arrays, and the main transmission line

to the proper point along the bridging line, one more matching stub

was necessary before the arr y was completely matched to the line.

Since at the junction the 300-ohm transmission line is connected in

effect to the two portions of the 300-ohm bridging line in parallel,

there is a 300-ohm to 150-ohm mismatch. The length and position along

the main line for a matching stub v.hich would eliminate the mismatch

(-n open one in this case) was found in the same manner as before, and

the stub was connected.

After the matching was completed, the voltage standing wave

ratio in the main transmission line was determined to be less than

1.4. This was considered satisfactory.

The main transmission line is routed beneath the wires of the

reflecting plane (maintaining at least 6" clearance) to the edge of the

array, and then via poles to the observatory building. Just outside

the building the transmission line is connected to a J-type, or half

wave, balun (balance to unbalance transformer made of RG-11/U 75-ohm

coaxial cable. This was necessary because one side of the receiver

input is grounded, whereas the open wire line is balanced with respect

to ground (also, it is much more convenient to bring coaxial cable

into a building than open wire line). The J-type balun provides a

4 to 1 impedance transformation, which in this case was desired.

Another type of balun made of coaxial cable, the TT-type, or quarter

wave, balun (also called the "bazooka"), does not alter the impedance.

Both types are described in references (23) and (24).

An L-section matching network (i.e., a series inductance and a

shunt capacitance) was used to match the 75-ohm cable to the receiver,

the input impedance of which was about 200 ohms. Approximate values

for L and C in the matching network were calculated from formulas in

reference (25), but the final adjustment was made with the aid of an

antenna bridge.

The antenna bridge, an extremely useful and relatively

inexpensive instrument, is essentially a Wheatstone bridge operating

at radio frequencies. A grid-dip meter tuned to 18 Mc/s is used as

the voltage source. The bridge indicates the value of the resistance

..r!-- tll:-r : i.; fiC r- c.il ii.:. I .. r,;r -- t nLErLjri r- i2 '_r.ii-

ma.: i ori :.in 1 '.y F p- 3r to bz pur- re i. r i.c% i.ih.:n ir-.p -Edin c

is not pure resistance, the bridge reading has no significance;

however, the non-zero null in such a case is a useful indication of

the fact that reactance is present.

The 16 Mc/E array has also been described by Barrow (26,27).

Receiving, Recording, and Calibration Equipment
used During the First Apparition

A block diagram of the entire system used during the first

apparition of the planets of interest, in the winter and spring of

1956-1957, is shovn in Figure 5.

The receiver was a Hallicrafters SX-62, a commercial com-

nmnications receiver. The bandwidth at the selectivity setting used

("sharp-normal") was estimated to be 3 to 5 Kc/s between half voltage

points. The audio output was rectified by means of a crystal diode

and was used to deflect an Esterline-Angus pen recorder. The recorder

time constant is about 1 second. A standard paper speed of 6 inches

per hour was employed for the daily records made with this recorder.

A Brush pen recorder having paper speeds up to 125 rm/s was operated

in addition, at the discretion of the observer, in order to obtain

higher resolution during periods of Jupiter activity. The amplifier

of the Brush recorder ::as also driven from the audio output of the

receiver, the audio frequency signal being rectified by means of a

crystal diod and 3moothed romexhat with a resist,.nce-capacitance

filter having a time constant of about 0.05 second. A loudspeaker

Fig. 5.-Block diagram of system used during first
apparition (M = matching network; D = diode rectifier).

v'. conTrectedJ to ther- same re-ivcr for aural monitlorltng.

In orJir that caiirbratiorn Et p- could toe added at .th- r-nd or

each r'corl on which h th,-e r.d tr: b-en any JJpipLtr activity, a I-mpe-ratur:-

liiratea noire dioie cali.briticn circuit .a, con:rtrlcted.. Tth circuit

is shown in Figure 6.

The shot-effect noise in the diode current can be determined

accurately when the current flow is limited by the filament temperature

-i.e., when all the emitted electrons are attracted to the plate. In

such a case, the noise component of the diode current is given by
i = 2eIAf, (_)

where I = rms value of noise current, in amperes, having frequency
components in the band Af (af being measured in c/s);
e = electronic charge (i.e., 1.59 x 1019 coulombs);

I = d-c diode current in amperes.

If the receiver input is connected in parallel with R, the two

having the same impedance, half the noise current will flow through

R and half through the receiver input resistance. The power delivered

to the receiver input will be (11)2R, from which

p = eIRAf/2, ()

where p = noise power delivered to the receiver input, in watts.

The noise power delivered from the antenna to the receiver input

as a result of a Jupiter disturbance is (assuming the noise spectrum

to be essentially flat over the receiver bandwidth),

p = plAaf/2, (10)

where p = power flux from upiter per unit bandwidth, measured in
watts m- (c/s)-;

Type 5722 At



110 v
60 cps

Fig. 6.--Ecsertials of calibration circuit
(various by-pass condensers and RF chokes have been
omitted). R .as 75 olms during the first apparition;
afterward it was changed to 300 ohms.

f. = ct it-- oCf : r ,t rln ia rr ry ntral to thI d irei:Lc.n
of Jjipit- r, in mater.".

in-. r-;:,-n for tnr -1Jaii.on by 2 in Eq. I'l1) i: that only. half

the power incident on any antenna is delivered to the receiver input

(assumed to be matched), the other half being re-radiated. If after

noise from Jupiter is recorded, the antenna is replaced by the

calibrator at the receiver input, and I is varied until the same

deflection is obtained as in the case of the Jupiter noise, then the

values of p from the two sources, as given by Eqs. (9) and (10), are

equal. It follows that

Pl = eIR/A. (11)
If high accuracy in the determination of pl is required, it is

then necessary to account for transmission line losses, and to deduct

for the contribution of galactic noise to the resultant deflection

(remembering that the square root of the sum of the squares of the

Jupiter and galactic deflection components gives the resultant

deflection). Eq. (11) then becomes

S= e(IJG I) R/AT, (lla)

where I = noise diode current giving the same deflection as the
planetary noise and the galactic noise combined;

IG = noise diode current giving the same deflection as the
galactic noise alone;

T = power transmission coefficient for the transmission line.

Eqs. (_1) and (lla) are correct if the radiation and the

antenna are both plane polarized, in the same plane. However, if the

radiation is circularly polarized and the antenna is plane polarized,

only half of the available power is received. In this case, the right

hand sijes of Els. (11) mnl (!la) usti be multiplied by th- factor 2.

Figure 7 shows the electronic and recording equipment used

during the winter and spring of 1956-1957.

Calculation of Broadside Array Pattern and Gain

Although a method for the measurement of the directional

pattern and power gain of an -ntenna array was later developed for

testing the corner reflector array, it was considered adequate to

calculate these parameters for the broadside array. The pattern

calculation can be performed either graphically by means of vectors,

or analytically. The graphical method is very instructive, helping

one to appreciate just how the various looes and nulls in the pattern

come about; however, the analytical development will be presented

here because it can be done more compactly.

The calculation of the 18 ec/s broadside array pattern is

begun by invoking two simplifying principles of antenna analysis.

The first has to do with image antennas. If an antenna is suspended

with its center a distance h above a perfectly conducting plane of

infinite extent, then for either transmitting or receiving, the

relative field intensity pattern above the plane is the same as that

which would be obtained if a mirror image of the antenna were located

a distance h below the plane, and the plane were removed. Current

components in the image antenna which are parallel to the plane must

be equal, but oppositely directed, to corresponding components in the

real antenna; image components perpendicular to the plane must be

equal to and in the same direction as those of the real antenna. This

Fig. 7.-Electronic and recording equipment, first

follows as a direct consequence of Maxwell's Equations. Although in

practice the reflecting plane is neither infinite nor a perfect con-

ductor, the method of images can often give a close approximation to

the correct result.

The second simplifying principle has to do with the method of

treatment of arrays of arrays. If an array is composed of regularly

spaced and identical sub-arrays (or dipoles), the pattern of the array

is equal to that of a single sub-array (or dipole) multiplied by that

which would be obtained if each sub-array (or dipole) were replaced

at its center of symmetry by an isotropic antenna, the phase relation-

ships between the isotropic antennas being the same as those of the

feed points of the sub-arrays.

The pattern of the 18 Mc/s broadside array in the east-west

vertical plane passing through the array center is thus proportional

to the product Fa(Q) Fb(9) Fc(8), where the functions represent the

respective patterns of the elementary configurations shown in Figure 8.

Similarly, the pattern of the 18 Mc/s broadside array in the

north-south vertical plane passing through the array center is pro-

portional to the product Fd () Fc (), where the symbols represent the

respective patterns of the elementary configurations shown in Figure 9.

It is here assumed that the two collinear sub-arrays of the

broadside array (giving rise to Fd in Figure 9) are connected in phase,

which was true for Jupiter observations during the first season. The

rscon there is no dipole factor in this c-se iz that the equatorial

pattern of a dipole is constant with respect to the angle.


West -4 East

0 0 0 0

4 cophased
spaced A.

antenna IX
above its

Fig. 8.-Factors making up the Pattern of the 18 Mc/s
Broadside Array in the East-test Vertical Plane.




South<- Niorth

0 0

Cophased pair of
isotropic antennas
spaced AX.

Isotropic antenna
SX above antiphased

Fig. 9.-Factors making up the Pattern of the 18 Mc/s
Broadside Array in the North-South Vertical Plane.

as the first -tep in deriving the complete expression for the

east-West pattern, the factor F a'), the pattern of a half--ave dipole

withtri a plane passing through the dipole, muJst be evaluated. This is

done for a transmitting dipole by integrating the radiation from

current elements along the entire dipole length, for the angle (8)

with respect to the normal. The pattern for a receiving dipole is the

same, by virtue of the principle of reciprocity. The derivation is

rather lengthy and can be found in standard references (28), so that

it will not be given here. The result is

Fa(9) = cos (~nsin 9)/cos 9. (12)

It is necessary next to derive an expression for Fb(9), the

pattern for an east-west row of cophased isotropic antennas, expressed

as a function of the angle from the zenith in the east-west plane (28).

(By "cophased" is meant that the antennas are assumed to be connected

to a receiver by equal lengths of transmission line.) Let WTa be a

wave front striking the row of antennas at angle 8, as in Figure 10.


<-A B A

Fig. 10.-Diagram for
Fb(9) derivation.

The path length to antenna B is longer than that to A by the

distance j sin 9. Similarly, the length of path to each following

antenna increases by this same amount. Thus the phases of the suces-

sive antennas are delayed by 2r(iXsin 9)/X-nsin 9 =#. In

complex vector notation, the resultant a-c voltage at the receiver is

proportional to

1 + eJ + e22j3+ e3j

= (eJ )/(e. -l)
e2jV e2J e-2j T
et (et- e-t)

= sin (2Y)/sin (A') eJ .

Inserting the factor 1 to make the maximum value equal to unity, the

amplitude of the complex voltage at the receiver input for the simple

case considered is thus proportional to

Fb(9) = i sin(2rr sin 9)/sin(rn sin 9). (1)

We must finally evaluate the factor Fc(9), the pattern of an

isotropic antenna and its antiphased image located a half wavelength

below it. (By "antiphased" it is meant that the respective transmission

lines from the isotropic antenna and the image antenna to the receiver

are assumed to differ in length by a half wavelength.) In Figure 11,

WW' represents a wave front striking two such antiphased antennas, the

incident rays making an angle 9 with respect to the vertical. The wave

front must travel an additional distance A\cos 9 to reach the lower

antenna after striking the upper one, corresponding to a phase delay

of 2n (AX cos 9)/A or n cos 9. There is an additional phase delay

I \ /

\ \

Fig. 11.--Diagram for Fc(9) derivation.

of rr due to the assumed half wavelength greater length of the trans-
mission line from the lower antenna to the receiver. Thus the
resultant voltage at the receiver input is proportional to
1 + j( + iT cos Q)

The real component of this is
1 + cos(n +rr cos ) = 1 cos(n cos @).
The imaginary component is
sin(n+n cos @) = -sin(n cos @).
The amplitude is the square root of the sum of the squares of these
two components, or
[2 2 cos( cos 9) = (2)1 [1 cos(n cos 9)]
= 2 sin(nrcos 9).

F,(Q) = sin(an cos 6), (14)
the factor 2 having been dropped to make the maximum value of the
function unity.
The complete expression for the pattern of the 18 Mc/s broad-
array in the east-west vertical plane is thus

Few(9) Fa(e) Fb(9) Fe(G)
cot, (jn sin 0) sin (2n sin 9) sin ( n co 9) (15)
4 cos 9 sin (in sin G)

The factor Fd(@) contained in the expression for the north-

south pattern must be evaluated next. This is the pattern of a pair

of isotropic antennas spaced a half wavelength apart, connected to a

receiver by equal lengths of transmission line. In Figure 12, let

WW' be a wavefront striking the two antennas, represented by circles,


Fig. 12.--iagram for Fd(@) derivation.

at the angle @ with respect to the line joining them. The wavefront

must travel an additional distance kX sin 8 to reach the left-hand

antenna after striking the right-hand one, corresponding to a phase

delay of 2Tr( Xsin Q)/X, or Tr sin @. Thus the resultant voltage at

the receiver input is proportional to

1 + ejusin .

The real component of this is 1 + cos (Trsin 9), and the imaginary

component is sin (n sin 9). The amplitude is the square root of the

sum of the squares of the two components, or

[2 + 2 cos ( sin 9)]

= (2) [2 2 sin2(jnsin 9)]

= 2 cos (I nsin 9).


l-' ( ) =- cos (I n -ir L1. (h.)

The complete expression for the pattern of the 18 Mc/s array

in the north-south vertical plane is

Fns(e) = Fd(Q) Fc() = cos (rn sin @) sin (ncos 9). (17)

The point by point computation of Few() and Fns() for

plotting is greatly simplified by the use of tables of the functions

sin (j S sin Q), sin (1 S cos 9), and cos ( S sin 9) for appropriate

values of S. Such tables can be found in reference (29).

Figure 13 is a plot of Few(@). It is seen that there is a null

in the pattern 300 to each side of the main lobe axis; there are small

secondary lobes centered about 420 to each side. The ratio in decibels

of Few(G) at a secondary lobe maximum to that at the main lobe maximum

is 20 log 0.15, or -16.5 db. The east-west half power beamwidth (i.e.,

the angle between the 0.707 values of Few ()) is 250.

Figure 14 is the plot of Fns(Q). There are no side lobes in

this case. The north-south half power beamwidth is 580

The power gain of an array is the ratio of the power which

would be delivered into a matched receiver input by the array, to that

which would be delivered into a matched receiver by a free space

dipole. It is assumed that the same intensity of radiation is incident

on the array and on the dipole, and that the source is in the direction

of the main lobe maximum of each. The ratio is usually expressed in

decibels, one advantage of this being that it is then unnecessary to

specify whether power gain or voltage gain is meant. The gain of an



30 E


Fig. 13.--East-west pattern of 18 Mc/s
broadside array, calculated from Sq. (1).

300 30N

600 \60N

Fig. 14.-North-south pattern of 18 Mc/s
broadside array, calculated from Eq. (1).

array can be calculated by either of two methods; one involves the

integration of the square of the pattern in three dimensions, and the

other involves determining mutual impedances between all possible

dipole pair combinations in the array. Both methods can be very

complicated. In the present case the gain of the broadside array

will be estimated from empirical data, as is most often done.

The resultant gain of an array can be expressed as the product

(or sum, if decibels are used) of component gains. In the case of the

18 Mc/s broadside array the component gains are those of (a) a four

element collinear array in free space, (b) a cophased pair of parallel

eipoles spaced a half wavelength apart, and (c) a single dipole a

quarter wavelength above a large plane reflector. All three component

gains can be found in reference (24) and are used to obtain the re-

sultant gain as follows:

a) 4 collinear elements, 4.3 db

b) Parallel dipole pair, spaced 1 X, 4.0

c) Dipole above reflector, Ht. X, 6.0 (or a bit less)

Total about 14 db.

Thus, the gain of the 18 Mc/s broadside array is about 14 db

(with respect to a free space dipole) when the main lobe is per-

pendicular to the reflecting plane.

During the first apparition, the array was operated with the

main lobe vertical during Jupiter watches. However, when Jupiter

reached the meridian it was still south of the main lobe axis by

about 300. It is thus necessary to calculate the effective gain

corresponding to thi of'-: .ci direction. From Fio-ur 1L at is seen

that F '.I- drop= to 0.i-07 i.e., db tblow the rraximu,) At ;bout

2o0. The effective gain in the direction o0 Jupiter at meridian

transit was therefore about 14 3 = 11 db.

Eq. (11) for the flux per unit bandwidth contains the effective

area of the array in the direction of the source. Gain and effective

area are proportional, the relation between them being

A = 1.64 Gk2/(4) = 0.130 GX2. (18)

(The factor 1.64 is the gain of a free space dipole relative to an

isotropic antenna.) In this formula G must be expressed as the power

ratio (relative to a free space dipole) rather than in decibels. If

Gdb = 11 db = 10 log G then Gp =12.6. For X = 54.7 feet = 16.7

meters, the corresponding value of A is 459 meters This is the

effective area of the array for Jupiter radiation (near meridian

transit) during the first observing season.

For Saturn observations during the first season, and Jupit,-r

and Saturn observations during the second season, the main lobe of the

18 Mc/s broadside array was not perpendicular to the reflecting plane,

but was tilted southward. This was accomplished by connecting the main

transmission line to a point north of the midpoint of the bridging line

between the two collinear sub-arrays, causing a phase difference to

exist between them. If a wave arrives from a direction 4 south of the

vertical, it must travel an additional distance 2 X sin 4P after

reaching the south sub-array before reaching the north one, correspond-

ing to a time difference (IX sin c)/c, where c is the propagation

velocity in free space. If it is desired that (P be the direction

of the main lobe axis, the length of line from the south sub-array

to the junction with the main transmission line must be made just

enough longer than that from the north sub-array to compensate for

this time difference. Then the two signals will add in phase at the

junction. Thus,

(jXsinr)/c = (2s)/(0.975 c),

where (2s) is the difference in lengths of the two lines and (0.975 c)

is the propagation velocity on the lines. The propagation velocity

on transmission lines is less than c; the actual values for common types

of lines can be found in references (23) and (24). The difference in

the lengths of the two parts of the bridging line is 2s when the

junction is a distance s north of center. Therefore,

s = L 0.975 X sin 9 (12)

is the required distance of the junction north of center to tilt the

beam an angle f south of the vertical.

The north-south pattern of the array after the beam is tilted

could, of course, be calculated. However, this is not considered

necessary. The beam no doubt becomes a bit broader in the north-south

plane, as well as having its maximum displaced, but the east-west

pattern is relatively unaffected (except, of course, that Few () is

now the pattern in the east-west plane inclined southward at the angle

4), rather than in the east-west vertical plane). When the beam is

displaced 450 southward, the main lobe gain is probably 1 or 2 db less

than when it is vertical. In this case the main lobe gain would be

about 12 db instead of 14 db.

'i hi 2-'2.2 1lc, Lco rn. Lei'l-ctor ; rr.,

c'h *:orner r.: l':.:Lor int-:r.., -pp[.r ntrl- origiri-it.d Ly hri,'Ad

(3U, Jit ti' L Z lth f. ri-, .i.,r pri,:c ipl ui optics I by i, L -, mult ipi -

.I'..e '.rc" produc'.d rom ~~g Le i.g t :our, pic.' : t.*.i.:..n t 'o

er..r cdrngi pli'ne mirror. It .ran ro,- LL, L-. 5,.o n g.;o..i.tr iic 1

th...L thrrc airtuL. i '-. -r'. forcm -d if Lh. heurrur. Lrterse;.t.t L IO,
or 1've Lmag-. if LII. LnLt r c Lion 1: L ,: In the ciE : of" t:

r oLe oa logu, t-h-- light i Jo4rc i: r:cl..ceJ '-.e idol' (or .e rie~

of dipoles ,i anr the mirrors L.- lacitilic rf.'lc:ct.ing pld i. Tnic diole

andrJ it.- virt. il unjg.- .. :.r, .onE Janrc:Ia ui. i-eila-.nt fi -an:n.

arr:'., rmi.z:L:.um ,directivity, occuarririg long a line drjirn is perpiendi.-ular

to the dipole iii .,hi:.h ti..:cL: the r flector -mit erslC ton .- gi:.

The- corrncr reflc-tor arra- hicch t : ;oa n trA,. a-i-.1 .-re !':r

op.rti.3n a. 22..; H:.- :on/ :t' of i collir r .our ,'Oup of four dioles

.usLend.d .L teen Lt c plazi-: r- fiecr.-tor L'ntL.-ra.S3 t.g i L ian L n-ir e of

,b. The iiii I'u Latu :3 are -holn i, Fi ga. i1..

The string of dipoles is parallel to the east-west line formed

by the intersection of the planes. The entire structure can be rotated

about this line, permitting the axis of the array beam to be swung to

any angle within an arc passing through the zenith and extending to

300 above the horizon in the north and to 300 above the horizon in the

south. By adjusting the relative phasing of the four dipoles, the beam

can also be swung eastward or westward in the plane bisecting the angle

between the reflectors. The half power beamwidth, as determined by a

method to be described later, is about 220 east and west, and about 450







0 C) a)0


0 C'>

*-H 0


north and touth. In operation, the array i; tilt.e L tho t Sr pproYLiSLte

acclination of the planet under obt.rvation and 1 locked at thi:

:urgl-. Then the btea i3 phased as far :;5stajra a: i: feasible r1-ithout

x.ceiZivE loss of gain, actually about L40. As the planet. progre-ses

across the s-Ik, tre et.,a ia sZhi'ted -E :tward in 150 stp-: at the

proper times by plugging appropriate additional cable lengths into the

transmission lines from the four dipoles. This operation is performed

at the receiver, the observer's presence not being required at the

antenna once it has been set to the proper declination. A photograph

of the antenna is shown in Figure 16.

Each of the two reflecting planes is 108 feet long (east to

west) and 48 feet from the vertex to the outer edge. Each reflector

consists of 30 parallel copper-clad steel wires (No. 18) stretched

east and west between large V-shaped supports made of aluminum

television tower sections. Each of the four dipoles is 20 feet long,

the ends of adjacent dipoles being separated by 3-foot lengths of wire

interspersed with insulators. The dipoles are made of No. 14 copper-

clad steel wire. The string of dipoles is suspended within the angle

formed by the intersecting reflectors at a distance of about one-half

wavelength (22 feet) from the vertex. The mast at each end of the

string of dipoles is rigidly attached within the V-member at that end.

The vertex of each V-member is pivoted on a steel base set on a

concrete foundation. At each end of the reflectors, a system of guys

from attachment points located every 6 feet along each leg of the V-

support converges to a pivoted guy anchor. The axles at the bases of



F'ig. i6.--Thi; 22.2 2c/s comrn reflector Iray as sec roan
the east.
i^Me+l "-.,*^

Fig. 16.--The 22.2 Hc/s cot-ner` reflector z'rray as seen rro'
the east.

Ih-: t ,C,' V-.,j pport. : rd t.I L .'I. : CLf Lt th ri 0 g % rc n thor: -11i 1 i.n t.h

same straight line, so that as the structure is tilted the tension in

the guys cannot change. The tilt is controlled by means of a pair

of windlasses, one to the north and the other to the south. Flexible

steel cables passing around pulleys connect each windlass to the nearer

legs of the V-supports. As cable is taken up on one windlass, tilting

the structure toward it, cable must be allowed to pay out from the other.

When the desired declination is reached, as read from a graduated scale

at one end of the pivoted bases, the structure is held securely by

locking both windlasses.

Each dipole is connected at its center to a separate 75-ohm

coaxial cable (RG-11/U). The radiation resistance of the dipoles can

be made very nearly 75 ohms by slight adjustment of the dipole height

above the reflector vertex. Transformation from the balanced dipole

feed points to the unbalanced coaxial line is accomplished without

change in impedance by means of a n-type balun at each dipole, as at

CD in Figure 15. The four coaxial lines lead into the observatory

building to a junction box; these lines are all the same length. The

junction box is shown schematically in Figure 17. It is provided with

pairs of sockets for inserting additional lengths of cable into the

four transmission lines in order to achieve the desired phase relation-

ship between the dipoles. The transmission lines and phasing cables

are made of il-11/U 75-ohm cable. After passing through the phasing

cables, signals from the four lines are brought to common point in

the junction box. The impedance at this point is one-fourth that of

1 2 3


Fig. 17.--Junction box for the 22.2 Mc/s corner
reflector array.


ii r : cr r..;.t. ch.. *I L- :- :ticn l r.?.:woio : !i Lhe

jull ii ol Ei- 1: ;. At;- o u -.t7 r hit'd. Iu JrL.F:.-Vnc to irth-t -.f Lh c nble

l.iuing to tric r.:ci- . i': r lt.a .: i. t irrI 5ng .'-: r-tto in iS-ch of

the four transmission lines was found by measurement to be less than

1.10 at the design frequency, 22.2 Mc/s.

The lengths of the phasing cables to be inserted into the four

lines for directing the beam axis to various angles 9 east or west of

the normal to the dipoles are given in Table 1. The line numbers

correspond to those of the dipoles, which are numbered from east to

west. Each quantity in parentheses represents a separate cable

length. L is the length of the shortest cables, which can be any

convenient length. &L for each value of 9 is given by the formula

AL = (v/c) S sin, G (20)

where v = velocity of propagation in the cable,

c = velocity of propagation in free space,

and S = distance between centers of adjacent dipoles (23 feet).

It is seen that if the phasing cables are equipped with plugs,

permitting them to be joined to each other as well as to the sockets in

the junction box, then any of the seven angles listed in Table 1 can be

obtained by choosing the appropriate cables from a stock of ten.

The pattern of the 22.2 Mc/s array w;as measured by en especially

developed method, to be described later in this chapter. The pattern

in the east-west and north-couth planes of symmetry of the array are

shown in Figures 18 and 19, respectively. As ;ws stated earlier, the

measured beamwidth between half power points is about 220 east-west

and about 450 north-south.



ir 0 >
>41 rO

r ^ r 1 'S


1 c O <1



4 +


1 0 1


o 0 0 UN0 0 0 0 0a,
0' 1 r-0 m 0 -
C- HQ H C-d -4


E- r


Fig. 16.--Measured east-west
pattern of the 22.2 Me/s corner re-
flector array.

30 S

Fig. 19.--Measured north-south
pAttern of the 22.2 i.c/s corner re-
flector array.

The g-inl of the arrajy w i rme. ;jred at th-:- z aiT t iu- Lht the

FaLttrn rwas Aetermnrlnd. The gaiFn crn I alo t1 e estirti.ed frow empirical

data. In reference (24) it is stated that a gain of about 10 db can

be obtained from a single-dipole corner reflector antenna with sides

one wavelength from vertex to edge. A factor of 4.3 db is given as

the gain of 4 collinear half wave dipoles end to end. Thus the gain

to be expected from the 22.2 Mc/s corner reflector array is 14.3 db.

However, the measured gain was about 11 db, or a bit more than 3 db

too low. Despite many changes in the array in an attempt to improve

it, many tests, and consultation with Professor Kraus at Ohio State

University, the cause of this discrepancy has not been determined.

Professor Kraus stated that a possible cause of the trouble lies in

dissipative or re-radiation losses in the reflectors. He stated that

600 corner reflector antennas are much more susceptible to such

difficulties than are the 900 type, and he strongly recommended

changing to the latter. However, this was not feasible at the time.

There is a possibility that as a result of more recent changes the

gain is now greater than 11 db. Unfortunately, there has not been

time to make the new series of tests which would be necessary to

determine this.

A Method for the Measurement of the Pattern
and Gain of Large Antennas

In connection with the testing of the corner reflector array,

a technique was developed for measuring directional patterns and gains

of large antenna arrays. In this method an airplane carrying a

transmitter flier3 at approximately constant altitude (about 5,000 feet)

along either an east-west or a north-south course passing through the

beam of the array under test. The signal received by the array is

compared with that received at the same time by a simple array of

known characteristics. This is accomplished by using a single

receiver-recorder channel, which is switched alternately between the

array under test and the standard array at a switching period of about

two seconds. The standard array consists of a horizontal east-west

half wave dipole suspended a quarter wavelength above a large horizontal

plane made of parallel wires. By drawing smooth curves through the

two sets of segments of the commutated record, relative signal strengths

from the two arrays are obtained as a function of time. The direction

of the airplane from the arrays is periodically indicated at 150

intervals on the same record by an observer. These directions are

obtained from the alignment of pairs of sighting wires with the passing

airplane, the pairs of wires being oriented at 150 intervals. A

typical commutated record is shown in Figure 20. The sighting structure

is shown in Figure 21.

In order to obtain the directional pattern of the array under

test from a commutated record such as that in Figure 20 it is necessary

to make use of the known pattern of the standard array. The latter

(i.e., the pattern of a horizontal half-wave dipole a quarter wavelength

above a perfectly reflecting horizontal plane) can be found in reference

(24). The unknown pattern is computed point by point by multiplying

the standard pattern by the ratio of the signal from the array under

)1-40r_ I.-.

1. .'


a. U) ,-0

0 r-4)
+) C"

H)a 0 a) 0
0- 4' 4
.H ~-. a)


o0co- coI

0 r'i H
a) -4 'a))


Fig. 21.--Sighting structure for deter-
mining direction of the airplane. Observer
notes times at which the airplane is aligned
with the lower wire (nearest his eye) and one
of the upper wires.

te:t to trh.t from the st.Lndard array; E ocusiurd Crom; Lhe re-cornd t

correspond -Lng a lc .

The gairl of the t-d;rJ arri;a i;. stout i rclati e to0

fr:e sF-pc dipole. The gain of the array under test is therefore

equal to 6 db plus the ratio in db of the beam-center signal from

this array to that from the standard array. It is, of course,

necessary that each of the arrays be properly matched to the trans-

mission line.

The transmitter used in the airplane is a spark transmitter,

designed for maximum simplicity of construction and operation. It

consists essentially of an automobile ignition coil, a spark plug,

and an automobile radio vibrator. The primary current, supplied from

a 6-volt storage battery, is interrupted by means of the vibrator,

causing rapidly repeated sparking of the spark plug. The airplane

antenna is coupled to the two sides of the spark gap. The transmitted

signal is very broad in frequency. The radiated power, although quite

low, is adequate for the purpose.

Two antennas are required in the airplane, one of which is

polarized for north-south flights and the other for e'st-west flights.

These antennas are dipoles, somewhat shorter than a half wavelength,

suspended beneath the craft.

The corner reflector array patterns shown in Figures 18 and 19

were obtained by the method just described. As an example of the use

of the method for the measurement of gain, the case represented by

Figure 20 will be considered. Here the ratio of maximum deflection

for the single-dipole 600 corner reflector array to that for the

standard array is 5.2 db, and the gain of the latter is 6 db. There-

fore the gain of the single dipole corner antenna must be 5.2 db +

6 db 11.2 db. This is in agreement with the generally accepted

gain for a single-dipole 600 corner reflector antenna with sides

one wavelength from vertex to outer edge (24).

Since the method outlined above involves comparison with a

standard antenna, it is relatively free from possible errors caused

by varying distance to the airplane, anisotropy of the airplane

antenna pattern, and fluctuations in transmitter power and receiver


The 18 Mc/s Yagi Array

Since the 18 Mc/s broadside array can effectively receive

radiation from a planet only while it is within about 200 of the

meridian, corresponding to about 3 hours of observing time, it was

decided to supplement this array with an 18 Mc/s Yagi array which

could easily be steered in azimuth, so as to keep the planet within

its beam for a longer time. Accordingly, a 5-element Yagi array

was purchased from Telrex, of Asbury Park, New Jersey. A mast

providing azimuth steering was constructed, and the array was

erected with the aid of a motor crane. The antenna is shown in

Figure 22. The height of the array above ground is 28 feet, or about

a half wavelength.

The mast consists of an outer frame of aluminum television

tower sections resting on a steel table set on a concrete base, with


tk S

4 A


H: C.,



Q) 4

r CC

Cd .



6-.h 40
'2 ,-

a 24" pipe inside the tower. The pipe rests on a thrust bearing

beneath the table, passes through a hole in the table, through the

entire height of the tower, and projects 10 feet above a bearing in

the top of the tower. The antenna boom is clamped at its center to

the projecting part of the pipe. An azimuth steering lever is

attached to the pipe beneath the steel table at the base, the table

being so constructed that the lever is unobstructed by the table

supports for a swing of 1800. The antenna can quickly be locked to

any of a series of azimuths 150 apart by means of a pin which can be

dropped through the steering lever into properly spaced holes in an

underlying stationary plank. The aluminum tower is guyed with three

wires which are broken up into non-resonant lengths by insulators.

Adjustment of the elevation angle of the antenna is made by loosening

the clamp holding the antenna boom to the vertical pipe, tilting the

boom to the desired elevation angle, and clamping again. The boom is

of such length (36 feet) that it sags if not given additional support

near the ends. This is accomplished by means of two nylon ropes,

which are attached to the ends of the boon, passed through pulleys at

the top of the 8-foot length of pipe extending above the antenna, and

tied. Whenever the elevation angle is changed, these ropes must be


Included with the purchased antenna were a matching loop and

a J-type balun, which match the antenna to 50-ohm coaxial cable.

About 300 feet of RG-8/U cable is used to connect the antenna with its


[he -. n o: Lhfe It ;;c/c i. i jrr:.i -s ..ec ified c... the

u nri'Lc'ur:r, i- L .5 ,: r.:l.. ..: to 'r-e sp.ce dipole.

Tnre 27.o I-Ic/s Yagi Array

In order that obser.-al ionr coul be rndc t an other frequric-.'

besides 13 rnd 22.2 Mc/s, i 27.6 M c/, ?-element ijea array vas lio

purcris--jd from Telrex. A saipleFr -.an more -atis['actory' na L than the

Previous one w-s conri.LrucLt-,, .and Lhe arra ha erected. Tie arraT is

20 feet, a bit ov,:r a haji w:lvel-ngth, above ground. It can tbe seen

in Figures 22 rul 23.

The matL contsiiL of a 25-foot Lelephone pole and a 2>-foot

length of 24" galvanized water pipe. The telephone pole was set in a

6-foot hole by the Gainesville Electric Department. The pipe is

fastened alongside the pole in such a way that it can rotate, and it

projects 81 feet above the top of the pole. A steel plug in the base

of the pipe rests on a single large ball bearing embedded in a steel

plate which is bolted to the pole, forming the thrust bearing on

which the pipe rotates. At the top of the pole, the pipe passes

through a hole in a right-angled bracket bolted to the pole to serve

as the upper bearing. The antenna boom is clamped at its center to

the pipe about two feet above the top of the pole. Nylon ropes, to

prevent the 36-foot long antenna from sagging, pass from its ends

through pulleys at the top of the pipe, and down to the level of the

antenna, where they are tied. These ropes and pulleys were also used

to hoist the antenna from the ground to its final position.

H- 0 0)


V, 00

U) E

3, 3-.

'c 0+
.- .

'3 3o
>-49 C)
-~ 3.




'hre azimuth of the array is controlled by merns of a steerLnr-

lever frztenrd to thc bse of the pip'., just ibove the: be irinri. Thi:

antenna can quickly be locked to any of a series of azimuths 150

apart by passing a pin through a hole in the end of the steering lever

into an appropriate matching hole in an underlying stationary plank.

To change the elevation anglb of the array, the clamp holding it to

the pipe must be loosened, the boom of the array tilted to the

desired angle, the nylon ropes readjusted, and the clamp tightened


The antenna was supplied with a matching loop and J-type

balun, which match it to the 50-ohm RG-8/U coaxial cable leading into

the observatory building.

The gain of the 27.6 Mc/s Yagi array, as specified by the

manufacturer, is "13 db plus" relative to a free space dipole.

The 22.2 Mc/s Polarimeter

In order to determine the degree and sense of the polarization

of radiation from Jupiter, a 22.2 Mc/s polarimeter was built. This

array and its associated switching circuits were constructed by Mr.

R. J. Pepple, and are described in detail by him in reference (31).

The antenna was designed by Mr. Pepple, and the switching circuitry

by the writer. The polarimeter antenna is shown in Figures 22 and 23.

The polarimeter antenna consists of a pair of identical 4-

element Yagi arrays mounted along the same axis but with their polari-

zation planes at right angles to each other (both planes being

inclined at 45 with respect to the horizontal). The common axis of

the pair of arrays can be steered along the celestial equator by

adjusting the guy ropes; however, for all the measurements made to

date, the axis lay approximately within the meridian plane.

Separate 75-ohm coaxial cables lead from gamma-matched outputs

of the two Yagi arrays to switching circuit SC1 (Figure 25) inside

the observatory, the two transmission lines up to this point being of

exactly the same electrical length. Switching circuit SC1 periodically

introduces an extra quarter wavelength of line first into one trans-

mission line and then into the other, the period of the complete

switching cycle being one second. The two lines then merge into a

single line which passes out of SC1 to M at the receiver input.

The rectified audio output of the receiver is switched periodic-

ally by circuit SC2 (Figure 25) between one channel and the other of

a dual channel, quick-response Brush pen recorder in synchronism with

the switching of the extra quarter wavelength of line alternately into

the two transmission lines by SC1. Thus, pen number 1 can show a

deflection only when the path length from antenna A is a quarter wave-

length greater than that from antenna B, and pen number 2 can show a

deflection only when the path length from antenna B is a quarter wave-

length greater than that from antenna A. The deflection sensitivities

of the two pens are made equal by adjustment of their associated d-c


The switching in SC1 and SC2 is accomplished by relays which

are actuated by a motor-operated switch in SC3. The switching in the

antrinnr circuiltt caiuse jppa rently unavoidstile tr.riEnE nts iue to

contractt poLtntial Effects. The usefulness of the polrimet~r was 't

first seriously impaired by these brief but relatively intense

.rainientE. However, the difficulty was solved by adding another

anitcr, also in SC3 (and actuated by the same motor as the previously

described switch), which momentarily short-circuits the audio output

of the receiver during the brief intervals that the transients are

being produced. This effectively prevents them from appearing at the

recorder. The transient-suppression feature is not described in

reference (31).

If an incident signal causes the two pens, in their respective

halves of the switching cycle, to deflect the same amount, the incident

radiation must be plane polarized. If pen 1 deflects and pen 2 does not,

the polarization is circular, and it is in the right-handed sense. If

pen 2 deflects and pen 1 does not, the polarization is again circular,

but in the left-handed sense. If both pens deflect, but one deflects

more than the other, the polarization is elliptical. The sense of

elliptical polarization is right-handed if pen 1 deflects more than pen

2, and left-handed if pen 2 deflects more than pen 1. The ratio of

major to minor axis lengths of the polarization ellipse can be deter-

mined from the relative deflections of the pens. The formula relating

the axial ratio to the deflections will now be derived.

The contribution of the galactic noise to the resultant

deflection of the pens is not negligible, and so must be taken into

account. Since the galactic radiation is randomly polarized, the

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