260 RADIO WAVE PROPAGATION EXPERIMENTS 
lation with wind direction exists, it is masked by the 
variation within a single flight. 
Equipment difficulties have just been overcome 
and work is getting under way to determine X-band 
values. One flight made on horizontal polarization 
shows values greater than 0.9 up to 3 degrees. On 
three flights made with vertical polarization the points 
have fallen just slightly above the theoretical curve. 
It is planned to carry on simultaneous measure- 
ments of X- and S-band values to determine the values 
to be expected on X band and to prove or disprove the 
correlation suggested above. 
1.0 
0.8 
0.7 
0.6 
0.5 
04 
0.3 
REFLECTION COEFFICIENT — VERTICAL POLARIZATION 
FLIGHTS FROM S 
o2- 11/22/43 To 12/30/43 © © 
Oto 4 2 3 4 
ELECTRICAL CONSTANTS OF THE GROUND, 
SEA, AND FRESH WATER 
To obtain reliable data on the reflection coefficient, 
dielectric constant, and conductivity of the ground 
and also of fresh and sea water, a series of radio ex- 
periments were performed*® which gave results that 
compared fairly well with those obtained in labora- 
tory experiments. The experimental conditions were 
telatively well defined and the physical characteristics 
of the ground or water derived from these experiments 
appear to be highly reliable. The wavelengths of the 
5 6 7? 8 9 10 
GRAZING ANGLES IN DEGREES 
FicurE 2. Reflection coefficient, vertical polarization, versus grazing angle. Sea water. Wavelength—S band. 
EARTH CONSTANTS IN 
THE MICROWAVE RANGE? 
Reflection Coefficients 
In writing a summary of the latest results, it was 
thought that the following grouping of the data 
would be useful. 
1. Determination of the electrical constants of the 
ground, sea, and fresh water. 
2. Study of ground and sea reflections under condi- 
tions encountered in actual operations. 
8. Irregular reflections or scattering. 
>By L. Goldstein, Columbia University Wave Propagation 
Group. 
radiation used in these experiments lie in the S band 
at 9 and 10.cm. 
In the experiments with 9-cm waves,’? the nature 
of the reflecting surface was prepared beforehand and 
its humidity, occasionally, well controlled. Similarly, 
with vegetation on the ground, the reflection could be 
measured with different heights of the turf which was 
grown on the grounds reserved for the measurements. 
The conditions of the ground in the experiments 
with 10-em waves were somewhat less well defined. 
However, the experimental setup was portable in 
this case, which proved to be advantageous. 
It seems desirable to give first the results obtained 
under the best-defined conditions’? (9 cm) for a 
variety of grounds and compare those with the re- 
