— 
REFLECTION COEFFICIENTS 263 
PLACE~ SHORT BEACH 
EARTH-MOIST SAND, SOME 
ALGAE, VERY SMOOTH 
H- APPROXIMATE THEORETICAL Ph 
V-APPROXIMATE THEORETICAL py 
4 300FT 
VERTICAL POLARIZATION. 2°90 FT 
0 SOOFT 
HORIZONTAL POLARIZATION | 9OFT 
REFLECTION COEFFICIENT p* 
° 4 8 12 16 20 24 28 
GRAZING ANGLE IN DEGREES 
Ficure 7. Reflection coefficient p’ versus ¥. A= 10 em. 
d=300, 90 ft. 
Fresh Water and 4% Salt Solution (or Sea Water) 
(1) Tap water. Table 3 gives the results on the reflec- 
tion coefficients of tap water (temperature not given). 
TABLE 3. Reflection coefficients of tap water. \ = 9 cm.1,2 
Grazing 
angle _—‘ Vertical polarization 
degrees Calculated Observed 
Horizontal polarization 
Calculated Observed 
20 0.51 0.51 0.92 0.90 
35 0.69 0.67 0.88 0.88 
45.5 0.73 0.70 0.85 0.83 
The vaiues of e, and e¢ which best represent both the 
Teflection and absorption data are «, = 80, o = 2.2 
mhos per m, and ¢ = 11.9. 
2. Fresh water pond. The results on 10-em waves 
are collected in Figure 8.° These data refer to a fresh 
water pond and the theoretical curve corresponds to 
a smooth and perfect dielectric surface with e, = 80. 
The curves do not fit too well at the smaller grazing 
angles. If the conductivity were taken into account, 
H—~ APPROXIMATE THEORETICAL Ph 
V—-APPROXIMATE THEORETICAL (7 
«,* 80 o20 
PLACE - KENYON FARM 
EARTH~FRESH WATER POND VERY 
CALM, SLIGHT BREEZE 
REFLECTION COEFFICIENT p* 
Oo SOFT 
. 5 225FT 
HORIZONTAL POLARIZATION C20 ET 
fo) 4 8 42 16 20 24 28 
GRAZING ANGLE IN DEGREES 
a 
# VERTICAL POLARIZATION 4 225 FT 
aN oS 
le ie 
ak 
Ficure 8. Reflection coefficient p’ versus y. \=10 cm. 
d=90, 225 ft. Fresh water pond. 
presumably a better fit might be achieved. Two points, 
marked Ford,1? taken from Table 3 were included 
for comparison. 
3. Salt solution. In order to simulate sea water a 
4 per cent salt solution was used for the determination 
of the reflection coefficient. At 9 em the best fit was 
obtained with «, = 80, o = 6.1 mhos per m, and g 
= 33. 
4, Sea water. Figure 9 gives the results obtained 
at 10 cm. The computed curves drawn to fit the data 
correspond to ¢, = 69, o = 6.5 mhos per m, ¢ = 39. 
It appears that the data can be fitted with the com- 
0.8 
€,569 0 =6.5MHOS/M 
O VERTICAL POLARIZATION 
% HORIZONTAL POLARIZATION 
° 
a 
H~APPROXIMATE THEORETICAL 
V-APPROXIMATE THEORETICAL 
0.4 
REFLECTION COEFFICIENT p* 
0.2 
PLACE - MERRICK CANAL 
EARTH~- TIDAL CANAL, 
4 INCH RIPPLES 
GRAZING ANGLE IN DEGREES 
Ficurs 9. Reflection coefficient p’ versus y. A=10 cm. 
d=130 ft. Sea water (tidal canal). 
puted curves as long as the ripples on the tidal canal 
are of small amplitude (about 1 in.). 
Figure 10, which also refers to sea reflection, cor- 
responds to ripples which had an amplitude of about 
2 in., and here the observed reflection coefficients for 
vertical polarization fall well below the computed 
curve at the larger values of grazing angle. Probably 
the choice of the dielectric constants used in the com- 
putations may account for at least a part of the dis- 
crepancy. 
Grass-Covered Ground. The following results ob- 
tained at the experimental grounds"? with 9-cm waves 
_ 08 
a = 6.5MHOS/M 
5 © VERTICAL POLARIZATION 
rr) X HORIZONTAL POLARIZATION 
2 06 H-APPROXIMATE THEORETICAL 
he aa THEORETICAL 
°o 
°o 
5 04 
Fa 
oO 
Ww 
= e PLAGE - SHORT BEACH 
! 0.2 g b EARTH- TIDAL FLAT COVERED 
Q WITH 18° OF 
2° RIPPLES 
Ce) 4 [} 12 16 20 24 28 
GRAZING ANGLE IN DEGREES wy 
Ficure 10. Reflection coefficient p’ versus y. A=10 cm. 
_ d=90 ft. Sea water. 
