142 



REFLECTION COEFFICIENTS 



4 8 12 16 



GRAZING ANGLE IN DEGREES ^ 



Figure 9. Reflection coefficient p' versus <p. X=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 

 3 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-Corcrcd Ground. The following results ob- 

 tained at the experimental grounds^'- with 9-cm waves 

 refer to various types of grass-covered earth. 



The results obtained with the portable 10-cm set 

 appear on Figures 11, 12, 13, and li. These graphs 



8 12 16 20 



GRAZING ANGLE IN DEGREES ^t 



show clearly the influence of vegetation on the re- 

 flection coefficient. Consult Table 5 for corresponding 

 results at 9 cm. 



4 

 GRAZING 



8 12 



ANGLE IN DEGREES <^ 



16 



Figure 11. Reflection coefficient p versus i^, X=10cm. 

 d = 225 ft. Grass covered ground. 



24 



GRAZING ANGlE in DEGREES ^ 



Figure 12. Reflection coefficient p versus f. \= 10 cm. 

 d = 100, 225 ft. Grass covered ground. 



8 12 16 20 



GRAZING ANGLE IN DEGREES '^ 



Figure 10. Reflection coefficient p' versus i/-. X=10cm. 

 d = 90 ft. Sea water. 



Figure 13. Reflection coefficient p versus ip. X= 10 cm. 

 d=100 ft. Beet 6eld witli weeds. 



