192 



TROPOSPHERIC PROPAGATION AND RADIO METEOROLOGY 



200 

 180 

 160 



§140 



m 120 

 u 



Id 



tc 



o 100 



80 

 60 

 40 

 20 

 



10 20 30 40 50 60 70 80 90 

 f IN DEGREES 



0. 



5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 

 f IN DEGREES 



10 20 30 40 50 60 70 80 90 

 f IN DEGREES 



0.5 1.0 1.5 2.0 2.5 3j0 3.5 4.0 4.5 5.0 5.5 

 TjT IN DEGREES 



Figure 4. Phase and magnitude of reflection coefficient for sea water. 



irregularities of the land surface. When these irregu- 

 larities are sufficiently small, reflection from land is 

 found to be considerable. 



Since the receiver, or target, is usually located at a 

 distance from the transmitter which is large in com- 

 parison to the height above the ground, the direct 

 and reflected rays are very nearly parallel, making an 

 angel /3 with the horizontal (Figure 2). The reflected 

 ray may be supposed to issue from an image trans- 

 mitter T", which is as far below the ground as the 



true transmitter is above it. The path difference be- 

 tween the direct and reflected rays is equal to the 

 distance T'A. By the figure this is equal to 2hi sin /3, 

 where hi is transmitter height. For small values of /3 

 this is practically equal to 2/^/3 if /3 is measured in 

 radians. The corresponding phase shift due to path 

 difference is equal to 



* = 2M y . 



At the point of reflection the phase of a ray changes 



