REFLECTION THEORY — PROPAGATION BEYOND THE HORIZON 633 



>^ AVERAGE e FOR 



\ ^'"TROPOSPHERE 



Fig. 4 — Schematic illustration of variation of the dielectric constant in the 

 troposphere. 



*-z 



Fig. 5 — Coordinate system for a beyond-the-horizon circuit. 



cal path length of 200 miles, is about 1,600 meters (1 mile) above the 

 earth or, since p = 2H, 3,200 meters from the z axis. 

 Equation 3 is used in all the calculations to follow. 



THE GRAZING ANGLE A 



The grazing angle A at the slightly tilted layer sho^^^l in Fig. 6 is 

 given by 



tan 2A 



2ap 



a^ — z^ — p2 



