224 



BELL SYSTEM TECHNICAL JOURNAL 



6 = 180, and the resultant field strength is zero as in the reflection 

 case treated above. 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 



MILES FROM TRANSMITTER 



Fig. 25 — Flight from transmitter. Altitude — 5000 feet; 

 wave-length — 4.3 meters, June 29, 1931. 



For large values of z'l and z'2, that is for hi and h^ large, F\ and F^ 

 approach unity, and /3i and /32 approach zero. Equation (4) then 

 reduces to the ordinary reflection case of equation (1). 



Note: The ratio of the difl'racted field strength to the field with edge 

 removed is 



1 



where. 





and, 



C = I cos " f/y = - + I 



cos — civ 



sin -;r- av 





