SPHERICAL EARTH 



73 



cP 



2. Compute m = 



4ka{hi + h^) 



3. Read b from Figure 15. 



4. Calculate di = - (1 + 6). 



From equation (70) 



/ii sd hi 



sd 2ka (1 — s)d 

 Simplifying, 



It should be noted that h may be the height of gs _ ^ §2 _ gl '—(h^ + h^) — 

 eitlier the transmitter or receiver. The only re- 2 Lrf- 2_ 



{l< 



1 



(1 - s)d 

 2ka 



+ '^-0. (74) 

 d^ 



0.3 



0.5 



U) 



Figure 15. Graph for obtaining b for given values of c and )«. (Marconi, Ltd.) 



strictions are that /zi > /12 and di represents the If s < < 1, the terms s^ and s= may be neglected 

 distance from /ii. to a first approximation, and 



Another method will now be given for calculating /ii 



di. This method will be particularly useful when 



di/d < < 1 and will be applied in Section 5.5.8 on (^'i + ''2) 



generalized coordinates. Let 



2ka 



(75) 



Hence 



di = sd, s < 1. 

 da = (1 - s)d. 



If d < < dj, (Section 5.1.5), h is well above the line 

 (73) of sight and s reduces to 



hi __ di 

 hi + hi d 



s = 



(76) 



