598 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1957 



with a path difference of one-half \va\'elength form the Isoundary of the 

 first Fresnel zone; similarly, the boundary of the n*^ Fresnel zone con- 

 sists of all points from which the path difference is n/2 wavelengths. 

 The n*'"' Fresnel zone clearance //„ at any distance di is given by: 



H^ 



n\di{d — di) 



d 



(6) 



Although the reflection coefficient is very nearly equal to —1 for 



— 6 



— 10 



— 20 



-50- 



— 100 



-200 



-600 



— 1000 



-2000 



— 5000 



— 10,000 



JL 



*h 



k- 



d--- 



->l 



-10 



-20 



-50 



-100 

 _ \ 



•200 



-500 



-1000 



-2000 



■5000 



-10,000 



•0.1 

 -0.2 



0.5 



2 



5 



20 



50., ' 



— 100 

 200 



— 500 

 ^1000 



CO 



LU 



-J 



z 



LU 

 O 



z 

 < 



10 



in 

 < 



z 

 z 

 111 

 I- 

 z 

 < 



o 



a. 

 o 



cc 

 t- 

 o 

 </) 



z 



LU 

 LU 



I- 



LU 

 CD 



to 



(O 

 O 



_) 



z 

 o 



10 



5 

 to 

 z 

 < 

 cc 



■70 



-80 



-90 



-100 



■110 



-120 



-130 



;140 

 'v. 

 v. 



■150 



-160 



notes: 



1. this chart is not valid 

 when the indicated received 

 power is greater than the 

 free space power shown on fig.l 



2. use the actual antenna height 

 or the minimum effective height 

 shown on fig. 3, whichever is the 



LARGER 



Fig. 2 — Transmission loss over plane earth. 



