SELECTIVE FADING OF SUPER-HIGH FREQUENCY SIGNALS 1201 



^ e 



O 



_l 



X 

 ^10-3 



4 8 12 16 20 24 28 32 36 40 44 



PATH LOSS IN DECIBELS (RELATIVE TO MIDDAY NORMAL) 



48 



Fig. 9 — Effect on transmission of use of frequency diversity in 3,750-4,150 

 mc range. 



and reduction of the per cent of time when there is fading deeper than 

 30 db also reduces the per cent of time when there is fading deeper than 

 25 db, etc. 



CONCLUSIONS 



Quantitative information on fading phenomena is essential in the 

 engineering of super-high-frequency systems and in evaluation of fre- 

 quency diversity arrangements. The data obtained from the field tests 

 and the statistical analysis reported herein, while limited to a single path 

 and particular season, fill a gap in previous knowledge. They have found 

 practical application in the design of diversity systems for improving 

 the reliability of radio relay systems. 



The principal conclusions that can be drawn from the available data 

 are: (1) all of the deep fading is definitely frequency selective, and is 

 caused by a complex multi-path transmission; (2) deep selective fading 



