SELECTIVE FADING OF MICROWAVES 



89 



frequeiicy-swcep patterns change with time. Tliese pictui'es were taken 

 at lO-second iiiter\'als. On this occasion there was good correlation l)e- 

 Iween the angle-of-arrival and free [uency -sweep data. Sucli was not 

 always the case, howe^'er, and considering the wide difference in opeiat- 

 ing frequencies, 24,000 mc and 4000 inc, instantaneous correlation should 

 not necessarily be expected. 



Although all the studies described in this paper were made on the two 

 local paths, the results are compatible with pi'opagation measurements 

 made by another group in the Laboratories during a survey for the 

 ti'anscontinental radio relay system. 



ACKNOWLEDGEMENTS 



The authors wish to acknowledge the contributions of W. M. Sharpless 

 who, for some time, was associated with this work; also to acknowledge 



1.0 

 0.8 



0.6 

 0.5 

 0.4 



0.3 



O 

 O 



3 0.08 



CO 



0.06 



I 0-05 



_l 0.04 

 < 



z 



0.03 

 to 



1 0.02 



l- 



LL 

 O 



I- 



z 



HI 



U 0.01 



S 0.008 

 CL 



0.006 



0.005 



-5 -10 -15 -20 -25 -30 -35 -40 



SIGNAL LEVEL RELATIVE TO NORMAL DAYTIME VALUE 



IN DECIBELS 



Fig. 14 — Time distribution curves of the signal levels observed on the Southard 

 Hill-Crawford Hill path. Data of 1947, 1948, 1949 and 1950. 



