PROPAGATION STUDIES AT MICRO WAVK FREQITENTIF.S 95 



SEPT 8 1950 n : 5 - !2,0iP.I| SEPT 8 1950 1 ) 7 ~ 2 P K 



Fi"-. 4 — Keceived i)ulses — disturbed transmission. 



there was comparatively little fading over the path in question at micro- 

 wave frequencies. There were, however, a few nights of considerable 

 activity and some interesting results were obtained. 



The series of pictures on Fig. 4 show one good example of multi-path 

 transmission \\-here the path length difference was great enough to pro- 

 duce complete resolution of pulses. At 11:05-20 there are two pulses, 

 each 7 millimicroseconds wide at the base and with their peaks just 7 

 millimicroseconds apart; in other words, the path difference was just 

 sufficient to produce two pulses with no overlap. The pulse at the left 

 is presumably coming by the main path and that at the right from some 

 second path resulting from bending of the rays caused by atmospheric 

 effects. At 1 1 : 07-20 the second path appears to have shortened, resulting 

 in a path difference of only about 5 millimicroseconds. This may actually 

 have been due to a change of length of the second path or it may have 

 been due to distortion of the second pulse by energy coming by way of a 

 third path. The pictures taken at 11:08-20 and 11:10-50 show evidence 

 of transmission by a third path. In the first of these, for example, the 

 width of the disturbance at the base line indicates the presence of the two 

 original pulses spaced 7 millimicroseconds apart but the midpoint of the 

 two no longer falls to the base line as was the case in the first picture. 

 This could be accounted for by the presence of a third pulse coming over 

 a path whose length was somewhere between that of the other two. Con- 

 ditions obtaining at 11 : 10-50 could also be accounted for by the presence 

 of pulses from three paths, that is, energy coming by way of a third path 

 might cancel part of one pulse and at the same time add to the other. 

 This could account for the fact that the spurious pulse is larger than the 



