sri-pins IX R.inio nh'o.mc.iST TR/ixsMfssfox 



191 



tion of transmission than periK'ndicuIar lo this direct ion. Iprjn 

 these limited data one might be tempted to pre(h"ct the presence of 

 interference bands across the Hne of transmission. 



The above discussion concerning space rehition of field strengths 

 has been included merely by way of contributing an additional bit 

 of evidence to the theory that the erratic type of fading ordinarily 



Fig. 36 — Single-frequency fading record from vertical antenna and two-loop antenna 



crossed at right angles 



experienced at night time is due to wave interference. The picture 

 is ^•ery small in terms of wave lengths but considering its content, its 

 very limits seem to imply wave interference rather than attenuation 

 alone. 



In connection with the wave interference theory thus far suggested 

 as responsible for a major part of fading Fig. 36 is introduced as 

 added evidence. The middle record of this group represents am- 

 plitude changes in the night-time reception of a carrier wave upon 

 a vertical antenna. The upper and lower records represent the 

 same for two loops turned at right angles to one another in the hori- 

 zontal plane. By daytime tests the interaction of this combina- 

 tion was found to be negligible. Night-time fading recorded simul- 

 taneously for these three separate receivers occupying as nearly the 

 same point in space as was possible, show that a high amplitude 



