ULTRA-SHORT-WAVE TRANSMISSION 



501 



moderate roller fading, a good coincidence between the two records 

 resulted. This is discussed later. 



Figure 6 is a sample of fading on horizontal polarization, at its worst. 

 This particular specimen shows the superposition of roller and fine 

 structure fading very well. No vertical-polarization record was taken 

 along with this. Figure 7 shows a typical example of fading simul- 

 taneously observed on vertical and horizontal polarization during bad 

 fading conditions. There is no coincidence. Figure 8, on the other 

 hand, records an unusual condition when a mild roller type of fading 

 shows a good coincidence on two polarizations. 



30 



20 



X 10 



50 



> 40 



30 



20 



1 = 30 RM. 



2:00 RM. 

 EASTERN STANDARD TIME 



2:30 RM. 



Fig 



. 8 — Comparison of simultaneous mild roller fading on horizontally and vertically 

 polarized transmissions. 



Effect of Wave-length on Fading 



The double wave-length records are not as contrasty as the double 

 polarization ones. In general the shorter wave has the worse fading, 

 either as higher fading rate, greater amplitude oscillation or both, and 

 the greater the wave spacing the more certain this is to be true. Ex- 

 ceptions have occurred, however, where the fading was much the same, 

 and one record was obtained where the fading rate on 4.7 meters was 

 noticeably greater than on 4.5 meters. 



Our first simultaneous records were taken at a wave-length ratio of 

 3 to 1 (4.7 to 1.58 meters) where the fading on the shorter wave was 



