Sirnil-S I.\ h'.ll'IO Hk'O.IDC.IST tr.ixsmission 



211 



In these oscillograms the uppei trace is the record of the signal from 

 the carrier and both side-bands, and the lower trace the signal from 

 the carrier and lower side-band. 



Thes ■ records illustrate by giving a graphic comparison the effect 

 of the phase changes of the component signals in the case where the 



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Fig. 50 — Slow record comparing the signal detected from carrier and one side-band 

 with signal detected from carrier and both side-bands. Made at Riverhead, L. I. 

 Upper trace carrier + both side-bands, lower trace carrier + one side-band. Strips 1 

 and 2, July 22, 1925, 1:46 a.m. 25()-cycle modulating tone. Strip 3, July 21, 1925, 

 3:10 a.m. 250-cycle modulating tone. Strips 4 and 5. July 23, 1925. 2:47 a.m., 500- 



cycle moflulating tone 



signal is detected from both side-bands. The amplitude of the signal 

 from both side-bands in some instances is very small but appreciable 

 amplitude is still indicated at the same instant for the signal from one 

 side-band. This is explained as meaning that the side-band phases 

 were such as to make the component signals 180 degrees out of phase 

 after detection and that the amplitudes of the components were 

 practically equal. The reverse situation is also observed where the 

 amplitude of the signal detected from the lower side-band is zero and 

 appreciable signal is recorded for the case where both side-bands are 

 used. This is interpreted to mean that the side-band signal was 

 eliminated by selective fading. In this event it was, of course, not 

 contributing to the signal which was detected from both side-band 

 signals. The recorded signal comes from the other side-band which 

 evidently was not eliminated at that instant by selective fading. 



