A SINGLE SIDEBAND MUSA RECEIVING SYSTEM 335 



shown by theory. It is a fairly common occurrence for a wave group 

 which has apparently traveled over a single general path to have 

 components which vary in transmission times by 100 or 200 micro- 

 seconds from others of the same group. The fading caused by such 

 small delay differences is not distinctly selective in effect and its 

 chief detriment is in causing volume variations which must be overcome 

 by the use of special devices. 



During some severe magnetic storms successive traces on the angle 

 monitoring cathode ray oscilloscope show little relatioij to each other. 

 It has been reasoned that a reduction in resolution might be beneficial 

 at such times but sufficient experience to prove this has not been 

 obtained. A reduction in resolution can be obtained easily by switch- 

 ing off the amplifiers associated with one group of eight antennas. 

 It has been found that fading on the front group of antennas is 

 generally at random to that on the rear group so that the two groups 

 can be used in space diversity if desired. No particular advantage 

 has been found to this arrangement. 



The use of delay compensation between the diversity branches 

 does not seem to have any advantage over the use of the automatic 

 branch selector. The output volume variations are slightly greater 

 with delay compensation because of the use of reconditioned carrier 

 for demodulation. On the other hand the use of the automatic 

 branch selector promises materially to reduce maintenance by elimi- 

 nating the necessity for keeping the phases of the various carrier and 

 sideband amplifiers alike. 



It has been amply demonstrated that the automatic adjusting 

 features provided are essential to the efficient operation of the 

 equipment. 



