406 



BELL SYSTEM TECHNICAL JOURNAL 



peaks corresponding to the inverse of fading is shown by the transcribed 

 motion picture record of the signal and noise meter variations, shown 

 in Fig. 40. Note the signal fades. 



A secondary improvement of 3 decibels is too high for two-station 

 space diversity; i.e., the signals do not add on a voltage basis.*" 



TABLE VI 



AnTEJJNAS 1 AND 6 IN DIVERSITY 



GBW 14,440 kilocycles 



The apparent line loss is 3.1 db. The calculated loss is 3.8 db. 

 The equivalent improvement is 3.6 db. 



Oscilloscope observations of the diversity combinations of the audio 

 outputs of two spaced antennas (No. 1 and No. 6 of the Holmdel 

 MUSA) indicate, however, that on the average the secondary improve- 

 ment is appreciable and probably about 2 decibels for two antennas 

 and 3 decibels for three antennas. This improvement depends upon 



u -I +10 

 o -^ 



io ? -10 



UJ (D 



NO. I ANTENNA 



1 & 6 IN DIVERSITY 



Fig. 40 — Sample of signal and noise variations occurring in diversity tests. The 

 arrows indicate noise levels beyond the scale of the meter. GBW (14,440 kilocycles) 

 Rugby, October 10, 1935. 1920 G.M.T. 



the number of wave bundles, their angular separation, their relative 

 delays, the spacing of the antennas and the frequency band occupied 

 by the signal. For a single compact wave bundle the secondary 

 improvements will be nearly 3 decibels and 4.8 decibels for two- and 



