522 



BELL SYSTEM TECHNICAL JOURNAL 



Q 50 



i2 40 

 O 



10 20 40 60 80 100 200 400 600 1000 



RADIO SIGNAL BANDWIDTH IN MEGACYCLES PER SECOND 



Fig. 16 — PCM-FM; performance with respect to fluctuation noise. Relations between 

 bandwidth, power, and audio signal-to-noise for 1000 4-kc channels, showing optimum 

 bases for different ratios of FM wave to noise. 



B 



log -yr because the FM })o\ver-to-noise ratio is maintained regardless of 



Ztb 



bandwidth. The total advantage of the FM case is therefore 



20 log - - 



(I - ') 



+ 4.8 + 10 log A 

 Zrb 



