BAND WIDTH AND TRANSMISSION PERFORMANCE 



517 



frequency and contributes audio power proportional to the product of 

 harmonic power and spectral density. The channel 6 Iter accepts only the 

 demodulated noise falling in the audio signal range. 



The marginal power curve has been drawn for a 3 db ratio of peak carrier 

 to peak interference or 12 db ratio of mean carrier power to mean fluctuation 

 noise power. Curves for specific amounts of received power are included as 



20 



400 600 1000 2000 4000 

 IN MEGACYCLES PER SECOND 



10,001 



40 60 80100 200 



RADIO SIGNAL BANDWIDTH 



Fig. 14 — P.\M-FM; perfcrmance with respect to CW and similar system interference 

 for 1000 4 kc ciiannels with ratio of FM wave to interference marginal. Relations between 

 bandwidth and audio signal-to-interference ratio. 



well as the curve of marginal received power vs. radio signal bandwidth for 

 a receiver with 15 db noise figure. 



Fig. 14— PAM-FM, CW and Similar System Interference 



CW interference can be calculated conveniently by assuming all channels 

 idle and determining at what frequency within the radio signal band a CW 

 component of fixed power produces ma.ximum disturbance of an audio chan- 

 nel. This worst possible amount of disturbance is then assumed not to be 

 much affected by the various channel loading conditions existing during 

 normal operation of the system. When all channels are idle, the transmitted 



