Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

COMMON- AND ADJACENT-CHANNEL INTERFERENCE 335Figure 19 shows how the beat-note then becomes unsymmetrical.At oneend of the swing the two signals have nearly the same frequency and thebeats come slowly. At the other end of the swing there is a considerablefrequency difference and the beats are very much more rapid. The peaksand dips are limited by the two curves:D ex *cEnvelope = cos 2ir\sl + —1 + x 2r x + 1(12)andD „ ,a xcos 2-w\d +2ir x(13)Fig. 19—Common-channel interference, interfering signal detuned.Fourier-Series Analysis of Distorted Output. If the desired frequencymodulatedsignal is:e i= E isin (u< -\ sin 2r{it)t 1 (14)and the interference is an unmodulated r-f carrier of angular frequency