Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

COMMON- AND ADJACENT-CMANNEL INTERFERENCE 331will be approximately 65 per cent of what it would be if all harmonics werepassed.If x = 0.5, it is evident that five or six harmonies will give nearlyundistorted output.As shown by Appendix I, this ratio of the peak output to the correspondingpeak for unlimited band width is equal to 1 — x n where n. is thenumber of harmonics passed.Common- and Adjacent-Channel InterferenceThe simplest case of frequency modulation interference(that of twoo2TT(jtFig. 14—Variation of distortion as interfering signal becomes stronger.unmodulated carriers of slightly different frequency) has already beendiscussed.If now the amplitudes of the two waves are kept constant, butthe frequency of one carrier is changed, the problem becomes one ofcommon- or adjacent-channel interference depending upon what range offrequencies the swings of the modulated carrier cover.If the deviationsof the one wave are about a mean frequency which coincides with thefrequency of the second carrier, the result is common-channel interference.If the mean frequencies are separated by the width of one channel, theresult will be adjacent-channel interference.