Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

DUPLEX SOUND AND FACSIMILE 401Before going to the experimental results it would be in order topoint out the types of cross-talk that can occur ifto pass this entire band as represented in Figure 6.the equipment failsIf the bandwidthof the single-tone transmission is restricted at the extreme ends, onlyharmonic distortion of the resulting detected tone will be present, anda few per cent of distortion of this type will be little noticed. This sameamount of restriction on the two-tone transmission will result quiteDEVIATION100 KG 80 60 40 20 - F, + 20 AO 60 8.0 100 KCVERV LOW AUDIO FRE8.AT 60-KC DEVIATIONFIRSTSIDEBAND, - ZOKC SI6NAL AT>v \15-KC DEVIATION120 KC—•SECOND SIDEBAND*40 KCFig. 4—Facsimile signal of Figure 3 added to verylow frequency signal at 60-kc deviation.differently, for such band limiting will act as a preliminary frequencydiscrimination and change various side-band frequency modulations toamplitude modulations. This will introduce cross-talk in a mannersimilar to the action of a non-linear tube in amplitude multiplexing.It should be pointed out that a small percentage of cross-talk is farmore objectionable than the same percentage of harmonic distortion.The process of detecting a frequency-modulated wave requires dif-