Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

MULTIPATH DISTORTION 281[B0° 4060° SO" 100° /SO' 140° 160° BO' 200°Sni.it——Fig. 3—Carrier envelope.Another interesting difference is that the two voltages come almost,but not quite, into phase at 30 degrees. This peak is therefore slightlylower than the others. The difference is caused by the fact that the sineof an angle is not linear, but departs from a straight line for largerangles.The maximum angle through which the one vector of Figure2 rotates with respect to the other is given byDz = 2 — sin -rrp,t radians (9)and this sine function introduces the nonlinearity. Further changesof the frequency merely move the curve along the axis, but effectslight changes in shape.Variation of the Envelope with DeviationFigure 4 shows the effect of changes of the maximum deviation D.The constants were chosen such that the two voltages are always inphase when 1-rr^t — degrees. For a small deviation, say D = 15,000cycles per second, the two voltages start to go out of phase as 2irfitincreases, but do not go completely out of phase.between the vectors in this case isThe maximum angleD-lSkcEO° 40° 60° ' 80° 100° 120° 140° 160° ISO' £rWFig. 4—Variation of carrier envelope with D.