Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

+[\284 FREQUENCY MODULATION, Volume Ideviations D. It took approximately 30,000 cycles per second deviationto cause the carrier to go from in-phase to out-of-phase.The oscillograms of Figure 9 show how the number of peaks andholes varies with the deviation D. They are seen to be very similar tothose of Figures 1, 3, 4, and 6. In each one, the two voltages werenearly equal.Figure 10 shows an oscillogram in which one signal is about 3.5times as strong as the second. The general shape is the same as thoseof Figure 9, but the holes do not go nearly so deep. The velocity ofpropagation in the cable was 66 per cent of that in free space; therefore,the effective path difference was 15,900 feet. This corresponds toa time delay of 16.2 microseconds.Determination of Time DelayLet the path difference be d and the time delay corresponding toFM SignalGenera tor75^1Short Coaxial Cable*f -tt-75sl-F rr^E] B-LONS CoAXJALCable t" /—Fig. 8—Circuit for studying interference.Oscilloscopethis difference be t . The unmodulated carrier frequency is a. Let A xbe the wavelength corresponding to