Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

loss and therefore the limiting Q factor.PUSH-PULL CIRCUIT 461K stands for the ratio of theoscillator frequency to the resonant frequency of the discriminator(K = f/fr ) . When the distortion is thus computed, the following tablerepresents the per cent of second harmonic distortion as compared tothe frequency swing, relative gain, and the mean frequency of the pointon the resonance curve against which the carrier issweeping.Second Harmonic in Per Cent ofRelativeK Fundamental, ±45 KC Gain0.98025.328.031.536.041.948.860.077.5123.0144.5156.0160.0180.0The curve is practically straight from K = 0.9972 to 0.9988. Thusa discriminator will cause negligible distortion if the total range ofmodulation is restricted to 80 kc for a 40-megacycle carrier. This isalso the portion of the characteristic which provides maximum output.The range actually used covered 30 kc in each push-pull component,thereby effectively covering 60 kc on the discriminator curve.The push-pull FM circuit presents a new tool which can be appliedto any mechanical translating or measuring device. As an example, intranslating the mechanical vibration of a reed it is possible to place thetwo outside plates of the push-pull condenser on each side of the reed,having the reed act as the center grounded plate.In that case largeamplitudes can be translated with minimum distortion without addinganything to the reed itself.3— Push-Pull FM Cutter CalibratorDuring recent years as the art of disk recording has become refined,a number of improvements were made in the recording head. Severalways were devised to measure the ability of the cutting head to repro-