Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

122 FREQUENCY MODULATION, Volume Imission line, commercial receivers of various makes, cathode-rayoscillographs, a special high-fidelity high-power audio amplifier, anRCA audio oscillator, an RCA noise and distortion meter, a harmonicanalyzer, disc-recording equipment, a high quality loudspeaker,unweighted volume indicators, volume indicators weighted for earresponse, a u-h-f signal generator, a u-h-f field intensity measuring(RCA type 301A) set, r-f transmission line calibrated attenuators,noise-producing devices including automobiles, diathermy machines,Pig. 9etc., audio voltage amplifiers, balanced variable pads, and a microphonefor recording.The i-f systems in these receivers were painstakingly designed andadjusted for FM-15, FM-75 and AM, and at intervals during the fieldtests they were checked with respect to filter characteristics, i-f characteristics,limiter action, discriminator performance, audio frequencyresponse, distortion,etc.A shielded mutual inductance type antenna attenuator was builtand calibrated for controlling the amount of signal or noise voltagereaching the Bellmore receiver input terminals from the antenna. Bycontrolling the power of W2XWG, the antenna attenuator and thenoise sources themselves, any desired carrier or noise voltages could