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Accurate Receiver Selectivity Testing

June 12th Fact-of-the-Day

Radio receiver selectivity generally can be measured most accurately by 1) tuning both a receiver and an unmodulated signal from a signal generator to a test frequency, 2) measuring the receiver sensitivity at that frequency in terms of the signal generator RF output level required to obtain a reference value of detector-stage DC output voltage (or current), 3) and then, with all receiver adjustments undisturbed, incrementally stepping the signal generator frequency in small steps above and below the initial test frequency, while increasing and measuring the signal generator output level required at each step to obtain the initial detector reference output voltage (or current). That method is superior to the more common sweep-frequency method, because automatic gain control (AGC) compensations and other amplitude nonlinearities are eliminated by bringing the detector output up to the same level at each test frequency. ©2005 Martek International All rights reserved.


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