TWIN_LED_TUNING_INDICATOR

Published:2009/7/3 3:33:00 Author:May | From:SeekIC

Provides maximum sensitivity at correct tuning point and indicates direction of mistuning. Both lamps are in feedback loop of one opamp, connected to serve as highlysensitive null detector.When set is tuned correctly, output of this opamp is at midpoint of supply voltage and neither LED is lit. Circuit is used with RCA CA3089 IF chip in which AFC output is a current. Capacitor across first 741 opamp removes modulation components from this input.-M. G. Smart, F.M. Tuning Indicators, Wireless World,Dec.1974,p 497.



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