TUNABLE_DUAL_COIL_CRYSTAL_RADIO

Published:2009/7/12 23:43:00 Author:May | From:SeekIC

The 12-turn primary winding couples the RF signal from the antenna/ground system to the 48 turn secondary winding. Here C1, a 365-pF variable capacitor, tunes the L/C circuit to the desired radio-frequency signal. A 1N34A germanium diode, D1, detects the audio and feeds it to the headphones (Z1). The various taps on L1's secondary allow impedance matching of the antenna/ground system and the detector diode, as well as the inductance value needed to tune to the desired RF signal.



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