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Audio transponder without battery circuit

Published on Dec 22 2010 // Telephone Communication Circuits

Audio transponder without battery circuit.

This transponder can be audio signals to 88-108MHZ FM band frequency on the FM receiver in order to receive the same, possible
(1), with FM radio to listen to TV sound. If while listening with headphones, wireless headset functionality can be achieved TV
(2) audio recorder to record TV programs;
(3) two-antenna single-card recorder recording. The transponder has a simple circuit; no batteries, easy-to-alignment features. Especially suitable for beginners as for practice.
See pay chart circuit, where C is the system inductance. The introduction of the audio voltage from the plug by the VD1, VD2 doubler rectifier C2, C3, R2p-type filter, light-emitting diode LED regulator, got about 1.5V voltage supply road work. VT, L, C1 and other high-frequency oscillation circuit composed of three , VT base while the oscillation frequency by the audio control so love to the FM, frequency modulation wave from the antenna (0.4m cords) radiation out. circuit installed, the first tune C6, to receive FM radio signals, then adjust the sound quality clear BP can be.