Introduction of AM Transponder Circuit in Record Player

Probe domestic double-head probe 038-BB-5.7L The shape of the two ends of the needle is outside the pointed needle

Single chip microcomputer STM32L151CCU6

Adjustable capacitor Murata genuine original

Photocoupler

The phonograph amplitude modulation transponder is actually a small amplitude modulation medium wave radio station, which can convert the audio signal output by the phonograph into an amplitude modulated high frequency electromagnetic wave to be launched into the air, and the adjacent medium wave radio can play the recording program after receiving the electromagnetic wave.
It is a typical inductive feedback type high frequency oscillator. When K is closed, the circuit can generate equal amplitude high frequency oscillation. The adjustment capacitor C4 can change the oscillation frequency, and CK is the pickup jack. If the plug of the record player is inserted into the CK, the audio signal picked up by the pickup will modulate the high frequency signal, so the transponder can radiate the modulated high frequency electromagnetic wave to the surrounding space. After receiving the nearby radio, it can be played out from the radio. The record came.