FM FM microphone production tutorial circuit diagram

Wireless microphone principle analysis articles:

The following is the circuit diagram of the FM wireless microphone, the circuit is very simple, there is no redundant device. The high-frequency triode V1 and the capacitors C3, C5, and C6 form a three-point capacitor oscillator. For beginners, we do not want to honing the specific working principle of the capacitor three-point type. We only need to know that this circuit structure is a high-frequency oscillator. The load of the collector of the triode C4, L constitutes a resonator, and the resonant frequency is the transmission frequency of the FM microphone. According to the parameters of the components in the figure, the transmission frequency can be between 88 and 108 MHz, which covers the receiving frequency of the FM radio. The value (stretch or compression coil L) can be easily changed to avoid the FM station. The transmitted signal is coupled to the antenna via C4 and transmitted.

R4 is the base bias resistor of V1, which provides a certain base current to the triode, so that V1 operates in the amplification region, and R5 is a DC feedback resistor, which functions to stabilize the working point of the triode.