FMPC microphone circuit diagram made by μpc1651

Crystal oscillator

High frequency probe high frequency line can be customized other specifications

Quartz Oscillator 3225 20M OSC

This circuit adopts, the circuit has high gain and stable operation, thus ensuring the high performance of the microphone. It is used to form the FM transmission circuit. It uses 40--50cm soft tow line as the antenna, and the effective emission distance is greater than 30M. Carefully adjust the L-pitch and trimming capacitor to make the transmission frequency cover 88--108MHZ.

The wireless microphone introduced in this example adopts the upc1651 integrated circuit produced by NEC Corporation of Japan as the main device, and has the characteristics of stable operation, reliable performance, easy production and easy debugging. The operating frequency can be selected in the FM band of 88~108MHz and received by the ordinary FM radio.

working principle

The core of the circuit is a high frequency oscillator consisting of a μPC1651 integrated circuit. The audio signal output from the MIC of the electret microphone is frequency-modulated by the C1 coupling to the μpc1651. The FM signal is coupled to the antenna via C5 for transmission.

The μPC1651 is a high-performance UHF broadband low-noise amplifier integrated circuit with a two-stage amplifier that is stable and reliable. It has only 4 pins of input, output, positive and negative power. Under the +5V working power supply, its quiescent current is about 20mA.

In order to further improve the frequency stability of the circuit, the three-terminal voltage regulator integrated circuit 7805 is used in the circuit to stabilize the μPC1651.