Single tube 1.5V micro wireless microphone circuit diagram

Crystal oscillator

Quartz Oscillator 3225 20M OSC

The miniature wireless microphone circuit described in this paper is composed of only one transistor plus a RC component, a microphone head and a micro button battery, and the volume can be made small. The launch distance can reach about 30m. The circuit schematic is as follows:

In the circuit, the triode and the inductor and capacitor form a high-frequency oscillator, and the audio signal output by the MIC directly modulates the frequency of the high-frequency oscillator through a capacitive coupling of 1 μF (changing the junction capacitance of the triode). The 10KΩ resistor is the base biasing resistor of the triode. In the production, the resistance of the triode can be changed according to the working current of the triode. The current is larger and the emission distance will be farther, but the battery consumption is faster.

The triode adopts 3DG130G, 9018 and other high frequency tubes. The inductor coil is wound around a 5 mm diameter round bar with a diameter of 0.5 mm. The center tap is connected to the antenna via a high frequency coupling capacitor. When the antenna uses a flexible wire of about half a meter long, it can be received with an FM radio, and the transmission distance can reach about 30 meters.

The RC components in the circuit are valued as shown, and the MIC is a miniature electret microphone.