The FM wireless microphone operates at a voltage of only 1.5V and is powered by a fifth battery or button battery, which consumes less power. The transmission frequency is set in the range of 88 to 108 MHz, and is received by a normal FM radio with a transmission distance greater than 100 m. All components can be mounted on a small circuit board of 3 cm x 1 cm. In the figure, BG1 and peripheral components constitute a three-point capacitor oscillator. The audio voltage generated by the MIC changes the junction capacitance of BG1. At high frequencies, even a small capacitance change causes a large frequency offset. The FM signal is amplified by BG2 and sent to the antenna for transmission. BG1 and BG2 can be 3DG201, 3DG6, etc., and β>80. The capacitor in the circuit uses small ceramic capacitors, the resistor uses 1/8W small resistor, L1 uses ∮0.6mm enameled wire to wrap around the ballpoint pen 7 times, taps at 3 turns, and adds a TV mid-week spiral core after the tire is released (also available) Short-wave radio local oscillator core, but the effect is a little worse), L2 is made of ∮0.35mm enameled wire around the ball-point pen core for 6 turns. The antenna can be used with a flexible wire of 80 mm length, and for convenience, a short wire of a plurality of core wires can also be used. If the printed board is assembled according to the device in the figure, it is generally not necessary to adjust. Turn on the FM radio, adjust the FM band and the L1 core to a certain point and the noise disappears. Uv Air Purifier,Air Purifier With Uv Light,Uvc Air Purifier,Uv Air Cleaner CIXI KYFEN ELECTRONICS CO.,LTD, , https://www.kyfengroup.com