1.5V miniature wireless FM microphone circuit

This article uses 12 components to make a miniature wireless FM microphone. The working frequency is stable, the transmission distance is about 30 meters, and it can reach more than 100 meters when powered by 6V. The circuit is as shown in the figure. BG1, C1, and C3 form a high-frequency oscillation circuit. The emission distance is related to the working current of the emission tube, and the upper bias resistor R2 can change the BG1 output current. When selecting BG1, the fT of the tube must be greater than 300MHz, but too high fT will affect the modulation. The inductor L is divided into two coils to be wound, but the winding direction must be the same. L1 is wound with a 0.5mm diameter enameled wire on a 5mm diameter frame. 4 turns, L2 goes around 3 turns. The antenna can use a 0.6 meter long flexible wire.