FM radio microphone RF-02FM from the "DIY" kit. Setting up, assembly and testing

I ordered a radio microphone for frequencies of 88-108 MHz from Aliexpress, this is a DIY kit, where you need to insert the parts into the board and solder them yourself. Model name RF-02FM.

The FM transmitter consists of a microphone amplifier on a 9014 transistor, a master oscillator and a power amplifier on 9018 transistors. The power supply is indicated in the specification from 3 to 6 volts, but I tested it with a power supply of 7.4-9 volts. The signal sound can be fed both to the microphone and from the output of a telephone or other sound source

Coil L1 contains 7 turns of wire approximately 0.25 mm on a frame with a diameter of 4 mm with a trimmer core. L2 and L4 have 8 turns of wire 0.4 wound on a mandrel with a diameter of 4 mm. L3 contains 5 turns of wire 0.4 mm also on a 4 mm mandrel (the diameter of the wire is approximate).

I tested the transmitter together with the antenna - a 35 cm long wire that comes with the kit

The parts have long leads and they need to be shortened

The numbering and designation of the parts are shown on the board, you just need to insert the parts into the hole and solder them

After connecting the power supply, you need to configure the transmitter. If you do not need a large range of the transmitter, no configuration is required. Receive the signal on the radio receiver, unless, of course, there is a broadcast radio station on this frequency. To configure for maximum power, I used a probe on two diodes and a power control LED. I connect the probe to the transmitter output, and the antenna to it (RF probe). Carefully screw the core into the L1 coil, you need to achieve maximum glow of the probe. There is also a frequency adjustment

Next, I remove the probe and connect it to the end of the antenna and adjust it to maximum brightness. This can be done immediately, but first you still need to see how brightly the probe shines in front of the antenna from the transmitter output

With this setting, the maximum range will be just over 150 meters with direct visibility