USB mono FM transmitter

This compact FM transmitter has a range of approximately 50 meters and is designed to connect to a USB port. Using multiple mini transmitters, you can have a comprehensive and feature-rich radio selection. High frequency stability is achieved thanks to USB port power supply. Alternatively, the receiver can operate using 5 to 12 volt batteries.

FM transmitter construction

The USB FM transmitter prototype does not require drilling holes in the transmitter PCB.

All components will be soldered to the board with their leads folded over, like this:

The two transistors and the LED are polarized: the transistor has a planar side, the longer lead of the LED is the anode (A), and the other is the cathode (K). The audio cable (mini-jack) must be converted from a stereo cable to a mono cable.

Mono sound: Solder the white and red cables together, ignoring the yellow cable (ground). Frequency setting will be done by gently turning the variable capacitor with a screwdriver or thin, stiff cardboard.

FM Transmitter Parts List:
1 x 510 Ohm Resistor (Green-Brown-Brown)
1 x 100 kOhm Resistor (Brown-Black-Yellow)
1 x 1 MOhm Resistor (Brown-Black-Green)
1 x 0.1 uF Capacitor (0.1)
1 x 47 nF Capacitor (0.047)
1 x 4.7 pF Capacitor (479)
2 x 22 pF Capacitors (22)
1 x Variable Capacitor (1.5 pF to 15 pF)
2 x BF 246 Transistors (F246A)
1 x Red LED
1 x Audio Cable (Mini Jack)