A simple mp3 fm transmitter circuit shown here can be built easily in few minutes if all parts are available with you. All the components used in this circuit are general purpose and low cost. The circuit will work as a best FM transmitter for simply broadcasting your music around your house and
yard, and can be used to broadcast the output of any equipment like walkman, mp3 player, ipod etc.
The coil L1 is equal to 8 to 10 turns of 22 guage wire wound on 6mm form, remove the form after winding the coil. At the adjacent to coil there is a 1-30 pF trimmer capacitor, which is used to adjust the frequency of this mp3 FM transmitter.
After building the circuit apply power and connect it to the audio output of your device, then set your FM radio frequency on a blank spot and slightly adjust the transmitter’s trimmer with a non conductive tool and stop where you found the sound of your music. Minimum antenna length should be 12 inches but if you want to increase the range then increase the antenna length to 30 inches. You can power this FM transmitter circuit with any size/type of 1.5V or 3V battery.