With this tiny FM transmitter , you can transmit your voice or audio to an FM Radio. Its range is 10-25 meters in the properly tuned condition.
The circuit uses only one Transistor for modulating the voice signals in the FM band. Trimmer capacitor VC1 and the coil L1 forms the Tank circuit. The sound signals captured by the condenser Mic is amplified by the transistor T1 and along with the tank circuit, T1 transmits the voice in the FM band lying between 88 MHz and 108 MHz.
Note – Assemble the components on the Common PCB carefully with minimum length for components. Mic should be connected directly to the PCB using two cut pieces of Resistor leads. Do not use wires because it may reduce the sensitivity. Use 10 cm plastic wire or Telescopic areal as Antenna . Connect 9 Volt battery or power supply and keep the unit near a Mobile phone with FM radio or an FM Radio. Press the Auto Scan of the FM radio. It will scan all available station and the FM transmitter. During testing, 97.9 – 98 bands showed maximum clear voice. If a hauling sound hears from the Radio, we can confirm the tuning of FM Transmitter . You can also adjust the Trimmer slightly to make the station clear. If there is disturbance, move away or change the position of Transmitter to get clear sound.