Using the UPC1651 FM transmitter circuit can be designed a very simple low cost FM transmitter electronic project. This UPC1651 FM transmitter circuit is specially designed as a wide band amplifier covering the HF band trough UHF band .
Some features of this monolithic integrated circuit are : high power gain, low voltage operation ( 5 volt required), small package.
The IC has a broad frequency response to 1200MHz and power gain up to 19dB .
Audio signal from the microphone are fed to the input pin (pin2) of the IC via capacitor C1. C1 acts as a noise filter. The modulated FM signal will be available at the output pin (pin4) of the IC. Inductor L1 and capacitor C3 forms the necessary LC circuit for creating the oscillations. L1 coil has 5 turns of 0.5 mm copper wire with 4 mm coil diameter. Adjusting the C3 capacitor will vary the frequency of the transmitter . For antenna , you can use a 50-70 cm long cu wire .