Here is the circuit of an FM transmitter with the IC UPC1651. UPC1651 is a broad band amplifier MMIC UHF silicon. The IC has a wide frequency response and power to win up to 1200MHz 19dB.The IC can be operated at 5V DC.
The audio signals picked up by the microphone is fed to the input terminal (pin 2) of the IC through the capacitor C1. C1 acts as a noise filter. The FM modulated signal will be available at the output pin (pin 4) of the IC. L1 inductor and capacitor C3 LC circuit forms necessary for the creation of the oscillations. Transmitter frequency can be varied by adjusting the capacitor C3.
Notes.
The circuit can be assembled on a Vero board.
Inductor L1 can be made by making 5 turns of 26SWG enameled copper wire on a 4mm diameter plastic former.
A ¾ meter insulated copper wire can be used as the antenna.
Do not give more than 6V to the IC.
Mic M1 can be a condenser microphone.
The audio signals picked up by the microphone is fed to the input terminal (pin 2) of the IC through the capacitor C1. C1 acts as a noise filter. The FM modulated signal will be available at the output pin (pin 4) of the IC. L1 inductor and capacitor C3 LC circuit forms necessary for the creation of the oscillations. Transmitter frequency can be varied by adjusting the capacitor C3.
Notes.
The circuit can be assembled on a Vero board.
Inductor L1 can be made by making 5 turns of 26SWG enameled copper wire on a 4mm diameter plastic former.
A ¾ meter insulated copper wire can be used as the antenna.
Do not give more than 6V to the IC.
Mic M1 can be a condenser microphone.
