DESIGN AND CONSTRUCTION OF FM TRANSMITTER

FM transmitter is a device which generates frequency modulated signal. The circuit diagram in this project work shows how the FM transmitter functions. The required electrical and electronic components for the circuit is the power supply of 9V, resistor, capacitor, inductor, mic, transmitter and antenna. We considered the microphone to understand the sound signals and inside the mic, there is a presence of the capacitive sensor. It produces according to the vibration to the change of air pressure on Air signal. The formation of oscillator circuit can be done through the transistor of 2N3904 by using the inductor and variable capacitor. The transistor used in this circuit is an NPN transistor used for general purpose amplification. If the current is passed at the inductor L1 and variable capacitor then the oscillator circuit will oscillate at the resonant carrier frequency of the FM modulation. The negative feedback will be the capacitor C2 to the oscillating tank circuit. To generate the radio frequency carrier waves the FM transmitter circuit requires an oscillator. The input audio signal from the mic penetrated to the base of the transistor, which modulates the LC oscillator circuit carrier frequency in FM format. The variable capacitor is used to change the resonant frequency for fine modification to the FM frequency band. The modulated signal from the antenna is radiated as radio waves at the FM frequency band and the antenna is nothing but copper wire of 20cm long and 24gauge.