“In this project, we have designed an FM broadcasting transmitter system with a bandwidth of about 433MHz suitable for radio broadcasting.
This is the simplest form of FM transmitter which has the capability of transferring broadcasted music or voice to a range of 50m depending on the type of antenna that has been used. The system works without the requirement of tuning and the crystal quarts used are locked to a maximum of 90MHz. This system can eliminate frequency drift which is a common effect of modern LC-based transmitter systems.
The system is built around low power audio amplifier LM386, PN2222Atransistor, 1SV149 varactor diode, 30MHz crystal quartz, and several other components like potentiometer, diodes, capacitors, and resistors.
The tank circuit built at the collector of PN2222A which is made up of inductor L1 and capacitor C5 has a tuning of 3 times what the crystal quartz is rated which is 90MHz. The 90MHz is boosted and then coupled through capacitor C4 to the wire antenna for the music or audio to be transmitted so that a 30 t0 50m away FM receiver can pick the transmission.”