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The digital like sound quality that FM offers is the reason that many people prefer to have their own transmitting station in FM band. The Quality FM Transmitter can transmit a chosen music piece in the FM band. To receive its signals, any conventional FM radio receiver can be used. It provides an easy way to transmit less distorted, low noise music with in a range of about 200 meters.
Just build yourself a simple FM transmitter, plug in the input via mobile or any other source and off you go with your own radio channel.Sounds exciting right !!
Things which you can learn:
*Application of transistor as amplifier.
*Working of variable resistor and trimmers.
*Concept and implementation of VHF using LC tuning Circuit
*Concept and implementation of Frequency modulation and antenna matching network
*Gain and maximum power transmission
The Quality FM Transmitter provides good signal strength up to a distance of 500meters with a power output of about 200 mW. It works off a 9V battery. The input to the transmitter can be given by various sources like mobile phones, mp3 players etc.
The audio-frequency modulation stage is built around transistor BF494 (T1), which is wired as a VHF oscillator and modulates the audio signal present at the base. Using preset VR1, one can adjust the audio signal level. The VHF frequency is decided by coil L1 and variable capacitor VC1. By reducing the value of VR2, a greater power output can be achieved. The next stage is built around transistor BC548 (T2), which serves as a Class-A power amplifier. This stage is inductively coupled to the audio-frequency modulation stage. The antenna matching network consists of variable capacitor VC2 and capacitor C9. By adjusting VC2, maximum power transmission and signal strength can be attained at the receiver end.