FM Bug Transmitter Mint Box Circuit

Posted on Feb 5, 2014

Here is the circuit for the FM Bug. In total there are 18 core components that are needed for the fm transmitter to work properly. The far left side has the electret microphone and then things move electrically to the right until they hit the antenna. Don`t let this microphone fool you, it`s extremely sensitive albeit a bit clunky and big. You co

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uld shop around for a smaller microphone I`m sure but for this project, a standard electret microphone does the trick. The input is pulled high with a 22k resistor and passed to the amplifier circuit. The amplifier`s job in this circuit is to take the audio input and beef up the voltage/current so that when it gets transmitted it travels further. More amplification means more higher fm transmitting power and longer range. The last portion of the circuit with the 2nd BC547 is where the oscillator for the FM frequency is generated and mixed with the audio signal inorder to form the frequency modulation used for FM radio. Don`t worry, if all this is described a bit too quickly, the theory will be desribed more indepth in the next section.

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