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Versatile FM Transmitter

2016-04-06 21:07  
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Description.

Here is the circuit diagram of a versatile FM transmitter that doesn’t have a coil. The circuit is simple and easy to assemble.

The gate N1 acts as a buffer for strengthening the signals from the condenser microphone. The inverter N2 with its  associated components forms a radio frequency oscillator in the FM region.The varicap diode  BB109 is used for frequency modulating the audio signal to the carrier wave generated by the oscillator.Inverters N4 t0 N6 are used to drive the antenna.As the N4,N5,N6 are connected in parallel their effective output impedance is very less and can easily drive the antenna.

Circuit diagram with  Parts list. 

fm-transmitter-without-coil.JPG

Notes. 

All electrolytic capacitors must be rated 10V. Use any general purpose condenser microphone.You can easily get one from old telephone or tape recorder. Use a 10 cm long wire as antenna. Gates N1 to N6 belong to same IC CD4069. The battery can be a 9V transistor radio battery.Adapters are not recommended because they would induce noise in the circuit.