FM transmitter on colpitts oscillator

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Hi,

I have designed a colpitts oscillator which works fine at 27HZ I have to turn it into an FM transmitter, what and where on the circuit should I add i.e diode microphone etc.I.e how do i turn this into a radio transmitter?

Many thanks in advance!
 

Because this is a common base type oscillator you can input audio from the microphone directly to the base of the transistor (using a DC coupling capacitor), turning the circuit into an FM modulator. And if using an antenna mutual coupled to L1 this can be a low range FM transmitter.
Other option is to place a varicap in parallel to C3, and modulate the bias of the varicap with the signal from the microphone
 

vfone,
Okay if i use the microphone, will the battery stay or do i need to remove it?also, how do I determine capacitor size?
 

Better is to remove the battery when doing the experiments.

Use a 100nF in series with the microphone.
 

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