Hi. How can I make a stable fm oscillator?
I have built this fm transmitter: http://www.art-pipes.com/electronics/tx500.htm . But the oscillator is not stable... How can I fix this??

 

L1 should be made with large enuf wire that it is self supporting and physically stable, don't wind it on plastic or wood. Use a negative temperature coefficient capacitor for C5. Values from -100PPM to -750PPM are available, you will have to experiment.

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I have tried that. It won't work.. If I buffer the oscilator, would that help? How can I build it more stable? Can I use crystal or ic for the local oscilator?

 

The buffer not solved the stability problem. Use PLL with XTAL like this cct.

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Hi. Tanks for replying.
The circuit looks good, but I cant get IC3 and BB105.. What is the value of the crystal?