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DIY FM Transmitter


911alertme
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Part of the circuit would be a small amplifier for the microphone I'd imagine but unfortunately I can't remember enough about electronics to tell you which part... you could replace the mic with a mono 3.5mm plug and send it some audio that way but you'd have to really keep the output of the source dfown very low... *very* low... a headphone jack outputs a lot more (even turned down very, very low) than a micorphone will so it would probably sound distorted and loud. It would be mono, and it wouldn't sound good, but it would work enough to get it to a radio.

It might be easier to find a schematic specifically designed for stereo and/or to take a headphone/line in input.

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The ratio of voltage from the microphone against an ordinary audio source could end up being quite crazy - beyond the realm of what's possible simply by turning the volume down.

As moonlit said, it would be best to find a dedicated circuit, without having to try and alter one...

Edited by TheMadProff
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So if I had the volume super low on my iPod it might work?  I Googled it and only found this one thing but it didn't have instructionshttp://www.volunteerlabrat.com/default.htm...to=fmtrans.html.  What if I created 2, one for right and one for left sound and outputted it to the same antenna?  Could it work?  I assume the quality would be bad.  Does anybody know of some stereo ones?

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It also depends on the type of microphone they've used in the circuit.

Some microphone capsules need a voltage bias (i.e. the pin of the actual microphone element that isn;t ground has to be held at a certain voltage), which I doubt would play nicely with any audio device connected in the microphone's place...

Edited by TheMadProff
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No, it still wouldn't work, as the way they send the data along the wires is different. A lot of mics change the capacitance, where as sound cable carrying audio (not from Mics) normally change the current...

I hope this helps...  :?

But shouldn't a changing capacitance should yield a changing current over time?

For a Capacitor:

I(t) = C * dV(t)/dt

I(t) = current over time

V(t) = voltage over time

For stereo, you'd need a way to get two input channels and transmit them in the right way.  Here's how stereo FM broadcasting works: http://en.wikipedia.org/wiki/FM_radio#FM_stereo

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