911alertme Posted May 5, 2007 Share Posted May 5, 2007 I am thinking of making this FM transmitter. http://www.uoguelph.ca/~antoon/circ/fmt1.htm. I was wondering if I could swap in a connection from a 3.5mm jack (ipod, mp3 player, computer) and put it where the microphone is? If it is possible would I only get mono instead of stero? Quote Link to comment Share on other sites More sharing options...
moonlit Posted May 5, 2007 Share Posted May 5, 2007 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. Quote Link to comment Share on other sites More sharing options...
TheMadProff Posted May 5, 2007 Share Posted May 5, 2007 (edited) 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 September 4, 2013 by TheMadProff Quote Link to comment Share on other sites More sharing options...
911alertme Posted May 5, 2007 Author Share Posted May 5, 2007 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? Quote Link to comment Share on other sites More sharing options...
TheMadProff Posted May 5, 2007 Share Posted May 5, 2007 (edited) 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 September 4, 2013 by TheMadProff Quote Link to comment Share on other sites More sharing options...
911alertme Posted May 5, 2007 Author Share Posted May 5, 2007 Thanks. I'll try to find a different plan. Quote Link to comment Share on other sites More sharing options...
darell108 Posted May 8, 2007 Share Posted May 8, 2007 at work we use a stereo mic for that it has to mics in it basically and feeds them out of 2 jack connectors that would give u left and right to an extent on a mixxer system Quote Link to comment Share on other sites More sharing options...
911alertme Posted May 8, 2007 Author Share Posted May 8, 2007 Interesting but I don't see how it could be incorporated into this. Quote Link to comment Share on other sites More sharing options...
tanda333 Posted May 9, 2007 Share Posted May 9, 2007 i think you would need to find out how stereo and mono signals are transmitted differently. Quote Link to comment Share on other sites More sharing options...
TrinitronX Posted May 10, 2007 Share Posted May 10, 2007 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 Quote Link to comment Share on other sites More sharing options...
natural_orange Posted May 12, 2007 Share Posted May 12, 2007 all you need to do is a add a pre-amp the signal coming out of an ipod is powered where as a mic is not. I have a high-end SHURE mic for my computer that uses XLR...so i have an adapter and a pre-amp Mic ---> Pre-Amp ---> Transmitter Quote Link to comment Share on other sites More sharing options...
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