DIY : Wireless Microphone .

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suggestion for cordless mic

Buy two UHF cbs, handheld, cheap and small but a high quality sound (uniden maybe) Modify the mic to be of a high quality, may need a new preamp for that.
Jam is all inside your mic (i said get a small one)
Hook it all up, set both to same channel and plug the headphone socket of one into an amp. Set one so it is alway transmitting. THe only problem besides sound quality will be that you will get yahooligans talking on your sound system if you live in a big town. Try on channel and if you get anyone talking you'll have to try another.
Another suggestion would be using cordless phone circuitry.
FM microphones are easy to build but probably wont cut it, they simply transmit onto the fm radio. THese are very easy to make and sound quality not bad however limited in reception.
Daniel
 
fm walkie-talkie method

Radio shack is always closing out this kind of items. I used a set of them; one end with the switched wired to always transmit, and the mic head wired to a cable with a tie-clip for attaching to shirt collar, etc: lavolier-style, right? The other end has a 1/4" connector for output to amp, mixer. Both ends work off 9v, and the receiving end could have a wall-wart soldered in. No idea yet of how long it will function as compared to a commercial product, which will, of course, sound and work better. The last post also points out that the DIY circuit requires you to find an empty area on the FM dial; this idea has you in the FRS area. You are also disobeying the "Don't transmit more than half the time" rule, but the range if it's a real cheap set is limited.
J
 
An AM wireless mic idea - looking for feedback

My job entails talking for hours on end almost daily in a fairly large room (roughly 30ft by 50 ft by 11ft, or 9m x 15m x 3.5m). There is no PA system, and the room is large enough so I have to choose between either damaging my voice over time, or being inaudible in parts of the room. I also need to be mobile (within the room) while talking.

The room in question is a classroom in a California public educational institution, which if you know anything about California (and more generally, US) public education policy, means that there is no budget for buying anything officially. I either have to build what I need, or pay for it myself from my own pocket.

I have tried playing with small DIY FM transmitter circuits, and encountered the problem of being quite unable to find a quiet spot on the FM dial - I live in a big city, surrounded by other big cities, and the entire FM band is jammed all the way from 88 MHz to 108 MHz.

The room in question has steel-framed walls that almost totally block AM radio waves; it is hard to pick up more than one or two of the strongest AM stations inside the room, and those only at the high end of the AM band, near 1.6 MHz, where the wavelengths are shortest. That has got me thinking that perhaps a good solution for me would be to construct an AM wireless mic, transmitting in the good old AM band.

I have access to some AM pocket-radio kits left over from an electronics class which could be used as the receiver or receivers. I also have access to some unused powered computer loudspeakers, which I could hook up to the output from the AM radio's detector stage to make low-powered PA speakers. The speakers are low-powered, but if I can build four or five of these and scatter them around the room, I think they would do the job passably.

After some more thought, I am now wondering why I shouldn't simply run the transmitter at 455 kHz, and build the radio kits without the input mixer/oscillator stage, so they are tuned to receive signals only at their IF frequency of 455 kHz. Since AM wavelengths hardly make it into the room, it seems reasonable that little RF from my transmitter will leak out of the room either, so I shouldn't cause any interference issues for people outside the room. As a bonus, I won't have to wind coils for my transmitter, I can probably simply use an IF transformer from one of the radio kits as the tuned circuit in my transmitter oscillator as well!

I know that an antenna of reasonable length (i.e. from my hip to my lapel or so) will be far too short to radiate efficiently at 455 kHz, but I only need 50 feet (15 m) of range, which I'm hoping I can achieve with a very low powered (mW) transmitter. I plan to use a cheapo electret mike, which should be more than adequate for decent speech quality.

Anyone have feedback on this idea? Any obvious problems or flaws?

TIA,
-flieslikeabeagle
 
@guitargully

Sorry, I forgot to mention that. Yes, it really needs to be hands-free. I was planning on using a cheap electret mic with some sort of clip to make it lapel-mount; I've also seen inexpensive lapel-mount mic's for use with cell-phones which might be useable.

You refer to a page with some stuff I might find interesting: did you perhaps forget to write down the URL, or are you referring to the idea using the two walkie-talkies at the top of this same thread? That sounds like quite a good idea, though it might end up being just as much work as building my own, by the time I convert the walkie-talkie to use a lavalier mic, wire it to permanently transmit, find a way to permanently power the receiver with a wall-wart, and then wire it all up to distribute the signal from the receiver to my several low-powered PC speakers.

Regards,

-flieslikeabeagle
 
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