Batboard

ok wiring guru's

here is a question for you ...

i have a ht1250 or could be an ex 600 but would probably be the ht ... i want to have a way to have a hand held mic say shure sm58 basically something not requiring phantom power, and feed that audio into the mic input of the radio, or selectively into a wireless belt transmitter for a wireless mic basically a give the user the ability to choose which to do.

Should I try and create a separate split of the mic signal and then into some type of contact closure ( what would i need here) to key the transmitter on the radio, or should i try and use vox, on the radio with some type of signal switch between the two selectively?

any thoughts issues or concerns here on the best design ? positives and negatives of each setup?

thanks in advance

Why in the world would you want to replace a communications microphone with an entertainment microphone? The radio is designed for an audio passband of something like 100 to 3000 Hz where the SM58's response goes to well above 12,000 Hz. Most if not all Motorola microphones of recent vintage use electronic switching systems in the microphone housing itself as well as the electronics for the usual electret microphone.

Leave the pro sound microphones alone and use the microphone that was designed for use with the radio. The only thing you're going to accomplish is lousy sounding, overdeviated FM transmissions.

i would want to do this so the op would only have to use one mic to communicate instead of having to grab a radio off of your hip and speak into it or fumble around with a lapel mic or something of the sort. ease of use based on need ...

it could be fed line or mic level easily and controlled via a dual pole toggle switch perhaps, what would i need to key the radio externally in this situation, or should i use vox on the input side so when the op hits a switch, a small one easily attached to the belt the audio could be fed into the radio instead of into the wireless transmitter ...

i understand the limitations of the radio transmit and audio quality that's not my goal ... i want usable audio passed into the two way for communication purposes.

Several companies make small microphone selector boxes, one of which would probably be adaptable to being worn on a belt. The real question is why you are trying to do this, and why you seem fixated on using a prosound mic in a comm environment, or so it would seem. Also, there's nothing inherently wrong with phantom power, and it's availability is usually part of a mic selector box, and further there are probably no wireless mic transmitters that DON'T use electret microphones these days, as do most all HTs, so why not use it? There are a zillion ways to electronically skin a cat, and if the Board members knew a bit more about your situation and requirements you might get some useful assistance.

well what i have is an op who uses a radio for "com" purposes in an eng type truck the com is fed into a transmitter and the op receives on two way, along with program etc.

on the op end the user has a mic wired to a small bat operated "mixer" if you will where they can adjust levels of the local mic and the 2 way rx audio, then the mic out is fed to a wireless mic transmitter and talk back is done on the standard lapel mic, however that has wires and different buttons everwhere what i would like is one belt mounted switch where they could use the hand held mic and have the audio fed into the mic transmitter then hit a button and have the radio transmit the audio while the button is being held.

no fumbling around for 2 mics attached to your shirt etc, hit a switch talk in the mic, use it to the wireless transmitter when necessary and then to radio to talk back when necessary.

Put a toggle switch across the ptt button of the spkr mic.

Been there, and done it.

First, I do agree an SM-anything on the surface is overkill, but where there is need...
The mics on the HT's are normally condenser elements, which take a small bias current and output sort of a medium signal level. If you get an HT acc connector (maybe scrapping one from a Mot or OTTO speaker mic...) you can find all the audio and control signals you'll need. What you probably WILL need to build is a little 1-transistor gain stage so the dynamic mic will have enough drive to properly modulate the radio. (someone mentioned "over-deviation" before - a good word-of-warning...) Your little gain stage could also have a little filtering in it so it rolls off the high end after 3,000 Hz. Also, another reason people often aren't happy with the end result is they forget about the dc bias going to the dynamic mic... which will slam the coil towards one end of the magnet. Watch your levels & impedence matching and you'll get good results.