Moto desk mic to computer sound card....

wheelman · Post by **wheelman** » Mon Dec 27, 2004 5:17 pm

Howdy.
I use Echolink which is a hybid radio / VOIP system linking ham radio repeaters around the world. I have been using my computer mic into the computer's sound card, but I got thinking... why not use a Motorola desk mike... maybe something like a TMN1004B.

1.)Anyone venture a guess as to whether this would work and;
2.)what would the wiring diagram look like? (Note: PTT is not a concern... just the audio.)

Thanks in advance
WM

ASTROMODAT · Post by **ASTROMODAT** » Mon Dec 27, 2004 7:42 pm

The Motorola desk mic has a far different impedance and output level as opposed to what the PC's mic Input port is "looking" for. If you are hell bent on using a Motorola desk mic, you will need something like a Shure FP-33 field audio mic/mixer. Once you go with a Shure mic amp/mixer, you can now use any commercial Pro audio mic, such as a Shure SM-7, or the like, which woluld be infinitely superior to any PC mic, or for that matter, compared to any Motorola 2-Way mic.

In the end, why go to all of this trouble and expense? Besides, IMHO at its best, Echolink sounds pretty krappy, so why spend the $1,700 on the Shure mic amp anyways?! A better bet might be to go with a 100% digital Internet system, such as D-STAR, rather than the old analog legacy stuff like IRLP, Echolink, etc. D-STAR wil give you a win-win situation.

larry

jistabout · Post by **jistabout** » Mon Dec 27, 2004 10:05 pm

I have a friend who has done this with an old JC Penney CB desk mike and it works great. I think that Echolink even has provisions in the program for equalizing audio response from a communications mic. If you do want PTT from the mic, simply wire it int the appropriate pin on whichever comport that Echolink is using, and set Echolink up to use it. My friend keys his and talks on it just like any other radio. Anyway, you should be able to make it work just fine, but if using a preamplified Motorola mic, you might need to supply power to the preamp. Have fun & good luck

kcbooboo · Post by **kcbooboo** » Tue Dec 28, 2004 5:17 am

Many of the Motorola mobile mikes, and some base station ones, have a preamp built into the mike. They need some DC power to run. Radios like the MaxTrac supply 9.6 volts through a (nominally) 560 ohm resistor, to the mike audio line, then couple the audio through a small capacitor to the rest of the radio. Something like this should work for you, but the exact wiring would depend on the microphone and cable you use. If you have a higher voltage available, increase the resistor value. Old Motracs and even some tube transmitters provided this voltage because they often used carbon microphones which needed DC to operate.

Bob M.

kcbooboo · Post by **kcbooboo** » Tue Dec 28, 2004 9:16 am

One more little thought. The signal level out of a Motorola mike with a preamp in it, will be around 0.1 to 0.3 volts RMS, as that's the level that the mike input would expect for full deviation. This is WAY louder than the average hi-fi microphone, or the level that a sound card would expect to see on a MIC input jack. The Motorola mike should work well if fed into the LINE input jack on a typical sound card.

Bob M.

ExKa|iBuR · Post by **ExKa|iBuR** » Tue Dec 28, 2004 11:02 am

Well if you're really serious about this and want to make it "realistic" to talking on a radio...

Get a Motorola desk mic. Rip out the guts. Then get a PC microphone, take the guts from that and put it in the Motorola desk mic.

Then, get yourself an old keyboard (USB), rip it apart...whatever key you use as the PTT button, wire a momentary switch to it, and hook that to the desk mic's PTT button.

It might take a bit of work which in my opinion might not be worth it, but hey...if you want to go for looks, it's probably your best bet.

-Mike

jistabout · Post by **jistabout** » Tue Dec 28, 2004 3:23 pm

Also, I think that most computer sound cards supply +5vdc at a few ma on the mic line.....

ASTROMODAT · Post by **ASTROMODAT** » Tue Dec 28, 2004 11:40 pm

why bother?!

wheelman · Post by **wheelman** » Wed Dec 29, 2004 3:21 pm

I dont know what possessed me. I'm over it. I'll just use the computer mic for Echolink. I must have lost my mind (temporarily).

Thanks for all of the guidance, though!
WM

jistabout · Post by **jistabout** » Fri Dec 31, 2004 1:33 am

Well now wait a minute you guys....

There are perfectly good reasons for doing this. My above-mentioned friend did it because it allows him to hide Echolink on his taskbar and key it thru the comport so that the program doesn't have to have focus every time he wants to key it. Also, his audio is now much more "communications quality" rather than muffled too-much-bass-full-blown 20hz-20khz computer mic audio. And lastly, it makes operating it more like a real radio. And besides, anything which compels one to pick up a soldering iron these days and work with it has got to be good, huh?

Happy New Year!

- DBH

Hoseman292 · Post by **Hoseman292** » Fri Dec 31, 2004 8:13 pm

I currently use a Radio Shack Omni-Directional Dynamic microphone (part number 33-3002) with a small preamp that has built in sound effects which I picked up at a hamfest for a few dollars. A cheap solution to the standard computer microphones and it sounds alot better.

Just my two cents.

Have fun playing,
Tim

Moto desk mic to computer sound card....

Moto desk mic to computer sound card....

moto mic