CDM1250 accessory mic

[ctgo4it]

Hi all,
I've been reading all the posts, but I'm stumped. I'm trying to connect a remote mic to my cdm1250 through the acc connector, I connected
pin 5 from mic to pin 2 on radio (mic audio)
pin 6 on mic to pin 3 on radio (PTT)
pin 4 on mic to pin 7 on radio(ground)

When mic is in metal (magnetic?) clip it keys in and transmits audio. When its out of clip, I can't activate PTT. I have pin 3 on radio set to 'external mic PTT' and ext PTT audio source set to 'Ext mic audio'.

Any help would be greatly appreciated.

[Bill_G]

Have you tried a different mic? Sounds like the cord is bad on the one you are experimenting with.

[Jim202]

Hi all,
I've been reading all the posts, but I'm stumped. I'm trying to connect a remote mic to my cdm1250 through the acc connector, I connected
pin 5 from mic to pin 2 on radio (mic audio)
pin 6 on mic to pin 3 on radio (PTT)
pin 4 on mic to pin 7 on radio(ground)

When mic is in metal (magnetic?) clip it keys in and transmits audio. When its out of clip, I can't activate PTT. I have pin 3 on radio set to 'external mic PTT' and ext PTT audio source set to 'Ext mic audio'.

Any help would be greatly appreciated.

You might also have to go into the software and make some minor changes. If you start up the software, read the radio and then double click on the "RADIO CONFIGURATION" line near the top.

Then click on the "ACCESSORIES CONFIGURATION" tab, you will find the "EXT PTT AUDIO SOURCE" selection on the lower right. Make sure this is set to the "External Mic Audio".

Next take a look at the "MICROPHONE" tab. There is a gain setting here for the external mic. Depending on what your using, you may have to jack the gain up or down to get the correct level on the "ACCESSORY MIC GAIN".

Last thing to check if your not even keying the radio is to go to the "ACCESSORY PINS" tab. Make sure that pin 3 is set to "External Mic PTT (input)". The "active level" should display "low".

If all this is set correctly, then I would try another mic. One word of caution here, if your not using a Motorola hand mic or desk mic, bear in mind that there is a DC bias on the mic hi line. You don't want to short this out. It may take adding a capacitor in series with the mic to prevent this. Also bear in mind that this circuit is looking for a fairly high mic level. A standard off the shelf mic probably won't work. It will need some sort of mic pre amp to get the level up to where the radio wants it.

Jim

[ctgo4it]

so I've been playing with this for a while. Haven't changed programming since last post. I can get the radio to key up when PTT is pushed, and I can short pin 3 (PTT) and pin 7 (GND) to key up as well. I just can't get it to transmit any sound. I also tries increasing gain but didn't help. But when I plug this mic into the actual radio, it works perfectly. I also noticed that the mic has 4 pins, but don't know if I need all, or how I would connect. Any insight would be greatly appreciated.

[jackhackett]

Make sure you have the numbering for your mic plug the right way around.

If you were to have it backwards then what you thought was mic pin 6 would really be pin 3, pin 3 is hook... that would be connected to radio PTT input and guess what would happen when you hang up the mic on a grounded clip?


edit: just re-read your original post... I thought you meant putting it in the hangup clip would cause it to key, but now I think maybe you meant you can only key it with the PTT button when it's in a clip? If that's what it is then I would think you have the ground on pin 3 instead of 4, causing the ground to have to pass through the hangup clip for the mic to work.

[ctgo4it]

Make sure you have the numbering for your mic plug the right way around.

If you were to have it backwards then what you thought was mic pin 6 would really be pin 3, pin 3 is hook... that would be connected to radio PTT input and guess what would happen when you hang up the mic on a grounded clip?


edit: just re-read your original post... I thought you meant putting it in the hangup clip would cause it to key, but now I think maybe you meant you can only key it with the PTT button when it's in a clip? If that's what it is then I would think you have the ground on pin 3 instead of 4, causing the ground to have to pass through the hangup clip for the mic to work.

I believe I have the mic numbering correct, when I connect it and push button on mic (not in magnetic clip) it keys up. I did try reversing it, but that just made it key in continually. My problem now is I can't transmit any audio. I have tried increasing the acc mic gain, but that didn't change anything. Any other thoughts or ideas?

Thank you

[jackhackett]

The 4 wires on a CDM mic are

pin 3 - hook (hang up button)
pin 4 - ground
pin 5 - mic audio
pin 6 - PTT

From the radio, you should have around 9 volts on pin 2 of the acc. jack (mic audio), if that pin got shorted to ground it's possible it could have burned one of the resistors feeding voltage to it (thanks to Moto for being super cheap and using 1/16th watt resistors).