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MCS2000 External Mic Compatability
Posted: Wed Nov 24, 2010 7:33 am
by ckonash
Hello,
I am a firefighter and in the process of installing a new radio console in our firehouse. I am an application engineer so I understand most everything with electronics but do not hold an electronics engineering degree.
We are installing 3 MCS2000 radios (1 Model III, 2 Model II's) into a custom console I made.
I have wired up three separate PTT switches, one for each radio, and wanted to use a Shure 503BG gooseneck microphone for all three radios. The microphone is a unidirectional dynamic mic with an actual impedance of 170 Ohms. Is it possible to use this mic on these radios? Does it need to have a preamplifier installed and if so what pin on the ACC connector do I use to input the mic into the radio. I was hoping to leave the RJ45 on the front of the radios empty.
Mic
http://www.delcomproducts.com/downloads/SHURE503BG.pdf
Radio Console
http://gallery.me.com/chris.konash#1000 ... &view=grid
Thanks,
Chris Konash
Re: MCS2000 External Mic Compatability
Posted: Wed Nov 24, 2010 1:53 pm
by Jim202
ckonash wrote:Hello,
I am a firefighter and in the process of installing a new radio console in our firehouse. I am an application engineer so I understand most everything with electronics but do not hold an electronics engineering degree.
We are installing 3 MCS2000 radios (1 Model III, 2 Model II's) into a custom console I made.
I have wired up three separate PTT switches, one for each radio, and wanted to use a Shure 503BG gooseneck microphone for all three radios. The microphone is a unidirectional dynamic mic with an actual impedance of 170 Ohms. Is it possible to use this mic on these radios? Does it need to have a preamplifier installed and if so what pin on the ACC connector do I use to input the mic into the radio. I was hoping to leave the RJ45 on the front of the radios empty.
Mic
http://www.delcomproducts.com/downloads/SHURE503BG.pdf
You will probably need the pre amp. Also try and remember that there is a DC bias on the
TX audio input connection. As such, you will need to use a 1.0 uf capacitor or so to
isolate the DC bias on the pin to keep from shorting this voltage out and killing any audio
you might be trying to push through the mic high connection. Hopefully you do have a
way of adjusting the external amp to control the level of the audio gain or voltage going
into the radio. If not, you will drive the TX audio way into compression and distort the
audio.
Jim
Radio Console
http://gallery.me.com/chris.konash#1000 ... &view=grid
Thanks,
Chris Konash
Re: MCS2000 External Mic Compatability
Posted: Wed Nov 24, 2010 3:08 pm
by Will
Good microphone but you will have to have a preamp. One source of a mic preamp is the circuit board from the full size Motorola hand mic with a couple of components changed.
Nice looking console.
I hope you are not using the Diamond antenna.. on the radio.
Re: MCS2000 External Mic Compatability
Posted: Sat Nov 27, 2010 3:06 pm
by ckonash
Hi Everyone,
Thank you very much for your replies.
In the last few days I have had time to play around to try and get my dynamic mic to work on the MCS2000 radios we have at our firehouse. However I have had no positive results.
I purchased a 1uf capacitor and installed that between the analog ground(pin10) and the mic in (pin 13) and I radio still does not recognize a line level input.
Is this the correct place to install the capacitor? If so what result should the cap have on the accessory pins. I am still metering 8volts between pin 13 and 10 with the cap installed.
I also tried taking apart a motorola palm mic and using the internal pcb to act as my preamp. I soldiered and replaced the internal mic element and replaced it with my new Shure element and it didn't work either. I did measure the impedence of the Motorola OEM mic element at 2.4K and my Shure elemet at 160 Ohms. I'm guessing the impedance difference is why it is not working?
Any help or advice anyone has would be appreciated.
Thanks
Re: MCS2000 External Mic Compatability
Posted: Sun Nov 28, 2010 9:19 am
by GlennD
Since you are a firefighter, the preamp from a David Clark mic works well.
I used one to interface a centracom cie gooseneck mic to an XTL5000
on an emergency van.
Re: MCS2000 External Mic Compatability
Posted: Sun Nov 28, 2010 9:23 am
by GlennD
As for a motorola preamp, you need one from a old metal mic. The current mics have a preamp for an electret mic and you need one for a dynamic mic. Also the preamp is powered from the radio so no isolating cap is used.
Re: MCS2000 External Mic Compatability
Posted: Tue Nov 30, 2010 8:48 am
by ckonash
Hi,
I think I had misunderstood what you had said. I was installing the 1uf cap between analog ground and pin 13 for 'mic in'.
I'm now thinking this should be inline between the pre-amped mic and pin 13(mic in), is this correct and will this solve the voltage bias problem for our dynamic mic or do I need any transformers or other components?
Thanks,
Chris