Microphone differences

Dail Terry · Post by **Dail Terry** » Mon Dec 06, 2004 5:17 am

Trying to find the difference between a HMN 1037 B and a HMN 1038 B Microphone.. I want to use the mic on a GTX Mobile.
TX
Dail

Will · Post by **Will** » Tue Dec 07, 2004 2:19 am

HMN1037B DTMF mic

HMN1038B Base mic

kcbooboo · Post by **kcbooboo** » Tue Dec 07, 2004 4:41 am

The GTX mobiles, at least those on 900 MHz, seem to use the same microphones as do MaxTracs and Radiuses, and probably GM300s. They all have an 8-pin RJ-45 style connector on them.

I'd like to say that any Motorola mike with this type plug will work with any of these radios, but don't hold me to this generalized statement.

Bob M.

Sam · Post by **Sam** » Tue Dec 07, 2004 7:38 am

OK, how about between HMN1001 (Mostar) and HMN1056 (Maxtrac)? I can get past the 6-pin/8-pin cable, and PTT works, but no audio. I assume they are both condenser elements by their size. Different voltage maybe? The 1056 is just too small and I'm too cheap to buy the 1035 for the Maxtrac...

odat · Post by **odat** » Tue Dec 07, 2004 3:58 pm

Maxtrac Mostar
3-Hook 3-PTT
4-Gnd 4-Mic audio
5-Mic audio 5-Gnd
6-PTT 6-PTT Gnd

Sam · Post by **Sam** » Tue Dec 07, 2004 6:31 pm

Yeah, I got the pinouts worked out, and PTT works okay, but there's no audio. I figure it must be a difference in the preamp circuits or bias voltage or something.

Oh well. Thanks anyway.

Will · Post by **Will** » Wed Dec 08, 2004 3:13 am

The Mic input circuit has been the same since the Motrac days. (1964)

600 ohm with aprox. 8 volts on it fed from the radio. Typical audio level 120mV RMS.

You can easaly follow the pins and change the connector to the RJ45 8 pin connector, even tho there is only 6 wires. You only need 4 on a Maxtrac, Radius, GM, CDM, MCX ect.

Ground
Mic Hi
PTT
Mic hang-up stud

Sam · Post by **Sam** » Wed Dec 08, 2004 4:12 pm

OK, I found my problem - a bad RJ-45 jack I was using to build an adapter. It works fine now. Thanks, everybody.