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Thread: GTX microphone question

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    Default GTX microphone question

    Good evening everyone.

    Got a bit of a problem with a GTX radio, more specifically the microphone. So I bought a GTX to work on a 900Mhz ham repeater that has recently been installing in my area. I also, bought a microphone from eBay after consulting an old parts and accessories manual from Motorola.
    The microphone that I bought is HMN1035C. When I plugged it into my GTX I found that it would key up. Thinking that the mic was bad i scrounged around in a box until I found a HMN3008A. I plugged this microphone in and it keyed up the radio and I tried to talk on it. Found out why this mic was in a box to begin with, the mic element is toast and kept cutting out.

    So my question is, what is the pin out for the 3008A so I can re-terminate the 1035C to work with this radio? The 3008A has four wires and the 1035C has 6.
    Poor planning leads to poor results-->Welcome to OKWIN.


  2. #2
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    The newer mic was in a two piece black housing. They should be the same as the Maxtrac/Radius, GM mobile mics.
    The surface mounted push button, PTT, turns on the mic circuit and the current the mic amp is sensed by the PTT transistor.

    In the later Radius service manula(s).

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    From Repeater-Builder:
    The GTX mobile radio can use the same microphones as MaxTracs, GM300s, and Radiuses. Probably any Motorola base or hand-held microphone with an 8-pin RJ-45 plug will work. The MIC connector pin-out is the same as on the above radios. (Microphones wired for a Desktrac base will not work.) Of the eight pins, six (pins 2 through 8) are the same as on MaxTracs with the following exception: the headset audio output (pin 8) is NOT at a constant level; it varies as the front panel volume control is rotated. Pin 1 (spare on a MaxTrac) is pulled to filtered A+ (+13V) through a 1k resistor. Pin 2 (spare on a MaxTrac) goes nowhere.
    http://www.repeater-builder.com/moto...fo-mobile.html

  4. #4
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    Quote Originally Posted by sgtslaughter501 View Post
    So my question is, what is the pin out for the 3008A so I can re-terminate the 1035C to work with this radio? The 3008A has four wires and the 1035C has 6.
    They use the same four wires. Mic Hi usually RED, GND BLK, PTT usually Green, and Hangup Blue. On some Maxtrac, Radius, mics there are all 8 wires in the RJ plug but only four are used in the mic.

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    Quote Originally Posted by foxtrotdelta View Post
    And that's where I got confused. That page lists different microphones models than this PDF scan from Motorola. http://www.repeater-builder.com/moto...bile-parts.pdf

    The microphones listed on that page is what I went off of when I ordered my microphone.
    Poor planning leads to poor results-->Welcome to OKWIN.

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    Meister's information often has mistakes......

  7. #7
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    Quote Originally Posted by sgtslaughter501 View Post
    And that's where I got confused. That page lists different microphones models than this PDF scan from Motorola. http://www.repeater-builder.com/moto...bile-parts.pdf

    The microphones listed on that page is what I went off of when I ordered my microphone.
    This is the same mic for the GM300 and M1225 radois, IIRC... Mobile compact mic HMM3413.

    BTW I am looking for few black compact mics damaged or no cords is fine...