GMA 345 Hand Mic

Discussion in 'Avionics and Upgrades' started by Nathan Miller, Mar 23, 2020.

  1. Nathan Miller

    Nathan Miller Filing Flight Plan

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    For those whom may have experience building their own harnesses for the Garmin Audio Panels, I'm installing a GMA 345 and after studying and searching through the installation manual, I can't find provisions for the handheld backup mic.

    I wrote it off as unnecessary and moved forward with the install without it. But I notice airplanes on TAP that have a GMA 340/5 with a hand held mic cradled on the center console. So, maybe Ik overlooking something.

    Without a separate input for a handheld key (only seeing inputs for the pilot and copilot keys), I can't see how it's supposed to be accommodated without wiring in parallel with the pilot or copilot's headset mic - which seems like it would introduce other problems (impedance mismatch, increase in ambient noise by having 2 open mics, etc).

    Should I skip wiring up the handheld mic? Would I miss it? I never use it anyway...

    Thanks in advance for the insight and info.

    Nathan
     
  2. Jesse Saint

    Jesse Saint Pre-takeoff checklist

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    The tip wire to the pilot and copilot mic jack is the key wire and is there for the handheld mic. You could just parallel out the pilot or copilot mic jack to a separate jack for a handheld mic.
     
  3. flyingron

    flyingron Touchdown! Greaser!

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    Are you sure it is connected to the audio panel and not just COMM1's second mike input?
     
  4. Nathan Miller

    Nathan Miller Filing Flight Plan

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    Oh, nice! I had to dig for it, but you're right - the GTR 225 has provisions for a 2nd mic

    I will wire up my audio panel as Mic 1 and the handheld jack to Mic 2 as a fall safe.
     
  5. flyingron

    flyingron Touchdown! Greaser!

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    Most hand mics disconnect the microphone from the sleave of the plug when the button is not pushed down (at least the common Telex 66T does). Therefore, it shouldn't mess anything up too badly if you have it paralleled with your PILOT mic input either into the audio panel. The PTT is pull to ground so that allows the two to be paralleled as well.

    Still, I like the idea of bypassing the audio panel (especially the piece of crap Garmin). If you aren't stuck not using the headset, you may not have the intercom/audio panel either.
     
    Last edited: Mar 23, 2020