KMA-20 / GNS430 Question

Discussion in 'Avionics and Upgrades' started by kbrown66, Sep 29, 2019.

  1. kbrown66

    kbrown66 Filing Flight Plan

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    I have access to Aircraft using a GNS-430 as Primary radio connected to a KMA-20 Audio Panel. Radio transmits and receives perfectly with one exception. If the radio is actively receiving a transmission, the microphones of the pilot/co-pilot stop working. When the transmission stops, pilot and co-pilot can continue to communicate. Kind of annoying when mid conversation. Panel switches are configured as in attached photo. What could be the issue and can it be corrected with existing equipment. Hoping this is not normal and is just a simple flip of a switch.
     

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  2. GRG55

    GRG55 Final Approach

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    The KMA-20 does not have a built in intercom. I assume you have a separate intercom wired into the audio circuit, and suspect it may be related to how that is wired in.

    Before you do anything else, you might want to center the "Auto" toggle, put the "Com 1" toggle down to the Phone position (assuming the 430 is Com 1) and see if that makes a difference.
     
    Last edited: Sep 29, 2019
  3. kbrown66

    kbrown66 Filing Flight Plan

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    Thanks...the was the next thing I was going to try.
     
  4. GRG55

    GRG55 Final Approach

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    Let us know how it works out please.
     
  5. kbrown66

    kbrown66 Filing Flight Plan

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    Unfortunately...No Joy. I was really hoping that was the solution. So, besides not being able to speak when radio is receiving...cannot hear ourselves when we transmit on the radio.
     
  6. GRG55

    GRG55 Final Approach

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    You are probably going to have to get a wiring diagram for how the intercom and audiopanel are wired.

    I had the exact same set up as you (KMA-20 + GNS-430) in the Aztec when I bought it. The intercom is a NAT (Northern Airborne Technologies) InterVOX 6-place. http://www.chiefaircraft.com/nat-aa85-001.html
    I don't have the problem you describe as long as I have the toggles in the positions I indicated in post #2. I suspect there's no switch position combination that will solve it, and it has something to do with the way it was wired.