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Thread: ptt/elt problem

  1. #1

    Join Date
    Apr 2007
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    ptt/elt problem

    The last few times I have been entering the pattern and keying the mic the ELT starts to go off. It only seems to happen while using the radio in the air and not while taxiing. Does anyone know what might be causing this problem?

  2. #2
    Clyde and Susan's Avatar
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    Dec 2005
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    It sounds like RF from the radio is getting into the ELT and setting it off. If this just started and you haven't moved either antenna or made any other wiring changes, you may have a broken or shorted coax at or near the antenna. The high VSWR that results from that can cause Radio Frequency energy to be picked up by wiring to the ELT, especially if the remote ELT wiring runs with or near the antenna coax. ...Clyde Davis

  3. #3
    irishfield's Avatar
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    Feb 2003
    Penetanguishene, Ontario Canada
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    The PTT button isn't the little red one on the panel....

  4. #4
    Nathan K. Hammond's Avatar
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    Nov 2002
    Danville, KY DVK
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    Maybe it's the backseater giving the airport a head's up? Just joking!!!

    Was maintenance done before you noticed the problem? There are very few coincidences in aviation which would make me think something got switched around, incorrectly, during that last round of tinkering.


  5. #5

    Join Date
    Jun 2004
    Houston, Ak
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    Have you tried to repeat this on the ground? Say, during a run-up or for a short while go even higher RPM? Any panel light changes when you key the mic? Any work done to your ignition system in the recent past? Does the problem not appear if you bring the engine back to idle in the air before keying the mic? As Clyde says it sounds like RF, but from your description it sounds like something else is generating the RF and the radio is just completing the circuit. From your description of it happening in the air and not on the ground it would appear as though the ignition system at higher RPM is generating the noise and the radio is enabling the cross-talk into your ELT.

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