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Thread: PTT screech

  1. #11
    New Member rosspet's Avatar
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    Quote Originally Posted by Peteridms View Post
    the 3 mike wires are round the wrong way,.... I had the same troble when I made the adaptor formy Yaesu to go onto the lead for a icom
    I found a site that showed how to make up the connectors with maplin jack plugs, I soldered the mike wires the wrong way on the pins,
    showed as transmitting but now speach inheadset and just hiss to ground station I have the info somewher...Ill have a look
    Thanks, but none of the wires are "home made" - if I connect a GA headset to the radio (i.e remove the red wiring, insert headset), PTT works fine, it's only when the helmet and MM016B are connected that the screech/howl appears when PTT is pressed.

    Update:-

    I've noticed that the tone changes if I move the radio about, it's a low pitched howl with the radio at full lead's length from my helmet, increasing in pitch and strength as I bring the radio closer to the helmet (with PTT pressed).

    Tried altering the sidetone on the radio from high to off - no difference.

    Tried switching ANL off in the radio menu, swapping between internal and external mic - no effect.

    Ross


  2. #12
    Captain Sean McDonald's Avatar
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    Have emailed you Ross


  3. #13
    Co-Pilot Aerial's Avatar
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    From previous experience in other fields of radio transmitters, it sounds like (forgive the pun!) Radio Frequency energy getting picked up in the microphone cabling.

    The cure is normally a very small value (0.001 micro-Farad) capacitor in parallel with the microphone. As I know nothing of your setup, how you go about fitting one I have no idea. I hope this may be useful.


  4. #14
    New Member rosspet's Avatar
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    I think I'm on top of the problem - Eddie at microavionics suggested moving the jumper inside the interface (MM016B) from pins 1&2 to pins 2&3 and that cleared the screech when the ptt was pressed. I'm now getting a "TX" on the radio - only trouble is I've got no sidetone, but that's a small price to pay for a useable system.
    Thanks to all for your help.

    Ross


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