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Thread: Headset wiring question - E/AB

  1. #1
    CarlOrton's Avatar
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    Headset wiring question - E/AB

    Hi, Folks; I'm in need of some avionics help with wiring my comm headset/mic jacks. I KNOW how to differentiate tip, ring, and common on both, and how to read on a schematic, but this is more of an implementation question. Some schematics have the PTT wired to the tip connection on the mic jack. Others just have the PTT connect directly from the switch to the edge connector on the harness. Electrically, they're almost the same. BUT, my question is....if I wire directly, bypassing the mic jack, does that do anything signal-wise like eliminate the side tone, or am I good to just wire from the stick to the harness, without connecting to the mic jack?

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  2. #2
    rwanttaja's Avatar
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    The tip should do nothing but put the radio into transmit mode. Whether it's connected at the switch or the edge connector, it shouldn't affect the side tone.

    Ron Wanttaja

  3. #3
    It depends on what you plug into the mic jack. For example, you might plug in a portable intercom that disables intercom mode when the pilot transmits. Or maybe sometimes the co-pilot uses an external PTT to handle the com radio. Or sometimes you use a hand held mike without headset. If the mic jacks are not wired in the PTT circuit, nothing connected to them can PTT.

  4. #4

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    The PTT is activated by grounding the pin on the harness. So you can actually have several PTT switches. Grounding anyone or more of them will activate transmit. Grounding two at the same time will not hurt the circuit. As mentioned above, you may want the mic jack wired for PTT in addition to a PTT button on the stick. Side Tone is a function of the radio so won't be affected by the type of PTT switch you have.

    Most new radios have a separate circuit for the co-pilot PTT. I believe the pilot PTT over rides the co-pilot PTT if they are pushed at the same time.

  5. #5
    FlyingRon's Avatar
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    Override? Is one guy's keying of the transmitter more important than the other? While I've seen radios with multiple microphone inputs, they all have the same PTT.

    What can tend to have multiple PTT lines is the AUDIO PANEL. This is because some audio panels allow the pilot and copilot to be controlling different radios.

  6. #6

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    The Garmin GTR200 has built in 2 place intercom which is a nice combination for VFR panels. There are other similar combinations from Garmin and other manufacturers. the GTR200 has separate PTT inputs for pilot and co-pilot. Pushing the co-pilot PTT button and talking into the pilot mic will transmit nothing. I haven't tried it, but I'd think one has to over ride the other when both buttons are pushed at the same time. On the other hand it could be that both mics are active. The Pilot Guide doesn't specify.

    If you have an audio panel, the GTR200 intercom can (must) be turned off, but the PTT buttons are still discrete and need to be wired separately. That would allow the pilot and copilot to control different radios through the audio panel.

  7. #7
    FlyingRon's Avatar
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    Nope, no priority on the GTX200. If you both push your PTTs both your mic audios are transmitted.

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