Headseat Microphone VOX sensitivity

Discussion in 'Instruments / Avionics / Electrical System' started by mcurcio1989, Oct 10, 2016.

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  1. Oct 10, 2016 #1

    mcurcio1989

    mcurcio1989

    mcurcio1989

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    I have a flightline 760 radio / intercom. It is a nice little unit and for the money I have been very pleased with it. Unlike most other radios I have used the VOX / squelch sensitivity is a setting you have to go in and change between 4 set points (HI-LO), not a dial. I wear a Bose A20 headset and the only time the VOX activates is when I talk, same thing with a standard DC headset I have been borrowing to use for passengers (just got into phase 2). I picked up a cheapo GCA - 4G headset so I don't have to keep borrowing the David Clarks and the only way I can keep them from activating the VOX is to clamp my finger over the mic. I even have an extra muff over the mic.

    Any tips or tricks here? I kind of thought all mic's were more or less created equal in this regard. Is there something I could wire into the passenger mic (like a reostat) to manually adjust the VOX sensitivity? I suppose I could go out and spend 3 times as much for a DC headset or 10 times as much for BOSE but I'd prefer not to.

    on a related not - all of these aviation headsets seem to have an opening for the the mic on the front (mouth side) and back (panel side) why is that? does one cancel out the other? If not why do they put a mic (which is clearly going to be used in a relatively noisy environment) away from the users mouth?
     
  2. Oct 10, 2016 #2

    Wanttaja

    Wanttaja

    Wanttaja

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    It's for noise reduction. Think of the side towards your mouth as positive, and the side away as negative, with the two sides added together for the final signal. Ambient sounds are picked up by both sides of the mic, and the net should be nearly zero. When you talk, it's picked up primarily on the positive side, so your voice becomes the predominant signal. This is why aviation mics are supposed to be set very close to the lips, to minimize the activation of the other side when you speak.


    Ron Wanttaja
     
  3. Oct 10, 2016 #3

    TFF

    TFF

    TFF

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    try a leather mic muff. Your problem is not uncommon.
     
  4. Oct 10, 2016 #4

    Aerowerx

    Aerowerx

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    I don't know about anyone else, but I would be very hesitant to use a VOX in such a noisy environment. In addition, any casual conversation with the passenger could activate the transmitter.
     
  5. Oct 10, 2016 #5

    mcurcio1989

    mcurcio1989

    mcurcio1989

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    I'm talking about VOX for the intercom. The radio transmission is PTT
     
  6. Oct 10, 2016 #6

    djschwartz

    djschwartz

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    The problem with the internal "intercom" function in all of the aircraft radios is that it is not a true intercom. When the VOX circuit activates it simply makes all of the mics in the aircraft hot. So, you get the noise picked up by all of the mics on top the the voice being picked up by only one. And the VOX is also seeing all that noise making it less reliable for detecting when someone is speaking. The only way to really improve this is to install a proper intercom unit and not use the internal intercom function of the radio.

    Dave
     

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