REFLECTOR: Intercom question

[Laurence Coen]

There is no mention of what kind of airplane your friend has.  The way to wire the audio is different for a metal plane than a glass plane.  In a metal plane, mounting the jack will ground it to the airframe and if you connect the shield at that point there will be two ground paths (ground loop).  With a glass plane the ground return can be via the shield since the jack is not grounded to the airframe. See the attached.

Larry Coen
N136LC


From: Matt Bucko 
Sent: Sunday, February 17, 2013 10:53 PM
To: Velocity Aircraft Owners and Builders list 
Subject: Re: REFLECTOR: Intercom question


Thank you.
Bucko

On 2/17/2013 9:05 PM, Glenn Falkenberg wrote:

  To float the shield means to not terminate it at the component or a ground.  Usually the shield is trimmed back a couple of inches and shrink sleeved or a solder sleeved. 

  On Feb 17, 2013 6:37 PM, "Matt Bucko" <mbuc310 at cox.net> wrote:

    Would you please describe "float the shield at the jack".

    Bucko

    On 2/17/2013 7:04 PM, Scott Derrick wrote:

      agreed 

      Glenn Falkenberg <airmech2 at gmail.com> wrote:


      I think the best way would be use a shielded twisted pair.  Float the shield at the Jack and take shield to ground at intercom panel.

      On Feb 17, 2013 4:25 PM, "Dan Schindler" <danpilot91 at gmail.com> wrote:

        My friends airplane intercom is wired in such a way that each jack only has 1 wire running to it. Utilizing the shielded portion of the wire as the common ground. Is this an acceptable way to do this. He is getting feedback in his headset when he pushes the PTT.

        Thank you,

        Dan Schindler
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