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Grounding shielded wires

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Speedy11(at)aol.com
Guest

Posted: Fri Mar 07, 2008 6:48 am Post subject: Grounding shielded wires

I know - the subject's been covered before.  And yes, I know - it's in  the archives.

 But, I can't find it in the archives and I'd appreciate some help.

 I'm getting conflicting advice from the radio harness maker and from the  intercom maker regarding the grounding of shielded wires.  One tells me to  ground the shield on only one end while the other says to ground both  ends.  Who to believe?

 My situation: SL30 with professionally wired harness.  Shields are all  grounded on the radio chassis.

 I'm building the harness for the intercom.  The intercom instructions  show shielding grounded at both ends only on the audio wires.  However,  email from intercom maker says to ground both ends of all shielded wire.

  

 1. Should shielded wires from SL30 to intercom be grounded at both  ends?

 2. Should those grounds be ganged together to connect to the single ground  pin on the intercom?

 3. Should mic phone plug wire shields be grounded at both ends?

 4. Should headphone plug wire shields be grounded at both ends?

 5. Should all shields be ganged together to connect to the single ground  pin on the intercom?

  

 Stumped,

 Stan Sutterfield



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nuckolls.bob(at)cox.net
Guest

Posted: Fri Mar 07, 2008 7:19 am Post subject: Grounding shielded wires

At 09:44 AM 3/7/2008 -0500, you wrote:



 	  Quote: 	
		  I know - the subject's been covered before.  And yes, I know - it's in the 

archives.

But, I can't find it in the archives and I'd appreciate some help.

I'm getting conflicting advice from the radio harness maker and from the 

intercom maker regarding the grounding of shielded wires.  One tells me to 

ground the shield on only one end while the other says to ground both 

ends.  Who to believe?

My situation: SL30 with professionally wired harness.  Shields are all 

grounded on the radio chassis.

I'm building the harness for the intercom.  The intercom instructions show 

shielding grounded at both ends only on the audio wires.  However, email 

from intercom maker says to ground both ends of all shielded wire.



1. Should shielded wires from SL30 to intercom be grounded at both ends?

2. Should those grounds be ganged together to connect to the single ground 

pin on the intercom?

3. Should mic phone plug wire shields be grounded at both ends?

4. Should headphone plug wire shields be grounded at both ends?

5. Should all shields be ganged together to connect to the single ground 

pin on the intercom?


	


    Follow the instructions. If the wiring diagram

    provided by the manufacturer SHOWS a ground connection

    at both ends, then there's a reason for it an

    the designer's intentions should be observed.



    However, the general rule of thumb is that shields

    are to be GROUNDED at one end only . . . that doesn't

    mean that the shield is not CONNECTED at both ends . . .

    the shield may have an important role to play with

    respect to signal or power return paths.



    A very common double-grounding error in aircraft

    audio systems occurs when headset and microphone

    jacks are allowed to find local ground at the

    point of attachment to the airframe. This is why

    insulating washers  . . .



http://www.aeroelectric.com/Pictures/Connectors/Audio/Jack_Insulation_Washers.jpg



    are recommended where the jacks are to me mounted

    to a conductive location on structure.



    The schematic for wiring the product should be

    quite explicit as to where the shields are connected.



    Bob . . .

        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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