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Headset jack cables - shielded or not?

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rv8ch

Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

Posted: Sat Apr 01, 2006 1:22 pm Post subject: Headset jack cables - shielded or not?

I've read the discussion on shielded wires on page

18-13, and it's pretty clear.  I still have a question

about it.  The intercom I'm installing (Flightcom 403)

does not indicated shielded wires to the headset and

mic jacks on the wiring diagram, but has this in the

instructions "You may need to use shielded wire on

audio, mic and headphone lines."



I take it that if I get some noise, then they suggest

re-wiring with shielded wire.



What is the "real world" experience with shielding

these wires?  Has anyone run unshielded and wished

they had run shielded?



I've got plenty of shielded wire handy, but this

sentence in Bob's text gives me pause:  "...there

is greater risk that shielding improperly terminated at

both ends is 100x more likely to be the root cause

of a noise problem (due to ground loop) than if the

wire had never been shielded in the first place

(electrostatic coupling to some high noise wiring)."



Barring better advice, what I plan to do is use the

shielded wire, and make sure that it is only grounded

at the intercom.  Thanks for your better advice!



-- 

Mickey Coggins

http://www.rv8.ch/

#82007 finishing

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_________________
Mickey Coggins
http://www.rv8.ch/

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 01, 2006 2:08 pm Post subject: Headset jack cables - shielded or not?

At 11:19 PM 4/1/2006 +0200, you wrote:



 	  Quote: 	
		  

<mick-matronics(at)rv8.ch>



I've read the discussion on shielded wires on page

18-13, and it's pretty clear.  I still have a question

about it.  The intercom I'm installing (Flightcom 403)

does not indicated shielded wires to the headset and

mic jacks on the wiring diagram, but has this in the

instructions "You may need to use shielded wire on

audio, mic and headphone lines."



I take it that if I get some noise, then they suggest

re-wiring with shielded wire.


	


   I suspect it's a CYA statement. I've never encountered

   a noise problem that was cured by converting properly

   installed microphone or headphone wiring from twisted

   individual strands to a shielded equivalent.



 	  Quote: 	
		  What is the "real world" experience with shielding

these wires?  Has anyone run unshielded and wished

they had run shielded?


	


   I don't believe so.

 	  Quote: 	
		  I've got plenty of shielded wire handy, but this

sentence in Bob's text gives me pause:  "...there

is greater risk that shielding improperly terminated at

both ends is 100x more likely to be the root cause

of a noise problem (due to ground loop) than if the

wire had never been shielded in the first place

(electrostatic coupling to some high noise wiring)."


	


   I LIKE shielded pairs, trios and quads for a LOT

   of applications that do not call for shielding. This

   is because I'm offered a multi-conductor bundle with

   a smooth outer surface that is easy to work with

   if you have the tools. I have strippers and solder

   sleeves that make multi-conductor bundles a snap

   whether the shielding is called for or not. More often

   than not, the shield provides yet another conductor

   in the bundle.

 	  Quote: 	
		  Barring better advice, what I plan to do is use the

shielded wire, and make sure that it is only grounded

at the intercom.  Thanks for your better advice!


	


   That will work. But know too that a single shielded

   and a twisted pair as a headset feeder are equally

   likely to perform as desired. The insulating washers

   or other isolation techniques used to separate mic

   and headset grounds from the airframe are far more

   critical than which style of wire you use.



   Bob . . .



      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sat Apr 01, 2006 4:00 pm Post subject: Headset jack cables - shielded or not?

Mickey Coggins wrote:



 	  Quote: 	
		   Barring better advice, what I plan to do is use the

 shielded wire, and make sure that it is only grounded

 at the intercom.  Thanks for your better advice!


	


That is the right answer.



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

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