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Headset jack cables - shielded or not?

 
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rv8ch



Joined: 10 Jan 2006
Posts: 250
Location: Switzerland

PostPosted: Sat Apr 01, 2006 1:22 pm    Post subject: Headset jack cables - shielded or not? Reply with quote

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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PostPosted: Sat Apr 01, 2006 2:08 pm    Post subject: Headset jack cables - shielded or not? Reply with quote

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

PostPosted: Sat Apr 01, 2006 4:00 pm    Post subject: Headset jack cables - shielded or not? Reply with quote

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-yak at lloyd dot com
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