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Jack plug question (shielded wires)

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f.miskelly(at)imperial.ac
Guest

Posted: Sun Jan 28, 2007 3:03 am Post subject: Jack plug question (shielded wires)

Hi Bob

My harness linking the radio to microphone and headphone jacks do not have shielding. Neither does the positive supply or the PTT switch wires. From another thread on this forum 'shielded wires' i see others use shielded wires in this situation. Your link below recommends shielded wires. Other points are: There is substantial interference in the radio and I wonder are shielded wires more important in a composite aircraft?

 

My questions are

a) Is there a method of testing whether a wire should be shielded eg wrap in aluminium foil to see the effect on the interference?

b) Do you think it is worth the hassle to return the full harness and ask them to replace the wires to the jacks, the PTT and the positive supply with shielded wires?

 

Many thanks

Frank

 



________________________________



From: owner-aeroelectric-list-server(at)matronics.com on behalf of Miskelly, Francis G

Sent: Wed 24/01/2007 17:16

To: aeroelectric-list(at)matronics.com

Subject: RE: RE: Jack plug question





Many thanks Bob.

The schematic in your link shows the harness linking the radio to the microphone jack is shielded. Not sure if mine is but will check.



I'm afraid i don't have a wiring diagram - they wouldn't give me one. Contacted the technician who did the wiring harness several times and he was vague about the need for a ground. Maybe he thought i had a metal panel or maybe he didn't understand the wiring and was just doing as he was told?



Think i'll install an earth on the microphone jack anyway. I presume it won't do any harm and may solve the problem. Also check the shielding



Thanks again

Frank



________________________________



From: owner-aeroelectric-list-server(at)matronics.com on behalf of Robert L. Nuckolls, III

Sent: Wed 24/01/2007 05:40

To: aeroelectric-list(at)matronics.com

Subject: RE: RE: Jack plug question






At 03:10 PM 1/22/2007 +0000, you wrote:



 	  Quote: 	
		  Thanks Bob.



The KX155 is 6 months old. This problem has been there from the beginning.

It came with harness pre-wired and i installed it. Sometimes i use a

handheld (ICOM A20) wired into the a/c power supply and aerial and there's

some ignition noise but not a serious problem. Its just the panel mounted

KX155. The microphone jack interferes with the volume (even with the

squelch turned off) and introduces interference

Two possibles i thought of were

1. The microphone socket may need an earth? The panel is fibreglass and

the socket has 2 wires running into it but is not earthed to the airframe

2. Could the wires in the microphone socket be transposed?



As the ICOM works OK that seems to exclude power supply or aerial issues?



Very grateful for your advice.



Frank


	


   If the push to talk circuit is active in your

   microphone wiring, then the mic jack would need

   two wires plus a ground. See:



http://aeroelectric.com/articles/micjack/micjack.html



   If your mic jack is intended to handle ONLY

   microphone audio and PTT is handled with other

   wiring, then only two wires would be required.

   Do you have a schematic of the pre-wired harness?

   Have you checked your harness against the diagram?



   Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Sun Jan 28, 2007 4:58 am Post subject: Jack plug question (shielded wires)

At 11:01 AM 1/28/2007 +0000, you wrote:

 	  Quote: 	
		  Hi Bob

My harness linking the radio to microphone and headphone jacks do not have 

shielding. Neither does the positive supply or the PTT switch wires. From 

another thread on this forum 'shielded wires' i see others use shielded 

wires in this situation. Your link below recommends shielded wires. Other 

points are: There is substantial interference in the radio and I wonder 

are shielded wires more important in a composite aircraft?



My questions are

a) Is there a method of testing whether a wire should be shielded eg wrap 

in aluminium foil to see the effect on the interference?

b) Do you think it is worth the hassle to return the full harness and ask 

them to replace the wires to the jacks, the PTT and the positive supply 

with shielded wires?


	


   I gotta tell you that shielding used on most wires in small

   aircraft has only a modicum if not zero benefits. The lengths

   of wires used to run between various black boxes and other

   components of a system are so short and the list of potential

   antagonists of the kind that are held at bay by shields is

   also tiny if not zero.



   The headphone and mic wiring of our radios will run just fine

   with twisted pairs or trios of wires. Having said that, I use

   a lot of shielded wire here in the shop and in some installations

   not because the shielding is necessary but because the wire

   is mechanically and logistically handy. I have off-the-spool,

   multi-conductor cables that are easy to use and have a sort

   of universal applicability.



   But here's the rub on a schematic or wiring diagram . . .

   there's nothing in the diagram that tells us how long any

   run of wire is nor what bundles that wire shares with other

   systems. One system installed in a C-150 would be at zero

   risk for electro-statically conducted noise in the C-150

   where the interconnected devices are inches apart but an

   entirely different matter when the same electro-whizzy is

   installed in bizjet with the two boxes perhaps several feet

   apart and the wires run in bundles with other, potentially

   antagonistic systems that don't even exist in the C-150.



   So the rule of thumb is, if there's any risk at any time

   for any possible installation for conduction of electro-

   static noise into a potential victim wire - shield it.

   The cost-delta for using shielded versus unshielded wire

   in a production environment is trivial . . . it's disappointing

   that the folks who made your harness "skimped" on this

   but their perceptions of low-risk are not incorrect. I'd

   leave the harness alone unless you DO experience a noise

   problem. Because you're more likely to have a problem due

   to poor attention to ground systems than because any

   one set of wires was not shielded.



   Give me the name of the company that did your harness

   and their phone number. If you have the name of the technician

   you talked to, I need his/her name too. I'll give them a

   call and see about shaking loose some data. There's no

   excuse for not supplying everything you need to know about

   a product they supplied to you.



   Bob . . .

f.miskelly(at)imperial.ac
Guest

Posted: Sun Jan 28, 2007 1:04 pm Post subject: Jack plug question (shielded wires)

Thanks for the offer (and explanation) Bob but i'm based in London, England and the harness was supplied by Harry Mendelssohn in Edinburgh, Scotland  www.gps.co.uk

I'm sure you're correct the problems is grounds rather than the harness. You don't need to be on this forum long to realise the importance of grounds. I tried to get a schematic but they said King didn't supply schematics for customers. 

 

For info (rather than action) their tel is 0044 131 447 7777 and technician is Danny.

I'll focus on the grounds and leave harness for now.

Thanks again

Frank



________________________________



From: owner-aeroelectric-list-server(at)matronics.com on behalf of Robert L. Nuckolls, III

Sent: Sun 28/01/2007 12:57

To: aeroelectric-list(at)matronics.com

Subject: RE: RE: Jack plug question (shielded wires)






At 11:01 AM 1/28/2007 +0000, you wrote:

 	  Quote: 	
		  Hi Bob

My harness linking the radio to microphone and headphone jacks do not have

shielding. Neither does the positive supply or the PTT switch wires. From

another thread on this forum 'shielded wires' i see others use shielded

wires in this situation. Your link below recommends shielded wires. Other

points are: There is substantial interference in the radio and I wonder

are shielded wires more important in a composite aircraft?



My questions are

a) Is there a method of testing whether a wire should be shielded eg wrap

in aluminium foil to see the effect on the interference?

b) Do you think it is worth the hassle to return the full harness and ask

them to replace the wires to the jacks, the PTT and the positive supply

with shielded wires?


	


   I gotta tell you that shielding used on most wires in small

   aircraft has only a modicum if not zero benefits. The lengths

   of wires used to run between various black boxes and other

   components of a system are so short and the list of potential

   antagonists of the kind that are held at bay by shields is

   also tiny if not zero.



   The headphone and mic wiring of our radios will run just fine

   with twisted pairs or trios of wires. Having said that, I use

   a lot of shielded wire here in the shop and in some installations

   not because the shielding is necessary but because the wire

   is mechanically and logistically handy. I have off-the-spool,

   multi-conductor cables that are easy to use and have a sort

   of universal applicability.



   But here's the rub on a schematic or wiring diagram . . .

   there's nothing in the diagram that tells us how long any

   run of wire is nor what bundles that wire shares with other

   systems. One system installed in a C-150 would be at zero

   risk for electro-statically conducted noise in the C-150

   where the interconnected devices are inches apart but an

   entirely different matter when the same electro-whizzy is

   installed in bizjet with the two boxes perhaps several feet

   apart and the wires run in bundles with other, potentially

   antagonistic systems that don't even exist in the C-150.



   So the rule of thumb is, if there's any risk at any time

   for any possible installation for conduction of electro-

   static noise into a potential victim wire - shield it.

   The cost-delta for using shielded versus unshielded wire

   in a production environment is trivial . . . it's disappointing

   that the folks who made your harness "skimped" on this

   but their perceptions of low-risk are not incorrect. I'd

   leave the harness alone unless you DO experience a noise

   problem. Because you're more likely to have a problem due

   to poor attention to ground systems than because any

   one set of wires was not shielded.



   Give me the name of the company that did your harness

   and their phone number. If you have the name of the technician

   you talked to, I need his/her name too. I'll give them a

   call and see about shaking loose some data. There's no

   excuse for not supplying everything you need to know about

   a product they supplied to you.



   Bob . . .

wgill10(at)comcast.net
Guest

Posted: Sun Jan 28, 2007 1:27 pm Post subject: Jack plug question (shielded wires)

What schematics do you need Frank? I may have something I can email to

you.



Bill

--

f.miskelly(at)imperial.ac
Guest

Posted: Sun Jan 28, 2007 1:48 pm Post subject: Jack plug question (shielded wires)

Thanks Bill.  

Its a KX 155 installation manual. Esp the wiring diagram. If that's possible it would be great!

Frank



________________________________



From: owner-aeroelectric-list-server(at)matronics.com on behalf of William Gill

Sent: Sun 28/01/2007 21:27

To: aeroelectric-list(at)matronics.com

Subject: RE: RE: Jack plug question (shielded wires)






What schematics do you need Frank? I may have something I can email to

you.



Bill

--

nuckollsr(at)cox.net
Guest

Posted: Sun Jan 28, 2007 3:14 pm Post subject: Jack plug question (shielded wires)

At 03:27 PM 1/28/2007 -0600, you wrote:

 	  Quote: 	
		  



What schematics do you need Frank? I may have something I can email to

you.



Bill


	


   Bill, if you have a KX-155 manual and can scan

   the wiring diagrams, I'd be pleased to add them

   to my website's installation data.



   Bob . . .

maurv8(at)bresnan.net
Guest

Posted: Sun Jan 28, 2007 4:34 pm Post subject: Jack plug question (shielded wires)

Bob,

 I have a complete KX-155/165 installation manual  I would gladly mail to you as I no longer have a need for it, if you want  it

  

 Mauri Morin

Polson, MT

RV-8 N808M (reserved)

C180 N2125Z  Flying

SEMPER FI

  

 ---

nuckollsr(at)cox.net
Guest

Posted: Sun Jan 28, 2007 4:52 pm Post subject: Jack plug question (shielded wires)

At 05:30 PM 1/28/2007 -0700, you wrote:

 	  Quote: 	
		  Bob,

I have a complete KX-155/165 installation manual I would gladly mail to 

you as I no longer have a need for it, if you want it


	


   Very kind of you sir. I'd be delighted.



   The website is moving to new quarters pretty soon

   and we should have a faster, more stable connection

   to the 'net along with much larger file space resources.

   I'm looking for ways to enhance our library of downloadable

   materials and the wiring diagrams for this popular

   radio would be a great candidate.



   Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Sun Jan 28, 2007 4:55 pm Post subject: Jack plug question (shielded wires)

At 05:30 PM 1/28/2007 -0700, you wrote:

 	  Quote: 	
		  Bob,

I have a complete KX-155/165 installation manual I would gladly mail to 

you as I no longer have a need for it, if you want it



Mauri Morin

Polson, MT

RV-8 N808M (reserved)

C180 N2125Z Flying

SEMPER FI


	


    Mauri. Hold off my friend. Another List member

    has just sent me a .pdf copy. Wasn't aware of it

    until I opened the message right after yours.

    I think I've got what I need. I'll get it

    checked over and then post what looks like

    would be most useful for our brother across the

    pond.



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Sun Jan 28, 2007 5:04 pm Post subject: Jack plug question (shielded wires)

At 11:01 AM 1/28/2007 +0000, you wrote:

 	  Quote: 	
		  Hi Bob



I'm afraid i don't have a wiring diagram - they wouldn't give me one. 

Contacted the technician who did the wiring harness several times and he 

was vague about the need for a ground. Maybe he thought i had a metal 

panel or maybe he didn't understand the wiring and was just doing as he 

was told?


	


   Frank. Send me your direct email and I'll forward a

   link for downloading a .pdf copy of the manual that has

   come into my possession.



   Bob . . .

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