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shielded tach wire

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talew(at)bellsouth.net
Guest

Posted: Thu Sep 09, 2010 11:37 am Post subject: shielded tach wire

Hi All '

This question is about the wiring in my CJ- 6A .

I was trying to track down a noise in my radio and noticed that the wires to the 

front tach indicator are shielded

but there is no shielding on the wires to the rear tach indicator in my plane .

Does anyone know if this is normal ? This is a 1965 model .

Terry Lewis

yakplt(at)yahoo.com
Guest

Posted: Thu Sep 09, 2010 2:21 pm Post subject: shielded tach wire

Terry, I don't know JACK about CJ's, (and I am sorry for not answering your question) but I do know something about Tach Generators.  They are extremely powerful generators of noise that can not only be picked up by a radio.... in one case I have seen it be so bad that it actually ruined the front end stage on a Balkan-5 receiver in a YAK-52!  That said, you should always ... as in ... ALWAYS ... use well shielded wire for anything hooked to a Tach Generator.  Remember though, the easiest way to determine if your noise is coming from that source is to simply unhook the cannon plug on the tach generator and see if the noise goes away.  Then work from there.  Two big sources of noise ... "P" leads and Tach generator wiring.  



There is nothing wrong with changing any original design to add shielded wire.  If the original design in the CJ did not use shielded wire, I kind of think they should have.  



A little trick you can also use ... grab a handheld radio and get an adapter so you can plug in a headset.  Then use the rubber ducky antenna as a "wand" to walk around your airplane with the engine running and holding the antenna near wiring bundles to try and determine where noise is coming from.  Pretty crude, but it does work.  



Good Luck. 



Mark

--- On Thu, 9/9/10, T A LEWIS <talew(at)bellsouth.net> wrote:



 	  Quote: 	
		   From: T A LEWIS <talew(at)bellsouth.net>

 Subject: shielded tach wire

 To: "yak list" <yak-list(at)matronics.com>

 Date: Thursday, September 9, 2010, 3:30 PM

 

 A LEWIS <talew(at)bellsouth.net>

 

 Hi All '

 This question is about the wiring in my CJ- 6A .

 I was trying to track down a noise in my radio and noticed

 that the wires to the 

 front tach indicator are shielded

 but there is no shielding on the wires to the rear tach

 indicator in my plane .

 Does anyone know if this is normal ? This is a 1965 model

 .

 Terry Lewis

 

 

 

 Forum -

 FAQ,

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

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 Dralle, List Admin.

talew(at)bellsouth.net
Guest

Posted: Thu Sep 09, 2010 2:42 pm Post subject: shielded tach wire

Thanks Mark,

I like your idea for the use of the hand held radio . I'll try

that this weekend .

Terry



---

yakplt(at)yahoo.com
Guest

Posted: Thu Sep 09, 2010 3:09 pm Post subject: shielded tach wire

Good luck... 



If you try the handheld method, the best way is to have a step attenuator on the front end so you can reduce receiver sensitivity.  You probably won't have that ... so time to improvise.  Lots of ways to do this, but worse come to worse, take off the rubber duck.  Stick a short (aboout 19 inches or so) safety wire into the center conductor hole of the rubber duck connector on the handheld (usually a BNC connector).  Hopefully not an SMA ... they are so small they are a pain to work with.  Regardless, if you get too much noise, just start cutting the antenna wire shorter and shorter.  



Another method.... hook a piece of coax to the antenna jack with a connector on it.  On the other end, strip back the shield to expose the center conductor (keep the dialectric on the center conductor, just remove the shield).  Around 22 inches is 137 Mhz or so...   But if you get too much noise... wrap the center exposed end up in a loop.  



Point is to reduce sensitivity... and you can do that by just making your antenna smaller and smaller.  



Yes, a step attentuator is the RIGHT way, but few folks have one of those laying around. 



Mark

--- On Thu, 9/9/10, T A LEWIS <talew(at)bellsouth.net> wrote:



[quote] From: T A LEWIS <talew(at)bellsouth.net>

 Subject: Re: shielded tach wire

 To: yak-list(at)matronics.com

 Date: Thursday, September 9, 2010, 6:38 PM

 

 A LEWIS <talew(at)bellsouth.net>

 

 Thanks Mark,

 I like your idea for the use of the hand held radio . I'll

 try

 that this weekend .

 Terry

 

 

 

 ---

wlannon(at)persona.ca
Guest

Posted: Thu Sep 09, 2010 6:53 pm Post subject: shielded tach wire

Terry;

I have two 1965 CJ's here at present.  Pretty sure all of the tach. wiring 

is shielded.  Check tomorrow and let you know.

Walt



---

N13472(at)aol.com
Guest

Posted: Thu Sep 09, 2010 9:42 pm Post subject: shielded tach wire

The wiring diagram shows shielded wire all leads TACH gen to term strip then

to

both front and rear indicators.



Tom Elliott

CJ-6A NX63727

702-595-2680  



--

wlannon(at)persona.ca
Guest

Posted: Sun Sep 12, 2010 9:01 am Post subject: shielded tach wire

Terry;



Sorry for the delay.

All tach. wiring shielded in the two 1965 models here.



Walt

---

talew(at)bellsouth.net
Guest

Posted: Sun Sep 12, 2010 10:10 am Post subject: shielded tach wire

Thanks Walt,

That info is just what I needed . I will shield the rear tach

wires.

Terry



---

yakplt(at)yahoo.com
Guest

Posted: Sun Sep 12, 2010 3:39 pm Post subject: shielded tach wire

Better yet... just remove the rear tach!   



Mark

--- On Sun, 9/12/10, T A LEWIS <talew(at)bellsouth.net> wrote:



[quote] From: T A LEWIS <talew(at)bellsouth.net>

 Subject: Re: shielded tach wire

 To: yak-list(at)matronics.com

 Date: Sunday, September 12, 2010, 2:08 PM

 

 A LEWIS <talew(at)bellsouth.net>

 

 Thanks Walt,

 That info is just what I needed . I will shield the rear

 tach

 wires.

 Terry

 

 

 

 ---

talew(at)bellsouth.net
Guest

Posted: Sun Sep 12, 2010 5:31 pm Post subject: shielded tach wire

Mark,

I hear you .

 I start on that shield project tomorrow .

As well as checking the "p" lead shields .

Terry



---

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