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Sheild pigtails.

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dean.psiropoulos(at)veriz
Guest

Posted: Sun Nov 05, 2006 9:20 pm Post subject: Sheild pigtails.

How does one use the little pigtails that are designed to bring the shield

of a coax cable out to a wire?  The ones I have are from Steinair and have a

special clear heatshrink with a metal ring in the center and a small wire

under the heatshrink and ring that can be attached to a terminal or pin.  I

slid the whole works over a stripped coax shield and put a heatgun on it.

The sleeve shrank around the coax just fine but the ring was a bit larger

than the shield and didn't melt like I expected (someone told me it was

solder ring that would melt around the shield and the pigtail wire). Is this

true?  Or am I supposed to crimp the metal ring before shrinking the

shrinkwrap. Or what......?????????????? Thanks.



Dean Psiropoulos

RV-6A  N197DM 

Finishing up wiring.

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Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Mon Nov 06, 2006 6:28 am Post subject: Re: Shield pigtails.

See:  http://www.emcesd.com/semdemos.htm



Here is a demonstration of a 5V square wave where the pigtail develops 1.5V across it. At pretty low frequencies too. At high frequencies...your signal has vanished into the ether.



The problem is that the reduction of the shield to a pigtail wrecks all the nice electrical characteristics that you paid for by using coaxial cable, by introducing an inductance. 



Proper termination of coaxial shields involves much more than twisting the shield into a "pigtail"--it involves coupling the shield to the ground or other other conductor with an inductance that is equal to- or lower than- the coax shield. 



So "pigtails" are for pigs. Let's keep it that way and learn how to do it right.



"Every act of conscious learning requires the willingness to suffer an

 injury to one's self-esteem...."

     -Thomas Szasz

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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

nuckollsr(at)cox.net
Guest

Posted: Mon Nov 06, 2006 6:53 am Post subject: Sheild pigtails.

At 12:18 AM 11/6/2006 -0500, you wrote:



 	  Quote: 	
		  

<dean.psiropoulos(at)verizon.net>



How does one use the little pigtails that are designed to bring the shield

of a coax cable out to a wire?  The ones I have are from Steinair and have a

special clear heatshrink with a metal ring in the center and a small wire

under the heatshrink and ring that can be attached to a terminal or pin.  I

slid the whole works over a stripped coax shield and put a heatgun on it.

The sleeve shrank around the coax just fine but the ring was a bit larger

than the shield and didn't melt like I expected (someone told me it was

solder ring that would melt around the shield and the pigtail wire). Is this

true?  Or am I supposed to crimp the metal ring before shrinking the

shrinkwrap. Or what......?????????????? Thanks.


	


  These are "Soldersleves" by Tyco/Raychem. They come in a variety

  of formats. Their use is illustrated in the last frame of an

  article at:  http://aeroelectric.com/articles/pigtail/pigtail.html



  The devices are described in part in documents at:



http://www.aeroelectric.com/Mfgr_Data/Misc/Raychem-Tyco



  The problem you're having suggests that your heatgun output

  is too cold and/or insufficiently concentrated on the length

  of the sleeve.



  My personal favorite gun right now is by Milwaukee and is similar

  to the one shown at:



  http://www.toolfetch.com/Category/Power_Tools/Heat_Guns/8975-6.htm



  There are over 200 listings for heat guns on ebay right now.

  Avoid the Milwaukee 1400 . . . looks cool, but only 300 watts.

  Dual heat guns are handy, variable heat guns are better.



  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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