[aprssig] Re: Cat5 jumpers for mic connections

Dale Blanchard wa7ixk at earthlink.net
Thu Apr 14 02:04:23 EDT 2005

Shielded cat 5 cable is used in Europe, but I can not find it in USA, 
altho Fry's carries the shielded connectors..
Cat 5 works because of the tight twist on the wire pairs. When using 
isolation transformers you are using a balanced pair
that cancels interference. Parallel cable can cause problems, but only 
if you have a problem.
Try it first and then fix it if a problem,
Same thing on vehicle grounding.

Stephen H. Smith wrote:

> I aways make my own shields for CAT5 cables used with ham gear.
> Take a length of RG-8 or RG-213 coax.  Cut a slit along the length of 
> the outer black jacket with an X-Acto knife and peel the black PVC 
> off, exposing the braided copper shield underneath.    Push the shield 
> braid inward so the diameter increases slightly and pull the center 
> conductor and dielectric out of the braid.  You now have a hollow 
> braided copper tube.  Push  a piece of round CAT5 cable through the 
> tube and then pull on the braid to make it's diameter shrink snugly 
> around the cable inside.  Note that this must be done before the 
> second connecter (mic plug, RJ connector, DB9 etc is attached to the 
> cable.    Since this outer braid is an electrostatic shield, not a 
> current conductor, ground it to the equipment case at only one end. 
> I've shielded runs of CAT5 cable up to 20-25 feet long this way.   
> Since the length of the braid tube increases as the diameter shrinks, 
> you will only need about 15-16 feet of original coax to shield about 
> 20 feet of CAT5.     This works perfectly, and is a great use for old 
> rotten, lossy RG-8, RG-11 or RG-213 coax since the the plastic parts 
> deteriorate but not the copper braid.  Obviously, this isn't going to 
> work with LMR-type cables or others that use wrapped foil rather than 
> traditional woven braid as the outer conductor.

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