[aprssig] Re: Cat5 jumpers for mic connections

Stephen H. Smith wa8lmf2 at aol.com
Thu Apr 14 01:21:55 EDT 2005

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. 

Stephen H. Smith             wa8lmf (at) aol.com
Home Page:                   http://wa8lmf.com

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