Ken, The foils you describe probably isn't going to work under rugged
conditions. The foil will split and crack axailly after with a few flexing
of the cable. Foil shielded and coiled keyboard cables are a good example. The
coil was there to take up the slack but still allow the user to stretch the
keyboard cable out during use. The coil had a memory and would return to its
original shape as the keyboard was pushed back towards the cpu etc. I forget
the exact number of extension/retractions but it wasn't many before there were
cracks in the foil.
Beldon has STP which is really cat 5 cable with each pair having its own
shield - and there should be at least two pair and I think it was really 4
pair. I also seem to remember it had an outershield over all of that - all of
them foil mind you.
Terminating the shields is problematic, and about the only mechanism I
ever saw that had any luck at all, was to strip the outer jacked and then fold
the foil back over itself, exposing the inner foiled layer. This also put the
"blue" coating back to back, and left a 360 degree exposed metallic outer
layer which could then be pressure clamped into a metal connector housing or
ferrule inside the connector. The connection lasted longer than the rest of
the cable simply because it was held pretty much immobile.
One other thing to consider with foiled shields is that the most common
ones don’t really make metallic contact all around the cable. Where the
shield overlaps itself the inner tin (?) metallic portion along the axis of
the wire rest on top of the blue material. There is a version called an "e"
fold that eliminates this longitudinal discontinuity. Basically done, by
making the foil slightly wider than normal and bringing the two metallic
surfaces together and folding these over together. I assume it cost extra and
you still end up with the same fragile foil.
Probably better off with a woven shield - and you can get those double
shielded. The higher the optical coverage the better the shielding but it
makes them slightly stiffer.
Gary
----- Original Message -----
From: Ken Javor <mailto:ken.ja...@emccompliance.com>
To: emc-p...@majordomo.ieee.org
Sent: Wednesday, September 17, 2003 5:17 PM
Subject: need shielded cable
List Members,
I am looking for a five conductor overall shielded cable. The wires need to
be stranded and very small gauge, AWG 26 or smaller. My customer is
interested in a double-shielded configuration - braid on the outside, foil
on the inside.
I have had no success finding such a product.
The application is such that I think that a cigarette wrap foil alone would
work, but I am concerned about its ruggedness; this product will be worn by
men at work. Any suggestions pro/con on using a foil shield under such
conditions, including how to terminate it gently but securely and
peripherally?
Thank you.
Ken Javor
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