> The inner foil usually has a plastic backing on the "inside" (the side
> away from the braid). In the case of quad or tri-shield cable the outer
> foil does not normally have a plastic coating. Remember that the outer
> foil is between the braids in the case of quad-shield cable so there
> needs to be electrical continuity between the various shields. Plastic
> layers would prevent this.
The inner foil should be bonded directly to the dielectric surrounding the
center conductor. Otherwise, the cable will have an outdoor life issue. I
can't recall the last cable I saw without the innermost foil bonded to the
dielectric. I suppose someone somewhere makes bad cable that will wick water
or trap moisture in that critical area. Normal reasonable quality cable has
a bonded foil, meaning the foil is bonded directly to the center dielectric.
There is a triaxial cable that has a layer of insulation between shields,
sometimes Mylar, but that is outside the innermost shields.
As hard as we look for something wrong with CATV cables, there is very
little to find wrong. Other than susceptibility to very low frequency
energy, which doesn't bother us unless lightning opens the foil, it is great
stuff.
The last stuff I would use outdoors is a woven braid without foil, and
without flooding. That's just asking for problems.
73 Tom
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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