That's not entirely true. Ever try to make a vhf or uhf duplexer on a
two way radio system work with only single shield interconnects on the
cavities? Especially with a close spaced system. You will never get the
isolation to stay put. Move a cable around and the isolation changes.
You don't have that problem with double shielded cables.
73
Gary k4FMX
::Gary, I agree with you, and that mirrors my experiences, too. And
actually, when I was with Comcast, we did a great deal of experimenting with
coaxial cables for distribution and the quad shielded cables which led to
the common RG6-Quad that's used everywhere today, absolutely performed
better in a variety of ways. If not, nobody'd bother paying extra to buy
it. One great test was to run the cable overground with a normally
conducted signal and then bombard the cable with 10v/m interference (same
signal, phase shifted) to see the effect on the demodulated video. This was
with double-crimp F connectors, perfectly installed, in repeated testing
using many different cables. We could make ghosts occur any old time we
wanted to with RG59/U, RG6/U, double-shielded braided cables and
double-shielded braid over foil cables. It wasn't until we tried quad
shielded cables (foil/braid/foil/braid) that we just plain couldn't create
ghosts at any interference level we could generate. I can't think of any
common amateur applications where any of this would matter, though....
-WB2WIK/6
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