In an attmept to beat this subject to death, here are a few more links
to usefull
information.

One measure of the degree of isolation bewteen a feedline the outside
is called
"transfer impedance".

From Fluke:
http://www.flukenetworks.com/us/_Promotions/ISV/Glossary.htm

"Transfer Impedance - For a specified cable length, transfer impedance
relates to a
current on one surface of a shield to the voltage drop generated by
this current on
the opposite surface of the shield. Transfer impedance is used to
determine shield effectiveness against both ingress and egress of
interfering signals. Shields with
lower transfer impedance are more effective than shields with higher
transfer
impedance."

Blue Jean Cables has a good simple article with chart.
http://www.bluejeanscable.com/articles/shielding.htm

Beldon has more info at:
http://www.belden-wire.com/Catalog/TechInfo/TechTransfer.htm

One test I made was to use my antenna noise bridge with an additonal
4:1
step down transformer to induce noise in a wire that I ran parallel to
my
coax and triax feedlines. I compared several different types of coax.
The crap
they sell at Radio Shack is marginal. It is better then twisted or zip
cord, but still
sucks. For LF/MW/HF any of the real coax is very close in "leakage". I
am
partial to Belden but there are othre good brands.

When I ran a 6' test "loop" in parallel, ~6" offset, with twisted or
zip cord the
induced/injected RF noise overwelamed evrything except for th e very
strongest
signals. With radio shack coax Ihad to place the test loop against the
coax
for significant ingress. With belden braid and foil coax I could barely
detect the
N, with Triax I couldn't detect it at all.

I tend to think of video as mid level , LF/MW/HF receivers are low
level and transmitters
are high level. While similar, each level has different issues. For
instance I might not
mind lossing 5% of a 100W 40M transmitted signal, but I damn sure don't
want that 5W
to show up in my shack. A 10uV engress in video will not be detectable.
A 10uV
engress in to my LF/MW/SW, or even VHF/UHF will cover all but the
strongest
signals. Coax does not provide 100% isolation, so I take some pains to
keep the
transmitt coax lines seprated from the receive coax lines and to insure
they don't
run parallel for any significant length.

And spiral wraped shielded cable is about the worst choice you can make
for either
video or RF. For very short video or audio runs, up to 1m, spiral might
work IF there
are no RFI sources nearby. Spiral cables are cheap and every VCR/DVD
that I have
seen comes with these cheapies.These should NEVER be used for even
short
connections to a SW!

An example: I have a RF patch bay and one night theAC mains went down.
I was in
mid rebuild so I wanted to patch my DX398 into my patch bay. I had just
installed a
high end DVD and still had the cables in my garbage can. I grabbed the
video (yellow
RCA) a patch to BNC, RCA to BNC, and a RCA to 3.5MM. I was amazed at
how much
RFI from laptop was getting in to the DX398. So I dug out the correct
patch cable, a
1M RG174 BNC to 3.5MM and when I switched cables the RFI vanished. In
disgust
I cut the cables in half and put them back in the trash.

http://www.audioholics.com/techtips/audioprinciples/interconnects/spiral_shield_cables.php

Terry