Tyler,
Thanks for the input. I agree that leakage can and does exist and can be
designed into a cable. I guess the three main points I was trying to make
were:
1. A quality grade coax should provide excellent shielding at HF frequencies
and leakage should not be a significant factor (in the milliwatt range) in
EMI/RFI problems. Its not a question whether leakage exists, it does, but
does it exist as a problem at the levels we're talking about?
2. Discussion on the subject has characterizd the leakage as diffusive, i.e.
leakage escaping in or out of the braid. That does not constitute a
completely valid picture of the problem. Literature on the subject refers
to diffusive, inductive and capacitive modes, which can act in varying
degrees and can be dependent on not simply the braid content, but dielectric
properties, spacing, and other factors.
3. A third point is that our transceivers and amplifiers are complex signal
generators. They generate a very big signal on an intended frequency, and
some signals on unintended frequencies. (Remember, the FCC only requires
these to be 30 dB down)
If you consider each signal as a seperate emission, it has its own power
level, its own SWR, its own radiating efficiency into a given antenna system.
Hardline very efficiently transfers these unintended emissions, even at high
SWR levels, to the antenna where they can be radiated. The hardline solution
may exacerbate, rather than solve problems.
The EMI/RFI monster has many heads. With quality cable in use, I personally
don't think leaky coax is one of them.
Thanks, Paul, KB8N
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