[TowerTalk] Fields and coax

[Tom Rauch]

> I didn't read the original post in this thread, so I don't
know
> the application, but it is critical to understand that
>
> 1) cable shields provide no magnetic shielding until the
frequency
> rises high enough for skin depth to come into play
(nowhere near
> audio)
>
> 2) virtually all power-related fields are magnetic fields,
and all
> home entertainment systems are in the near field (the near
field
> of 100 Hz is within roughly 200 miles of a source).
>
> I would say that given the above facts, coiling up a piece
of
> coaxial cable that carries AUDIO (or baseband video) in
the
> presence of a strong AUDIO magnetic field is a really dumb
idea,
> and likely to induce lots of hum and buzz into the system
in
> question.


The original comment was coiling the coax it was a problem
at radio frequencies and especially at VHF because it added
inductive reactance inside the cable since the shield can't
shield magnetic fields.

But of course here on Towertalk we all know once a shield
with very small gaps is several skin depths thick neither
field passes through.