Re: NEC-LIST: Coax, Skin effect or Proximity effect ?

This is somewhat of a question of definitions. Skin effect and proximity
effect are both cause by current crowding due to the interior magnetic field
in the conductors. Skin effect is symmetrical and all there is in the
isolated coaxial cable you hypothesize. In a bank of parallel
current-carrying wires, the current-crowding causes an unsymmetrical
distribution in each wire, or, at least, an uneven distribution. If I
recall correctly, Glenn Smith's analysis of proximity effect assumes first a
skin effect distribution, that is, the current is effectively crowded into
an outer layer on each conductor. Then he calculates the redistribution due
to proximity of the other conductors.

Regards,
Doug Miron

<hideho.yamamura.wj_at_hitachi.com> writes:

Hello all,

Excuse me if this is a bit off topic.
I have a very basic question.

It is said that Loss of coaxial cables has frequency dependency
due to skin effect.
The inner conductor has current concentrated on the outer surface,
and outer conductor on the inner surface.

Here, I encounter a basic question:
"when the current is concentrated on the INNER surface,
 is it due to skin effect ?"

Obviously, the current is on the INNER surface,
because there is current in the inner conductor.
So, isn't that due to Proximity effect ?

How about the inner conductor ?
Skin effect and Proximity effect mixed ?

If so, is the loss proportional to the square-root of the frequency ?
(I believe resistance change due to Proximity effect is different
 and stronger than the square-root of the frequency, but not sure.)
If so, the fact that actual coax cables show square-root dependency
is because Proximity effect is masked and dominated by Skin effect ?

I would appreciate any related info.

Hideho YAMAMURA. //

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