JP wrote:

Skin depth and what cause it:

http://en.wikipedia.org/wiki/Skin_depth


The Wikipedia treatment is not incorrect, but it may create a false
impression that the skin effect is limited to some particular type or
cross-section of conductor.

There is a more general derivation by Davidson that has far fewer
restrictions about the assumed geometry. There is a scanned copy at:
http://www.ifwtech.co.uk/g3sek/misc/skin.htm

Davidson shows much more clearly that the existence of a skin effect
does not depend on any particular shape or size of conductor, or any
particular type of electrical circuit. If RF current is flowing in a
conductor - regardless of the reason - then the skin effect will be
present.

That is a very powerful conclusion. Because we know the skin effect will
be present, it helps us to trace the RF current pathways on complex
shapes such as coaxial cables and shielded loops.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek