Jim Kelley wrote:
Decrease of RF current with depth below the surface of a conductor
is only a true exponential if the available conductor depth is
infinite. In the modeled situations where there is 'competition' from
a skin effect on the opposite side of the conductor, the solution is
a Bessel function which does pass through zero and reverse direction
at certain depths.
In other words, the model is behaving as expected.
Programs such as NEC and Maxwell are not released until they have
gone through a very detailed process of checking and validation. The
first step is to check against special cases that can be
independently solved by analytical methods (in other words, pure
math). The work isn't complete until all the results agree within
close margins, and the reasons for any differences are fully understood.
By the time we amateurs come to hear about these programs, they have
already been thoroughly validated by developers and professional
users. That doesn't make them immune from further criticism... but
only by people who have done the work to earn that right.

Hi Ian,

Please know that my comment was never intended as a slight of anyone's
work.

I didn't think that for a moment, Jim.

I simply don't presume to know anything about it other than to observe
that the citation appears to contradict the assertion that skin depth
is limitless and exponential in real conductors.

As noted above, that commonly-held assertion is only true for conductors
of limitless depth.


--

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