Ian White GM3SEK wrote:
Jim Kelley wrote:
Dave wrote:
"Art Unwin" wrote in message
...


( I am assuming that skin depthg is not limitless.)
of course it is limitless, it is an exponential function so it never
goes to zero. the so called 'skin depth' is only the point where the
current has dropped to 1/e or about 37% of the surface value, still a
significant current.

The plots at the link Frank provided show current going rather
abruptly to zero - even negative ("contrary"?) in some cases. I
wouldn't presume to know whether it is modeled correctly.


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 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.

73, ac6xg