Art Unwin wrote:
It (the phase) then abruptly chamges ...
Many thanks for what time you may give to this

Standing wave current creates some strange
illusions like zero current points accompanied
by an abrupt large phase shift on each side
of the current node. If you deal with the
underlying traveling waves instead of the total
component wave, things become a lot clearer.

The abrupt phase change happens every so often
in a standing wave antenna. It is presented for
an EDZ in graph form on page 465, Figure 14-4 of
"Antennas" by Kraus, 3rd edition available for
a few bucks at:

http://www.abebooks.com/servlet/Sear...nnas&x=55&y=10
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com