Jim Kelley wrote:
It's no coincidence that the phase of the standing wave varies by 90
degrees along the length of a 90 degree standing wave antenna.

But it doesn't, Jim. Both Kraus and EZNEC agree that
standing wave current phase varies by only ~3 degrees
over the entire length of a 180 degree wire dipole
(referenced to the phase at the feedpoint).

If you slide a current probe up and down a 1/2WL wire
dipole, you will find that the phase referenced to
the phase at the feedpoint barely changes and cannot
be used to determine position on the dipole. The
position along the dipole is contained in the amplitude.
The ARCCOS of the relative amplitude will yield the
position along the dipole.

Please read what Gene Fuller said:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe,
there is no remaining phase information. Any specific phase
characteristics of the traveling waves died out when the startup
transients died out.

Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be
seen again.

The only "phase" remaining is the cos (kz) term, which is really
an amplitude description, not a phase.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com