christofire wrote:
Then the
assumption of equal forward and reflected traveling waves of current can't
be right, because that would imply no radiation ...

Of course you are right. But the forward and reflected waves
are equal at the ends of the dipole. At the feedpoint of a
1/2WL dipole the reflected current is only ~10% down from
the forward current so the equal current assumption through
the center loading coil is definitely only an approximation.

The question remains: How can the current on a standing wave
antenna, known to change by only 2-3 degrees in 90 degrees
of antenna, be used to measure the delay through a loading
coil installed in the standing wave antenna?

Incidentally, the equal amplitude and opposite phase of the
forward current and reflected current at the ends of a 1/2WL
dipole is the reason that the ends don't radiate much. The
two currents are acting like transmission line currents and
thus any radiated fields tend to cancel because of destructive
interference.

The forward current and reflected current are in phase at
the feedpoint. Their fields interfere constructively and
thus radiation is maximum at that maximum current point.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com