Keith Dysart wrote:
From assertion A above, is it your contention that far from
the antennas it is "interference" that causes the variation
in field strength, but that on the line drawn between the two
antennas some other mechanism is responsible?

Of course not - please don't be ridiculous. If the two
antenna elements were isotropic point sources, on a
line drawn between them, there could be no interference
and there would be only standing waves in free space
along that line assuming no reflections from nearby
objects, etc.

Everywhere else there are components of waves traveling
in the same direction so interference is possible anywhere
except on that line between the point sources. When the
sources are not a point, seems to me, interference could
occur at any and all points in space.

My "assertion A above" was about transmission lines,
an essentially one-dimensional context. Two waves in
a transmission line are either traveling in opposite
directions or in the same direction.

Incidentally, I came across another interesting quote
from one of my college textbooks, "Electrical Communication",
by Albert. "Such a plot of voltage is usually referred to
as a *voltage standing wave* or as a *stationary wave*. Neither
of these terms is particularly descriptive of the phenomenon.
A *plot* of the effective values of voltage ... is *not a wave*
in the usual sense. However, the term "standing wave" is in
wide-spread use." [Emphasis is the author's]
--
73, Cecil http://www.w5dxp.com