Jim, AC6XG wrote:
"But the impedance "at" such points does not affect the current "at"
such points?"

"At" is a perfectly good preposition. R-F current can`t properly be said
to be "in" the wire due to skin effect.

The point I invoked was that at a certain distance along an antenna or a
transmission line, or at a certain distance from some reference point
there are values which are functions of the location. Often the load is
the reference chosen for a transmission line. Often the tip end of a
standing-wave antenna is used as a reference for distributions along an
antenna. When we know how many degrees a point lies back from the open
end of an ordinary standing-wave antenna a point is, we can predict many
characteristics of that point.

Impedance is a function of position on an antenna or on a transmission
line with reflections. Impedance is a voltage to current imposed on a
point.

On a standing-wave antenna, there are two significant actions which are
related but separate which I want to mention. The first is a somewhat
uniform, but declining due to radiation, incident power flow toward the
open-circuit end of the antenna. The second is a somewhat uniform, but
declining reflected power flow back from the open-circuit end of the
antenna which travels back toward the generator of the power.

Just as in a transmission line, were you to sense the power flowing each
direction alone, via a directional coupler, no standing waves would be
seen. It is only the superposition of the forward (incident) and
reflected waves that produces the familiar display that we might sense
with a slotted (trough) line. The value of standing waves is mainly as
an indicator of mismatch.

A transmission line has an iron-clad Zo due to its construction which
imposes the same voltage to current ratio (Zo) on incident and reflected
waves at every spot along the transmission line. Not so with the surge
impedance (Zo) of the antenna wire. Zo of the antenna wire can be
measured and calculated. It is a function of position along tjhe
antenna. For some calculations an average Zo of an antenna is useful.

I don`t remember everything from my studies over a half century ago.
Even If I did, most readers would either drop off to sleep or find a
more interesting activity.

I have no intention of trying to teach a course in antennas and
transmission lines. My impression is that Cecil is right on target in
this thread.

Best regards, Richard Harrison, KB5WZI