Indeed, Ian. Just so.

It's amazing to me that this thread has gone on for so many postings.
(And here I am contributing to it! ;-) But I go back to the very first
posting in the thread, where Reg said it all. Well, maybe not QUITE
all, but close. I'd invite folk to go back and look at that posting.
I believe Reg noted that a real physical (single-layer solenoid) coil
has: inductance, capacitance (with a radial electric field), wire
resistance and radiation resistance. One additional item I'd like to
note is turn-to-turn capacitance; Reg may have been thinking of that
one too, but I didn't get it explicitly from his posting.

Measuring currents doesn't present too much of a challenge if one is
careful about it, but measuring voltage is an entirely different
matter, since it's in the presence of a time-varying magnetic field if
there is any current in the coil. But it is possible to measure the
electric field and the magnetic field if one wishes.

I have not been following this thread very closely, because I really do
NOT expect "the answer" to be any different than what, as Reg noted in
that initial posting, is predicted by an ACCURATE model. People who
designed travelling wave tubes understood very well the properties of a
helix of wire with respect to propagating a wave. The software I've
been using for years now to predict single-layer solenoid coil
behaviour takes into account all the interesting effects, and will
predict quite accurately the first parallel resonance and the first
series resonance, the Q, the inductance, and fundamental transmission
line characteristics below resonance. I have other resources that let
me predict the change in behaviour when a coil is inside a shield.
I've never been surprised by any of the results: taken to correct
limits, they all join up, as Ian notes, with conventional circuit
theory. In fact, even the complex models match conventional circuit
theory, just with more elements in the model.

I do note that one must be careful about exactly what conventional
circuit theory actually says. For example, many people seem to think
that Kirchoff's Voltage Law is something like, "voltages around a loop
add up to zero." That is an abbreviated statement of the law, and is
in general not correct.

Cheers,
Tom