Roy Lewallen wrote:
Important for what? No matter how long the coil or how many turns of
the wire, a small *diameter* (in terms of wavelength) inductor won't
act like a slow wave structure or an axial mode helical antenna. . .

So many words trying to avoid the real issue which is: What is
the percentage of a wavelength occupied by a loading coil. It
doesn't matter what the size of the coil is. In the real world,
a loading coil occupies a certain percentage of a wavelength.

For a small coil, that percentage will be small. For a large
coil that percentage will be large.

We have had to throw out your phase measurements using the phase
of standing wave currents because that phase you used is unchanging
whether in a wire or in a coil. Your phase measurements tell us
zero information about the delay through a coil.

That leaves us only with indirect measurements based on the self-
resonant frequency of the coil in the mobile environment or the
phase information left in the standing wave current amplitude over
the 90 degree antenna.

My self-resonant frequency measurements indicate that a 75m loading-
coil occupies 40-60 degrees of a 360 degree wavelength. That's
11%-17% of a wavelength. Dr. Corum's papers agree with that
estimate.

Another way of estimating the percentage of the antenna occupied
by the loading coil would be to plot the current segments from
feedpoint to tip. Then draw a cosine wave on the same graph with
0 degrees at the feedpoint and 90 degrees at the tip. A rough
estimate of the percentage occupied by the coil would be the
slice of the cosine wave from the bottom of the coil to the
top of the coil.

Mere words are not going to change the percentage of a wavelength
occupied by a real-world loading coil.
--
73, Cecil http://www.qsl.net/w5dxp