Roy Lewallen wrote:
I maintain that there's no such group as "other coils", but that coils
act quite differently depending on their physical sizes and the amount
of coupling between turns.

What's wrong with grouping coils that act quite differently
into a set called "other coils"?

But if you wind a helix that's
short in terms of wavelength and with a reasonable length/diameter
ratio, the field from the current in each turn couples to all other
turns, which makes the propagation axially from one end to the other
close to the speed of light.

This is easily proven not to be true by self-resonance testing.
My 75m bugcatcher is self-resonant on my GMC pickup at about
6.6 MHz. If the signal were "propagating axially from one end to
the other close to the speed of light", the self-resonant frequency
would be close to 1 GHz.
--
73, Cecil http://www.qsl.net/w5dxp