Cecil, W5DXP wrote:
"The following web page is representative of the side that asserts there
is virtually zero delay through a 75m loading coil. But the backers of
that argument have grown strangely silent of late."

Coils generate counter-emf as a result of forward current and the
necessary magnetic field grows no faster than the current grows. Its
growth is delayed by the counter-emf.

Current does not jump off the rails in a coil. It follows the coil wire
as it follows a straight wire elsewhere. Terman says so and here is a
quotation from the "Lenkurt Demodulator of August 1965 which describes
the operation of a Traveling Wave Tube (TWT). Lenkurt used some of these
in heterodyne repeaters operating at 6 GHz because of their wide
bandwidth. Lenkurt`s description is very similar to Terman`s
description:
"The signal to be amplified by the tube is coupled into the gun end of
the helix. This RF signal travels as a surface wave around the turns of
the helix, toward the collector, at about the velocity of light. The
forward movement of the wave is analogous to the travel of a finely
threaded screw (I called it a bolt in my analogy) where many turns are
required to drive it into position. The signal wave generates an axial
electric field which travels*with it along the longitudinal axis of
the helix. This alternating electric field interacts or velocity
modulates the electrons in the beam."

The beam is pencil thin centered inside the helix. The beam is formed
and focused much like that inside a cathode ray tube. Its electrons are
accelerated by a high positive d-c voltage on the collector and
elsewhere in the tube. But that`s not all. Signal voltage on the helix
speeds and slows the beam at multiple points along the helix which is
many wavelengths long at 6 GHz. This advancement and retardation along
the length of the helix bunches up the electrons producing the velocity
modulation of the beam.

The helix is just a long spiral of wire inside the TWT. There are many
cycles of the 6 GHz signal distributed along the wave`s travel route.

Terman and Lenkurt say the signal route is along the wire in the coil. I
believe them.

Best regards, Richard Harrison, KB5WZI