Roy Lewallen wrote:
A coil itself isn't a slow wave transmission line. In conjunction with
shunt C, it can be analyzed as a transmission line, but only in
conjunction with shunt C.

A 75m bugcatcher has its own shunt C called "distributed capacitance".
It's what causes the self-resonant frequency of my 75m bugcatcher coil
to be only 60% higher than the 4 MHz operating frequency.

Remove the shunt C and it ceases looking like a transmission line.

That's true *only* for a lumped-circuit inductance. It is NOT true
for a 75m bugcatcher which has it very own distributed capacitance
built in. It is *IMPOSSIBLE* to remove the distributed shunt
capacitance from a 75m bugcatcher coil.

The earlier example of the modification to Cecil's
EZNEC model illustrated this -- when the ground (the other side of the
shunt capacitor) was removed, the current drop across the coil disappeared.

That may be true but please tell us how to remove the ground from a
75m mobile bugcatcher mobile antenna installation.

Coils of the dimensions of loading coils in mobile
antennas are orders of magnitude too small to support the TM and TE
modes required for slow wave propagation.

Sorry Roy, Dr. Corum disagrees with your statement. You really should
read the details of the Dr. Corum web page references that I posted.

His test for the validity of his helix equations is:

5*N*D^2/lamda(0) = 1 where N is number of turns, D is diameter,
and lamda(0) is the self-resonant frequency.

That value for my 75m bugcatcher coil is 0.4 so his equation for
velocity factor is valid. The velocity factor for my 75m bugcatcher
coil calculates out to be 0.0175. Now that's what I call a "slow
wave" coil.

But I have offered all these references weeks ago. Are you too
arrogant to even have read them? (Another rhetorical question)
--
73, Cecil http://www.qsl.net/w5dxp