Roy Lewallen wrote:
Well, not a "slow wave" transmission line. We shouldn't confuse an
ordinary lumped LC transmission line approximation with a true slow wave
structure such as a helical waveguide (next item). The propagation
velocity of the equivalent transmission line is omega/sqrt(LC), so the
speed depends equally on the series L and the shunt C.

Dr. Corum gives a formula for calculating the velocity factor of coils
which meet a certain criteria. My 75m bugcatcher coil meets that
criteria. It's velocity factor calculates out to be 0.0175. It's
measured velocity factor is 0.015. That sounds like a "slow wave"
device to me.

The coil in the EZNEC model on Cecil's web page acts just like we'd
expect an inductor to act. With ground present constituting a C, the
circuit acts like an L network made of lumped L and C which behaves
similarly to a transmission line. With ground, hence external C, absent,
it acts like a lumped L.

The subject is 75m bugcatcher loading coils mounted on GMC pickups.
How the heck does the ground get removed?

Important for what? No matter how long the coil or how many turns of the
wire, a small (in terms of wavelength) inductor won't act like a slow
wave structure ...

A 75m bugcatcher coil is not small.
--
73, Cecil http://www.qsl.net/w5dxp