Cecil Moore wrote:
Tom Donaly wrote:

What's the formula, Cecil?


http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (32)

The velocity factor can also be measured from the self-
resonant frequency at 1/4WL. VF = 0.25(1/f)

I suppose you also
have something that will tell us how to find your coil's characteristic
impedance; o.k., out with it.


http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43)

The characteristic impedance can also be measured at
1/2 the self-resonant frequency at 1/8WL. For a lossless
case, the impedance is j1.0, normalized to the
characteristic impedance so |Z0| = |XL|.
For a Q = 300 coil, that should have some ballpark accuracy.

We don't need extreme accuracy here. We just need enough to
indicate a trend that the velocity factor of a well-designed
coil doesn't increase by a factor of 5 when going from 16
MHz to 4 MHz.

In "Antennas for All Applications", Kraus gives us the phase
of the standing wave current on standing wave antennas like
a 1/2WL dipole and mobile antennas. 3rd edition, Figure 14-2.
It clearly shows that the phase of the standing wave is virtually
constant tip-to-tip for a 1/2WL dipole. It is constant whether
a coil is present or not. There is no reason to keep measuring
that phase shift over and over, ad infinitum. There is virtually
no phase shift unless the dipole is longer than 1/2WL and then
it abruptly shifts phase by 180 degrees.

I agree with Kraus and concede that the current phase shift in
the midst of standing waves is at or near zero. There is no
need to keep providing measurement results and references.

You load your antennas with a Tesla coil? Did you read the part
about a Tesla coil going to a lumped inductor when it was shortened?
73,
Tom Donaly, KA6RUH