"Gene Fuller" wrote:

W5DXP wrote:
For the 4 TPI, 6" diameter coil, the VF formula yields 0.02.

The pitch divided by the circumference yields 0.013.

Since you have fallen back to the old "round and round the helix" model
there is little hope for agreement. It is interesting, however, that
even the Corum model for Vf at resonance is not as slow as the purely
geometric model. Must be those standing waves again.

Anyone who says the current goes "round and round the helix"
is wrong. Anyone who says the current goes like a "short circuit
through the coil is wrong."

There is NO rail "round and round the helix'! There is NO rail
"short circuit through the coil"! There is, as usual, something in
between the two rails. Looking at Fig. 1 in Dr. Corum's IEEE paper:

For a diameter/wavelength ratio of 10^-3

If the coil is1000 turns/wavelength, the VF is 0.8 which is closer
to a "short circuit through the coil" than it is to "round and round
the helix".

If the coil is 5000 turns/wavelength, the VF is 0.18 which is
closer to "round and round the helix" than it is to a "short
circuit through the coil".

The field coupling between the coils is responsible for the VF
not being as slow as the purely geometric model but there is
a practical physical limit to the number of coils that are being
coupled.

Coils are a combination of primary and secondary characteristics.
All the primary characteristics need to be taken into account. Some
of the secondary characteristics can be omitted under certain
conditions.
--
73, Cecil, W5DXP