Here are some valid conclusions that can drawn from the
"Current through coils" thread.

A mobile antenna is a standing wave antennas. Some mobile
antennas use loading coils within that standing wave
environment.

There is no useful phase information in standing wave
current. Therefore, standing wave current cannot be used
to determine the percentage of a wavelength that is
occupied by the coil.

Standing wave current cannot even be used to determine
what percentage of a wavelength is occupied by the whip
above the coil. Standing wave current has virtually
unchanging phase the entire length of the mobile antenna.

The percentage of a wavelength occupied by any element
can be estimated using that element's velocity factor.
The velocity factor of the whip is known. The velocity
factor of the coil can be measured or estimated using
applicable formulas.

The presuppositions of the lumped-circuit model render
it ineffective in any attempt to analyze large coils
in a standing wave environment. Either the distributed
network model or Maxwell's equations must be used to
obtain valid analysis results.
--
73, Cecil http://www.qsl.net/w5dxp