Ian White, G3SEK wrote:
An
ideal loading inductance does *not* radiate; therefore the current at
its two terminals *must* be the same.

This is misleading. Since virtually all coil-loaded mobile antennas
are *STANDING WAVE* antennas, there are two current components which
superpose to your total current. Let's assume a certain loading coil
does not radiate. The forward current is the same magnitude at the
bottom of the coil and at the top of the coil. The reflected current
is the same at the bottom of the coil and at the top of the coil.
There is a phase shift through the coil that affects both those
currents. The total current is the phasor sum of the forward current
and reflected currents. That phasor sum is different at the bottom
of the coil and at the top of the coil. The constant current principle
definitely applies but there are two component currents with phase
shifts to worry about, just as there are in a transmission line with
reflections.

Do you use circuit analysis on a transmission line with reflections?
If not, why do you use circuit analysis on an antenna with reflections?

I keep coming back to the same point: until someone correctly
understands what pure unadulterated inductance does in an antenna, he
can never *truly* understand how a real-life loading coil works.

Ian, using circuit analysis on a standing-wave antenna is not valid.
Until someone correctly understands that only a distributed network
analysis works on a standing-wave antenna, he can never *truly* understand
how a real-life loading coil works. Hint: When installed in a standing-
wave antenna, a loading coil works like a transmission line so circuit
analysis is an invalid approach. The cosine current distribution on a
1/2WL standing-wave antenna is just 180 degrees of a standing current
wave which necessarily must possess two superposed current components,
forward and reflected.

This is just another example of an invalid math model trying to
dictate reality instead of reality dictating a valid math model.

Until someone understands the nature of forward current and reflected
current on standing-wave antennas, one will remain confused and be
tempted to use that invalid circuit model.

Your circuit model can be used on traveling-wave antennas. It is NOT
valid for standing-wave antennas.
--
73, Cecil http://www.qsl.net/w5dxp


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