Ian White GM3SEK wrote:
1. The magnitude and phase of the current flowing into the loading
inductance are both the same as that of the current flowing out (this is
a fundamental property of pure inductANCE).

That is a fundamental property of a pure inductance in a lumped
circuit analysis which assumes a DC current or a pure traveling-
wave current. It is NOT a fundamental property of a pure inductance
if the current you are talking about is a net standing wave
current. Your stated principle is simply false for a standing
wave environment. In a transmission line, it is easy to install
a coil that has zero current at one end and an amp of current
at the other end.

It simply doesn't apply in a standing wave environment - and a
75m bugcatcher loaded mobile antenna is a standing wave antenna.
Please take a look at my example and questionaire to understand
what is wrong with your above statement.

The measured current at the bottom of a loading coil is primarily
standing wave current. IT IS NOT FLOWING.

The measured current at the top of a loading coil is primarily
standing wave current. IT IS NOT FLOWING.

Since neither of these two currents are flowing, they don't
have to be equal. They just stand there.

If I present to you a black box with zero amps at one terminal
and one amp at the other terminal, what can we conclude? One
possibility is 1/4 wavelength of coiled up coax with an
infinite SWR. Please ponder that and apply it to your coil
assertion above.

The currents that are doing the flowing are the underlying
current components, the forward current and the reflected
current and they are close to equal. Everything you say
about a coil is true for the forward current and the
reflected current. It is simply not true for the standing
wave current which is just a conceptual construct and not
a flowing phasor at all.

If you really want to accurately apply the principles you are
asserting, you must treat the forward current and reflected
current separately and then superpose the results. Applying
your above principle to standing wave current is akin to
superposing power and that's a no-no.

I have never seen such a wide-spread blind spot.

Take the transmission line example.

---------------------------X----------------------------
Ifor=1.0amp -- --Iref=1.0amp

There's a black box at 'X'. Inside the black box is 1/4WL
of coiled up transmission line. The current measured at
left of the black box is zero amps. The current measured
at the right of the black box is 2 amps. That doesn't
violate any laws of physics. That obeys the laws of physics
for a transmission line with reflections. You are measuring
the currents at a current node and at a current loop. It's
absolutely no big deal.
--
73, Cecil http://www.qsl.net/w5dxp