Richard Harrison wrote:
Tom, W8JI wrote:
"Many people vizualize current in a small loading inductor as starting
at one end and traveling through the conductor turn-by-turn.

That`s how the experts say the coul in a TWT works, and it is no
different from other coils.


That's not correct at all Richard. The coil in a TWT tube behaves
considerably different than a small inductor operted at a low
frequency.

Nearly everyone on this thread seems to understand mutal coupling is
very high in a conventional loading inductor. This is why the inductor
comes close to following a square of the turns change in inductance. A
TWT has a loose coil operated in an entitrely different mode, behaving
much more like a axial mode helice than an inductor.

It can easily be proven inductors don't behave the same way when they
have wide turns spacing and long form factor and low values of
distributed capacitive reactance to the outhside world...when compared
to an inductor who's displacement current is very low compared to
through current.

Coils or inductors can range from having very low phase difference
between each terminal (almost immeasureable) to very high values (a
helical antenna or tesla coil at resonance).

The only real argument against this seems to be from Cecil, and as I
understood it he thinks standing waves are what causes current to be
different at each end and somehow sets the phase difference between
ends of the inductor.

I can have a fixed style of antenna on a fixed frequency, change only
the inductor design, and go from something that almost perfectly
behaves like a lumped component to something that has noticable current
taper across the component.

Most people had this stuff right from about post one.

I rarely see a thread go nowhere like this one has. It reminds me of
the Fractal antenna threads years ago, or that silly conjugate match
stuff that went on for years and years.

800 posts later the same major group of people seem to agree, the same
one or two people seem to think something magical occurs in an antenna
making a regular lumped inductor behave like a self-resonant helice
with standing waves and all.

It's sure a time waster.

73 Tom