Tom Donaly wrote:
This whole thing
boils down to an engineering question, anyway, which is, is it possible
to engineer a loading coil to be small enough at the lower end of the
HF spectrum so that it can be modeled using network analysis?

That situation can be called pure single-point inductive loading. It may
not be totally practical, but it is still vital to this discussion.

There is an infinite range of real-life loading coils of various shapes
and sizes. Pure single-point inductive loading is the limiting case that
marks one end of that range. Any successful theory has GOT to get this
case right - and if it can't, it fails.

Regardless of the actual method used, any correct analysis of the whole
antenna MUST conclude that, for the limiting case of pure inductive
loading, the voltage/current/phase relationships at the loading
inductance are the SAME as those predicted by conventional circuit
analysis. This limiting case is where the two kinds of analysis come
together, and here they MUST agree.

That means a correct analysis for the whole antenna MUST predict zero
phase shift in the current (It = I0 cos wt) between the terminals of the
loading inductance. This requirement only applies for pure inductance,
and only at that single point where the inductor is inserted into the
antenna; but for that limiting case the requirement to join up with
circuit theory is real, absolute and non-negotiable.

Let's be clear: in this context, "current" is the plain ordinary
alternating current that we learned about in school: It = I0 cos wt. It
is the simple back-and-forth movement of electrons (charge) past a given
point.

Nobody denies that for real-life loading coils there can be a phase
shift in the current from end to end, and that it will become larger as
the coil becomes longer and skinnier. That isn't the question I'm
addressing here. But the question of what happens when the coil shrinks
down to become a single-point loading inductance is equally important:
it cannot be evaded, and it is a definitive deal-breaker.

It's hard to tell for sure from the avalanche of messages, but Cecil's
analysis apparently fails in the limiting case of pure inductance - or
rather, he seems to deny that the test is even a valid one.

In principle there is nothing wrong with attempting a traveling-wave
analysis for a loaded whip. Done correctly, it will give the right
results that join up seamlessly with circuit theory as well.

It's just that Cecil has NOT done it correctly. I think there are
several reasons, and until he corrects them all, his theory will
continue to fail... and he will continue in denial of that.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek