Gentleman,

The point of my post was not to point out the obvious
fact that lumped circuit analysis has some limitations
when used in the context of antenna loading coils. The
debate (at least the one I am familiar with), was whether
or not the current magnitude across an antenna loading
coil varied as the current would vary in a linear section
of antenna having same physical length as the loading
coil, or whether the current magnitude would vary as the
current would vary in a linear section of antenna have
the same physical length as the section of antenna that
the loading coil replaced.

In either case, distributed effects not accounted for
in simple lumped element models are recognized to be
at work. For the former scenario to be true, the current
retardation through the loading coil is presumed to be
roughly equal to that observed in a linear section having
the same physical length as the loading coil. In this case
the retardation would be Tau = length physical/Vp. This
scenario recognizes that distributed effects are at work
(hence the small, but finite current taper), but suggests
that the dominant factor responsible for the loading of
the antenna is the phase shift between the inductor
current and the voltage across it.

The latter case also suggests that distributed effects are
at work, but to a much greater degree than in the former.
In this case, the loading of the antenna is presumed to
be the result of the large current retardation introduced by
the loading coil. In this case, the retardation is presumed
to be Tau = length effective/Vp or Tau = length replaced/Vp.
In this scenario, the effect of the phase shift between the
loading coil current and the voltage across its terminals
seems to be considered incidental and is largely ignored.

The point of my loaded transmission line example was
to show that under either set of assumptions, the
loading coil will produce the desired result. That is to
say that it will load the physically short structure (in the
case of my example, a transmission line) thus bringing
it into so-called resonance. Thus the fact that the loading
coil produces the desired result (e.g. input impedance
match) can't be pointed to as proof that one physical
mechanism is dominate and the other is not. The
transmission line stub loading network doesn't have to
behave the same way as the lumped inductor loading
coil to produce the same desired result (e.g. input
impedance match, resonance, or whatever you want to
call it).

What I am getting at, is that both camps may be
wrong. The answer may lie somewhere in between
these two extremes (e.g. taper equivalent to physical
length vs taper equivalent to electrical length), but this
isn't attractive because its ambiguous and doesn't make
for nice diagrams that can be placed on websites, in
textbooks, or in antenna handbooks (not to mention
all of the accompanying self-righteous chest beating).

73 de Mike, W4EF.................................

P.S. for those of you who have already heard all this
please accept my apologies as I missed out on last
months debate.


"Richard Harrison" wrote in message
...
Richard Clark wrote:
"I thought this was dead long ago."

So did I. This recent posting is a repetition for me, but sometimes
repetition is needed for those who weren`t there in whole or in part for
the earlier postings.

I don`t expect anyone to accept a statement without proof from me that
ordinary circuit analysis does not apply to antennas, but from 3 E.E.
Sc. D.`s who were at the time they made the statement giving their very
best for victory in WW-2, I would expect some serious consideration and
at least a first assumption that the opinion is correct.

Best regards, Richard Harrison, KB5WZI