Yuri Blanarovich wrote:

The conclusion was:
"There IS a drop, difference in RF current across the antenna loading coil."
The significance (to me anyway): Efficiency of the radiator, antenna is
proportional to the area under the (cosine) curve of the current
distribution across the radiator.

That is where we disagree. While it has been years, as I recall you
claimed the electrical degrees the inductor replaced caused the slope
across the inductor.

The point I (and others) tried to make was that in a small inductor
current was essentially equal at both ends of the coil, and any change
had to be caused by capacitance from the coil to the outside world that
was large compared to the termination impedance at the top of the
inductor.

It really is a shame you flew off the handle so fast and we didn't talk
through the problem. That's why misunderstandings start and drag on for
years.

This has become a "let's get him" thing instead of "let's figure out
how it works".

So in the typical loaded (mobile or shortened) vertical we are trying to
maximize the efficiency and it is important to know what is the current
distribution across the radiator. If the coil has a drop in order of 40 -
60% as it appears to be, than that is significant to me to take it into the
account. Knowing how to apply this effect will allow me to optimize,
maximize the antenna performance.

If you look at the measurements at:

http://www.w8ji.com/mobile_antenna_c...ts_at_w8ji.htm

you'll see for a given antenna structure, I can change the current
distrution all around. The current in a small loading coil of
reasonable form factor is essentially uniform at both ends of the
inductor.

This is because the inductor does not replace a certain "electrical
degrees" and have a cosine current drop related to those degrees. Any
drop in current is caused by displacement current from the inductor to
the outside world.

By the way, this is DIFFERENT than the self-resonance capacitance Cecil
refers to. The capacitance causing a self-resonance is actually a
mixture of capacitance to the outside world (that DOES change
distribution) and capacitance from turn to turn (that does NOT change
slope of current except by how it affects effective inductance).

3. Then Tom, W8JI and his followers, with some "backing" from literature
(plenty are wrong), some experiments, modeling, came to "prove" that it
can't be so. His conclusion: "The current in the antenna loading coil is the
same at both ends". Then the "fight" and controversy started.
It appears to me that JI camp is coming from the theoretical end of it,
applying laws of physics and theories that do not apply to the case in
question.

First, it is not "my camp". I know people like to make things like this
personal issues, but they really are not. How things work are how
things work. I like to learn how things work just as much as anyone
else. The problem is when people start getting personal and saying
things they would never dare say to another person's face, I get
uncooperative.
Most people behave that way.

Putting personal issues aside, anything can be resolved.

5. Not so fast. JI camp vehemently defended their "equal current" case,
using examples, modeling, tailored to support their claims, for some reason
ignoring the reality, measurements, experiments done to set the coil in the
spot where current can be, and is the same (no argument with that).

I can make current virtually equal at virtually any spot, and make it
very unequal at virtually any spot, just by changing the quality and
physical size of the loading inductor. I'll bet money on this,
provided we use real instruments.

The only time current will be substantially unequal will be when the
inductor has a large amount of capacitance to the outside world (acting
like a distributed network of displacement C's and series L's with
poor coupling) compared to the termination impedance at the inductor's
top.

I can take an antenna of specific height and vary current taper in the
inductor quite a bit just by changing the style of loading coil.

It is the idea that the loading coil drops a certain current because of
"electrical degrees" that is so untrue.


10. According W8JI camp, looking at the quarter wave loaded whip, the
current goes up the radiator according to cosine curve, then is the same
across the coil, then tapers to zero at the tip in the triangular shape
(should be the rest of the cosine curve, but close enough approximation). We
are talking about typical loaded resonant quarter wave ant, (not any coil in
any circuit).

Again, this isn't my camp. Repeatedly trying to make this a personal
issue really just stops the scientific process.

The current distribution described above is indeed how an antenna
works. This of course assumes the inductor is compact and has minimal
distributed capaciatnce to the outside world compared to the
termination impedance presented by the whip.

It can be proven.

73 Tom