Yuri Blanarovich wrote:

Roy,
the above are the attempts to illustrate and add some more to understanding
and reasoning why the current across (alonng) the loading coil, roughly half
way or 2/3 up the resonant quarter wave radiator is larger at the bottom and
drops about 40 - 60% at the top. While one side argues that it is (almost)
the same, we argue that it drops. That is the argument and not detours to
degrees, phasors, and rest of the mud that was rehashed here.

You still haven't told us who this "side" is that argues that the
current is the same at the bottom and top. I assume it's those unnamed
"gurus" who you haven't identified. It shouldn't be a problem to show
that the other "side" is wrong if it doesn't exist.

If I remember correctly you inserted the coil at the base and I am not sure
if it was resonant quarter wave radiator. Can you describe the setup, length
and frequencies used? You should try to use quarter wave resonant radiator
with coil about 1/2 to 2/3 up the mast and tell us what the current values
are. W9UCW has pictures and data measured, we should try to emulate this
situation, that is the object of controversy. Cecil mentioned cases when
current can be the same, or lower at the top, or bottom, depending where the
same coil is placed in relation to the standing wave and current
distribution on the radiator. Are you denying that this is the case or
something wrong with W9UCW test setup and results?

You can find my earlier postings at groups.google.com. The results
you're asking about were posted on Nov. 11, 2003. You can find your own
comments about my measurements there also, on the same date.

I'm sorry, but I don't have time to try and model or carefully analyze
W9UCW's results. The results for a toroid show more current difference
than I'd expect, and suspect that's due to the shunt capacitance of the
physically large meters he was using.

Before, you complained because the coil wasn't physically long enough.
Now you want it placed somewhere else along the radiator. Sorry, after
the reaction I got to my previous test, I have no interest at all in
making additional ones.


The controversy is about the claims that the current at the ends of the
typical loading coil is the same or different in range of 40 -60% drop. Its
not my theory, it is the reality that we are trying to bring forth and
correct misconceptions that are obviously floating around since 1953. My
approximation and explanation (latest) I mentioned is in one of my posts in
reply to W8JI "arguments" (to do with impedances).

The only posting I see that fits that description is your posting on
this thread on April 7. As I read it, you say that as you put a coil
higher and higher in an antenna, the inductance required to maintain
resonance increases, and the difference in current between the bottom
and top of the coil increases as the coil is made larger. I don't see
any values or way of calculating them, but don't have any disagreement
with the qualitative statements you made there.

[Yuri wrote:]
Again, when applied in modeling programs, wrong assumption will produce
erroneous results, which will be magnified in multielement antenna
designs.
So the "gurus" basically ignore behavior of coil in the standing wave
environment along the loaded radiator, where the current drops from max
at base to zero at the tip, but coil would magicaly resist that, because,
bla, bla, bla.... (see their "reasons")
[I wrote:]
Would you name these "gurus" so we can read their postings and see what
you're talking about?

[Yuri wrote:]
Mostly the "equal current camp".

I take that as a "no", you can't name the "gurus". The advantage of
arguing against imaginary "gurus" is that you can have them claim
anything you want. It shouldn't have taken you so many postings to prove
them wrong.

I have not verified it, but W9UCW claims using ferite inductor and got very
similar results. I believe your test, you used coil near the base. I will
run test with different inductors from bugcatcher type, "no good" Hustler,
to ferite and in different positions.

Then you and Cecil have quite different theories, it seems. His doesn't
predict the drop I measured. Those of us who are tired of the endless
arguments should sit back and let you and Cecil go at it until you come
to an agreement.

Looks like the size of the coil has small effect on current variation
(unless high resistance). Position of the coil in relation to current
distribution along the radiator would cause equal (special case), less on
the top of coil or more, depending where on the standing wave curve coils is
located. In our case we are arguing about 2/3 up the resonant radiator.

I don't know who "we" is. The technical theory I subscribe to doesn't
require any particular placement of the coil.

Now with solenoid generation in EZNEC 4.0 it helps to get away from the
lumped inductance and it shows that there is current drop, reflecting
situations in question. Also the loading stub produces similar results.
Cecil showed the cases and with different positions along the current curve,
demonstrated in EZNEC huge differences in current at the ends of the coil.
But this is getting strangely ignored and instead we get all kinds of
"reasons" why it can't be.

I replaced the whip in one of Cecil's models with a lumped RC and got
the same result. Then I eliminated the ground and reduced the current
drop to near zero. I've commented on that on several occasions. That
certainly doesn't constitute "strangely ignoring" Cecil's model.

I am sorry I dropped out of this due to AOL dropping NG, and I thought that
reality would be understood by now. Only when Cecil told me that subject
flared up again and nothing changed, I rejoined the discussions. I think
really at this point, it is beating the dead horse. I will do the tests and
write it up. I will try to corellate the tests with modeling in EZNEC. If
someone denies the reality, that's their choice. I will post the progress on
my web page.

Let us know when it's available. Hopefully it'll actually happen this
time. Again, I'll be interested in knowing of any significant difference
between modeling and measurement results.

I can't stomach W8JI "exchanges" any more. No answer to questions or
following the points, just twist and jive.

Funny, that's just the way most of your postings appear to me and, I'm
sure, to Tom.

I didn't look it up, but is there way in EZNEC to know or calculate the
inductance of modeled solenoid? Or better, specify the inductance and let
the EZNEC "make" the coil of prescribed diameter and TPI?

The answer to your second question is no. To your first, yes. What I've
done is model the inductor in free space with ends extended to the helix
axis (an option when creating it). Put a wire end-to-end down the center
of the coil with a source in the middle. Src Data will show you the
reactance, from which you can get the inductance. This seems to work
reasonably well provided that the frequency is low enough that the coil
is well below self resonance and low enough that it doesn't radiate much
but high enough that NEC-2 doesn't have trouble with the loop size. If
it shows good results in the Average Gain test, it's probably ok.

Roy Lewallen, W7EL