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

Roy Lewallen wrote:
Mike Coslo wrote:

Yuri Blanarovich wrote:

Check my article that describes the controversy, shows some proof of
reality and then efforts of the "gurus" to deny it and "reason" why
it can't be so. http://www.k3bu.us/loadingcoils.htm The problem is
that back in 1953 in QST article there was erroneous
conclusion/statement made, which propagated through the books, until
W9UCW measured the current across the loading coils and found that
there is significant drop from one end to the other, and the rest is
(ongoing) history


Hmm, certainly it would seem to make sense that:

The current in a typical loading coil in the shortened antennas drops
across the coil roughly corresponding to the segment of the radiator
it replaces.


Quote from your page.

I would not expect anything else. If the loading coil is making the
antenna act like a physically longer antenna, other "qualities" of
that simulation are likely to be similar.

Is there a reason why the coil would *not* do this?


Yes, many, and they've been discussed here at length.

Okay. Seems like a more constructive use of bits than most of this
thread 8^)



That this concept
is wrong can and has been shown by theory, modeling, and measurement. I
made and posted measurements on this newsgroup in November 2003 which
demonstrated clearly that the presumption is false.

Okay. It looks like we have at least some measurements that differ. Any
idea why that would be?

Do you remember the name of the thread?

The loading coil isn't making the antenna act like a physically longer
antenna. In the extreme case of a physically short inductor at the
feedpoint, it's simply modifying the feedpoint impedance and has no
effect whatever on the antenna's radiation.

Would the inductor then be best right past the feedpoint? Certainly
having the inductor at the far end, or in the middle seems like a bad
place for it. (not talking about trap antennas)

As the inductor gets longer,
it does become some part of the antenna, but adding an inductor which
resonates, say, a 45 degree physical radiator doesn't make the antenna
act like a 90 degree physical radiator.

- 73 de Mike KB3EIA -

"Roy Lewallen" wrote

K3BU wrote: 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.


Then there is your answer to who is "gurus" and who is "we".
"Gurus" know that current in loading coil is the same.
"We" know, measured it properly and argue that that is significantly
different.
I am sorry, you are wrong. I tried to follow some stepts to get to the
point, Tom ignores my points and jumps to lecture how, bla, bla...

I am really done here, you guys can believe what you want. Just that reality
doesn't jive with your "can't be".

73 Yuri

Mike Coslo wrote:
Roy Lewallen wrote:

That this concept is wrong can and has been shown by theory, modeling,
and measurement. I made and posted measurements on this newsgroup in
November 2003 which demonstrated clearly that the presumption is false.

Okay. It looks like we have at least some measurements that differ.
Any idea why that would be?

The amount the magnitude of the current drops across an inductor is
determined primarily by the amount of inductance and the capacitance
from the inductor to ground or the other half of the antenna. This is
easily explained by simple lumped constant circuit theory. There's also
some variation due to radiation and imperfect coupling between turns. In
the extreme case of a very loose helix, coupling is poor and radiation
is high, so the helix acts more like a wire than an inductance. This
requires a more complex analysis, but that's also in the realm of well
known phenomena. With this wide variation in physical possibilities,
different results can't be avoided. What some of us have tried to do is
explain why the results occur.

I don't know of differing results from the same physical setup, but it
could surely happen. Making good measurements isn't a trivial task.

Do you remember the name of the thread?

Current in antenna loading coils controversy (long). I made two sets of
measurements. The second was posted on Nov. 11, 2003 and the first a few
days earlier.

The loading coil isn't making the antenna act like a physically longer
antenna. In the extreme case of a physically short inductor at the
feedpoint, it's simply modifying the feedpoint impedance and has no
effect whatever on the antenna's radiation.

Would the inductor then be best right past the feedpoint? Certainly
having the inductor at the far end, or in the middle seems like a bad
place for it. (not talking about trap antennas)

Generally not, but it depends on several factors. Moving the coil upward
increases the radiation resistance of the system, which improves
efficiency in the presence of ground loss. However, it also requires a
larger coil, so the coil's resistance is greater. But the current at the
location of the coil is lower, so overall I^R loss of the coil is often
less with the coil somewhere around halfway up. The relative amount of
coil and ground loss, as well as the amount of top loading if any, are
all factors in determining which position is best. This is really a
separate question, and I don't have varied enough experience with HF
mobile setups to be anywhere near an expert. Tom, W8JI, is though. You
can take what he says on the subject to the bank.

Roy Lewallen, W7EL

wrote:
An inductance changes the relationship between phase of voltage and
current, NOT current through the inductance from terminal to terminal.

That's true only for a lumped inductance which doesn't exist
in reality.

Yuri again distorts fact. What everyone is saying is there can be a
current change, but it is not caused by standing waves or missing
antenna area. It is caused by displacement current, and so can have a
wide range of change in a given antenna.

In the graphic at: http://www.qsl.net/w5dxp/test316.GIF
in the right hand configuration the current at the bottom
of the coil is 1.3 amps and the current at the top of the
coil is 2.1 amps.

Your explaination for more current at the top of the coil
than at the bottom is that 0.8 amps of displacement current
is jumping up from earth ground into the side of the coil
and flowing out the top?

Would you please describe that bit of magic in a little more
detail?
--
73, Cecil http://www.qsl.net/w5dxp

Roy Lewallen wrote:
Then you and Cecil have quite different theories, it seems. His doesn't
predict the drop I measured.

The current can be a DROP or a RISE or EQUAL depending upon
where it is installed in the standing wave environment.

That
certainly doesn't constitute "strangely ignoring" Cecil's model.

You have completely ignored the EZNEC results posted at:
http://www.qsl.net/test316.GIF where the current at the top
of the coil is greater than the current at the bottom of the
coil. How would your theory handle a current RISE through a
coil?
--
73, Cecil http://www.qsl.net/w5dxp

Mike Coslo wrote:
Would the inductor then be best right past the feedpoint? Certainly
having the inductor at the far end, or in the middle seems like a bad
place for it. (not talking about trap antennas)

Here's a graphic that might help: http://www.qsl.net/w5dxp/1WLDIP.GIF

The coil can have a current DROP, a current RISE, or equal currents
depending upon where it is placed in the standing wave system.

Most of the discussion has been about base-loaded mobile antennas.

Everyone have a nice Easter. I'll be away from my computer until
Monday.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil,

I gave you a very specific reference to demonstrate your supposition was
incorrect. You came back with nothing but, "Because I say so." You have
not offered one shred of backing for your constant Vf argument.

And it is up to ME to further prove something?

I don't think so.

73,
Gene
W4SZ


Cecil Moore wrote:
Gene Fuller wrote:

I will retain the entire message below, so that I am not accused of
misattribution.


Gene, to the best of my knowledge, you have never
misattributed anything.

Where did you get this idea that the velocity factor is constant?


The equation for velocity factor includes coil diameter,
turns per inch, and wavelength. Keeping the coil diameter
constant, the turns per inch constant, and the wavelength
constant should ensure that the velocity factor is constant.

Specifically, why is the velocity factor of a resonant coil the same
as the velocity factor of a significantly shorter coil? It is pretty
well accepted that the inductance of coils does not scale linearly
with the length of the coil. Therefore any arguments about based on
direct calculation of Vf from L and C would seem to fail to support
your model.


You are obviously mistaken. If you increase the L by lengthening
the coil, you have also increased the C by the same percentage.
The L and C for any unit length are the same no matter how long
the coil or transmission line is.

" . . . an approximation for M has been determined by Kandoian and
Sichak which is appropriate **for quarter-wave resonance** and is
valid for helices . . ."


Yes, but if one doesn't change the frequency or the diameter or
the turns per inch, the approximation should hold since nothing
in the VF equation changes by shortening the coil. One should be
able to shorten or lengthen the coil andmaintain the same VF.

Seems it is up to you to prove what you are saying. Please prove
that the ratio of L to C ratio of a coil changes with length. That
should be an interesting proof.

Cecil Moore wrote:

You have completely ignored the EZNEC results posted at:
http://www.qsl.net/test316.GIF where the current at the top
of the coil is greater than the current at the bottom of the
coil. How would your theory handle a current RISE through a
coil?


Cecil,

Do you suppose that maybe the displacement current can actually work in
either direction? Did someone put a diode in the aether?

73,
Gene
W4SZ

Gene Fuller wrote:
....
Cecil,

Do you suppose that maybe the displacement current can actually work in
either direction? Did someone put a diode in the aether?

73,
Gene
W4SZ

Yes, some time earlier today than that exchange, I posted elsewhere in
this thread a specific circuit, complete with values, how the same
thing is easily accomplished with the infamous ideal lumped components.
No standing waves need apply. But of course if one used distributed
reactances, one could easily get the same effect, and the analysis can
easily be done w/o any reference to standing or travelling waves.

Cheers,
Tom