Cecil Moore wrote in message

2. The second antenna is electrically 3/4 wavelength long. This one
illustrates how the current at the top of the loading coil can be
greater than the current at the bottom of the loading coil.

http://www.qsl.net/w5dxp/octcoil2.gif
http://www.qsl.net/w5dxp/octcoil2.ez

Why the 3/4 wave example? This is NOT what I had in mind. What I would
like to see, is you take a 8 ft mobile whip for 80m. Start with a
center load. Note the current taper. Then place the coil below the
midpoint level. Note the current taper. Then place the coil above the
midpoint level. Note the current taper.
You should be able to find a configuration that provides max current
at the top of the coil, if what you claim is true. I want to see max
current at the top of the coil in the SHORT loaded 8ft mobile whip for
80m. Not a funky overly tall 3/4 wave antenna. I'd try it myself, but
I only have the demo of eznec and don't have the segment capability.
Then if you can see this happen in the model, I'd like to see it
confirmed in the real world. If this occurs, then I might start to
think what you claim holds some water. I'll reserve further comment
until you can try this simple test. MK

Tdonaly wrote:
That's code. It means "I do not rail against all math models, just the
ones that don't agree with me. I require my math models to give the
answer I've already made up in my head."

No, I require a math model of a coil that agrees with Roy's and
Tom's measurements. A lumped inductive reactance doesn't do
that. My math models are dictated by reality. Therefore, I
live in the real world and you live in a world created and
dictated by your math models. I prefer my world. You obviously
prefer yours.
--
73, Cecil http://www.qsl.net/w5dxp



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Mark Keith wrote:
Why the 3/4 wave example?

In order to illustrate higher current at the top of the coil than
at the bottom, of course.

You should be able to find a configuration that provides max current
at the top of the coil, if what you claim is true.

I just did in the 3/4WL example. One cannot get higher current at
the top of the coil in a 1/4WL electrically long antenna. For a
1/4WL antenna, the maximum current is at the feedpoint and tapers
down to the tip.

I want to see max current at the top of the coil in the SHORT
loaded 8ft mobile whip for 80m.

Well, good luck on that one. I think it's impossible. Blood out
of a turnip comes to mind. If you think I ever said or implied
that I could do that, you are as mistaken as you can possibly be.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Mark Keith wrote:
Why the 3/4 wave example?

In order to illustrate higher current at the top of the coil than
at the bottom, of course.

You should be able to find a configuration that provides max current
at the top of the coil, if what you claim is true.

I just did in the 3/4WL example. One cannot get higher current at
the top of the coil in a 1/4WL electrically long antenna. For a
1/4WL antenna, the maximum current is at the feedpoint and tapers
down to the tip.

uh huh.....

I want to see max current at the top of the coil in the SHORT
loaded 8ft mobile whip for 80m.

Well, good luck on that one. I think it's impossible. Blood out
of a turnip comes to mind. If you think I ever said or implied
that I could do that, you are as mistaken as you can possibly be.

What has all this been about? Bugcatchers and other short loaded mobile
antennas. All shorter than 1/4 wave.
Good grief....I rest my case.
My theory? I still think the current across the coil is *fairly*
constant.
I'm *still* of the opinion that the *apparent* radical taper across the
coil is more due to the presence of the capacitance above the coil. I
think Roy described this in more accurate terms, but I have to reread
the thread.
I'm *still* of the opinion that if you could measure the current INSIDE
the windings of the coil, a couple or three turns in from each end, you
would not see near the difference you all do. I do think it's quite
normal to have a slight taper, as you would with any other radiator that
is shorter than 1/4 wave. So what? But these are just my gut instincts
using my built in BS filter. I'm absolutely certain than any error in
modeling a short mobile antenna using lumped coils is not worth worrying
about. This was the main gist of the argument by Yuri. It was the bottom
line. He claimed we were modeling in fairly gross error due to this new
found revelation of coil current taper. He promised a new revelation in
coil positioning that would turn the mobile antenna world on it's head.
Or at least the hype seemed to imply this. But I'm afraid many beat him
to it years ago. As far as phasing coils, yep, you might have an issue
there. But it appears you may have been enlightened to a workaround even
in that case. Isn't life grand? MK
--
http://web.wt.net/~nm5k

On Fri, 06 Feb 2004 18:33:24 -0600, Mark Keith wrote:

I'm absolutely certain than any error in
modeling a short mobile antenna using lumped coils is not worth worrying
about.

That has been shown several times - unless your skin crawls with
differences of 0.5dB

This was the main gist of the argument by Yuri. It was the bottom
line. He claimed we were modeling in fairly gross error due to this new
found revelation of coil current taper.

And that pilot's error was addressed before the soap opera began.

He promised a new revelation in
coil positioning that would turn the mobile antenna world on it's head.

Umm yes. The excuse is snow, but given the tapering heat wave
reports, the coils should clear that away in half an hour. Patents
pending!!! - any further discussion constitutes a violation of
Intellectual Property rights subject to suit (40R w/2 pair of pants).

73's
Richard Clark, KB7QHC

Mark Keith wrote:
I'm *still* of the opinion that if you could measure the current INSIDE
the windings of the coil, a couple or three turns in from each end, you
would not see near the difference you all do.

Wes's and my modeling show a smooth current taper through the coil.
Here's the taper predicted by EZNEC through the coil for octcoil1.ez

http://www.qsl.net/w5dxp/taper1.gif

I do think it's quite normal to have a slight taper, ....

Then you disagree with the guys who say it has no taper. Guess what,
Mark? That puts you on my and Yuri's side of the argument.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil wrote,

Mark Keith wrote:
I'm *still* of the opinion that if you could measure the current INSIDE
the windings of the coil, a couple or three turns in from each end, you
would not see near the difference you all do.

Wes's and my modeling show a smooth current taper through the coil.
Here's the taper predicted by EZNEC through the coil for octcoil1.ez

http://www.qsl.net/w5dxp/taper1.gif

I do think it's quite normal to have a slight taper, ....

Then you disagree with the guys who say it has no taper. Guess what,
Mark? That puts you on my and Yuri's side of the argument.
--
73, Cecil http://www.qsl.net/w5dxp


This is an order of magnitude error. In the thirteenth century, the
scholastics would tell their pupils that, since the earth is a ball,
if you build two buildings side by side and use a plumb line to build
each one, the buildings will be farther apart at the top than at the bottom.
Also, if you have a swimming pool with a perfectly flat bottom, the
center will be deeper than the sides because it's closer to the center
of the earth.
No normal people paid any attention to these fellows. The scholastics never
specified
what things meant in terms of real numbers. Cecil says there's a taper but he
doesn't
attempt to say how much. Yuri thinks it's a lot. Cecil seems to agree
with him, but neither fellow has been willing to back his theory with a
$$$$ NEW $$$ [{### IMPROVED ###}] mobile antenna. I think any
rational observer would have to conclude that if Yuri and Cecil are right,
they're only right in the 13th cent. scholastic sense, and that their whole
argument doesn't amount to a hill of beans.
73,
Tom Donaly, KA6RUH

Tom Donaly, KA6RUH:

The scholastics never
specified
what things meant in terms of real numbers. Cecil says there's a taper but he
doesn't
attempt to say how much. Yuri thinks it's a lot. Cecil seems to agree
with him, but neither fellow has been willing to back his theory with a
$$$$ NEW $$$ [{### IMPROVED ###}] mobile antenna.


Go to www.K3BU.us and look at the article, measurements and pictures.
http://www.k3bu.us/loadingcoils.htm

Cecil explained what's happening, shined some light on it and the work is in
progress to enlighten the flat earth society.
It is not "our theory", it is reality that was described before us by Kraus,
ON4UN and others.

I used the knowledge to design more efficient mobile antenna for 160.

If you understand the current distribution along the loaded antenna, then you
can maximize it for better efficiency (roughly proportional to the area under
the current curve).

Stand by.

Yuri, K3BU.us

Yuri Blanarovich wrote:
It is not "our theory", it is reality that was described before us by Kraus,
ON4UN and others.

And demonstrated through actual measurements made by W7EL and W8JI.
It's hard to believe anyone rejects those measurements.
--
73, Cecil http://www.qsl.net/w5dxp



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On 07 Feb 2004 03:46:51 GMT, oUsama (Yuri Blanarovich)
wrote:
I used the knowledge to design more efficient mobile antenna for 160.

What design did you start with and at what efficiency?

What design did you end up with and at what efficiency?

If you understand the current distribution along the loaded antenna, then you
can maximize it for better efficiency (roughly proportional to the area under
the current curve).

What was the improvement in efficiency?

Hi Yuri,

Marketing claims are cheap and I need only pick up a copy of People
Magazine off the newsstand to read them for free.

I've already played the game through modeling using the exact methods
described at your page. Results were less than 1dB; average
difference ran towards 0.5dB. Since that time, the argument has
bloomed to include coils the size of a cadillac on 3/4 wavelength
structures to no greater efficiency gained. I've also seen this
described in terms of half cycles of instantaneous variable phase
*net* current moving in opposite directions through a resistor!
Heating and cooling? ;-)

So, what gets responded to, the efficiency or Cecil's goofball claims?

73's
Richard Clark, KB7QHC