Richard KB7QHC writes:

I've visited your page, and in an effort to wean out the details (you
don't go to much effort to offer an unadorned, plain, vanilla
specification for the radiator). I had to guess about the coil length
(judging from its only metric being 2.5" diameter) and inductance (you
dismiss the importance of its Q and wholly leave this metric blank).

Our major disagreement with W8JI was is the current accros antenna loading the
same or is it appreciably different. I was just trying to argue that it is
signifficantly different, W9UCW has done multitude of tests and measurements
and supported my position. I had practical experience of knowing that bottom of
uniform coils get hotter than middle or top, I fried heatshrink tubing at the
bottom of the coils and this was good enough for my practical knowledge that
current must by higher at the bottom. ON4UN book also supports that.

The second step in our quest of properly mastering the phenomena is to
investigate the relationships, magnitudes and have it properly accounted for in
the modeling software. W9UCW provided some info, data and pictures, he has lot
more and is willing to cooperate further, be it writing concise article (he is
preparing material for the book also) or answer questions or provide more info.
I told him about this NG, so he might show up. So if we are ready to bridge the
idea that current is different and implement that in the software, lets roll.
So far it appears that Roy still has a problem with understanding what is going
on.

Yuri

On 03 Nov 2003 21:43:22 GMT, oSaddam (Yuri Blanarovich)
wrote:

So if we are ready to bridge the
idea that current is different and implement that in the software, lets roll.
So far it appears that Roy still has a problem with understanding what is going
on.

Yuri

Hi Yuri,

That, in fact, is not so. The problem as expressed by you was
acknowledged and a solution offered BEFORE you started this thread.
There was a protocol given THEN to obtain a correct perspective to the
issue.

Do you propose to offer additional data showing the current
distribution over the entire radiator, or are we going to be indulged
in retread arguments that have been answered?

73's
Richard Clark, KB7QHC

Richard Clark wrote:
Cecil, you have two stubs and they are driven antiphase (typical of a
doublet) and through symmetry would have equal antiphase currents when
compared to their opposites, but not necessarily equal currents within
their twin-pair of lines. The sum of ALL currents (and not just the
myopic view of one of two stubs) would suggest exactly what Roy has
offered.

Sorry, Richard, 1/2 of the loaded dipole turned vertical doesn't
show a trace of horizontal radiation. Sorry about that.

Roy suggested the stubs might be radiating. EZNEC says they are not.
You can add two inches of vertical wire to the ends of the antenna
and see the red vertical radiation. The stubs are 0.04WL, #14 wire,
and 6 inch spacing. How much could they radiate on 75m? The difference
in current is not due to radiation. It is due to the phase shift
between Ifwd and Iref through the stub.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Clark wrote:
That, in fact, is not so. The problem as expressed by you was
acknowledged and a solution offered BEFORE you started this thread.

For those of us who missed the solution, what was it?
--
73, Cecil http://www.qsl.net/w5dxp



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So, in short, I don't disagree with Balanis.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

I don't have Balanis. Can you provide a short quote where he states
that the current at the terminals of a two-terminal lumped component
are unequal?


He doesn't use lumped components and probably for good reason. But here's
the quote that allows my analysis. "Standing wave antennas, such as the
dipole, can be analyzed as traveling wave antennas with waves propagating
in opposite directions (forward and backward) and represented by traveling
wave currents 'If' and 'Ib' in Figure 10.1(a)." This means that net total
current equals If+Ib.

The fact that the feedpoint current occurs at a current maximum point ties
both ends down. 'If' must traverse 90 degrees and 'Ib' must traverse 90
degrees in addition to the 180 degree phase shift due to reflection from
the open end. Besides the coil, an 8' whip gives about 22 degrees phase
shift in a round trip. Adding the 180 degree phase shift due to the open
end reflection gives 202 degrees. But we know the phase shift is actually
360 degrees. Where can the additional 158 degrees of phase shift
come from except from the coil?

Center-loaded mobile antennas are still an electrical 1/4 wavelength. If
there's no phase shift through the coil, where's the missing 158 degrees
of phase shift taking place?

Good. And I see from your other response that you understand the question.

So now we have a simple series circuit consisting of a generator, the
loading inductor, and the R + L or C we used to substitute for the
antenna. And your "no" response indicates you've agreed that the voltage
across and current through the inductor are the same as when it was
connected to the antenna.

Now, choose any values you'd like for the generator voltage or current
and the component values, and write the equations showing that the
current into the inductor is different in any way (amplitude or phase)
from the current going out. Or, if that's too taxing, I'll choose some
values for you.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

So, was that a yes or a no? I have trouble with your accent.


It's a no. Lumped inductors are not conscious of anything
including their locations.

Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:
Cecil Moore wrote:
Roy Lewallen wrote:

Are you referring to something you emailed me? If so, I haven't received
it. I'll be glad to look at it when I do.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

Because you're seeing different currents at the two stub terminals,
you must be modeling it with wires, which should reflect reality quite
well. Look carefully at the currents along the stub and you'll find
they're not equal and opposite on the two conductors. Such a radiating
stub *is* very different from a coil.


Instead of a knee-jerk defense of your ideas, why don't you actually take
a look at the problem? Those stubs are vertical. EZNEC shows virtually zero
vertically polarized radiation. According to EZNEC, those stubs are
radiating
a negligible amount, just like the lumped inductance. Why the 40%
difference
in current between the two configurations? Is this a characteristic of NEC?

Roy Lewallen wrote:
So, in short, I don't disagree with Balanis.

Yes, you have disagreed with an analysis based on Balanis's
'If' and 'Ib'. You even quoted some author saying that an
antenna could not be analyzed in the manner that Balanis
proposes.

Cecil Moore wrote:
He doesn't use lumped components and probably for good reason. But here's
the quote that allows my analysis. "Standing wave antennas, such as the
dipole, can be analyzed as traveling wave antennas with waves propagating
in opposite directions (forward and backward) and represented by
traveling
wave currents 'If' and 'Ib' in Figure 10.1(a)." This means that net total
current equals If+Ib.
--
73, Cecil http://www.qsl.net/w5dxp



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To assume a short-circuited, sideways protuding stub line, intended to
replace a loading coil, will give the same results as the coil it replaces
is unbelievable STUPIDITY.

EZNEC will quite correctly treat the stub line as an essential part of the
radiating system, itself much longer than the overall height of the short
vertical antenna it is supposed to be loading.

In fact, the length of wire in the stub line needed to resonate the antenna,
plus the height of the antenna, will be of the same order as a full size
quarter-wave vertical.

Roy, you are wasting your time trying to educate such baffle-gabbing old
wives. I make this comment because you are a much too polite gentleman
(approaching the English variety) to send them packing yourself with tails
between their legs. And I've just finished a glass of South African red.

Yelp, yelp! Can you hear them fading into the distance? ;o) ;o) ;o)
---
Reg.