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Old April 23rd 09, 10:22 PM posted to rec.radio.amateur.antenna
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Default Loading coils: was Dish reflector

Tom Donaly wrote:

There aren't many people who would support a lumped-element analysis on
this newsgroup. Most people know the limitations of using network theory
in these circumstances. The technical arguments against Cecil's approach
were offered a long time ago. This latest is just a flareup that will
soon die down. You shouldn't be confused. The transmission line model of
antennas is well accepted and hoary with age, particularly for
bi-conical antennas (see Schelkunoff). There are a couple of other types
of models with equal validity. If you really want to know the physical
score, though, you have to get an electromagnetics text that discusses
the integral equations that govern antenna behavior. Pay particular
attention to the parts that explain why numerical methods like EZNEC
have to be used for solutions rather than the symbolic math most people
would expect and want.

73,
Tom Donaly, KA6RUH


I did and do support lumped element analysis for a very small toroidal
loading inductor, and extensively posted the reasons why in this
newsgroup about six years ago ("Current in antenna coils controversy",
2003). Cecil and Yuri were arguing that the coil would replace some
number of "degrees of antenna" and its current therefore would have a
substantial phase difference between input and output ends. I made and
posted careful measurements to support my statement, after which Cecil
invented his "standing wave current" and went off in various directions.

Roy Lewallen, W7EL
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Old April 23rd 09, 11:39 PM posted to rec.radio.amateur.antenna
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Default Loading coils: was Dish reflector

Roy Lewallen wrote:
I did and do support lumped element analysis for a very small toroidal
loading inductor, and extensively posted the reasons why in this
newsgroup about six years ago ("Current in antenna coils controversy",
2003). Cecil and Yuri were arguing that the coil would replace some
number of "degrees of antenna" and its current therefore would have a
substantial phase difference between input and output ends. I made and
posted careful measurements to support my statement, after which Cecil
invented his "standing wave current" and went off in various directions.


I didn't invent "standing wave current". Standing wave
current is what EZNEC displays for standing wave antennas.
Standing wave current is what Kraus describes graphically
on page 464, Figure 14-2, of "Antennas ...", 3rd edition.
Standing wave current is what Ramo and Whinnery describe
mathematically in "Fields and Waves ...".

It has been at least 5 years since I explained why
the phase of the current on a standing wave antenna cannot
be used to determine the delay in a wire or in a coil.
EZNEC, Kraus, Balanis, and Ramo and Whinnery all agree
with me and disagree with you. I explained, 5 years ago,
how the magnitude of the current can be used to calculate
the delay through a coil. All my explanations fell on
deaf ears and you called them gobblygook, or some such.

Once again, most of the current in a standing wave antenna
is of the form,

I = Imax*cos(kx)*cos(wt)

For any given time = t1, the phase of the current all up
and down the antenna does not change with x. The phase
is the same at the feedpoint, at the bottom of the coil,
at the top of the coil, and at the top of the stinger.
The phase of that current cannot be used to calculate
delay in a wire or through a coil.

You once said you were quick to admit a mistake. It has
been 5+ years since you made that conceptual mistake
and you have not admitted it yet.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com
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Old April 24th 09, 12:44 AM posted to rec.radio.amateur.antenna
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Default Loading coils: was Dish reflector

Roy Lewallen wrote:
Tom Donaly wrote:

There aren't many people who would support a lumped-element analysis on
this newsgroup. Most people know the limitations of using network theory
in these circumstances. The technical arguments against Cecil's approach
were offered a long time ago. This latest is just a flareup that will
soon die down. You shouldn't be confused. The transmission line model of
antennas is well accepted and hoary with age, particularly for
bi-conical antennas (see Schelkunoff). There are a couple of other
types of models with equal validity. If you really want to know the
physical
score, though, you have to get an electromagnetics text that discusses
the integral equations that govern antenna behavior. Pay particular
attention to the parts that explain why numerical methods like EZNEC
have to be used for solutions rather than the symbolic math most
people would expect and want.

73,
Tom Donaly, KA6RUH


I did and do support lumped element analysis for a very small toroidal
loading inductor, and extensively posted the reasons why in this
newsgroup about six years ago ("Current in antenna coils controversy",
2003). Cecil and Yuri were arguing that the coil would replace some
number of "degrees of antenna" and its current therefore would have a
substantial phase difference between input and output ends. I made and
posted careful measurements to support my statement, after which Cecil
invented his "standing wave current" and went off in various directions.

Roy Lewallen, W7EL


I should have specified a large, solenoidal loading coil such as Cecil
is so fond of using. Cecil has since eschewed his "degrees of antenna"
position, but, for some reason, he keeps claiming your tests on the
small solenoid were wrong.
73,
Tom Donaly, KA6RUH
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Old April 24th 09, 02:11 AM posted to rec.radio.amateur.antenna
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Default Loading coils: was Dish reflector

Tom Donaly wrote:
I should have specified a large, solenoidal loading coil such as Cecil
is so fond of using. Cecil has since eschewed his "degrees of antenna"
position, but, for some reason, he keeps claiming your tests on the
small solenoid were wrong.


Yes, I have fine-tuned my concepts over the past 5 years.
What rational person would not adjust their concepts to
match the technical evidence? (It's a rhetorical question.
We all know who refuses to do that.)

Roy's tests were wrong in the sense that they were meaningless
no matter how accurate the readings. Quoting my web page:

"All of the reported conclusions based on loading coil
measurements using the current on standing-wave antennas
are conceptually flawed."
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com
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