Loading coils: was Dish reflector
 

On Apr 23, 10:44*pm, Roy Lewallen wrote:

Yes, you would see this in the real world. EZNEC does a very good job of
modeling a wire antenna with a loading coil, provided that you model the
coil as a wire helix rather than lumped "load", and you can trust the
results. As I've implied, a lumped load is quite a good model for a
physically small, essentially non-radiating loading coil like a toroid
on a magnetic core.

Roy: thanks for the unequivocal and clear answer.

Steve G3TXQ

Loading coils: was Dish reflector
 

On Apr 23, 3:22*pm, Cecil Moore wrote:
Art Unwin wrote:
You based your proof of a magnetic wave in a vacuum but it is an
accelerating charge
which obviously must have mass, that is radiation ala the particle.

The accelerating charges are slow-moving electrons.
The RF current moves at the speed of light in the
(conductive) medium. Therefore, the RF current is
associated with photons emitted by the electrons.
Photons have zero rest mass and zero electric charge.
Photons are the particles associated with RF waves.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Cecil there you go again with the idea that zero mass and zero energy
is something that can exist which some have termed as "photons"
Point to the laws of nature that support that notion. At one time it
was the same
as a particle without mass. Presence science now state that particular
particle does have mass which is why the World spent millions for the
CERN project. Your technical expertise is built on the state of
science 50 years ago and you are now building a castle on sand or
excuses to justify your unwillingness to embrace change. It took 7
days to build the Universe by the initial expenditure of kinetic
energy which embraces the laws of nature and the concept of a cycle or
equilibrium. Remember the words" let there be light" which aligns with
energy expenditure upon mass ie everything starts with the expenditure
of energy upon or from mass it is not a chicken or egg analogy.
And it is expenditure of energy upon mass that makes it a particle
unconnected to all
mass around it such that the particle is unbound and cannot be
absorbed by another state. Lets face it, Adam and Eve knew nothing
regarding equilibrium and the notion of frequency or period. All the
work had been completed way belong that came upon the scene,, which is
why religeon exists as the sole explanation of who and what was and is
in charge with respect to the laws of nature. Again it is impossible
for something to exist without mass.
Art

Loading coils: was Dish reflector
 

"Tom Donaly" wrote in
:

....
not be easy. Finally, a modest question: if you have EZNEC, why would
you be wasting time with something inferior? The gold standard is the
gold standard.

NEC (in whatever form) might give a good estimate of the inductance of some
helices, although many practical inductors require smaller segment lengths
that would normally be advised for NEC models, but it does not provide a
good loss estimate in many interesting cases.

My post entitled was about that
topic, and apart from Jim's suggestion of a sensitivity analysis, there was
no solution to evaluating the effective resistance of an inductor of
closely spaced turns (so proximity effect is signficant) made from a
braided round conductor and with a thin dielectric jacket. All three of
these factors are, as I understand it, not modelled in NEC-2.

Owen

Loading coils: was Dish reflector
 

On Apr 23, 4:10*pm, Roy Lewallen wrote:
steveeh131047 wrote:
. . .
Now here's my problem:

* The results I get using a model based on transmission-line analysis
are very close to my EZNEC predictions - not perfect, but way better
than any lumped-element analysis results
* I don't see quantitative, non-empirical, arguments being put forward
to support lumped-element analysis
* I see numeric arguments being put forward by Cecil to support a
transmission-line approach - they look convincing to me and, although
I see a lot of unpleasant personal attacks on him, I don't see any
scientific challenge to his figures
* On the other hand I see folk whose work I rate highly, seemingly
willfully to misunderstand some of the points which Cecil puts forward

Please don't think I'm trying to defend Cecil - I wouldn't be so
presumptuous, and anyway he's old enough to look after himself! I'm
just trying to understand why, what seems to me to be such a
persuasive argument, generates such opposition. Either there's some
glaring technical error here which I haven't yet spotted, or perhaps
there's a long "history" between various "personalities" of which I'm
ignorant?

Still confused,

Steve G3TXQ

Some of your questions can be answered by doing a google groups search
of this newsgroup for the topic "Current in antenna coils controversy"
in 2003. There are several other lengthy threads at later dates, such as
"Current across the loading coil - from scratch", "Loading coils; was :
Vincent antenna", "Standing-Wave Current vs Traveling-Wave Current", and
a number of threads prior to 2003.

Roy Lewallen, W7EL

This is so wrong. The term "wave" is an adjective and a "particle" is
a noun. An adjective is the enunciation of a function that describes a
noun.
Art

Loading coils: was Dish reflector
 

Cecil Moore wrote:
Jim Kelley wrote:
... and as any good dry labber knows, it's a dead giveaway to report a
precision greater than one can actually measure. :-)

I have reported no precision - my 100 MHz scope has
not been calibrated since I retired.

Precision is the number of sig figs. You "might" have calculated three,
rounded up, and reported two.

ac6xg

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

Loading coils: was Dish reflector
 

steveeh131047 wrote:
I see 1A at
the base of the coil increasing to 1.07A at the centre of the coil and
then dropping to 0.69A at the top of the coil.

FYI Steve, five years ago I showed Roy how to estimate
the phase shift through the coil using ARCSIN(0.69) =
~46 degrees. To this day, he refuses to acknowledge
what EZNEC is telling him about current on a standing
wave antenna which is: A current phase measurement
on a standing wave antenna is meaningless. Here's a
couple of graphic that illustrate what I am saying:

http://www.w5dxp.com/coil.gif

http://www.w5dxp.com/phasor.gif

These graphs are very close to your measurements
above.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Loading coils: was Dish reflector
 

Art Unwin wrote:
Cecil there you go again with the idea that zero mass and zero energy
is something that can exist which some have termed as "photons"
Point to the laws of nature that support that notion.

It's part of the standard model, Art, with which I am
not about to disagree.

http://en.wikipedia.org/wiki/Standard_Model
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Loading coils: was Dish reflector
 

On Apr 23, 4:36*pm, steveeh131047 wrote:
On Apr 23, 10:10*pm, Roy Lewallen wrote:



Some of your questions can be answered by doing a google groups search
of this newsgroup for the topic "Current in antenna coils controversy"
in 2003.

Roy, I've glanced at some of those references and it looks like
there's years of "catch-up" reading for me :)

It seems like the starting point for one of the earliest discussions
was whether or not there is a variation in current amplitude along the
length of a loading coil, with some pretty strong opinion saying that
there isn't. I don't want to go over old ground, but perhaps you can
give me a simple answer to this one question:

When I use EZNEC to model a 6ft whip above a loading coil (40T, 6"
diameter, 12" long), and look at the current distribution across the
coil at the resonant frequency of the antenna (3.79 MHz), I see 1A at
the base of the coil increasing to 1.07A at the centre of the coil and
then dropping to 0.69A at the top of the coil. My question is: "Can I
believe that I would see a similar current variation in the 'real
world', or is this some failing of EZNEC to model the antenna
properly?"

Regards,
Steve G3TXQ

Steve.
To determine the accuracy of Eznec first requires the use of a program
with the ability to change input so that it relates to the
requirements of Maxwell' radiation laws This means a program with an
optimiser function which adheres strictly with Maxwells laws and its
applicability produced which means all forces are accounted for. You
have then established a datum line for a radiator where all forces
are accounted for per Maxwell. When that final configuration per
Maxwell' laws emerges one should be able to insert this same
configuration into Eznec to check to see if all relative factors are
the same as that provided by the program with optimizer abilities. Any
differences that come about is a measurement of deviation from
Maxwell's laws and thus its applicability. There are other programs
that are available that are useable only for
predetermined planar forms such as the Yagi where all forces are not
accounted for
such as the Corriollis effect i.e. that force is ignored thus Maxwells
laws are not applicable.
Regards
Art
Art

Loading coils: was Dish reflector
 

Jim Lux wrote:
Tom Donaly wrote:
Finally, a modest question: if you have EZNEC, why would you
be wasting time with something inferior? The gold standard is the gold
standard.
Perhaps more the silver or electrum standard.
EZNEC doesn't do dielectric loading, for instance. (unless you get the
Nec4 engine from Roy)
And, it's a MoM code, so things not well represented by collections of
wires aren't necessarily modeled well.

Nothing is perfect, but which is better, EZNEC or the Cecil-Corum method
of modeling antennas?
73,
Tom Donaly, KA6RUH