Loading coils: was Dish reflector
 

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

Loading coils: was Dish reflector
 

Roy Lewallen wrote:
What is the delay through a physically very small toroidal coil with the
same inductance as the solenoidal coil? Why?

A toroidal coil cannot be modeled using the Dr. Corum
formulas. But I will take a stab at the answer.

In a physically very small toroidal coil, all the
turns are tightly coupled, i.e. the flux caused by
one coil links all of the other windings so the
delay should be quite small. In any case, one
cannot use a current with unchanging phase (referenced
to the source phase) to calculate the delay through
anything. The only phase information left in a
standing wave is in the magnitude. If the current
magnitude at the bottom of the coil is 1.0, the phase
shift is the ARCCOSine of the current magnitude at
the top of the coil for a base-loaded resonant
antenna. Actual phase measurements on the current
in standing-wave antennas is meaningless. We already
know it hardly changes at all with length. EZNEC
confirms that statement.

In an air-core solenoidal coil, like the one w8ji
used, the flux linkage tends to be associated with
adjacent turns so all the flux does not link all
the coils. Tom's coil was 100 turns, 10 TPI, 2"
diameter. The first turn was 10 inches away from
the last turn. The delay through that coil calculates
out to be about 25 nS.

If we setup a 2" transmit coil and a 2" receive
coil 10 inches away in air, the energy transfer
efficiency would be very small. I don't have a
formula for such but I assume one (or more) exists.

Bottom line: There are now formulas for calculating
the Z0 and VF of large air-core loading coils which
are known to be in the family of *slow-wave* devices.

I doubt that a toroidal coil is in the family of
slow-wave devices.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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steveeh131047 wrote:


Tom,

Yes I have EZNEC and recognise what a great tool it is. Its
predictions were the benchmark against which I tested the various coil
models I read about, and no-one has yet suggested that it can't be
trusted for modelling a helix.

I'm not on some "philosophical quest" - I'm just an old, retired, guy
who still likes learning and wants to understand more about how things
work; I hope that never leaves me! I stumbled on this discussion quite
by chance and tried to understand the various "positions" being taken.
Perhaps I'm over-simplifying, but it seemed to me there was a group
who favoured the transmission-line model and a group against it. I've
tried dispassionately to understand the various arguments and to form
my own conclusions.

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

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

Loading coils: was Dish reflector
 

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

Loading coils: was Dish reflector
 

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.

It doesn't take much precision to know that there's
something wrong when two measurements are a magnitude
apart or when someone asserts a 3 nS delay through
a 10 inch long slow-wave solenoid coil with a VF of
0.033. :-)
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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

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)

All program types, including the demo, of EZNEC v. 4.0 and later do
dielectric loading similar to NEC-4. (The method came from sources other
than NEC-4.) Like the NEC-4 implementation, it's of limited accuracy and
usefulness -- it's really good only for thin wire insulation of moderate
permittivity.

And, it's a MoM code, so things not well represented by collections of
wires aren't necessarily modeled well.

Absolutely true. And it can't handle things like patch antennas or
antennas printed on a PCB.

Roy Lewallen, W7EL

Loading coils: was Dish reflector
 

Jim Lux wrote:
Roy Lewallen wrote:

Let's see how well the principles involved are understood.

What is the delay through a physically very small toroidal coil with
the same inductance as the solenoidal coil? Why?
As in a coil wound on a toroidal magnetic core? or a air cored solenoid
bent in a circle?

I'll say one wound on a magnetic core, simply to keep the size small,
the coupling tight, and the field confined. I don't, however, care how
long a piece of wire it's wound with.

Roy Lewallen, W7EL

Loading coils: was Dish reflector
 

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

Loading coils: was Dish reflector
 

steveeh131047 wrote:

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

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 Lewallen, W7EL

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

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

Loading coils: was Dish reflector
 

Owen Duffy wrote:
"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

So, what does model all the factors you mentioned, and how well does the
Cecil-Corum method do in this regard?
73,
Tom Donaly, KA6RUH

Loading coils: was Dish reflector
 

On Apr 23, 2:32*pm, Roy Lewallen wrote:
Jim Lux wrote:
Roy Lewallen wrote:

Let's see how well the principles involved are understood.

What is the delay through a physically very small toroidal coil with
the same inductance as the solenoidal coil? Why?
As in a coil wound on a toroidal magnetic core? or a air cored solenoid
bent in a circle?

I'll say one wound on a magnetic core, simply to keep the size small,
the coupling tight, and the field confined. I don't, however, care how
long a piece of wire it's wound with.

Roy Lewallen, W7EL

There are some other configurations that I personally think are
interesting to ponder. You might never actually build one this way,
but you'll probably gain some insights considering it: an antenna,
say a nominally 1/4 wave vertical for 40 meters made from 4" diameter
aluminum tube (irrigation pipe) twenty feet long, resonated with a
loading coil placed inside the tube across a gap of two or three
inches in the pipe. Capacitance from the coil is almost entirely to
the pipe in this case, not to the world outside the pipe, so the
effect is capacitance in parallel with the coil, not as in a
transmission line where the capacitance is to ground. That's a
different situation than one where a coil with a diameter much larger
than the antenna conductor is used, where the coil has significant
capacitance to the outside world (e.g. to ground).

It's also worth considering that the charge distribution on an antenna
is dynamic, so it's probably not a good idea to try to analyze the
antenna as if there was the same capacitance to ground from the coil
as there would be if the charge distribution on the antenna wire were
static (that is, the DC case, or at a frequency that's a tiny fraction
of the lowest natural resonance of the antenna system).

Analyzing exactly how even a simple wire antenna works in detail is
far from trivial, and when you add in a coil that has significant
physical size, it further complicates things. If you use a simplified
model, it can be useful to gain insights into what's going on, but
don't expect the details to be correct. Be wary about gaining
insights that aren't actually true.

Cheers,
Tom

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

You are quoting the aproach of the bookswhere it is acknowledged that
radiationn cannot fully be explained
For me I am quoting an alternative that does provide the explanation.
If current moves at the speed of light within the Universe ( the
speed of light relative to Earth is slower which creates delay
compared to the former. Insertion of Plank's constant I believe is
a metric that represents the ratio of that delay)
it imparts the same speed to a static particle when impacted, where
the acceleration is determined by Newton's law u.t +f.t sq/2. Since
the particle is static the "u.t" portion equals zero and f.t.sq/2 is
the acceleration from zero to that of the speed of current of the
particle, which is a measure of the expended kinetic energy that
creates the initial format of radiation. I state again without mass
there can be no acceleration.Period
Regards
Art

Loading coils: was Dish reflector
 

Roy Lewallen wrote:


Regards,
Steve G3TXQ

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 Lewallen, W7EL

which makes perfect sense...
NEC is a MoM code and is ideally suited to calculating the current
induced in one wire by the currents in other wires. I should think it
would do an excellent job modeling a air core solenoid, especially if
the wire diameter is small compared to the spacing between turns,etc,
assuming that you don't get into numerical precision problems.

Loading coils: was Dish reflector
 

"Art Unwin" wrote in message
...
I state again

and again, and again, adding bafflegab and gobbledygook with every
iteration... I love it art, how much deeper can you go with this?

Loading coils: was Dish reflector
 

Roy Lewallen wrote:
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)

All program types, including the demo, of EZNEC v. 4.0 and later do
dielectric loading similar to NEC-4. (The method came from sources other
than NEC-4.) Like the NEC-4 implementation, it's of limited accuracy and
usefulness -- it's really good only for thin wire insulation of moderate
permittivity.

I stand corrected. Thanks.


And, it's a MoM code, so things not well represented by collections of
wires aren't necessarily modeled well.

Absolutely true. And it can't handle things like patch antennas or
antennas printed on a PCB.

NEC does OK at microstrip patches with air dielectric (or foam with very
low permittivity). I've used it to model an array of 9 patches and the
port to port coupling calculated by NEC and measured by a VNA were
pretty close (within measurement uncertainty).

It's pretty darn slow at this, though (lots and lots of wires in each
patch), I used lumped loads for the matching network model (capacitive
probe feed)

Loading coils: was Dish reflector
 

Tom Donaly wrote:
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?

Depends on what your modeling needs are. NEC and it's ilk are more
generalized, but take more computational effort. The Corums have an
analytical approximation that is reasonably good for a certain class of
configurations, although I have to say that for the original Corum
application of Tesla Coils, a lumped approximation gets you almost as
close, at much less work, considering the usual construction tolerances
in a tesla coil. Modern Tesla Coil modeling is typically done with
either a lumped model or a FEM code that assumes it's axially symmetric
and often an assumed voltage distribution. The assumed distribution the
result of a combination of more detailed analytical modeling and some
experimental measurements on real coils, and speeds up the computation
drastically, while not adversely affecting the accuracy of the results
(that is, the changes are less than a few percent, comparable to
construction tolerances on these things).



73,
Tom Donaly, KA6RUH

Loading coils: was Dish reflector
 

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

EZNEC and the Cecil-Corum method are in agreement.
How would you measure the delay through a wire
or through a coil using the following current
reported by EZNEC through a 90 degree monopole?

EZNEC+ ver. 4.0
thin-wire 1/4WL vertical 4/23/2009 8:01:44 PM
--------------- CURRENT DATA ---------------
Frequency = 7.29 MHz
Wire No. 1:
Segment Conn Magnitude (A.) Phase (Deg.)
1 Ground 1 0.00
2 .97651 -0.42
3 .93005 -0.83
4 .86159 -1.19
5 .77258 -1.50
6 .66485 -1.78
7 .54059 -2.04
8 .40213 -2.28
9 .25161 -2.50
10 Open .08883 -2.71

Exactly how does one use a current that changes phase
by 2.71 degrees in 90 degrees of antenna to obtain
the delay through anything?

Your silence on this subject speaks volumes.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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

Loading coils: was Dish reflector
 

On Apr 23, 6:59*pm, K7ITM wrote:
On Apr 23, 2:32*pm, Roy Lewallen wrote:

Jim Lux wrote:
Roy Lewallen wrote:

Let's see how well the principles involved are understood.

What is the delay through a physically very small toroidal coil with
the same inductance as the solenoidal coil? Why?
As in a coil wound on a toroidal magnetic core? or a air cored solenoid
bent in a circle?

I'll say one wound on a magnetic core, simply to keep the size small,
the coupling tight, and the field confined. I don't, however, care how
long a piece of wire it's wound with.

Roy Lewallen, W7EL

There are some other configurations that I personally think are
interesting to ponder. *You might never actually build one this way,
but you'll probably gain some insights considering it: *an antenna,
say a nominally 1/4 wave vertical for 40 meters made from 4" diameter
aluminum tube (irrigation pipe) twenty feet long, resonated with a
loading coil placed inside the tube across a gap of two or three
inches in the pipe. *Capacitance from the coil is almost entirely to
the pipe in this case, not to the world outside the pipe, so the
effect is capacitance in parallel with the coil, not as in a
transmission line where the capacitance is to ground. *That's a
different situation than one where a coil with a diameter much larger
than the antenna conductor is used, where the coil has significant
capacitance to the outside world (e.g. to ground).

It's also worth considering that the charge distribution on an antenna
is dynamic, so it's probably not a good idea to try to analyze the
antenna as if there was the same capacitance to ground from the coil
as there would be if the charge distribution on the antenna wire were
static (that is, the DC case, or at a frequency that's a tiny fraction
of the lowest natural resonance of the antenna system).

Analyzing exactly how even a simple wire antenna works in detail is
far from trivial, and when you add in a coil that has significant
physical size, it further complicates things. *If you use a simplified
model, it can be useful to gain insights into what's going on, but
don't expect the details to be correct. *Be wary about gaining
insights that aren't actually true.

Cheers,
Tom

Tom you are correct in not making a descision on the basis of one
observation but consideration of all the observable facts. The analogy
of this is only with the use of alln segtments of a jigsaw puzzle can
there be confidance of the ensuing picture.
Roy stated that his conclusion was only based on one observable and
where his statement said he did not care beyond that single observable
which matched a predetermined picture. An accurate production of the
ensuing picture comes about only with a matching relationship between
all the parts of the jigsaw and certainly not based on the visual of
one. Your last sentence speaks volumes regarding Roy;'s responce
Regards
Art

Loading coils: was Dish reflector
 

Jim Lux wrote:
Roy Lewallen wrote:

Absolutely true. And it can't handle things like patch antennas or
antennas printed on a PCB.

NEC does OK at microstrip patches with air dielectric (or foam with very
low permittivity). I've used it to model an array of 9 patches and the
port to port coupling calculated by NEC and measured by a VNA were
pretty close (within measurement uncertainty).

Yes, I meant patch antennas with common dielectrics, which are far more
common. It's of course the dielectric that NEC can't account for. I've
designed quite a few antennas on PCB material, but use a fudge factor
based on comparison between measured and EZNEC results of a simple
antenna near the same frequency. This gets me pretty close, but even
this approach wouldn't be adequate if field coupling through the
dielectric is significant.

It's pretty darn slow at this, though (lots and lots of wires in each
patch), I used lumped loads for the matching network model (capacitive
probe feed)

For large models, calculation time goes up as the cube of the number of
segments, so big models can get slow all right. However, EZNEC has
undergone a pretty dramatic speed improvement over time as various code
substitutions and updated compilers have been used, and it's much, much
faster than older NEC compilations. And some versions of NEC have been
similarly updated, so people using different NEC compilations can
experience pretty different calculation speeds.

Roy Lewallen, W7EL

Loading coils: was Dish reflector
 

On Apr 23, 7:42*pm, "Dave" wrote:
"Art Unwin" wrote in message

...

I state again

and again, and again, adding bafflegab and gobbledygook with every
iteration... I love it art, how much deeper can you go with this?

Well I am following the laws of physics. Since you were asleep during
part of the lecture When the examination comes along you can only
rely on baffle gab rather than ALLthe facts given during the lecture.
Fortunately, one can graduate by providing some incorrect answers up
to a limit where as total attention is the only route to a 100 percent
score. You would be wise to accept that your knowledge on physics is
not totally without error because of the baffle gab that you provided
instead
Regards
Art

Loading coils: was Dish reflector
 

On Apr 23, 7:49*pm, Jim Lux wrote:
Tom Donaly wrote:
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?

Depends on what your modeling needs are. *NEC and it's ilk are more
generalized, but take more computational effort. *The Corums have an
analytical approximation that is reasonably good for a certain class of
configurations, although I have to say that for the original Corum
application of Tesla Coils, a lumped approximation gets you almost as
close, at much less work, considering the usual construction tolerances
in a tesla coil. *Modern Tesla Coil modeling is typically done with
either a lumped model or a FEM code that assumes it's axially symmetric
and often an assumed voltage distribution. The assumed distribution the
result of a combination of more detailed analytical modeling and some
experimental measurements on real coils, and speeds up the computation
drastically, while not adversely affecting the accuracy of the results
(that is, the changes are less than a few percent, comparable to
construction tolerances on these things).

73,
Tom Donaly, KA6RUH

You are correct in pointing out that a Tesla coil is a lumped
inductance. A "preponderance" of a lumped load disqualifies the use of
Maxwell's statements
The only metrics he supplied to justify the presence of equilibrium
were distributed loads and no more.
Regards
Art

Loading coils: was Dish reflector
 

On Apr 23, 7:40*pm, Jim Lux wrote:
Roy Lewallen wrote:

Regards,
Steve G3TXQ

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 Lewallen, W7EL

which makes perfect sense...
NEC is a MoM code and is ideally suited to calculating the current
induced in one wire by the currents in other wires. I should think it
would do an excellent job modeling a air core solenoid, especially if
the wire diameter is small compared to the spacing between turns,etc,
assuming that you don't get into numerical precision problems.

If eznec does not take into account dielectric loading then the
application is not in equilibrium and thus Maxwells laws are not
applicable. Maxwells laws are based solely on the presence of
equilibrium or accountability of all loads applied which when all are
added equals zero per Newtons laws.
Regards
Art

Loading coils: was Dish reflector
 

On Apr 23, 8:43*pm, Roy Lewallen wrote:
Jim Lux wrote:
Roy Lewallen wrote:

Absolutely true. And it can't handle things like patch antennas or
antennas printed on a PCB.

NEC does OK at microstrip patches with air dielectric (or foam with very
low permittivity). *I've used it to model an array of 9 patches and the
port to port coupling calculated by NEC and measured by a VNA were
pretty close (within measurement uncertainty).

Yes, I meant patch antennas with common dielectrics, which are far more
common. It's of course the dielectric that NEC can't account for. I've
designed quite a few antennas on PCB material, but use a fudge factor
based on comparison between measured and EZNEC results of a simple
antenna near the same frequency. This gets me pretty close, but even
this approach wouldn't be adequate if field coupling through the
dielectric is significant.
Exactly. Maxwells law application is solely on the condition of all
forces be accounted for such that the summation is equal zero.
Omission of consideration of a force that is present prevents the
summation from equaling zero which means the creation of an error.
Very simple my dear Watson. This is tantamount to creating an abitrary
border where one omits recording the full amount of flux created.
Regards
Art

It's pretty darn slow at this, though (lots and lots of wires in each
patch), I used lumped loads for the matching network model (capacitive
probe feed)

For large models, calculation time goes up as the cube of the number of
segments, so big models can get slow all right. However, EZNEC has
undergone a pretty dramatic speed improvement over time as various code
substitutions and updated compilers have been used, and it's much, much
faster than older NEC compilations. And some versions of NEC have been
similarly updated, so people using different NEC compilations can
experience pretty different calculation speeds.

Roy Lewallen, W7EL

Loading coils: was Dish reflector
 

K7ITM wrote:
On Apr 23, 2:32 pm, Roy Lewallen wrote:
Jim Lux wrote:
Roy Lewallen wrote:
Let's see how well the principles involved are understood.
What is the delay through a physically very small toroidal coil with
the same inductance as the solenoidal coil? Why?
As in a coil wound on a toroidal magnetic core? or a air cored solenoid
bent in a circle?
I'll say one wound on a magnetic core, simply to keep the size small,
the coupling tight, and the field confined. I don't, however, care how
long a piece of wire it's wound with.

Roy Lewallen, W7EL

There are some other configurations that I personally think are
interesting to ponder. You might never actually build one this way,
but you'll probably gain some insights considering it: an antenna,
say a nominally 1/4 wave vertical for 40 meters made from 4" diameter
aluminum tube (irrigation pipe) twenty feet long, resonated with a
loading coil placed inside the tube across a gap of two or three
inches in the pipe. Capacitance from the coil is almost entirely to
the pipe in this case, not to the world outside the pipe, so the
effect is capacitance in parallel with the coil, not as in a
transmission line where the capacitance is to ground. That's a
different situation than one where a coil with a diameter much larger
than the antenna conductor is used, where the coil has significant
capacitance to the outside world (e.g. to ground).

It's also worth considering that the charge distribution on an antenna
is dynamic, so it's probably not a good idea to try to analyze the
antenna as if there was the same capacitance to ground from the coil
as there would be if the charge distribution on the antenna wire were
static (that is, the DC case, or at a frequency that's a tiny fraction
of the lowest natural resonance of the antenna system).

Analyzing exactly how even a simple wire antenna works in detail is
far from trivial, and when you add in a coil that has significant
physical size, it further complicates things. If you use a simplified
model, it can be useful to gain insights into what's going on, but
don't expect the details to be correct. Be wary about gaining
insights that aren't actually true.

Cheers,
Tom

I didn't do exactly as you say, Tom, but I did take a homemade coil
(140mm long, 155mm in diameter) and wrapped it with a sheet of .005 inch
copper foil separated by a couple of strips of double sided foam tape.
It acted more like a transmission line than the bare coil, but it had
some peculiarities that made its behavior puzzling to say the least.
73,
Tom Donaly, KA6RUH

Loading coils: was Dish reflector
 

On Apr 23, 8:04*pm, Cecil Moore wrote:
Tom Donaly wrote:
Nothing is perfect, but which is better, EZNEC or the Cecil-Corum method
of modeling antennas?

EZNEC and the Cecil-Corum method are in agreement.
Correct but the solution is in error as equilibrium demands that the
radiator is in equilibrium ie equal to a period or multiples there of.
Both of the above determined that resonance alone without reference
to the period was a reflection of equilibrium.
This may account for Krauss's error in determiming gain via Maxwells
law by determining a half wave was in equilibrium and thus determined
gain was approx
3db more than that was actually attainable. Later measurements mad by
others show that Kraus over estimated the gain by 100 % the equivalent
of 3db or the doubling of gain or energy expenditure.This error is
actually a reflection of pitch of windings which is a fraction of the
possible generated electric field for maximum efficiency.

Lesson
One must account for all actual vectors used within a boundary for
equilibrium
where the addition of all vectors finish at the starting point of the
period. The idea that a coil does not radiate is fallacious since the
charge is still accelerating but to a lesser extent than when current
moves along a straight wire. The total velocity factor is the average
velocity of that of a slow wave plus the velocity without the addition
of lumped loads ie straight radiator addition.This being equal to the
total length of wire
required with tha absence of lumped loading ie straight.
Regards
Art




--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

Loading coils: was Dish reflector now: Delay Lines
 

"Jim Kelley" wrote in message
...

For a more quantitative illustration of how distributed reactance in
transmission lines causes delay see
http://www.rhombus-ind.com/dlcat/app1_pas.pdf

73, ac6xg

In graduate school, more years ago than I care to admit, I scrapped a
surplus computer for parts. The computer had been custom built for the
Savannah River nuclear facility. In addition to the many hundreds of
2N404A germanium transistors, I found the core memory made of ferrite
cores about 0.1 inches in diameter and about 30 mils thick. But the most
unusual thing, at least to me, was a flexible coaxial cable about six
feet long made of a ferrite-loaded rubber core wound with 40 gauge
enameled wire, wrapped in a thin cellulose acetate film (Scotch tape?),
covered with a braid shield with a vinyl covering. Of course, it was a
distributed delay line. I never measured its impedance and delay
properties accurately, but the cable had a significant delay that could
easily be seen on a 5 MHz bandwidth scope. Even with an approximate
termination, the cable's losses were quite high.

This was obviously a commercial cable, but in all of the years since, I
have never seen anything like it.

By the way, after dismantling one panel covered with terminal strips, I
found a typed note inside that said, "Built by pigmies in darkest
Africa."

--
73, Dr. Barry L. Ornitz WA4VZQ

Loading coils: was Dish reflector
 

On Thu, 23 Apr 2009 15:29:04 -0700, Jim Kelley
wrote:

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.

Precision is NOT accuracy. Resolution is NOT precision. Accuracy is
defined with precision to a resolution.

You can state a value with great precision and be 100% in error.

100 V is quite precise; "about" 100 V is less precise.

100 V has three places of resolution.

If the true value is actually 201.45 V then 100 V is precise, somewhat
resolved, but inaccurate. On the other hand, 201.45 V is very
precise, highly resolved, and accurate to within 0.005 V (if we are to
trust it as a reference) or 25 parts per million.

I can anticipate the objection (to confound my statement above) that
100 V has both resolution and precision. True, but that objection
would miss the point. Some standards are nominal (or cardinal) values
such as an 1 MHz URQ-23 frequency standard: 1 place of resolution, but
highly precise with an accuracy of (from my experience) of 6 parts per
trillion (after calibration against a cesium beam standard).

I can anticipate the fine objection that the nominal value of 1 is
actually 1.00000000000. Again, true, but in a world where you own an
URQ-23 (and no one has access to HP 5071 cesium clocks), then you get
to snub that objection and demand: "It IS exactly 1!"

73's
Richard Clark, KB7QHC