Tom Donaly wrote:

Cecil Moore wrote:
Yet many keep insisting that the net currents at each end of a
loading coil are the same magnitude.

No, "many" don't keep insisting anything of the sort. Those
interested should go to Tom Rauch's web site, read everything
he wrote on the subject, and come to their own conclusions as
to what "many" think.

That's exactly what I am talking about. W8JI completely ignores
the increase in current through a loading coil. How does he explain
the current inside the coil being of a greater magnitude than anywhere
else in the system, including at the feedpoint? (Hint: he doesn't as
he apparently believes that would be a violation of Kirchhoff's laws!)
But it happens all the time in distributed network configurations.

Here's a quote from http://www.w8ji.com

"How much difference is there in loading coil current ENTERING the coil
and loading coil current EXITING the far end? If the antenna beyond the
coil has a low self-impedance compared to the impedance of the shunting
capacitance from the coil to "ground", the currents at each end of the
coil will be essentially equal."

We can imply that w8ji believes that STANDING WAVE currents flow,
"ENTERING" the bottom of the coil and "EXITING" the top. With a
false premise like that, he cannot possibly get anything right from
that point on.

However, if we accept Kraus' approximation in the following quote from
"Antennas For All Applications", ZERO net current will be flowing
through that coil.

Speaking of thin linear standing wave antennas:
"Current-distribution MEASURMENTS indicate that this is a good
assumption provided that the antenna is thin, i.e., when the conductor
diameter is less than, say, 0.01WL. Thus, the sinusoidal current
distribution approximates the natural (current) distribution on thin
antennas." ... "A sinusoidal current distribution may be regarded as
the STANDING WAVE produced by two uniform (unattenuated) traveling waves
of equal amplitude moving in opposite directions along the antenna."

The diameter of #16 wire on 10m is about 0.0001WL, beating Kraus' above
approximation requirement by a couple of magnitudes. (The actual difference
in the forward current and reflected current through the coil appears to
be in the neighborhood of about 5% for a loaded mobile antenna.)
--
73, Cecil http://www.qsl.net/w5dxp


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Unfortunate I have only a NEC 2 based program (Nittany Scientific's NEC-Win
Pro), but with the Sommerfeld/Norton ground model you can approach the
ground to within 1/1000 of a wavelength closely approximating the results of
buried wires, and in very close agreement with your "RADIALS2" program. NEC
programs do require a value for ground permittivity. NEC 4 based software
is more expensive, being in the $800.00 range, plus a $500.00 license from
the Lawrence Livermore Laboratory. In any case the data are easily compared
with your program results.

I have measured my ground conductivity, but not yet attempted to measure the
permittivity.

If anybody wants to get serious with antenna modeling I recommend Ansoft's
HFSS (Often known as "Highly Frustrating Structure Simulator"). It costs a
mere $30,000, with a $10,000 per year support payment.

Regards,

Frank


"Reg Edwards" wrote in message
...
Frank wrote -
I have also used your software for modeling verticals, and it is
in very close to the results produced by NEC. The one problem with NEC 2
(Though not with NEC 4) is that it cannot model buried radials, but can
get
very close to the ground.

================================

The only program I am reasonably familiar with is the several years old
free
EZNEC. I don't know whether it has been updated or not and I make very
little use of it. Come to think of it, I don't make much use of my own
programs either.

Regarding shallow buried radials in conjunction with a vertical, have you
tried my recent program RADIALS2 ?

It is intended to demonstrate performance of the radials themselves in a
given ground rather than antenna performance. Which I suspect is the
reverse
of NEC-4.

As you probably know, the effects of above-ground radials change very
rapidly as they get within a few inches of the ground surface. But once in
the ground they tend to remain static.

RADIALS2 uses an entirely different, unconventional form of performance
analysis. If other programs don't take soil permittivity into account at
HF,
predictions must lose accuracy. Are the inputs and outputs of NEC-4 in a
form suitable for a direct comparison with my simple program?

But in view of the large uncertainties involving ground conditions,
accuracy
is not worth making much of a song and dance about.
----
Reg, G4FGQ

Cecil,

You appear to have some unique views of superposition and of standing waves.

In simple terms superposition says that one can combine two inputs, and
the combined output is equal to the sum of the individual outputs. Not
all systems exhibit superposition, of course, but I believe the
elementary antennas considered here do indeed follow the principle of
superposition with regard to current.

Why do you believe the "net" current somehow has different properties
than simply the sum of the two component traveling current waves? You
use the term "artifact", as if the net current is inconsequential or
even incorrect. Does superposition break down? Distributed network vs.
DC or AC model is not an issue, since the superposition must be
performed independently at each point in the region of interest.

(You seem to like to use "net", but "total" or "algebraic sum" mean the
same thing. I am not interested in any argument about performing the
vector math correctly. That must be assumed.)

Standing waves are not static. The current may not "flow", whatever that
means, but there is certainly real non-zero current at every point
except the exact nodes of the standing wave. If you prefer, the standing
wave current oscillates rather than flows, but that is of no special
importance here.

Why do you believe standing waves are somehow inferior to traveling waves?

(This message is absolutely serious. No tricks or trolling. If you want
to play word games, see ya later.)

73,
Gene
W4SZ


Cecil Moore wrote:


There is forward current flowing into the bottom of the coil and out
the top. There is reflected current flowing into the top of the coil
and out the bottom. The net current is a standing current wave. If we,
as Kraus suggests, assume that the forward current equals the reflected
current (relatively small error in doing so) then there is zero net current
flowing in and out of the coil. The standing wave current is, well, just
standing there and is not "going" anywhere.

The gross error that a lot of people are making is that standing
wave current flows. If the forward and reflected currents are equal,
as Kraus assumes for purpose of discussion, then there is zero net
current flow through the coil. Yet, net current is what everyone
is measuring. What they are actually measuring is the value of
the standing wave current at each end of the coil and it is not
flowing. It is only an artifact of the superposition of the two
waves that are flowing.

"Wes Stewart" wrote in message
...
On Sun, 07 Nov 2004 04:31:00 GMT, "Frank"
wrote:


Hi Frank,

|Thanks for your comments Reg. The fact is my graph is produced in Excel
......
|...........validity of my results -- or the validity of the code.

I haven't run your code, but I did something similar, and announced
the results here, almost a year ago. Perhaps that explains the lack of
response.

http://www.qsl.net/n7ws/Loaded%20antennas.htm

or in downloadable form:

http://www.qsl.net/n7ws/Loaded_Antennas.pdf

the antenna files are he

http://www.qsl.net/n7ws/AntennaModels.zip

Regards,

Wes

Thanks for the information Wes. I have only recently noticed the loading
coil discussions going on, so guess I missed a lot of the earlier postings.
Your curves are very similar to mine, although I plotted only those currents
within the loading coil, that are spaced by the winding separation (Which
happens to be the same as the overall segmentation). The far field is
proportional to the portion of the current (within the helix) in the "z"
direction, and assume that the x and y components are cancelled out. Such
plotting seems to be supported by computing the integral of I(z)dz -- while
realizing the limitation of such expressions.

I just tried to run your EZNEC files, but cannot since I only have the demo
program. Will have to figure out a way to extract the NEC code.

The qsl.net site is incredibly slow, I had to make a couple of attempts to
download your files.

Regards,

Frank

Gene Fuller wrote:
Why do you believe the "net" current somehow has different properties
than simply the sum of the two component traveling current waves?

Because the net current is a *STANDING WAVE* made up of equal magnitudes
of current flowing in opposite directions. That makes the net current
zero, Gene. Standing wave current doesn't flow. The RMS value stands still.
Standing waves are only an artifact of the superposition process. Everything
that needs to be known involves the two traveling waves that cause the
standing wave. Asserting that standing waves flow into the bottom of a
loading coil and out the top shows a complete ignorance of how standing
wave antennas really work. After that false premise, none of the
associated conclusions are valid.

Standing waves are not static.

The RMS value of a standing wave at any point is indeed static.

The current may not "flow", whatever that
means, but there is certainly real non-zero current at every point
except the exact nodes of the standing wave. If you prefer, the standing
wave current oscillates rather than flows, but that is of no special
importance here.

It is of infinite importance. If the standing wave current oscillates in
place, it doesn't flow through the coil. W8JI says it flows into the bottom
of the coil and out the top. Nothing could be farther from the facts of physics.

Why do you believe standing waves are somehow inferior to traveling waves?

Standing waves are an artifact of the superposition of two traveling waves.
Standing waves have a constant differing RMS value at every point on the
transmission line. Traveling waves travel and have the same RMS value all
up and down a lossless transmission line. What is it about that concept
that you don't understand?
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil,

Thanks.

I thought I understood the situation. Now I am certain.

Bye. :-)

73,
Gene
W4SZ

Cecil Moore wrote:
Gene Fuller wrote:

Why do you believe the "net" current somehow has different properties
than simply the sum of the two component traveling current waves?


Because the net current is a *STANDING WAVE* made up of equal magnitudes
of current flowing in opposite directions. That makes the net current
zero, Gene. Standing wave current doesn't flow. The RMS value stands still.
Standing waves are only an artifact of the superposition process.
Everything
that needs to be known involves the two traveling waves that cause the
standing wave. Asserting that standing waves flow into the bottom of a
loading coil and out the top shows a complete ignorance of how standing
wave antennas really work. After that false premise, none of the
associated conclusions are valid.

Standing waves are not static.


The RMS value of a standing wave at any point is indeed static.

The current may not "flow", whatever that means, but there is
certainly real non-zero current at every point except the exact nodes
of the standing wave. If you prefer, the standing wave current
oscillates rather than flows, but that is of no special importance here.


It is of infinite importance. If the standing wave current oscillates in
place, it doesn't flow through the coil. W8JI says it flows into the bottom
of the coil and out the top. Nothing could be farther from the facts of
physics.

Why do you believe standing waves are somehow inferior to traveling
waves?


Standing waves are an artifact of the superposition of two traveling waves.
Standing waves have a constant differing RMS value at every point on the
transmission line. Traveling waves travel and have the same RMS value all
up and down a lossless transmission line. What is it about that concept
that you don't understand?

Gene Fuller wrote:
I thought I understood the situation. Now I am certain.

Hopefully, we can lay this thing to rest soon. The forward current
flows into the bottom of the coil and out the top. The reflected
current flows into the top of the coil and out the bottom. Those
two currents are very close to being equal magnitudes but their
phases are rotating in opposite directions. That is not a job
for the lumped circuit model. That's a job for the distributed
network model, something that you guys seem to have first ignored
and later tried to sweep under the rug.
--
73, Cecil http://www.qsl.net/w5dxp


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Gene, W4SZ wrote:
"Standing waves are not static."

Incredible!

My "American College dictionary" defines "standing wave": "a
distribution of wave displacements , such that the distribution in space
is periodic, with fixed maximum and minimum points, with the maxima
occuring everywhere at the same time, as in vibration of strings,
electric potentials, acoustic pressures, etc."

Note the word "fixed" in the definition. That`s a synonym for "static".

For how this applies to antennas and transmission lines, see page 177 of
Kraus` "Antennas", third edition, Figure 6-7. Notice that current
reverses 1/2-wavelength back from the antenna`s open-circuit endjust as
it does in the case of the open-circuit transmission-line, as shown by
Terman on page 92 of "Electronic and Radio Engineering", 1955 edition,
and on page 94 in FiG. 4-5 (a). This all starts at the reflection point
and progresses the same regardless of the length of the antenna or
transmission-line. It is due to superposition of the forward and
reflected waves, just as Cecil maintains.

Advice: Never argue with Kraus and Terman.

Best regards, Richard Harrison, KB5WZI

"Cecil Moore" wrote in message
...
Reg Edwards wrote:
By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight.

I hear the French are pi$$ed at us for our small boycott of
French wine, French vacations, French Fries, etc. :-) Ever
notice that us and US mean the same thing for us?
--
73, Cecil http://www.qsl.net/w5dxp


Don't know if it is true, but I heard that France had a problem that
wiped out one type or area of grapes and they imported some of the same type
from the U.S. True?

73,
--
Steve N, K,9;d, c. i My email has no u's.

Steve Nosko wrote:
"Cecil Moore" wrote in message
...

Reg Edwards wrote:

By the way, I'm on Dourthe No.1, Bordeaux 2001, tonight.

I hear the French are pi$$ed at us for our small boycott of
French wine, French vacations, French Fries, etc. :-) Ever
notice that us and US mean the same thing for us?
--
73, Cecil http://www.qsl.net/w5dxp



Don't know if it is true, but I heard that France had a problem that
wiped out one type or area of grapes and they imported some of the same type
from the U.S. True?

73,

The French wine industry was decimated in the 19th century by
a phylloxera infestation from America. The problem was solved by
using native American root stock onto which French grape vines were
grafted. Most wine grapes in America have European ancestry.
I doubt whether there's a grape vine in the world that cares
who is president of the U.S.
73,
Tom Donaly, KA6RUH