Given the length and diameter of the top and bottom antenna sections, and
the LENGTH and DIAMETER of the loading coil, program LOADCOIL will calculate
coil inductance and the number of turns needed to resonate the antenna to
any required 1/4-wave frequency.


The program allows the coil to slide up and down the antenna to optimise
radiating efficiency versus physical implementation. The inductance value,
number of turns and wire gauge are automatically varied to maintain 1/4-wave
resonance versus height.


As a self-check on resonance and other results, the base feedpoint Zin is
calculated. Zin can be used in another program to calculate tuner L and C
settings. A base loading coil can be conveniently included in a tuner.


The distribution of current along the antenna, including along the coil
especially if it is a long helix, and phase relationships, are necessarily
taken into account to estimate loss and radiation resistances. But such data
is not outputted because it's of no practical use to anybody and not worth
the screen space.


The simple radiation pattern of short vertical antennas is already very well
known.


Download program LOADCOIL in a few seconds from website below and run
immediately.
----
=======================
Regards from Reg, G4FGQ
For Free Radio Design Software
go to http://www.g4fgq.com
=======================

Yuri, K3BU wrote:
"W8JI used this picture (Fig 10) to "see, it is constant".

But that was only by specification. It`s the same as saying, "Let`s say
the line is lossless".

The text reads:
"The loading coil acts as the lumped constant that it is, and
disregarding losses and coil radiation, maintains the same current flow
throughout."

This says that in the impossible case of zero radiation and zero loss,
the coil current is the same at both ends of the coil. This is close
enough for a coil at 50 Hz, but unlikely at 5 MHz.

A real loading coil such as a bug catcher, has a real length. The
combination of incident and reflected waves at each point along the
length of the antenna produces a different voltage, just as seen in a
transmission line. This effect prevails in an antenna, too.

Just as on a transmission line, the voltage variation represents an
impedance variation. Impedance is high at the open-circuit end of the
antenna , and it it is low 90-degrees back from that open circuit. Since
some length is filled with the coil, there is a difference in volts at
the ends of the coil due to the standing wave on the antenna.

The feed paths to the coil are unbalanced as shown in Fig 6. That is not
shown in Fig 10 which is meant to show the difference in antenna current
above and below the coil, not what happens in the coil itself. The
authors specify an idealized coil which has the same current in and out.
This is only a declaration, not a real world situation.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
This says that in the impossible case of zero radiation and zero loss,
the coil current is the same at both ends of the coil.

This would be true for traveling-wave antennas. But in a standing-wave
antenna, the net current is the sum of the forward current and the
reflected current. Even if the coil had zero radiation and zero loss,
a real-world coil would have a delay through the coil. That delay
changes the relative phase between the forward and reflected currents
making the net current different at each end of the coil even for a
coil with zero radiation and zero loss. The forward currents would be
equal into and out of the coil. The reflected currents would be equal
into and out of the coil. But their phasor sum would differ due to
phasing.

Assume the forward current and reflected current are in phase at zero
degrees at the feedpoint. The net current is simply the algebraic sum of
those two values. But 45 degrees out from the feedpoint, the forward
current is at 45 degrees and less than at the feedpoint. The reflected
current is at -45 degrees and greater than at the feedpoint and the
sum of the two currents is the sum of two phasor currents 90 degrees
apart. At 90 degrees, at the end of the antenna, the forward current
and reflected current are equal and phasor sum to zero.
--
73, Cecil http://www.qsl.net/w5dxp



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On Thu, 13 Nov 2003 06:57:17 GMT, Richard Clark
wrote:

[interesting comments snipped]
|
|All fairly typical behaviors for our supposed avocation; but growing
|rarer with the haughty attitude that mental gymnastics can answer it
|all. To this point I've finished viewing one of Robert Pease's Online
|seminars (Use and Mis-use of Amplifiers) and his single thumped home
|admonition was to "Eschew SPICE."
|
|For those who want the straight skinny from a battle hardened bench
|designer, I recommend his online work at:
|http://www.national.com/rap/
|on the other hand, for those looking for cut-and-paste greek
|citations, they will be put against the wall. :-)

No, they'll just swithch to the Taguchi method.

Richard,
You have written quite extensively on this thread, a lot of it being
comments that I just dont understand. If you don't like the way it is
going or the people involved are not coming to you' as is their job,
to present absolute proof then why bother with these people or the
thread.
Since you and Tom are like minded establish a thread that you can
banter back and forth without interuption from the roudies. Tom
mentioned somebody else
so you may have a quarum to go your own way, which would be a pity
Can't you bend just a bit and go with the flow when unsurmountable
proof is not presented to you first, which you say is everybodies job.
Looking at the posters that are already involved with this thread
including
those who have now decided to abstain it would appear that there is
some interest in the subject. Didn't you yourself invite me to
participate ? If so you must certainly had some interest in what the
lesser people were saying.
Why not look at the possitives presented and put aside attempts to
deflate
or deride honest attempts to explain. You are apparently a computor
expert so why not derive a system where a inductance is transfered to
a system that can easily be modeled since there seems to be some
interest in the matter and you would good chance of becoming a hero
to all.
Still your friend and hanging on
Art



(Tdonaly) wrote in message ...
Richard wrote,


On 13 Nov 2003 04:21:58 GMT, oSaddam (Yuri Blanarovich)
wrote:
I want to see how well can we track modeling, and what is the proper way to
model the inductors and "force" the Eznec et al to tell the truth?

Hi Yuri,

This is the problem of framing the question. The choice of a lumped
component in EZNEC (as I understand it) is entirely your choice, just
as is the choice in the number of radials to put under an antenna. If
the lumped component is inappropriate (just as would be a non
representative ground system or incorrect choice of ground models)
that is the consequence of your bad choice. Your page already offers
the solution for a solenoid, a simple protocol that fits the situation
you presented and to which you identified and presented Tom as
performing inappropriately. In other words, he did not practice the
protocol, and so it seems, neither have you.

This returns us to the adequacy of actually framing the specification
(instead of the question). Can you present a format for testing BOTH
the physical model and the software model that allows the software
model to be accurate? To this point, no. Not knowing the particulars
that lead to the data offered, and then comparing to a poor model was
in fact no proof at all. That data, and even my model barely
reconcile to any of but one possible fact: a current differential
across a long solenoid (something that Roy has not dismissed even if
that answer has been projected upon him by theory spinners). It
conforms to your thesis, but it hardly proves it (simply because it
inverts your expectations shown in this so-called data).

Take the simple question I offered you some time ago: "What is the
value of this inductor?" You have never responded to this, nor
offered an anticipated value for your own, future work. You condemned
Tom for his poor work, and yet he is the only one to offer a working
value; and if the lack of resonance in my model is any indication, it
is an entirely wrong value, but to this point it is the ONLY specific
value offered by ANYONE. What value is this data, your proof, if you
cannot provide such a fundamental characteristic?

OK, so you are going to abandon it as anecdotal and replace it with
your own effort. Do you have an estimated value for such fundamental
issues as the size of the radiator, the solenoid, its value, its
placement, the ground system? It took me less effort to spin up a
model than write this missive. What overwhelming problems do you
dwell on such that this discussion goes mute?

I am puzzled how you can demand that others perform the benchwork when
you cannot present the problem for them to examine. Roy opened a new
thread doing just that, and the sneer review pointed out it was not
the same (as what?). Of course it wasn't, no one has any but the
barest of details. His inductor was too small and in the wrong place
to accept as a valid representation of the issue goes the rebuttal;
but it proved you right by conforming to all the particulars. Now if
that doesn't hold the record for self-contradiction, I am sure it will
be eclipsed tomorrow. That was an exercise in framing the answer, a
practice of the cut-and-paste theorists that speed read through their
bibles looking for a passage in greek that corresponds to their view
of the world.

When these threads turn to examining "the truth," it is more than
obvious that such a pursuit is bogged down from the beginning and not
necessarily due to an artifact of any tool as it is of the mind.

73's
Richard Clark, KB7QHC



Hi Richard,
it's obvious that the purpose of these discussions among
the pathologically competitive is not to reveal truth, but to enhance the
reputation for
infallibility of the professional egos involved. (I'm not writing of you, Roy,
or Keith.)
For those of us who like to lurk, such discussions can be entertaining, but are
essentially worthless, since they usually only consist of pronouncements
from on high unaccompanied by anything resembling logic or proof. Some
baseless technical rhetoric can be thought-provoking, however, just as some
religious beliefs are. Too bad most of it isn't.
73,
Tom Donaly, KA6RUH

Cecil Moore wrote:

Jim Kelley wrote:

I'd like to hear an explanation for ANY current difference across a coil
that is supposedly behaving as a lumped inductor. But the test really
should be for the same type of antenna used in Yuri's discussion;

Jim, did you fail to notice that arc-cos(0.95) = 18.2 degrees?

No. But I have failed to notice any explanation for it other than you
and Yuri have provided.

73, Jim AC6XG

Cecil Moore wrote in message ...
Mark Keith wrote:
More thoughts from the rubber room...Lets say you, Yuri and crew are
correct and the current taper is large across the coil.
Lets say the coil is still a 1 ft long bugcatcher coil.
Lets say the current is fairly constant below the coil.
What will the real world effect be of this phenomenon?

Roy's measurements vindicated Yuri's prediction. Current in equals 1.0 amp
at zero degrees. Measured current out equals 0.95 amps. arc-cos(0.95) =
18 degrees. Yuri's prediction was right on. What else is there to argue
about? Even the small toroidal coil functioned exactly as predicted by
Yuri.

My argument boils down to: What does this mean to the antenna builder
or modeler? If any discrepancy is so small to be barely measurable,
all this speculation about gross error when modeling is *to me* a load
of hooey. Even if the current varies, which BTW, I never claimed would
be exactly perfect front to back, it should have so little effect on
accuracy to be a non issue. Where is the beef that this claimed
variation of current across a coil causes drastic modeling or coil
placement calculation errors? Sorry, I just don't see it. What am I
missing here? MK

Mark Keith wrote:
My argument boils down to: What does this mean to the antenna builder
or modeler?

To the antenna user, or the antenna builder/modeler who doesn't care
about current distribution, it would probably mean nothing.

If any discrepancy is so small to be barely measurable,
all this speculation about gross error when modeling is *to me* a load
of hooey.

The discrepancy varies anywhere from barely measureable to very
measureable.

Where is the beef that this claimed
variation of current across a coil causes drastic modeling or coil
placement calculation errors? Sorry, I just don't see it. What am I
missing here? MK

I think it should only matter to people who want to give advice on the
subject.

73, Jim AC6XG

Mark, I have often wondered about the meaning of the American word "hooey".

Following a few speed-reads of this disgraceful, un-ending thread, in
conjunction with your description, I now have a better understanding.

Thank you.

Who says the Internet is not educational?
---
Reg.

Jim Kelley wrote:

Cecil Moore wrote:
Jim, did you fail to notice that arc-cos(0.95) = 18.2 degrees?

No. But I have failed to notice any explanation for it other than you
and Yuri have provided.

Assuming the forward current and reflected current are in phase
at the feedpoint, the 5% reduction in net current at the other
end of the coil appears to be because the forward current and
reflected current are not in zero phase at that point. The phase
of the forward and reflected currents are changing in a predictable
manner but the phase of their sum, the net current, doesn't change
much if they are in the ballpark of the same magnitudes. I think Roy
measured that net current phase.
--
73, Cecil, W5DXP