Roy Lewallen wrote:
If you answered "yes", please explain how and why, and how we'd
calculate the current through and voltage across the inductor. If we
moved it an inch up the transmission line from the antenna base, can it
still tell?

Forget about an inductor becoming conscious. The impedance looking
into a six foot whip is the same whether the coil is there or not.
The impedance looking into the bottom of the coil is certainly not
the same as looking into the six foot whip. I suspect this can be
proven by modeling a mobile antenna and then moving the source point
from just under the coil to just above the coil.

If you answered "no", please write us the equations showing just how
much the current should be expected to be different from one end of the
inductor to the other.

The current will be approximately the same as at the two points
of wire it replaces in the antenna without the inductor. I earlier
asked you a question that you seem to have missed. Do you agree
or disagree with Fig 9-22 of ON4UN`s "Low-Band DXing", included
on Yuri`s web pages.?

And where those coulombs are going, that go into
one end and don't come out the other.

You can answer your own question. Where do the coulombs go that enter
one end of a 1/4WL stub and don't exit the other end? Please stop
using lumped circuit analysis on distributed network problems. You
know and I know that it doesn't work.
--
73, Cecil http://www.qsl.net/w5dxp



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On 03 Nov 2003 15:46:01 GMT, oSaddam (Yuri Blanarovich)
wrote:

|
|Can you post a link to this so I know what it is that you think I
|said, or what I said that I don't remember saying?
|
|Wes Stewart N7WS
|
|
|You are right. It wasn't you, it was and credit belongs to Richard Clark,
|KB7QHC.
|I apologize for the error, which was caused by my confusion between two of you
|7's.
|Now that you made posting on eHam.net I went back to the archives and found the
|posting and its rightful author.

Why did it take my posting on eHam to get you do do this? The quote
above was directed to you in this forum days ago.


|Sorry if it caused any problems and made you to jump to conclusion that I am
|making things up. I will be more careful with references.

Okay. Thanks.

On Mon, 03 Nov 2003 09:26:05 -0600, Cecil Moore
wrote:

|Roy Lewallen wrote:
| If you could build an antenna from
| straight conductors and lumped inductors, the result would be very close
| to EZNEC's predictions.
|
|Hard to prove since lumped inductors are impossible in reality. Why
|does EZNEC show so much difference between lumped inductors and stub
|inductors?

I see no such difference in my model.

|The difference in coils Vs stubs in reality is virtually
|nill.

N7WS:

Why did it take my posting on eHam to get you do do this? The quote
above was directed to you in this forum days ago.


I thought it was you, didn't make much of it. If it was so important and you
accused me of making things up, implying that article was misleading, I
investigated Google search options and found the proper posting by KB7QHC and
posted the correction. Ju's human me, sorry.

Yuri

Wes Stewart wrote:
On Mon, 03 Nov 2003 09:26:05 -0600, Cecil Moore
wrote:

|Roy Lewallen wrote:
| If you could build an antenna from
| straight conductors and lumped inductors, the result would be very close
| to EZNEC's predictions.
|
|Hard to prove since lumped inductors are impossible in reality. Why
|does EZNEC show so much difference between lumped inductors and stub
|inductors?

I see no such difference in my model.

There shouldn't be a lot of difference. I have modeled two short dipoles,
one loaded with a lumped inductive reactance and one modeled with the
same reactance using an inductive stub. EZNEC reports the following:

Inductance lumped j335 10'stub

current in segment just before the coil .8374 amp .8384 amp

current in segment just after the coil .7971 amp .5642 amp

The relative difference just before the coil is quite small, 0.12%.

The relative difference just after the coil is quite large, 41.28%.

There just cannot be that amount of difference between a coil and a
stub.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Harrison wrote:
The purpose of a loading coil in a short loaded vertical antenna is
often to add to the existing degrees of antenna length to reach a
resonant length of 90-degrees, as shown in Fig 9-22 of ON4UN`s "Low-Band
DXing", and included on Yuri`s web pages.

In order for a current maximum to exist at the feedpoint of a shortened
(less than 1/4WL) vertical, the forward current must undergo a phase
shift of 90 degrees, followed by the 180 degree phase shift from being
reflected by an open circuit, followed by another 90 degree phase shift
in the reflected current wave. An 8 foot whip gives about 11 degrees of
phase shift end to end on 75m for a total of 22 degrees. If the coil
causes no phase shift, where does the other 338 degrees of phase shift
come from?
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:

I use lumped circuit analysis when dealing with lumped circuits, and
distributed circuit analysis when dealing with distributed circuits.
EZNEC's loads are lumped elements, so when you're talking about EZNEC
loads, you're talking about lumped elements.

Roy Lewallen, W7EL

Hi Roy,

Wouldn't it be better not to lump any portions of an antenna that are a
part of its electrical length?

73, Jim AC6XG

On 03 Nov 2003 15:46:01 GMT, oSaddam (Yuri Blanarovich)
wrote:

You are right. It wasn't you, it was and credit belongs to Richard Clark,
KB7QHC.

Hi Yuri,

The observation was hardly original and I thought it answered the same
question that launched this current thread (in other words, your
complaint of the shortfall of modeling was already acknowledged with a
work-around offered).

What I do not see is any follow-through for that same suggestion. The
complaint has been offered twice, but the resolution abandoned as
though it had never been made.

I've visited your page, and in an effort to wean out the details (you
don't go to much effort to offer an unadorned, plain, vanilla
specification for the radiator). I had to guess about the coil length
(judging from its only metric being 2.5" diameter) and inductance (you
dismiss the importance of its Q and wholly leave this metric blank).
Tom cites a 300µH inductor, but if we are to believe he's unreliable,
then why are there no better sources of this fundamental information?
Using that same metric (coil diameter) I guess the vertical element
was 3/8" (but one picture clearly shows a thin whip which makes
charges of mismodeling a sure prospect regardless of honest effort).
60 radials are suggested, but no mention of length (if my attempts to
model it yield answers that don't fit your numbers - is it my fault?).

So I proceed with any number of presumptions and with every prospect
of charges of cooking results - this is the same odds offered in
prospecting eh/cfa claims.

OK, the plain vanilla radiator 93" tall (3/8" stock) in 93 segments
surrounded by 60 X 93" radials (#12 wire) ALL elevated 6" above a
real, medium ground.
SRC DATA @ 7.1MHz = 0.7995 - J 810.9 ohms
Current varies from 1A at drive point to 0 at tip

The adornment consists of this underspecified coil being decimated and
spread across 10 inches of space in the middle of the radiator with
lumped values of 30µH each. For the life of me, I don't know what
this exercise was to prove given the results:
SRC DATA @ 7.1MHz = 1.258 - J 1561 ohms
Current varies from 1A at the drive point to 0 at the tip
One variation on the first pass design is that when this current hits
the decimated inductor, the current drops to 0 a few inches before the
first inductor section and quickly develops an 180° shift over those
next few inches which persists on out to the tip. At the bottom of
the coil sections, the current again picks up to roughly 100mA
climbing to roughly 150mA at the top and then declining over the
remaining length of radiator. It would seem that anyone could craft
any assortment of conditions to support any of a dozen new theories
from this kind of legerdemain.

As far as I am concerned, these are merely a list of facts based upon
a poor specification supporting an argument that suffers from an
indistinct agenda apart from its lengthy round of 't'ain't so-isms.
Yuri, I still see no effort from you to fill in the current
distribution readings apart from a rather thin data-set of the two
points offered. Your call of warning was already answered some time
ago. Does the current vary across the inductor by this offered
method: yes! and in spades. Does it vary as you describe it? No, but
simple heat can explain that.

73's
Richard Clark, KB7QHC

I don't have Balanis. Can you provide a short quote where he states that
the current at the terminals of a two-terminal lumped component are unequal?

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

Yes, I disagree with that.


Then you disagree with Balanis.

A radiating stub does act differently than a lumped inductor, in both
modeling and reality. EZNEC should reflect this difference accurately.
If you're aware of a situation where you think it doesn't, please email
me the models illustrating the difficulty.

If you model a stub using a transmission line model, it should behave
exactly the same as a lossless lumped inductor at a given frequency.
However, it's an accurate model of reality only if the real stub has
exactly equal and opposite currents on the two conductors. That is, it's
an entirely non-radiating stub.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

If you could build an antenna from straight conductors and lumped
inductors, the result would be very close to EZNEC's predictions.


Hard to prove since lumped inductors are impossible in reality. Why
does EZNEC show so much difference between lumped inductors and stub
inductors? The difference in coils Vs stubs in reality is virtually
nill.