oSaddam (Yuri Blanarovich) wrote in message ...
But....Just using my built in
"BS" filter only, which rarely seems to fails me, and ignoring all
other influences, I still have to side with Tom. I still think the
current is fairly constant.

Nothing
personal either way...But I have learned never to ignore my BS filter,
so I'm going with it. MK


Same here,
did your filter filtered out W5DXP pudding? The "theoretical" proof is right
there. Or are you drinking the same coolaide as Tom? :-)

Yuri

Reality vs. Speculations? Duuuh?

I found this comment interesting. Note this is from one that actually
has tried measuring the current in coils. This was from the site you
mention...

quote
I once had an occasion where the bottom of a coil did get warm, while
the top did not. Yet my RF ammeters showed the same current on both
ends. What was going on?

I ultimately determined that the soldered connection from the coil to
the lower antenna mast (for experimentation, it was copper) was adding
some undesireable resistance. Solder is not a particularly good
conductor of electricity. I copper-plated over the solder joint. Not
only did the bottom section of the coil no longer get warm, but the
two RF ammeters both showed about 20% more current flowing in the
antenna. And my far-field instruments showed a 1.5dB increase in field
strength.

unquote

This is one example of being fooled....If you took coil temp at face
value, you would think the current taper was quite steep, judging from
the temp's of the windings. But nope...A resistive connection seemed
to be the culprit. Note that his meters showed the same current on
both ends. :/ You can see why I'm afraid of that "hook" that usually
is lurking ready to bite at a moments notice.
Don't worry, if you are right, it will come out in the end. But that
hook...Ouch.. MK

I once had an occasion where the bottom of a coil did get warm, while
the top did not. Yet my RF ammeters showed the same current on both
ends. What was going on?


What was he measuring, where was the coil?
W9UCW used 100 mA at the bottom, I doubt that this would "cook" the coil. You
see the pictures, they are good quality coils and he use two meters and
flippped the coil to eliminate possible error as described here.

I ultimately determined that the soldered connection from the coil to
the lower antenna mast (for experimentation, it was copper) was adding
some undesireable resistance. Solder is not a particularly good
conductor of electricity. I copper-plated over the solder joint. Not
only did the bottom section of the coil no longer get warm, but the
two RF ammeters both showed about 20% more current flowing in the
antenna. And my far-field instruments showed a 1.5dB increase in field
strength.


Again, put on the fricken Hustler 80m resonator, feed it 100W and feel it! No
meters, no hokus pokus, just "naked" antenna.


This is one example of being fooled....If you took coil temp at face
value, you would think the current taper was quite steep, judging from
the temp's of the windings. But nope...A resistive connection seemed
to be the culprit. Note that his meters showed the same current on
both ends. :/ You can see why I'm afraid of that "hook" that usually
is lurking ready to bite at a moments notice.
Don't worry, if you are right, it will come out in the end. But that
hook...Ouch.. MK


One insufficiently described measurement is enough to throw rest out of the
window? W9UCW has shown data from various measurements and positions of the
coil (pictures how it was done) and W5DXP backed it up with explanation of
reflected wave and simulation and comparison with loading stub. It came out,
this is the ned. If you choose not to believe, its a free country :-)

Yuri

More pudding!

I added picture of current distribution when using inductance in the form of
loading stub as described earlier and from Eznec file supplied by Cecil. It is
at the end of the article at

http://www.k3bu.us/loadingcoils.htm

It shows the jump accross the stub, but when replaced by lumped inductor, the
Eznec shows constant current accross the coil.

Yuri

I haven't had the time to participate in this, but in a brief look, it
looks pretty silly. Of course EZNEC shows no current difference across a
load. The EZNEC model of a load has zero length, so the current at both
terminals has to be the same. You will see a current change over the
length of a model of a conductor, because it does have length. The coil
in the web site pictures certainly has length, so why should you be
surprised to find a current change over its length? Did the experimenter
perhaps do the same test with the meters placed the same distance apart
with just a conductor in between? Would there be some great revelation
in finding that the current was different at the two points?

I was intrigued by the claim that a toroid measured significantly
different from one end to the other. I wonder if the tester tried
reversing the meters to verify that he got the same reading in both
cases. If he did, I'd be interested in learning more details.

Unfortunately, the main objective of the web site seems to be to insult
Tom, W8JI, rather than to be objective. So in my mind that leaves the
possibility open that the experimenter is more interested in finding
evidence that would disprove Tom than in presenting carefully measured
and objective data.

Roy Lewallen, W7EL

Yuri Blanarovich wrote:
More pudding!

I added picture of current distribution when using inductance in the form of
loading stub as described earlier and from Eznec file supplied by Cecil. It is
at the end of the article at

http://www.k3bu.us/loadingcoils.htm

It shows the jump accross the stub, but when replaced by lumped inductor, the
Eznec shows constant current accross the coil.

Yuri

Roy Lewallen wrote:
I haven't had the time to participate in this, but in a brief look, it
looks pretty silly. Of course EZNEC shows no current difference across a
load. The EZNEC model of a load has zero length, so the current at both
terminals has to be the same.

It appears that EZNEC also doesn't account for phase shifts across
a zero length coil.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Of course it doesn't account for phase shifts of current, since there
aren't any. It does account for voltage phase shift. It uses the same
equations I learned in freshman circuits class. Perhaps they taught
those same equations in Texas, too, but I can't be sure.

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

I haven't had the time to participate in this, but in a brief look, it
looks pretty silly. Of course EZNEC shows no current difference across
a load. The EZNEC model of a load has zero length, so the current at
both terminals has to be the same.


It appears that EZNEC also doesn't account for phase shifts across
a zero length coil.

Roy Lewallen wrote:
Of course it doesn't account for phase shifts of current, since there
aren't any. It does account for voltage phase shift. It uses the same
equations I learned in freshman circuits class. Perhaps they taught
those same equations in Texas, too, but I can't be sure.

Roy,
We are talking about distributed networks. Of course, there is a phase
shift in the current as well as the voltage. You and W8JI seem to be
using lumped circuit analysis when you should be using distributed
network analysis. The center loading coil for a 75m mobile antenna
is an appreciable percentage of an electrical wavelength so you cannot
use your lumped circuit analysis without introducing errors.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Roy Lewallen wrote:
Of course it doesn't account for phase shifts of current, since there
aren't any.

You seem to be disagreeing with John Devoldere's "Bible" - "ON4UN's Low
Band DXing", 3rd Edition, on page 9-34 at:

http://www.k3bu.us/loadingcoils.htm

A little thought should prove there is a current phase shift (delay) through
the coil. Let's look at an 8 foot long center-loaded mobile antenna for 75m.
The 4 feet below the coil gives a phase shift of about 5 degrees. Assume zero
phase shift through the coil. The 4 feet above the coil gives a phase shift
of another 5 degrees for a total of 10 degrees at the end reflection point.
It's an open circuit, so a 180 degree phase shift takes place. That puts the
reflected current at 190 degrees. Add the 10 degrees coming back and we see
the reflected current arrives mostly out of phase with the forward current
at the feedpoint. Since the feedpoint impedance is known to be around 15 ohms,
these superposed currents cannot possibly be out of phase and must necessarily
be in phase.

The phase shift (delay) of the current simply cannot be the same with and
without the coil.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

I haven't had the time to participate in this, but in a brief look, it
looks pretty silly. Of course EZNEC shows no current difference across a
load. The EZNEC model of a load has zero length, so the current at both
terminals has to be the same. You will see a current change over the
length of a model of a conductor, because it does have length. The coil
in the web site pictures certainly has length, so why should you be
surprised to find a current change over its length?

W8JI used it as a "proof" that current in the loading coil is virtually the
same at both ends. We were not surprised, but W8JI was insisting that it is,
used Eznec to prove it (go see his web site) and ridiculed us.

Did the experimenter
perhaps do the same test with the meters placed the same distance apart
with just a conductor in between? Would there be some great revelation
in finding that the current was different at the two points?

Not to us, but see W8JI arguments speculating and "knowing" that current must
be the same.

I was intrigued by the claim that a toroid measured significantly
different from one end to the other. I wonder if the tester tried
reversing the meters to verify that he got the same reading in both
cases. If he did, I'd be interested in learning more details.

I believe he did use the same method, and W9UCW can answer that. Looks like you
are also not getting the main point of the argument. Appears that the rule is:
"loading inductance (whatever form) inserted in the radiating element exhibits
current magnitudes at its ends corresponding to the current in the length of
radiator in electrical degrees that it replaces." Replacing inductance with
piece of wire won't do the simulation, it has to have properties of inductor
(replacing radiator's segment in degrees, inductance). Toroid, loading stub,
and lumped inductors do the same thing.

Unfortunately, the main objective of the web site seems to be to insult
Tom, W8JI, rather than to be objective. So in my mind that leaves the
possibility open that the experimenter is more interested in finding
evidence that would disprove Tom than in presenting carefully measured
and objective data.

Not so, first I posted on eHam.net fact that current is different at the ends
of loading coil. To which W8JI rode in with his "answers" and ridiculed me in
public (I don't know the laws, didn't read the books, etc.) to which I
responded in kind, provided proof and defended my (and others) position.
Because this has happened about fifth time (he did it to others too) I simply
will not take the crap and bite back. He is parading as a knowitall guru and
pontificating with sometimes erroneous information. If anyone questions or
challenges that, he does his routine. If you read the trail from the start you
would get the picture. If he discussed the matters in a civil manner, there
would be no problem, we can exchange arguments, learn something and mainly give
a credit where is due. That's what professionals do. He first argues wrong,
then goes away for a while and then emerges with change as a guru or inventor.
That does not give hams good name and is poor example for those no-coders
coming into ham radio.
From the past postings, you could probably see that I can discuss the subjects
in a civil manner, but when someone who is wrong starts pulling out smart ass
remarks and ridicule, the gloves are off and I will defend the truth to the
end. It is not just proving Tom wrong, it is to set the record straight, to
bring aspect of antenna engineering to light (after 50 years of perpetuation of
wrong in some antenna books), to alert software designers to the problem so
they can accommodate the proper procedure or workarounds. I hope you can see
how inaccurate results will EZnec produce if you simply inserted 0 size
inductors in elements of 3 el. 80m shortened parasitic beam. Magnitudes and
current distribution will be off, producing skewed results. Optimizing programs
will be chasing wrong tail.

Again, I apologize for the tone, but I will not give in to the bully. If he
doesn't learn and shape up, I will be at his case, pointing out the wrongs that
he is disseminating (he has some more on his web site).

We were hoping that you were around, following the discussions, helping to
point where we are wrong, suggest workarounds or proper procedure for modeling
and we are willing to help with testing and verifications. Cecil brought some
insight from the theoretical side, I (and W9UCW?) can do measurements and all
this can bring greater understanding of the phenomena, rather than propagating
misconceptions and wrong ideas.
I found a lot more help and expertise on this NG than on eHam.net no-code flat
earth society, for which I am grateful.

Can we now look at the modeling problems? Seems that Cecil's way of
substituting the lumped inductance with loading stubs allows closer
approximation of configuration for the modeling programs. But this can still
distort the true picture. I would like to point out, that W6?? replaced loading
stubs in 3 el. 80m KLM beam with coils and the performance of the beam,
especially pattern improved tremendously. So it looks like loading wires and
radiation from them (folded along the element) upset the current distribution
and resulting deterioration of performance. (So much for nice, low loss
loading.) This was done, tested, measured and verified, no speculations. Is
there better way of modeling the case, can we use cosine of degree of
electrical length of wire that coil replaces?

Roy Lewallen, W7EL

Yuri, K3BU

On Sun, 02 Nov 2003 03:44:03 -0800, Roy Lewallen
wrote:

|I haven't had the time to participate in this, but in a brief look, it
|looks pretty silly. Of course EZNEC shows no current difference across a
|load. The EZNEC model of a load has zero length, so the current at both
|terminals has to be the same. You will see a current change over the
|length of a model of a conductor, because it does have length. The coil
|in the web site pictures certainly has length, so why should you be
|surprised to find a current change over its length? Did the experimenter
|perhaps do the same test with the meters placed the same distance apart
|with just a conductor in between? Would there be some great revelation
|in finding that the current was different at the two points?

I too have been lurking and while I didn't spend any time reading the
eham stuff what was going on here got me looking at a model of this
situation.

I used MultiNEC to invoke EZNEC for all calculations. I modeled a
shorter-than-quarter-wavelength vertical, loaded with an inductor, all
of this over perfect ground. Using MultiNEC, I used equations to
change the length of the radiator, the position of the inductor, keep
the segment length as short as guidelines allow and resonate the
result after each change.

Nothing I did solved this argument but I did make a couple of slightly
related observations. Unless I'm mistaken (always a distinct
possibility):

1) When the radiator is electrically very short and near resonant the
current does not follow the classic patterns shown in most of the ham
literature, i.e. nearly constant below the inductor and close to a
straight line taper above. The current actually peaks at the inductor;
in other words, the highest current point on the structure is at the
inductor.

Hanson's paper (Robert C. Hanson, "Optimum Inductive Loading of Short
Whip Antennas", IEEE Transactions On Vehicular Technology, Vol VT-24,
No. 2, May 1975, pp 21-29) shows this, although his graphs show a
steady decrease in current from the feedpoint to where the peaking
begins. I did not see that, but instead a steadly increasing current
from the feedpoint to the current peak.

Not only that, the peaking is almost independent of inductor Q.
"Almost" meaning that my model shows that the current is actually
slightly higher in a lower Q inductor.

2) The structure Q, defined as the change in reactance with respect
to frequency, is independent of inductor Q.

3) For a give length radiator, gain is unaffected by where the
inductor is located along the length of the radiator and by inductor
Q.

If 3 is correct then I can remove the inductor from the radiator
without effecting the gain and place it before the feedpoint to
resonate the structure. Once out of the radiator, the current through
the inductor is constant. Just like it is in the antenna if it has
zero length.

By now you're all saying, "Huh?" But remember, this is for an antenna
over perfect (zero loss) ground.

So instead of worrying about perfecting our antennas, we should be
trying to perfect ground and/or zero length loading coils.

|
|I was intrigued by the claim that a toroid measured significantly
|different from one end to the other. I wonder if the tester tried
|reversing the meters to verify that he got the same reading in both
|cases. If he did, I'd be interested in learning more details.

Considering that *anything* inserted in the structure upsets the
current distribution, as Roy says above, why wouldn't the answer be
different. Even the toroid, or the distance between the insertion
points, have *some* length.
|
|Unfortunately, the main objective of the web site seems to be to insult
|Tom, W8JI, rather than to be objective. So in my mind that leaves the
|possibility open that the experimenter is more interested in finding
|evidence that would disprove Tom than in presenting carefully measured
|and objective data.

Eureka!


Wes Stewart N7WS