On Tue, 8 Jan 2008 19:57:18 -0500, "AI4QJ" wrote:

measures delta I**2 or delta V**2

What is delta, specifically as you use it here?

73's
Richard Clark, KB7QHC

On 8 Jan, 17:26, "AI4QJ" wrote:
"Richard Clark" wrote in message

...

Now, if you want to discard EZNEC (which for some odd reason you seem
to approach method of moments with a sneer), conventional methods
would still bear out the same results.

The NEC program is just a computer model, for discussion purposes only. I
think there are far too many variables in real life for the program to take
into account. It may be valuable but I am not yet convinced it is
infallible.

Lord knows I've sat at the
bench doing it the conventional way for thousands of measurements.

That is the only way to do it in my opinion. I am not very convinced that
the NEC models can be used as a first source to support any proposals in
these discussions although they are useful as a secondary level of
corroboration. Although we accept them because we are usually too busy to
perform hardware measurements, at least one should consider exactly how one
"would" or "could" make a hardware emasurement in real life. The less likely
you are able to measure in real life, the more likely your proposal is heavy
on abstractions and light on reality. For example. I think the more
significant recent developments in quantum theory, such as "string theory",
although they may attract a lot of research dollars to fund professors at
our Universities, are actually quite useless in practice because no one will
ever be able to prove it true by empirical measurments. I can say "God
created the universe" which may seem plausible until I am challenged to
prove the existence of God, which I cannot now and never will be able to do.
Belief requires faith or even a suspension of logical thought, neither of
which I am prepared to do for science.

I've probably made more physical measurements in a day, than anyone
here has in a lifetime.

Others, don't bore us with indignities about all your SWR meter
readings in reply to that last statement. * :-)

So now to the shoe you dropped:
I know this was not your
main point, it was just an aside, but I don't agree with it

What was my main point, and how is yours conflict with it?

You were arguing about an SWR on a NEC model being 8:1, due, I have heard,
to an erroneous assumption of Zo. No problem with me. But when you made an
assertion that I thought could not be measured easily, I hesitated to take
it true using faith based science. As you can see, the NEC model falls apart
by making one simple erroneous assumption. Or was it? You can argue about
that. That is the problem with these models, nobody is so intelligent that
they are free of errors and no model is infallible either.

Is yours a
philosophical triviality so common to these threads, or does it come
with physical measurements experience?

It is philosophical as above but I do not consider it trivial. To me it was
not a waste of time; thanks for the exchange Richard.

AI4QJ

Oh my!
I wish I was as eloquent as you. You would explained the problem so
much better than I did. When an assumption was made in addition to the
use of Maxwell's laws it was to make the program conform with known
results. And then the assuption made regarding sino soidal current
flow was made is found to be in error, thus the absolute validity of
the programs comes into question. Were they generated to follow
Maxwells laws explicably or were they made to reflect empirical
results? I suspect that Maxwells laws overode external human
influences
imposed by the programmer who are not infallable
Best regards
Art Unwin...KB9MZ...xg (uk).

Dave wrote:
"AI4QJ" wrote in message
...
The VSWR meter on the ham rig is merely looking at the balance of forward
and reflected "power" and it is calibrated to read it out as VSWR (or
SWR). It may as well say "ISWR"; it is all the same thing. But it is not
measured by sensing either voltage ot current going into the antenna...it
measures the delta power.


how do you measure 'power'?? you don't. and no swr meter in the world
measures 'power'. they all take samples of voltage and/or current and drive
a simple meter circuit that just happens to be calibrated in units of watts
because thats what most users of cheap meters want to see. they could just
as easily be calibrated in volts or amps referenced to 50 ohms



SWR meters calibrated in watts? Really, where?

However, I do find it enough that my watt meter reads 2.5 KW and my
linear is 5 KW--loaded lightly to achieve the 2.5 KW. Somehow it just
makes sense ... and, I am running it into a dummy load--of course! :-D

Regards,
JS

On Tue, 8 Jan 2008 20:26:03 -0500, "AI4QJ" wrote:


"Richard Clark" wrote in message
.. .

Now, if you want to discard EZNEC (which for some odd reason you seem
to approach method of moments with a sneer), conventional methods
would still bear out the same results.

The NEC program is just a computer model,

Hi Dan,

"Just a" is a familiar dismissal for almost anything offered. Without
corroborating evidence for the fear that is associated with its usage;
then such an expression is a totem or religious chant to chase away
spirits.

"Computer model"s are as useful as they are predictive. EZNEC
conforms to NEC which in turn conforms to field tests. The chain of
evidence is quite strong and I have yet to hear of any real-life
design that has defied NEC analysis.

for discussion purposes only. I
think there are far too many variables in real life for the program to take
into account. It may be valuable but I am not yet convinced it is
infallible.

"Infallible" is a feeble demand to the gods for proof of their
existence. I very seriously doubt you have ever encountered anything
infallible in your life, so why start now? This desire for guarantee
is usually a crutch for the turmoil of nervous youth.

A computer model is explicitly not "real life" except to the extent by
which it is included as a parameter. You don't name anything in
particular that troubles you about "real life," so you don't appear to
be looking for assurance, just negation.

NEC has certainly responded to "real life" through the iterations of
its successive designs (something that Roy may have more to say).
There are explicit allowances for Ohmic loss of the conductor, and
dielectric loss of insulation. Also added is the issue of the
proximity of earth, and NEC offers similar parameter controls for
describing it. In fact, you (or anyone) is probably far more ignorant
of the characteristics of the earth in their "real life" than would be
the problem of NEC to successfully model it.

As to this last statement, the problem with modeling is far more
operator error borne than computer borne. If you have any suspicions,
gripes, grief, or indecision, it can frequently be laid at the feet of
the designer. That is why I use the designer's own designs to split
open their logic to reveal the corruption. If the model lacks
interior fidelity, it is not the fault of NEC.

Any review of EZNEC's help files will quickly reveal there are many
trip points that can result in low accuracy, or outright errors. These
can be investigated by simply asking for the model and examining it
yourself. I revealed a couple from Cecil's offering: a strongly earth
associated design modeled against a perfect earth; remote stimulus. I
explicitly described changes of one or two parameters (expressly
demanded by Cecil) and revealed that Traveling Wave antennas have
Standing Waves upon them. This is hardly a monumental observation -
except when it upsets the horse cart of celebrity.

If you want to remain unconvinced, that is a rather passive activity
of low participation and little information. I would suspect that of
the 6 billion inhabitants of earth, there are 6 billion like you, but
they don't write here. Their motivations lie elsewhere where they
participate in activities to their interests.

What was my main point, and how is yours conflict with it?

You were arguing about an SWR on a NEC model being 8:1, due, I have heard,
to an erroneous assumption of Zo.

Well, with nothing more substantial than that, this is not a
particularly condemning point. You should note that you are trapped
by your own passivity into accepting other people's "word for it."
This is an odd position to be in when you are writing in a community
of Modelers who exchange designs for review and can either confirm or
deny claims against rather more substantial evidence than what was
overheard.

No problem with me. But when you made an
assertion that I thought could not be measured easily, I hesitated to take
it true using faith based science. As you can see, the NEC model falls apart
by making one simple erroneous assumption. Or was it? You can argue about
that. That is the problem with these models, nobody is so intelligent that
they are free of errors and no model is infallible either.

You would stand to learn far more by examining the model yourself than
have me swear on my credentials. You could stand to learn far more by
asking for data instead of pondering the emotional chemistry of
writing to a newsgroup, or second guessing how a model might fail.

Those that stand to lose the most in celebrity, rarely offer
correlating data or respond in true faith to enquiry for details. This
is, after all, the point of the exchange of correspondence where
celebrities post merely to pronounce their claims a spark of invention
to be validated here. That just isn't the way it works here, or in
"real life" either.

73's
Richard Clark, KB7QHC

On Tue, 8 Jan 2008 20:38:40 -0500, "AI4QJ" wrote:


"Richard Clark" wrote in message
.. .
On Tue, 8 Jan 2008 19:57:18 -0500, "AI4QJ" wrote:

measures delta I**2 or delta V**2

What is delta, specifically as you use it here?

The delta between what is sent forward and what is reflected back. If the
delta is zero, SWR = 1:1.


Hi Dan,

I was trying to untangle this expression from your statement:
I have not seen a meter that
appears to directly measure the ratio of Vmax forward/Vmax reflected or Imax
forward/Imax reflected, which *would* be a direct SWR measurement.

How does you lack of exposure to such an instrument impact this
thread? Do you need it for assurance? Does it demonstrate something
lacking in other methods of determination? I've already written to a
method of determining not only SWR but the phase of reflections using
one meter, switched between three points along a line (or probed
directly). Such a method does not deny the accuracy of other methods
or reveal any more information.

In short, what significance is there in a "direct SWR measurement?" My
skill at it is hardly remarkable until you get to some rather obscure
situations (and a lot of what is obscure here passes as discovery of
the ages stuff, but those discoverers lack the skill).

73's
Richard Clark, KB7QHC

AI4QJ wrote:

The NEC program is just a computer model, for discussion purposes only. I
think there are far too many variables in real life for the program to take
into account. It may be valuable but I am not yet convinced it is
infallible. . .

Exactly the same can be said of any of the other models we successfully
use daily. "Resistances", "impedances", "capacitances", and other
objects we routinely use in circuit analysis, are "just" models of real
objects. Likewise, the equations we use for solving all kinds of
problems, including transmission line and circuit analysis problems, are
"just" models of actual behavior. Ohm's law is "just" a model of the
relationship among V, I, and Z. The fundamental equations relating
currents and fields, Maxwell's equations, and all other equations used
in engineering are "just" models of real behavior.

*All* models are subject to intelligent use. A person modeling a real
resistor as a pure resistance at 50 GHz will get just as bad results as
a person modeling a dipole on a circuit board in a smart key in a pocket
as a free-space dipole. No model, not even a simple resistance, is
infallible -- even it can be misused by someone not having the
underlying knowledge necessary to apply it. So of course computer models
aren't infallible either.

But there are many, many real life antennas which can be modeled with
great accuracy with NEC. I use EZNEC regularly myself in my consulting
work to design antennas, and find very good correlation with anechoic
chamber pattern tests, network analyzer impedance tests, and performance
results. So do the many aerospace companies, military organizations,
space agencies, universities, research labs, domestic and international
broadcasters, and many other companies that use EZNEC daily to help
design real antennas that work as predicted. But those aren't the only
people successfully modeling with EZNEC -- a large number of amateurs
successfully use it also.

I'm not sure what it is that makes models inherently less accurate or
believable if the equations are solved with a computer than if they're
solved by some other method. Perhaps you could explain.

Roy Lewallen, W7EL

Richard Clark wrote:
. . .
"Computer model"s are as useful as they are predictive. EZNEC
conforms to NEC which in turn conforms to field tests. The chain of
evidence is quite strong and I have yet to hear of any real-life
design that has defied NEC analysis.

I don't think you said quite what you meant.

There are many real-life designs which are beyond NEC's (and hence
EZNEC's) ability to analyze. One common example is a microstrip (patch)
antenna; NEC has no way to account for the dielectric. A user with even
minimal knowledge should realize the significance of this shortcoming,
and not expect to be able to get accurate results from a model with the
dielectric excluded.

However, and I think this is probably what you meant, the accuracy of
NEC is strikingly good whenever a model can be constructed that does a
good job of mimicking the real antenna. All this really proves are two
things: 1. The fundamental electromagnetic equations solved by NEC are
sound, and 2. Most of the bugs have been worked out of the code, so it
correctly solves the equations.

The equations solved by NEC can't be solved in closed form. That means
there is no formula into which you can plug numbers and calculate a
result. The method it uses can be done manually for very simple cases
and with very limited accuracy -- see Kraus' _Antennas_, 2nd Edition or
later, for a good example. A number of very simple antennas with simple
geometry can be analyzed using approximations which have been developed
over the years, but they're usually strictly limited to a narrow range
of conditions. For example, there have been many methods developed for
finding the input impedance of a simple, straight dipole of various
lengths and diameters. (I have a large collection of papers and
references on this topic, accumulated before MININEC became available.)
All are based on approximations, and some are better than others at
certain lengths and diameters. None are terribly good over a wide range,
and bending the elements, for example, invalidates any of the methods.
Now, why should we expect results from these methods to be better in
some way than results from NEC, "just" a computer model, when NEC can
solve the problem for any length, diameter, and shape, to an arbitrary
degree of accuracy, in a fraction of a second?

Roy Lewallen, W7EL

On Tue, 8 Jan 2008 22:17:40 -0500, "AI4QJ" wrote:


"Richard Clark" wrote in message
.. .

Those that stand to lose the most in celebrity, rarely offer
correlating data or respond in true faith to enquiry for details. This
is, after all, the point of the exchange of correspondence where
celebrities post merely to pronounce their claims a spark of invention
to be validated here. That just isn't the way it works here, or in
"real life" either.

Your entire post seems to indicate that, in order to participate in this
newsgroup, you must use EZNEC.

Hi Dan,

No, it explicitly informs you that if you don't have any modeler, you
are only guessing. Modelers offer solutions that I doubt you could
obtain through your own efforts.

Forget about all those tiresome formulae and
the concept building; you need not know how a standing wave works or the
mathematics thereof.

Forget? Well, this certainly describes someone who will certainly
contribute to pilot error. I dare say, those who are eminently
familiar with how a standing wave works, or the math, use modelers.
Those who don't know how a standing wave works, or the math, are
rather flat-footed.

I'm sure it was a boon for you when the slide rule was
replaced by the electronic calculator, leaving your mind free from having to
wrestle with the true science and mathematics that is going on with your
engineering problems and just let the machine do it for you.

Fortunately, I don't pursue issues that don't survive a simple
rationality check. This can even eclipse the need of a slide rule
with a few figures sketch on a paper, and some simple computations.

If you make a
stupid mistake, don't fret, somebody will correct the parameters and re-run
the program until it fits. No need to understand maxwell, calculus, vectors,
phasors, just let the program do it all for your using the brute force
method of moments. Transistors are dirt cheap and efficient calculations are
no longer necessary. No need for analog computers. Just plug it into a
method of moments calculator and you are done.

Ah, but the introduction of this last quote is significant: the
mistake is caught. One needn't be a conductor to enjoy music. On the
other hand, a conductor is eminently qualified (if one can use the
word) to enjoy music.

What's missing with this, of course, is the part your grey matter is
supposed to do. Grey matter can take a permenent vacation.

Again, you have already revealed a thought process of recognizing a
mistake. Stupid or otherwise is merely a value to the problem, not to
the process of obtaining the solution.

I see no problem using a NEC to confirm a calculation or concept. But you
seem to advocate its exclusive use as the only authoritative, indeed,
available, tool.

I am still waiting for you to reveal something that does it better.
Simply throwing brain cells at it hasn't offered us much product here
- except when the internal logic of some proclamation fails on the
starting blocks.

Of course, I disagree and think that rraa still has room for real math and
scientific concepts and indeed there is room for NEC. However, if the choice
is given to prefer one over the other, I prefer the former because creative
design does not occur by arbitrary and random use computer problems such as
NEC, CADAM and the like, it comes from scientific method which requires
human thought.

A long and winding road, that. But cursing at air traffic because it
gets others there faster doesn't make blisters on your feet ennobling,
especially when you are as likely to arrive at the wrong destination
as any air traveler.

73's
Richard Clark, KB7QHC

On 8 Jan, 19:01, Roy Lewallen wrote:
AI4QJ wrote:

The NEC program is just a computer model, for discussion purposes only. I
think there are far too many variables in real life for the program to take
into account. It may be valuable but I am not yet convinced it is
infallible. . .

Exactly the same can be said of any of the other models we successfully
use daily. "Resistances", "impedances", "capacitances", and other
objects we routinely use in circuit analysis, are "just" models of real
objects. Likewise, the equations we use for solving all kinds of
problems, including transmission line and circuit analysis problems, are
"just" models of actual behavior. Ohm's law is "just" a model of the
relationship among V, I, and Z. The fundamental equations relating
currents and fields, Maxwell's equations, and all other equations used
in engineering are "just" models of real behavior.

*All* models are subject to intelligent use. A person modeling a real
resistor as a pure resistance at 50 GHz will get just as bad results as
a person modeling a dipole on a circuit board in a smart key in a pocket
as a free-space dipole. No model, not even a simple resistance, is
infallible -- even it can be misused by someone not having the
underlying knowledge necessary to apply it. So of course computer models
aren't infallible either.

But there are many, many real life antennas which can be modeled with
great accuracy with NEC. I use EZNEC regularly myself in my consulting
work to design antennas, and find very good correlation with anechoic
chamber pattern tests, network analyzer impedance tests, and performance
results. So do the many aerospace companies, military organizations,
space agencies, universities, research labs, domestic and international
broadcasters, and many other companies that use EZNEC daily to help
design real antennas that work as predicted. But those aren't the only
people successfully modeling with EZNEC -- a large number of amateurs
successfully use it also.

I'm not sure what it is that makes models inherently less accurate or
believable if the equations are solved with a computer than if they're
solved by some other method. Perhaps you could explain.

Roy Lewallen, W7EL

Answer why Maxwells laws must have a proviso added when they are
considered LAWS
nOT theory but law When you jump the traffic lights you have broken
the law.
Maybe your exception has a good reason but by its very use you have
invalidated the laws that you are seeking to abide by.This does not
mean that the program does not reproduce actual antennas because
numourous modifications to make sure that it does. Doing this is
tantamount to saying that Maxwells laws need the help of experts such
as your self. Seems like a good job is being done but it doesn't
change the facts. You have taken the lead offered by Maxwell but have
reserved the right to modify these laws to obtain a better computor
model.
Why was this deviation added when the discharge of a capacitor is in
no way sino-soidal?
Same goes for a inductor. Explain your deviation from the laws of
Maxwell!
As a computor programmer you never gave credence to other antenna
programs that produced tipped radiators for maximum gain for the
polararisation required? You stayed quiet to protect the sales of your
own program and thus by your silence allowed true facts to be
distorted on this newsgroup. There were many opportunities for you to
say that Eznec confirmed this finding
but you said nothing, which in itself is a insult to ham radio. You
modified Maxwell's laws and that is prohibited in mathematics if one
is to follow a mathematical law which you then invalidate.
Nothing personal intended, just a statement of facts as I see them. I
will accept factual changes if you deign to point them out in detail
so they can be confirmed or denied.
Art

On Tue, 8 Jan 2008 22:24:09 -0500, "AI4QJ" wrote:

The measurement itself will change the SWR significantly once you start
adding probes to the antenna.

Hi Dan,

I've done it with remote, fiber optic probes. If this is another
absolutism about "change" then my being on the same planet will
disturb that certainly.

73's
Richard Clark, KB7QHC