K1TTT wrote:

you can have a spherically symetric static electric field as is easily
shown by gauss's law. but in order to have 'radiation' (implying em
wave propagating through space) you must have movement of some kind,
that immediately removes the spherical symetry by creating an axis
defined by the direction of movement. this is why even the
theoretical infinitesimal dipole still produces a doughnut shaped
field in free space.

That's a very clever qualitative explanation of, for, instance, why
isotropic antennas cannot exist. (without resorting to things like the
Hairy Ball Theorem, which is great for explaining polarization)

On 5/12/2010 2:26 PM, Art Unwin wrote:
the element resonance. I wouldn't be surprised if the next generation
moved away from the present
algerithms and rely purely on number crunching to obtain systems in
equilibrium. I personaly believe

WTF? Number crunching. Algorithms. Treated as separable.

What an astonishing idea.

tom
K0TAR

On 5/12/2010 3:16 PM, K7ITM wrote:
On May 12, 12:58 pm, wrote:
...
To see what I mean, try entering D=10mm, N=10, len.=20mm,
d=1mm, and check what C(L,p) is reported. Now try changing D in 1mm
increments up and down. OK, so I don't trust the reported C(L,p)
value, ...

OK, it also helps to RTFM. The text down below the inductance
calculator explains about this some. Also, I should have said that
you need to set the "design frequency" to something low (e.g. 10MHz)
to see the effect. However, the text suggests that C(L,p) value would
be larger than expected...and I've also seen it for some coils to be
considerably smaller. So I end up, then, not finding the lumped model
including C(L,p) being very useful for the things I do, where I want a
model that gives me _decent_ agreement over a broader frequency range,
rather than perhaps more exact agreement over a very limited frequency
range (as happens when the reported value of C(L,p) gets very large;
try "design frequency" = 1MHz for that coil).

Cheers,
Tom



You are amusing in an engineer unix geek kind of way. Just the kind of
thing that annoyed my ex.

tom
K0TAR

On 5/12/2010 3:49 PM, Art Unwin wrote:

Again I state. If you are using Maxwell equations you cannot stray
from the units supplied.Hams do not follow the rules with respect

"stray from the units"? How can one stray? All the units we are
talking about here are freely convertible.

Is this now religion?

tom
K0TAR

On 5/12/2010 2:26 PM, Art Unwin wrote:
the element resonance. I wouldn't be surprised if the next generation
moved away from the present
algerithms and rely purely on number crunching to obtain systems in
equilibrium. I personaly believe

WTF? Number crunching. Algorithms. Treated as separable.

What an astonishing idea.

Hi Tom,

It would have been called "coin flipping" by the Indus valley people
of Mehrgarh if someone had had the foresight to invent pockets that
could hold a dime. Unfortunately, it would be another 6000 years
before the first coins were struck. Instead, they flipped mud tablets
performing the world's first "binary search:" Is this the solution?

They solved a lot of the state-of-the-art electromagnetics problems
back then within two to three tosses. Few disputed their claims (mud
is a form of ground) or challenged their accuracies of -50% to +100%
for water conductivity (will the Indus overflow this season? - an
equilibrium problem of the first order).

It would be that same 6000 years later before algerithms would advance
to the point where Archimedes could model equilibrium of water (note
its pre-eminence again) in a bath tub. This improved accuracies to
-50% to +100% once again (the ancient work had been lost in a flood of
the Indus and only recently un-earthed).

Little might have changed since, except that the fluorescence of
newsgroup gurus have enlightened modern civilization with advances in
accuracies now verging on ±6dB where the pre-eminence of water has
been overthrown in favor of photon-stream control. The binary search
that was formerly the cornerstone of modeling has been replaced with
the unary declaration that is self-proven by having been uttered (or
posted to a group that has a vague resemblance to the topic). Hence,
the inaccuracies of coins has been wholly removed to yield perfect
understanding (within ±6dB, of course).

73's
Richard Clark, KB7QHC

On Wed, 12 May 2010 22:06:49 -0700, Richard Clark
wrote:

Little might have changed since, except that the fluorescence of
newsgroup gurus have enlightened modern civilization with advances in
accuracies now verging on ±6dB where the pre-eminence of water has
been overthrown in favor of photon-stream control. The binary search
that was formerly the cornerstone of modeling has been replaced with
the unary declaration that is self-proven by having been uttered (or
posted to a group that has a vague resemblance to the topic). Hence,
the inaccuracies of coins has been wholly removed to yield perfect
understanding (within ±6dB, of course).

That's a fair description of the digital part of antenna design, but
prior to the invention of computing, all such antennas were analog in
nature. The ancient pagans, that found the ideal size and shape of
trees necessary to obtain the attention of the gods were using analog
cut-n-try techniques. Given sufficient time and trees, the design was
eventually optimized.

Somewhat later, the Romans and Greeks discovered that the E and H
directions, the ratio of which was defined by the golden section.
Again, this was not a digital model, but determined with analog
techniques. Once the ratios were accurately determined, the resultant
telephone pole like structure could be used for everything from art to
executions. One of the reasons the Roman Empire lasted so long is
that they didn't have a symbol for zero, thus avoiding the divide by
zero problem. In any case, the design was demonstratively functions,
as installing the design on a hill top, would invariably draw
lightning.

After about a millennium, people started running out of hilltops and
tall trees, and found it more convenient to produce their own
lightning. The previously functional structures were wrapped in
metallic wires and waved around a magnet, thus resulting in home made
lightning. Calculations were again attempted, but since the zero had
been invented, none of the math would work. Once again, civilization
rested on the tried and true analog method of cut-n-try.

Modern antenna design followed the same analog patterns. With the aid
of the analog slide rule, accuracy could be improved to about 2
significant figures. That worked fine until the invention of the
digital computer. Suddenly, 2 sig fig was not enough. The digital
computer could calculate to amazing levels of precision and suddenly
everything had to conform to this standard. Instead of "cut to fit"
and "tweak and tune" it was now necessary to justify the cost of the
new digital computers with absurd accuracies. Good enough lasted only
until the next model computer.

So, here we are, debating the relative merits of the umpteenth decimal
place, splitting hairs multiple times, and digitally modeling to
quantum levels. While useful for justifying the computers, the
resultant antennas look roughly the same as the old cut-n-try models
designed with an analog slide rule.

Whatever your vision of modeling history, one historical observation
remains constant. One must always suffer before enlightenment and
this newsgroup provides that function.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Wed, 12 May 2010 23:05:23 -0700, Jeff Liebermann
wrote:

Whatever your vision of modeling history, one historical observation
remains constant. One must always suffer before enlightenment and
this newsgroup provides that function.

The Aztecs had a far more accurate model of the calendar than Mini NEC
has for antennas.

As for suffering, the Aztecs also experimented with open-heart surgery
- of a sort. Unfortunately like Art, they never perfected nor did
they care about the recovery phase. There were always plenty of
models (aka prisoners) to replace failures. If you could carve, you
had proven your point and a party generally followed.

A superior technology (conquistadors) took over rapidly. The success
rate of open-heart surgery didn't improve, but the population of
models was enlarged to include All of South America (less Brazil where
Portuguese total-heart bypass was attempted), greater Central America,
and portions of North America.

Basically, we have a theory here that has gutted the heart of RF from
electromagnetics to transplant it with magnetics using a broken
stopwatch.

73's
Richard Clark, KB7QHC

K1TTT wrote:
On May 11, 8:30 pm, Art Unwin wrote:
When an array is
in equilibrium then Maxwell's equations are exact.

maxwell's equations are ALWAYS exact, it is digital models that are
inexact and have limitations due to the approximations made and the
numeric representations used.

Inexactness of the solution isn't because the method is digital. The
field equations solved by the digital methods simply can't be solved by
other methods, except for a relatively few very simple cases. Many
non-digital methods were developed over the years before high speed
computers to arrive at various approximate solutions, but all have
shortcomings. For example, I have a thick file of papers devoted to the
apparently simple problem of finding the input impedance of a dipole of
arbitrary length and diameter. Even that can't be solved in closed form.
Solution by digital methods is vastly superior, and is capable of giving
much more accurate results, than solution by any known method.

Roy Lewallen, W7EL

Jim Lux wrote:
Art Unwin wrote:
On May 11, 4:02 pm, Jim Lux wrote:


Again you preach but obviously you are not qualified to address the
issue.

Opinions on qualification differ.

AO pro by Beasley consistently produces an array in equilibrium when
the optimizer is used as well as including the presence of particles
dictated by Gauss., The program is of Minninec foundation which
obviously does not require the patch work aproach that NEC has.

Interestingly, MININEC uses the very same method of moments that NEC
does, but, because it's "mini" it has substantial limitations. It was
developed to fit in small microcomputers of the day. I'd hardly call
NEC "patchwork". The two programs do use different formulations for the
basis function defining the current on the segment.
. . .

That difference in choice of basis functions has profound effects on the
limitations and quirks of the program, however -- they're quite
different for NEC and MININEC. MININEC is, in fact, able to do some
things that NEC can't, despite its simpler formulation.

Roy Lewallen, W7EL

On Wed, 12 May 2010 23:05:23 -0700, Jeff Liebermann wrote:
One must always suffer before enlightenment
and this newsgroup provides that function.


YIPES!!! A new usenet sig !!!