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wrote:
1) Cecil: I believe I understand how the Corum transmission line model
accounts nicely for the reduced current at the top of the coil. Does
it also account for the slight increase in current a short way from
the bottom?

I will say, apparently not. The Corum equations are stated
to be plus or minus 10 percent. The current increase in the
coil appears to be about 10%.

Typically, the current increases from a normalized 1.0 at
the bottom of the coil to about 1.1 close to the middle
and then falls off from there to 0.8 or so. Empirically,
it seems that one can take the rise in current, i.e. 0.1,
from the bottom of the coil to the middle of the coil and
subtract that value from the current at the top of the
coil to compensate mathematically for the curve not being
a pure cosine curve because of end-effects of the coil.

Example: Given a coil with a current of 1.0 at the bottom,
1.1 at the midpoint, and 0.8 at the top. It appears that
the ARCCOS(0.8-0.1) = ARCCOS(0.7) may yield an approximation
for the delay in degrees through the coil, i.e. ARCCOS(0.7)
equals ~45 degrees.

This makes sense to me since the current profile through
the coil is obviously not a pure cosine wave. It is obviously
distorted by the turn-to-turn coupling of the fields. But
just as obviously, this is an empirical curve-fitting technique
as used by Drs. Corum.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Jim Kelley wrote:
Personally, I think some actual measurements would help enormously in
formulating/evaluating a model. Otherwise all we have is hand waving
and proselytizing.

I have reported my 25 nS actual measurements
using my dual-trace 100 MHz o'scope.

I assume that your physics lab has the ability
to perform such a simple measurement. May I
suggest that you simply perform the experiment
and report the results - or get one of your
students to do it.

I suspect that others have done such experiments,
measured what I measured, and are withholding the
results for obvious reasons.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Art wrote:
"Thus Kraus`s antennas are not in equilibrium and thus deviated away
from Maxwell`s laws."

Impossible.

Maxwell`s laws are all that is nscessary and sufficient to describe
radiation from any antenna.

On page 37 of Kraus & Marthelka`s "Antennas for All Applications" one
can read:

"Although a charge moving with uniform velocity along a sreaighr
conductor does not radiate, a charge moving back and forth in simple
harmonic motion along the conductor is subject to aceleration (and
deceleration) and radiates."

To better understand Maxwell and radiation, I recommend
"Radio-Electronic Transmission Fundamentals" by B. Whitfield Griffith,
Jr (now reprinted by Scitech Publishing Inc..

See "Directive Patterns Over Real Groind" in the "ARRL Antenna Book"
for how rays combine to make a pattern.

Best regards, Richard Harrison, KB5WZI

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Cecil Moore wrote:

I assume that your physics lab has the ability
to perform such a simple measurement. May I
suggest that you simply perform the experiment
and report the results - or get one of your
students to do it.

I'm not the one hawking the tonic, Cecil. But send me the coil, and
I'll happily test it, report back, and return it to you after.

ac6xg

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Jim,

I don't have the measurement capabilities that some of you folk have,
so I'm just using EZNEC as my "experimental equipment". I'm being
assured that it's representative of what I would see "for real", and
it's easier pressing keys than building new test equipment :) Are you
suggesting that "real world" current measurements would be
significantly different than the EZNEC predictions?

I gather from your response that you feel the Corum model is
inappropriate for the "bugcatcher", but you're not advocating an
alternative? That's the part I struggle with - if a model gets close
(albeit not perfect) to predicting "real world" performance, and
there's no other alternative being put forward, I don't see the reason
for rejecting it so forcefully?

73,
Steve G3TXQ


On May 8, 8:21*pm, Jim Kelley wrote

Hi Steve,

Personally, I think some actual measurements would help enormously in
formulating/evaluating a model. *Otherwise all we have is hand waving
and proselytizing.

73, ac6xg

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Hi Tom,

Well I don't know as much about antennas as I would like :)

I take your response to mean that you think only MoM can model a
"bugcatcher" coil accurately, and that you are dismissing the apparent
accuracy with which the Corum model predicts some coil performance
parameters?

I don't subscribe to the Corum-Moore "label". The genesis of the
transmission-line approach to coil analysis seems to go back a long
way from what I've read, and I don't think Cecil deserves or claims
any recognition for it. Besides the method might suddenly begin to
appear in all the text books - think how you'd feel then if it
included his name;)

Steve G3TXQ



On May 8, 10:44*pm, "Tom Donaly" wrote:

You know quite a bit about antennas, Steve, so you should know the
answer to the following:
1. Mathematically, what does MoM do?
2. Why would anyone use MoM if there were a set of symbolic equations
that would work just as well?
3. When are we going to see the Corum-Moore method in the textbooks?
73,
Tom Donaly, KA6RUH

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"Art Unwin" wrote in message
...
Atta boy,
Keep using that slide rule from your school days, there is absolutely
no reason why you should change and update

actually, i think i still have one or two of those laying around here
somewhere.

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Art Unwin wrote:

Atta boy,
Keep using that slide rule from your school days, there is absolutely
no reason why you should change and update

Art

Your answers are just as wrong with a slide rule, an HP15C, Fortran IV
on a 360/65, C on a 64 bit AMD or anything else you can find.

And denigrating slide rules is silly. Most of the world that surrounds
you was calculated with a slide rule's resolution. When used properly
they give answers that are as accurate as is needed for engineering.

You obviously have no clue as to what it takes to do engineering
calculations.

Richard, if I used terms improperly, I ask forgiveness.

tom
K0TAR