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steveeh131047 wrote:

Cecil: that's a VERY significant result. If I feed the dimensions of
W8JI's coil into Equation 32 in the Corum Bros paper it predicts an
axial Velocity Factor of 0.033. That would equate to a time delay of
24.7nS across the 10" long coil !!!!

Regards,
Steve G3TXQ

Let's see how well the principles involved are understood.

What is the delay through a physically very small toroidal coil with the
same inductance as the solenoidal coil? Why?

Roy Lewallen, W7EL

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Jim Kelley wrote:
steveeh131047 wrote:
Cecil: that's a VERY significant result. If I feed the dimensions of
W8JI's coil into Equation 32 in the Corum Bros paper it predicts an
axial Velocity Factor of 0.033. That would equate to a time delay of
24.7nS across the 10" long coil !!!!

You're right. The numbers are amazingly close - almost as if his
'experimental apparatus' had calculated the result rather than measure it.

Why do you say "approximately 25 nS" and 24.7 nS are
amazingly close? "Approximately 25 nS" might include
an unknown measurement inaccuracy.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Art Unwin wrote:
Cecil, reference you comment that a straight wire does NOT have a
characteristic impedance, this is one place where you misunderstanding
things.

That quote was not mine, Art, it was Roy's. My argument
is that since free space itself has a characteristic
impedance then a wire in free space must also have
a characteristic impedance and act as a waveguide
of sorts.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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On Apr 23, 1:34*pm, "Tom Donaly" wrote:
steveeh131047 wrote:
On Apr 23, 4:42 pm, Jim Kelley wrote:
For a more quantitative illustration of how distributed reactance in
transmission lines causes delay seehttp://www.rhombus-ind.com/dlcat/app1_pas.pdf

73, ac6xg

Jim, thanks for the reference.

Perhaps I should have expressed myself more clearly. What I've not
seen, for example, is a lumped-element analysis which takes just the
coil dimensions as input, and predicts theoretically - without a lot
of empirical "tweaking" - the reactance at a particular frequency;
particularly a frequency close to self-resonance. There may be one out
there, but I've not yet found it!

In contrast, the ON4AA calculator - based on Corums' transmission-line
analysis - does just that, and produces results which seem to match
well the EZNEC modelling results.

Regards,
Steve G3TXQ

EZNEC is a mathematical model just as the transmission line model is
a model. EZNEC doesn't use a transmission line
analog in order to reach its conclusions. If you're really interested
in this subject, you have to read Schelkunoff and others who did the
research on this years ago. A big, honking loading coil doesn't
act much like a lumped component. It makes a pretty shabby transmission
line, too. If you want to understand it, you have to study
electromagnetics and approach it from that standpoint, which may not
be easy. Finally, a modest question: if you have EZNEC, why would you
be wasting time with something inferior? The gold standard is the gold
standard. Or are you on some philosophical quest, like Cecil?
73,
Tom Donaly, KA6RUH

Tom,TomTom.
Eznec DOES use the transmission line analogy because like Gauss it
uses an abitrary border where the contents are in equilibriumn or in a
state of balance where all forces are accounted for when a time
varying field is applied. The same goes for a transmission line where
the radiation factor is also accounted for.
The radiation force losses are accounted for by the depreciating
impedance with time
which is also shown by the deprecating amplitude of occilation where
each period loss of amplitude represents radiation energy. If the
amplitude showed no change then you have a tank circuit without
friction or other losses. No losses means perpetual motion and vica
versa. If on Earth friction is always there which is also equal to the
energy for an acceleration of a particle. On the reverse side, a
deccelerating force on a particle represents kinetic energy as opposed
to the potential energy supplied for radiation where the product is
seen as light. As with a light bulb radiant heat is what we know as
light. Just classical physics no less
Art

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On Apr 23, 7:34*pm, "Tom Donaly" wrote:
Finally, a modest question: if you have EZNEC, why would you
be wasting time with something inferior? The gold standard is the gold
standard. Or are you on some philosophical quest, like Cecil?

Tom,

Yes I have EZNEC and recognise what a great tool it is. Its
predictions were the benchmark against which I tested the various coil
models I read about, and no-one has yet suggested that it can't be
trusted for modelling a helix.

I'm not on some "philosophical quest" - I'm just an old, retired, guy
who still likes learning and wants to understand more about how things
work; I hope that never leaves me! I stumbled on this discussion quite
by chance and tried to understand the various "positions" being taken.
Perhaps I'm over-simplifying, but it seemed to me there was a group
who favoured the transmission-line model and a group against it. I've
tried dispassionately to understand the various arguments and to form
my own conclusions.

Now here's my problem:

* The results I get using a model based on transmission-line analysis
are very close to my EZNEC predictions - not perfect, but way better
than any lumped-element analysis results
* I don't see quantitative, non-empirical, arguments being put forward
to support lumped-element analysis
* I see numeric arguments being put forward by Cecil to support a
transmission-line approach - they look convincing to me and, although
I see a lot of unpleasant personal attacks on him, I don't see any
scientific challenge to his figures
* On the other hand I see folk whose work I rate highly, seemingly
willfully to misunderstand some of the points which Cecil puts forward

Please don't think I'm trying to defend Cecil - I wouldn't be so
presumptuous, and anyway he's old enough to look after himself! I'm
just trying to understand why, what seems to me to be such a
persuasive argument, generates such opposition. Either there's some
glaring technical error here which I haven't yet spotted, or perhaps
there's a long "history" between various "personalities" of which I'm
ignorant?

Still confused,

Steve G3TXQ

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steveeh131047 wrote:
In contrast, the ON4AA calculator - based on Corums' transmission-line
analysis - does just that, and produces results which seem to match
well the EZNEC modelling results.

I don't see where that calculator gives the Z0 and VF
of the loading coil so I have generated an EXCEL file
that gives those two parameters based on the formulas
in Dr. Corum's IEEE paper. Note that 75m loading coils
are slow-wave devices with a VF in the neighborhood
of 0.02 for a Texas Bugcatcher coil or 0.033 for w8ji's
skinny 10 TPI, 2" diameter coil.

http://www.w5dxp.com/CoilZ0VF.xls
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

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Cecil Moore wrote:
Jim Kelley wrote:
steveeh131047 wrote:
Cecil: that's a VERY significant result. If I feed the dimensions of
W8JI's coil into Equation 32 in the Corum Bros paper it predicts an
axial Velocity Factor of 0.033. That would equate to a time delay of
24.7nS across the 10" long coil !!!!

You're right. The numbers are amazingly close - almost as if his
'experimental apparatus' had calculated the result rather than measure
it.

Why do you say "approximately 25 nS" and 24.7 nS are
amazingly close?

I was being facetious.

"Approximately 25 nS" might include
an unknown measurement inaccuracy.

There's that, and as any good dry labber knows, it's a dead giveaway to
report a precision greater than one can actually measure. :-)

73, ac6xg

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Tom Donaly wrote:
Finally, a modest question: if you have EZNEC, why would you
be wasting time with something inferior? The gold standard is the gold
standard.
Perhaps more the silver or electrum standard.
EZNEC doesn't do dielectric loading, for instance. (unless you get the
Nec4 engine from Roy)
And, it's a MoM code, so things not well represented by collections of
wires aren't necessarily modeled well.

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On Apr 23, 2:29*pm, Roy Lewallen wrote:
* steveeh131047 wrote:
Cecil: that's a VERY significant result. If I feed the dimensions of
W8JI's coil into Equation 32 in the Corum Bros paper it predicts an
axial Velocity Factor of 0.033. That would equate to a time delay of
24.7nS across the 10" long coil !!!!

Regards,
Steve G3TXQ

Let's see how well the principles involved are understood.

What is the delay through a physically very small toroidal coil with the
same inductance as the solenoidal coil? Why?

Roy Lewallen, W7EL

A toroidal coil retains magnetism via hysteresis versus zero
hysteresis for a coil made of a diamagnetic material. A coil is in
equilibrium because all forces are accounted for
over one or more periods. A toroidal coil is not in equilibrium
because the energy that provides the hysterisis happens only once per
unit of time where as for equilibrium that same energy is provided for
every period and cancelled by same.
If a unit of energy is supplied to a radiator in equilibrium then the
unit of energy must be added to or increased to represent the
hysteresis lossesof the toroid The ratio of the original unit of
energy will represent the difference in time or delay required to
represent balance between the two. The above is based on a coil in the
medium of air and not magnetic core as the term "solenoid" suggests.
Roy doesn't see my posts either so somebody else has to pass this on.
Art

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Roy Lewallen wrote:
steveeh131047 wrote:

Cecil: that's a VERY significant result. If I feed the dimensions of
W8JI's coil into Equation 32 in the Corum Bros paper it predicts an
axial Velocity Factor of 0.033. That would equate to a time delay of
24.7nS across the 10" long coil !!!!

Regards,
Steve G3TXQ

Let's see how well the principles involved are understood.

What is the delay through a physically very small toroidal coil with the
same inductance as the solenoidal coil? Why?
As in a coil wound on a toroidal magnetic core? or a air cored solenoid
bent in a circle?