Cecil Moore wrote:
Jim Kelley wrote:
How well does your answer compare with the curves in Fig. 1 given the
number of turns in a Bugcatcher coil?

Since the curves are generated from the equation,
they should match perfectly. As a matter of fact,
I have a dot on that graph at 0.004 and 5k. The
VF is ~0.02.

Presumably there is a lower limit to the number of turns the coil would
have to have, or an upper limit to the pitch angle, in order to behave
as described - a helical sheath. Tesla coils usually have at least a
few hundred turns wound closely together, and often operate at
wavelengths considerably longer that 75 meters. One could easily argue
that 30 turns do not a Tesla coil make, in which case Eq. 32 would not
apply.

ac6xg

Jim Kelley wrote:
Presumably there is a lower limit to the number of turns the coil would
have to have, or an upper limit to the pitch angle, in order to behave
as described - a helical sheath. Tesla coils usually have at least a
few hundred turns wound closely together, and often operate at
wavelengths considerably longer that 75 meters. One could easily argue
that 30 turns do not a Tesla coil make, in which case Eq. 32 would not
apply.

Dr. Corum says that it behaves as a helical sheath when
it is electrically longer than 15 degrees (0.04WL). The
frequency doesn't matter - just the electrical length.
Of course, it takes more turns at a lower frequency
since the reactance is proportional to frequency. Eq.
32 is not concerned with the number of turns, just that
the coil is electrically longer than 15 degrees and is
therefore outside the range for which the lumped-circuit
model is valid.

Note that the title of the paper is: "RF Coils,
Helical Resonators and Voltage Magnification
by Coherent Spatial Modes". "Tesla coil" does not
even appear in the title.

A Tesla coil can be 1/4WL self-resonant all by itself.
Thus, 30 turns could easily be a Tesla coil over a
certain range of HF frequencies.

Some Tesla coils have a top hat and are operated below
their 1/4WL self-resonant frequency.

In Dr. Corum's paper, take a look at "Figure 2, A
capacitively tuned distributed resonator" and tell
us how it differs from a 75m mobile antenna with a
top hat.

The 1/4WL self-resonant frequency for a 75m Texas
Bugcatcher coil has been measured at ~6.5 MHz where
it is known to be electrically 90 degrees long. Why
does anyone have a problem with it being electrically
40 degrees long on 4 MHz?

In "Fields and Waves ...", by Ramo and Whinnery, the
analysis of a helical sheath assumes an infinitely
long helical sheath for the purpose of eliminating
reflections. Does that ring a bell? Hint: The current
on a standing-wave antenna cannot be used to measure
phase shift or delay. Yet, that is exactly what w8ji
and w7el tried to do.

I once turned my 75m mobile Texas Bugcatcher system
into a Tesla coil. I had a latch to which I could
connect the top ball of the antenna when I needed
to lean it over for more clearence. I was at a hamfest
at night and had forgotten I had the antenna latched
down. I started transmitting and my friend told me
I was drawing a two-inch arc from the tip of my antenna
to the pickup body. It was indeed "Voltage Magnification
by Coherent Spatial Modes".

http://www.ttr.com/TELSIKS2001-MASTER-1.pdf
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Cecil Moore wrote:
Jim Kelley wrote:
Presumably there is a lower limit to the number of turns the coil
would have to have, or an upper limit to the pitch angle, in order to
behave as described - a helical sheath. Tesla coils usually have at
least a few hundred turns wound closely together, and often operate at
wavelengths considerably longer that 75 meters. One could easily
argue that 30 turns do not a Tesla coil make, in which case Eq. 32
would not apply.

Dr. Corum says that it behaves as a helical sheath when
it is electrically longer than 15 degrees (0.04WL). The
frequency doesn't matter - just the electrical length.

:-) And obviously it's electrical length depends on Vp, which depends on
whether it behaves as a helical sheath.

Note that the title of the paper is: "RF Coils,
Helical Resonators and Voltage Magnification
by Coherent Spatial Modes". "Tesla coil" does not
even appear in the title.

Are you trying to imply that the paper isn't about Tesla coils?

In Dr. Corum's paper, take a look at "Figure 2, A
capacitively tuned distributed resonator" and tell
us how it differs from a 75m mobile antenna with a
top hat.

Hopefully you're not serious. Because, borrowing from Richard Clark,
it's a 'cartoon'.

The 1/4WL self-resonant frequency for a 75m Texas
Bugcatcher coil has been measured at ~6.5 MHz where
it is known to be electrically 90 degrees long. Why
does anyone have a problem with it being electrically
40 degrees long on 4 MHz?

Maybe it is. I happen to think that because of its simplicity, it's an
attractive notion. But it's not clear to me that the article applies to
coils with these parameters, and I haven't seen any (reputable)
empirical evidence to support it.

In "Fields and Waves ...", by Ramo and Whinnery, the
analysis of a helical sheath assumes an infinitely
long helical sheath for the purpose of eliminating
reflections. Does that ring a bell? Hint: The current
on a standing-wave antenna cannot be used to measure
phase shift or delay. Yet, that is exactly what w8ji
and w7el tried to do.

What do you suppose Corum^2 meant when they wrote "Experimentally, the
wave velocity and velocity factor may be measured by determining the
axial length of the standing wave pattern on the helical structure"?

I once turned my 75m mobile Texas Bugcatcher system
into a Tesla coil. I had a latch to which I could
connect the top ball of the antenna when I needed
to lean it over for more clearence. I was at a hamfest
at night and had forgotten I had the antenna latched
down. I started transmitting and my friend told me
I was drawing a two-inch arc from the tip of my antenna
to the pickup body. It was indeed "Voltage Magnification
by Coherent Spatial Modes".

No offense, but some of their work seems aimed squarely at the 'Art
Bell' crowd. Describing constructive interference as "voltage
magnification" is an example. It's as if they were publishing in the
19th century.

ac6xg

Jim Kelley wrote:
Cecil Moore wrote:

:-) And obviously it's electrical length depends on Vp, which depends on
whether it behaves as a helical sheath.

There is a test equation in the Drs. Corum paper that
indicates whether a particular coil meets the requirements
for a helical sheath or not. A 75m Texas Bugcatcher coil
meets the requirements. A small toroidal coil does not.
If you had ever actually read the article, you would know that.

Are you trying to imply that the paper isn't about Tesla coils?

No, I am asserting that the paper isn't *only* about Tesla
coils. It is about RF coils in general. Hint: "RF Coils"
are the first two words in the title.

it's a 'cartoon'.

Actually, it's a graphic diagram of a Tesla coil with
a top hat or a 75m Texas Bugcatcher with a top hat.
There is no conceptual difference in the diagrams.
The only difference is that we hams avoid arcing
by running reduced power compared to Tesla coils.

But it's not clear to me that the article applies to
coils with these parameters, and I haven't seen any (reputable)
empirical evidence to support it.

Then I would suggest that you read the article. There is
a test for validity on page 4. Let's see if you can
use your "expertise" to locate it.

Actually, I will make it easy for you. Here is an EXCEL
file that I generated based on the Corum paper which
includes the test for validity in red.

http://www.w5dxp.com/CoilZ0VF.xls

What do you suppose Corum^2 meant when they wrote "Experimentally, the
wave velocity and velocity factor may be measured by determining the
axial length of the standing wave pattern on the helical structure"?

EZNEC can do that for us since EZNEC will display the
current in each segment. I have been explaining that
for five+ years. Have you not looked at any of the
EZNEC results I have posted or have you just not been
able to comprehend them? It can also be done, as it
was for Tesla coils, by measuring the electric field
along the coil.

Describing constructive interference as "voltage
magnification" is an example.

Well, don't blame me. Drs. Corum think they are the
same thing, just using different words. I understand
what they mean. Obviously, the highest "voltage
magnification" occurs at the point where the forward
and reflected voltages are in phase, i.e. constructive
interference. If you disagree, let's hear your theory
on the subject.

Jim, you seem to object to anyone, including Drs. Corum,
choosing slightly different words from the ones you would
choose. Are you actually omniscient?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On May 7, 12:43*pm, Cecil Moore wrote:
Jim Kelley wrote:
Cecil Moore wrote:
:-) And obviously it's electrical length depends on Vp, which depends on
whether it behaves as a helical sheath.

There is a test equation in the Drs. Corum paper that
indicates whether a particular coil meets the requirements
for a helical sheath or not. A 75m Texas Bugcatcher coil
meets the requirements. A small toroidal coil does not.
If you had ever actually read the article, you would know that.

Are you trying to imply that the paper isn't about Tesla coils?

No, I am asserting that the paper isn't *only* about Tesla
coils. It is about RF coils in general. Hint: "RF Coils"
are the first two words in the title.

it's a 'cartoon'.

Actually, it's a graphic diagram of a Tesla coil with
a top hat or a 75m Texas Bugcatcher with a top hat.
There is no conceptual difference in the diagrams.
The only difference is that we hams avoid arcing
by running reduced power compared to Tesla coils.

But it's not clear to me that the article applies to
coils with these parameters, and I haven't seen any (reputable)
empirical evidence to support it.

Then I would suggest that you read the article. There is
a test for validity on page 4. Let's see if you can
use your "expertise" to locate it.

Actually, I will make it easy for you. Here is an EXCEL
file that I generated based on the Corum paper which
includes the test for validity in red.

http://www.w5dxp.com/CoilZ0VF.xls

What do you suppose Corum^2 meant when they wrote "Experimentally, the
wave velocity and velocity factor may be measured by determining the
axial length of the standing wave pattern on the helical structure"?

EZNEC can do that for us since EZNEC will display the
current in each segment. I have been explaining that
for five+ years. Have you not looked at any of the
EZNEC results I have posted or have you just not been
able to comprehend them? It can also be done, as it
was for Tesla coils, by measuring the electric field
along the coil.

Describing constructive interference as "voltage
magnification" is an example.

Well, don't blame me. Drs. Corum think they are the
same thing, just using different words. I understand
what they mean. Obviously, the highest "voltage
magnification" occurs at the point where the forward
and reflected voltages are in phase, i.e. constructive
interference. If you disagree, let's hear your theory
on the subject.

Jim, you seem to object to anyone, including Drs. Corum,
choosing slightly different words from the ones you would
choose. Are you actually omniscient?
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

But Cecil the Bugcatcher does not conform with Maxwell's laws and
EZNEC has no provision to explain to you when you deviate from
Maxwell's laws with invalid designs
All Eznec does is to apply the best math available via approximations
to what you direct it to do. It is not able to inform you or change
the input so it does conform to Maxwell's equations. A typical
description of garbage in garbage out with respect to a rigourous
examination for accuracy. So to refer to Eznec as an authority of
accuracy is the same as an author who details all that agree with him
at the outset. This is not
to say that EZNEC is not a useful tool or not close in it's
approximations. It is a tool that matches the requirements of the
average ham and the education given him.
Art

Art Unwin wrote:
But Cecil the Bugcatcher does not conform with Maxwell's laws

In what way does a Bugcatcher not conform with
Maxwell's equations? In "Fields and Waves ...",
Ramo and Whinnery give the actual Maxwell equations
for a loading coil.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On May 7, 2:31*pm, Cecil Moore wrote:
Art Unwin wrote:
But Cecil the Bugcatcher does not conform with Maxwell's laws

In what way does a Bugcatcher not conform with
Maxwell's equations? In "Fields and Waves ...",
Ramo and Whinnery give the actual Maxwell equations
for a loading coil.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

I looked up the references and here are my comments
1 a helical is not in a state of equilibrium
2 A radiator that is not a WL or multiple thereof is not in
equilibrium
3 It refered to boundary laws and then mis used them.
4 The beginning was littered with "assume" and terms of" Aproximation"
5 It then went on to change the configuration of a helix to a
configuration that
he thinks he has solved when using the approximations. He also assumed
that the speed of light could be exceeded
6 I saw no evidence of accounting for the flux in a clockwise versus a
counterclockwise action tho apparently he made assumptions that
circular motion was zero.
7Frankly Cecil he knew what answer was to be accepted by reviwing
Krauss's work and devised his mathematics accordingly
8 Krauss's work was on the subject of a helical that was not in
equilibrium which thus forced him to include the helix angle which
also is nowhere to be seen in Maxwells laws.
The reference he used is not credible but name dropping of those that
he agrees with
is a confidence builder for those you judge plagurism as being with co
believers.
This is the same as those who defined light as a wave where academics
followed
with smiles and without question.
It all still comes back to the fact that in boundary laws the contents
must be in equilibrium and nothing about your antennamatches that
requirement
Sorry about that Cecil No harm meant
Art

Cecil Moore wrote:

Are you actually omniscient?

I know bullcrap when I see it.

ac6xg

Jim Kelley wrote:
Cecil Moore wrote:
Are you actually omniscient?

I know bullcrap when I see it.

So you have the omniscient gift of recognizing
bullcrap just by observing it with absolutely
no technical rebuttal and no possibility of
your being conceptually wrong? Exactly what
is it about Drs. Corum paper that you don't
understand?

Jim, if you want to retain one iota of respect,
please present a technical argument to refute
what I have asserted. Your gut feelings of
"bullcrap" are completely irrelevant. How about
your equations that prove Dr. Corums's IEEE
paper's equations are wrong?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Cecil Moore wrote:
Jim, if you want to retain one iota of respect,
please present a technical argument to refute
what I have asserted.

Sorry OM, you haven't proven your argument. You've provided no
substantive data, and have shown nothing that indicates that this coil
would conduct surface waves or behave as a tightly wound slow wave
structure. It that's a Tesla coil, then so is any other coil. I'm just
stating the obvious here.

ac6xg