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