"Cecil Moore" wrote in message
...
John KD5YI wrote:

(snip)

A 75m Texas Bugcatcher coil is an example of the type
of air-core loading coil that I am talking about. It's
about 6" diameter, 4 tpi, and 6.75" long. Dr. Corum's
equations indicate a VF of ~0.02 for such a coil used
on 4 MHz which makes it electrically about 28 degrees
long.

You appear to be trying to make lumped components into distributed
components to suit your arguments. Shame on you.

No, just the opposite. I am trying to keep others
from considering large air-core distributed network
loading coils to be lumped components (which they
obviously are not). Dr. Corum says any coil electrically
longer than 15 degrees (0.04WL) needs to be treated
as a distrubuted network, not as a lumped-circuit.


Wake up, Cecil. The 6.75 inch long Texas Bugcatcher coil falls into the
lumped component category (being only .002WL at 75m).

John

John KD5YI wrote:
Wake up, Cecil. The 6.75 inch long Texas Bugcatcher coil falls into the
lumped component category (being only .002WL at 75m).

Sorry John, we are not talking about *physical* length
- we are talking about *electrical* length which, like
a piece of coax, depends upon the velocity factor. The
velocity factor for a Texas Bugcatcher coil is ~0.02.

6.75"/0.02=337.5", 337.5"/12 = 28 feet,
28'/(246'/lamda) = 0.114 WL

Thus a 75m Texas Bugcatcher loading coil is electrically
about 41 degrees long at 4 MHz. Hint: It is a slow-wave
structure described in "Fields and Waves ..." by
Ramo, Whinnery, and Van Duzer, 3rd edition, page 476.

The equation for the approximate velocity factor for
an RF coil meeting the specified physical conditions
is given in equation 32 on page 4 of:

http://www.ttr.com/TELSIKS2001-MASTER-1.pdf

Fig. 1 gives the VF for various diameter/wavelength
ratios and turns/wavelength. Here's how to determine
the VF from the Fig. 1 graph.

For the coil in question, calculate the
diameter/wavelength ratio and plot it on the x axis.

The diameter/wavelength ratio for the Texas Bugcatcher
is ~0.5/246 = 0.002, i.e. 2x10^-3 on the graph.

For the coil in question, calculate the
turns/wavelength ratio and select the proper curve.

The turns/wavelength ratio for the Texas Bugcatcher
is 4tpi*12*246' = 11,800, i.e. slightly to the left
of the left-most 10k curve.

That puts the Texas Bugcatcher squarely in the slow-
wave category with a velocity factor of ~0.02.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

"Cecil Moore" wrote in message
...
John KD5YI wrote:
Wake up, Cecil. The 6.75 inch long Texas Bugcatcher coil falls into the
lumped component category (being only .002WL at 75m).

Sorry John, we are not talking about *physical* length
- we are talking about *electrical* length which, like
a piece of coax, depends upon the velocity factor. The
velocity factor for a Texas Bugcatcher coil is ~0.02.


I think any inductor with the same inductance, Q, and self-resonant
frequency will give the same velocity factor and delay as your Bugcatcher. I
don't think that neither the coil nor the "stinger" knows how the inductor
is constructed. I think the slight difference due to radiation from the
Bugcatcher can be ignored since it is small physically.

I think you will measure the same velocity factor with any other coil that
gives the same inductance, Q, and self-resonant frequency regardless of
whether it is wound on air, a toroid core, a ferrite rod, or a beer can. If
so, then that coil will be a distributed component according to you because
it meets the electrical requirements.

John

John KD5YI wrote:
I think any inductor with the same inductance, Q, and self-resonant
frequency will give the same velocity factor and delay as your
Bugcatcher.

That may or may not be true - I don't have an
opinion one way or another - and it is NOT part
of my argument. My argument deals only with
75m Texas Bugcatcher coils and other large air-
core loading coils used on 75m.

My argument is that the velocity factor of a 75m
Texas Bugcatcher coil is ~0.02, occupies ~41
electrical degrees on 4 MHz, and exhibits a
delay of ~28 nS through the coil. That is my only
argument. I am not interested in diversions from
that argument.

My argument also includes the 100 turn, 10 inch long,
2 inch diameter coil that w8ji used for his 3 nS delay
"measurements". If he had used traveling wave current
for the measurement, he would have measured approximately
25 nS.

Maxwell's equations for slow-wave structures (like
a 75m Texas Bugcatcher loading coil) are given in
"Fields and Waves ...", by Ramo and Whinnery:
pages 467-479 in the 2nd edition. This is one of
the references in the Corum IEEE paper.

What do you make of Roy's (w7el) statement at:

http://www.w8ji.com/agreeing_measurements.htm

"As described in my posting on rraa of November 11,
the inductor 'replaces' about 33 electrical degrees
of the antenna."
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

"Cecil Moore" wrote in message
...
John KD5YI wrote:
I think any inductor with the same inductance, Q, and self-resonant
frequency will give the same velocity factor and delay as your
Bugcatcher.

That may or may not be true - I don't have an
opinion one way or another - and it is NOT part
of my argument. My argument deals only with
75m Texas Bugcatcher coils and other large air-
core loading coils used on 75m.

If it IS true, then the point I tried to make that you are making a
distributed component from a lumped one is valid. That's what caused me to
object to your earlier post.

And, by the way, I feel the same way you do except about people who are
afraid to consider lumped components. Perhaps they do not have what it takes
to judge when a proper substitution can be made.

John

John KD5YI wrote:

"Cecil Moore" wrote in message
...
John KD5YI wrote:
I think any inductor with the same inductance, Q, and self-resonant
frequency will give the same velocity factor and delay as your
Bugcatcher.

That may or may not be true - I don't have an
opinion one way or another - and it is NOT part
of my argument. My argument deals only with
75m Texas Bugcatcher coils and other large air-
core loading coils used on 75m.

If it IS true, then the point I tried to make that you are making a
distributed component from a lumped one is valid. That's what caused me
to object to your earlier post.

And, by the way, I feel the same way you do except about people who are
afraid to consider lumped components. Perhaps they do not have what it
takes to judge when a proper substitution can be made.

John

Anyone can take a small inductor, such as Roy described, and try to
analyze all the currents and such in it using a distributed model at low
or moderate frequencies. If they do, though, they'll just come up with
what they'd have come up with treating their small inductor as a
lumped element. Cecil has distributed elements on the brain. It's what
comes of falling in love with your own theories.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Anyone can take a small inductor, such as Roy described, and try to
analyze all the currents and such in it using a distributed model at low
or moderate frequencies. If they do, though, they'll just come up with
what they'd have come up with treating their small inductor as a
lumped element.

One wonders why some people insist on a "small
toroidal inductor" which obviously agrees with
the lumped-circuit model instead of analyzing
a 75m Texas Bugcatcher loading coil which just
as obviously violates the presuppositions of
the lumped-circuit model.

Instead of the "small toroidal inductor", let's
discuss w8ji's 100 turn, 2" diameter, 10 inch
long air-core coil through which he measured that
ridiculous 3 nS delay after which w7el posted some
"agreeing measurements" while asserting that the
electrical length of the coil was 33 degrees.

Does anyone else realize that 33 degrees in 3 nS
at 4 MHz is faster than light speed?

Are you guys so afraid of losing face that you
are willing to post technical falsehoods?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

John KD5YI wrote:
If it IS true, then the point I tried to make that you are making a
distributed component from a lumped one is valid. That's what caused me
to object to your earlier post.

There are coils for which the lumped-circuit model
is valid.

There are coils for which the lumped-circuit model
is not valid.

I am only interested in discussing coils for which
the lumped-circuit model is invalid, i.e. coils that
are electrically longer than 15 degrees, e.g. a large
air-core 75m Texas Bugcatcher coil which measures
about 40 degrees on 4 MHz.

I honestly don't know if the lumped-circuit model
works for 70 uH toroidal coils. I do know it doesn't
work for a 75m Texas Bugcatcher coil.

The people who insist on analyzing tiny toroidal coils
instead of 75m Texas Bugcatcher coils are afraid of
the technical truth and it's easy to see why.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Cecil Moore wrote:
John KD5YI wrote:
I think any inductor with the same inductance, Q, and self-resonant
frequency will give the same velocity factor and delay as your
Bugcatcher.

That may or may not be true - I don't have an
opinion one way or another - and it is NOT part
of my argument. My argument deals only with
75m Texas Bugcatcher coils and other large air-
core loading coils used on 75m.

My argument is that the velocity factor of a 75m
Texas Bugcatcher coil is ~0.02, occupies ~41
electrical degrees on 4 MHz, and exhibits a
delay of ~28 nS through the coil. That is my only
argument. I am not interested in diversions from
that argument.

Meaning you don't want anyone to disagree with you.



My argument also includes the 100 turn, 10 inch long,
2 inch diameter coil that w8ji used for his 3 nS delay
"measurements". If he had used traveling wave current
for the measurement, he would have measured approximately
25 nS.

No he wouldn't. You don't know what he would have measured.
You don't know how to measure it yourself because you don't have
any idea of what's going on, theoretically.



Maxwell's equations for slow-wave structures (like
a 75m Texas Bugcatcher loading coil) are given in
"Fields and Waves ...", by Ramo and Whinnery:
pages 467-479 in the 2nd edition. This is one of
the references in the Corum IEEE paper.

Maxwell's equations don't say anything about "slow-wave
structures." If they did, you couldn't understand the vector
calculus involved, anyway. This is more picking and choosing
from authorities.



What do you make of Roy's (w7el) statement at:

http://www.w8ji.com/agreeing_measurements.htm

"As described in my posting on rraa of November 11,
the inductor 'replaces' about 33 electrical degrees
of the antenna."

Are you sure that isn't a quote from Reg Edwards, whose ideas
you stole in the first place? Reg thought that antennas were
transmission lines. There's nothing wrong with that. Reg even
worked out some practical formulas based on his ideas that seemed
to work well enough for who they were for. What he didn't do was
discover any laws of nature, any more than you have.

73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Meaning you don't want anyone to disagree with you.

What I invite is someone disagreeing with me about
a 75m Texas Bugcatcher coil along with some technical
proof that I am wrong. All I have gotten so far is
ad hominem attacks. Where's the beef?

Dr. Corum's empirically-based equations do not work
for toroidal inductors so they are outside the scope
of my discussion. Why not discuss the most common
large air-core coils used for loading 75m mobile
antennas?

No he wouldn't. You don't know what he would have measured.

I have exactly the same coil that Tom used for his
"measurements". I have measured the traveling wave
delay through the coil by loading it with a 5k
resistor to eliminate reflections. I do know what
he would measure if he would only run the experiment
correctly. You could do it too if you so chose. x and
y are the current sample points.

source---x-Tom's coil-y--5k load
+-------------------------+

Maxwell's equations don't say anything about "slow-wave
structures."

If you are saying that Maxwell's equations are invalid
for slow-wave structures, your argument is with Ramo,
Whinnery, and Dr. Corum, not with me.

http://www.w8ji.com/agreeing_measurements.htm

"As described in my posting on rraa of November 11,
the inductor 'replaces' about 33 electrical degrees
of the antenna."

Are you sure that isn't a quote from Reg Edwards, whose ideas
you stole in the first place?

You are free to access the above web page to see who
wrote it. If Dr. Corum stole Reg's ideas, he should
have given him the credit. Dr. Corum does provide
50 references for his paper but Reg is not one of them.
However, here is a partial list:
7. J. D. Kraus, "Antennas"
19. F. E. Terman, "Resonant Lines in Radio Circuits"
23. J. D. Ryder, "Networks, Lines, and Fields"
29. S. Ramo and J. R. Whinnery, "Fields and Waves in Modern Radio"
30. R. W. P. King, "Electromagnetic Engineering"
43. M. Born and E. Wolf, "Principles of Optics"
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com