Cecil Moore wrote:
Tom Donaly wrote:

People who want to know what W8JI actually believes, as
opposed to what Cecil says he believes, should go to W8JI's
website.

I agree, Tom, and here is the URL:

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

W8JI takes a 2" dia, 100 turn, 10 inch long coil, and
claims the actual delay through that coil is 3 nS or
4.5 degrees. (The formula for the velocity factor of
such a coil yields ~0.033 at 4 MHz making the actual
delay ~37 degrees or ~25 nS at 4 MHz.)

W8JI's mistake was using standing wave current to try
to measure that delay. The phase of standing wave current
changes hardly at all and is useless for measuring delay.

If the delay is to be measured by observing phase shifts,
then traveling wave current should be used. That would
require loading the coil with a resistor equal to its
characteristic impedance.

Another way to measure the delay is to set the coil up
as a helical antenna over a ground plane and find the
self-resonant frequency which would mean the phase shift
through the coil is 90 degrees at that self-resonant
frequency. Even though the delay changes with frequency,
it is highly unlikely to drop from 90 degrees to 4.5
degrees in a few MHz.

... your little theory about phase shifts across
loading coils, which you can't substantiate through experiment, or
even through any type of rigorous theory, is nothing more than
an exercise in philosophical fantasy.

Actually, it is an exercise in the physics of reality.
A 3nS delay through a 100 uH coil is the real "exercise
in philosophical fantasy" and obviously impossible. Try
it with a TDR and see what you get. Heck, try it at DC
and see what you get.

At his request, I sent a test setup schematic to one of
the gurus on this newsgroup so he could prove me wrong.
He has gone silent and stopped answering my emails. I
expect to see a paper or magazine article announcing
"his discovery".

What is the characteristic impedance of Tom's coil? How do you
define the characteristic impedance of a coil of wire? If you
were to replace Tom's coil with a shorted length of transmission
line, given that jXl = jZo(tan(BL)), which one of the infinite
combinations of Zo and L would you use, given that any of them would
resonate your antenna? Would they all have the same "phase shift?"
What's your formula for the velocity factor of Tom's coil? Is it from
the same Tesla coil crackpot you quoted in previous posts? Have you
used the test setup you mentioned, yourself? Spit out some numbers.
73,
Tom Donaly, KA6RUH

(P.S. For those who don't know: "B" is my version of the Greek letter
"Beta," and L is the length of the transmission line, so BL is the
length of the line in radians. In order for jXl to stay the same,
given a change in Zo, the length of the transmission line has to
change, too. Since the length isn't unique, the delay isn't either,
and even if Cecil's transmission line coil did act like a transmission
line, the delay could be changed to anything anyone wanted it to, just
by changing the coil dimensions. Of course, Cecil can't prove that his
coil is much of a transmission line, so the point is moot.)

Tom Donaly wrote:
What is the characteristic impedance of Tom's coil?

A few thousand ohms. Use equation 50 at:

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

What's your formula for the velocity factor of Tom's coil? Is it from
the same Tesla coil crackpot you quoted in previous posts?

Do you reject all IEEE white papers? The formula
is equation 32.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Tom Donaly wrote:
What is the characteristic impedance of Tom's coil?

A few thousand ohms. Use equation 50 at:

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

What's your formula for the velocity factor of Tom's coil? Is it from
the same Tesla coil crackpot you quoted in previous posts?

Do you reject all IEEE white papers? The formula
is equation 32.

That's what I thought. Nice try, Cecil.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Cecil Moore wrote:
Do you reject all IEEE white papers? The formula
is equation 32.

That's what I thought. Nice try, Cecil.

Is your technique to avoid losing an argument
to reject the technical proof provided by the
other side in an IEEE white paper? Of course, you
have a right to reject technical information that
is useful to amateur radio operators but please
don't stand in the way of that learning process
being used by others.

A 3nS delay through a 2" dia, 100 turn, 10 inch
long coil at 4 MHz is impossible, Tom. I think
you know that. Coils are often used for delaying
signals, not for speeding them up.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Tom Donaly wrote:
What is the characteristic impedance of Tom's coil?

A few thousand ohms. Use equation 50 at:

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

What's your formula for the velocity factor of Tom's coil? Is it from
the same Tesla coil crackpot you quoted in previous posts?

Do you reject all IEEE white papers? The formula
is equation 32.

Cecil,

Have you actually read and understood that article? Corum mentions
several times that everything he reduces to the simple formulas applies
only to quarter-wave resonance conditions.

Look at the author's highlight between equations 31 and 32. Look at the
discussion near equation 47. Look at the discussion following equation
60. Read the entire discussion in section 5.

Note that he does not say the characteristic impedance is a constant
that can be deduced from resonance conditions and then applied to
operating conditions. In fact, he says exactly the opposite.

"It is worth noting that, for a helical anisotropic wave guide, the
effective characteristic impedance is not merely a function of the
geometrical configuration of the conductors (as it would be for lossless
TEM coaxial cables and twin-lead transmission lines), but it is also a
function of the excitation frequency."

I have no comment on the validity of the Corum analysis. He makes a lot
of approximations and simplifications which may or may not be completely
correct. However, it is clear that you are mis-quoting him.


73,
Gene
W4SZ

Gene Fuller wrote:
Have you actually read and understood that article? Corum mentions
several times that everything he reduces to the simple formulas applies
only to quarter-wave resonance conditions.

Yes, a mobile 75m bugcatcher antenna is quarter-wave resonant.
It is clear that you have not taken time to understand the
paper. Figure 2 looks just like a loading-coil, stinger, and
top hat which is 1/4WL resonant. Note that the coil is conceptually
replaced with a length of transmission line and that's exactly
how mobile loaded antennas work. Here are the conditions:

At the feedpoint is a piece of transmission line with a Z0 of
4000 ohms and a VF of 0.02 - physical length to be determined.

Attached to that is a piece of transmission line with a Z0 of
400 ohms and a VF of 1.0. This element is 8 feet long.

The frequency of operation is 4.0 MHz. What physical length
of the 4000 ohm line will cause 1/4WL resonance?

If you can solve that problem, you will understand how loaded
mobile antennas work. Hint: the delay through the 4000 ohm
section is NOT 3 nS.

Look at the author's highlight between equations 31 and 32. Look at the
discussion near equation 47. Look at the discussion following equation
60. Read the entire discussion in section 5.

I have done that, Gene. A 75m bugcatcher coil falls within
the specified test conditions and thus the VF equation should
be within ten percent accuracy.

Note that he does not say the characteristic impedance is a constant
that can be deduced from resonance conditions and then applied to
operating conditions. In fact, he says exactly the opposite.

Yes, and I have never stated otherwise. The approach that works
is to take a 1/4WL self-resonant coil and use only a percentage
*at the same frequency*. The VF and Z0 will remain approximately
the same as long as we don't change frequencies.

Here is what can be done. Take a 75m bugcatcher coil and extend
the number of turns until it is self-resonant at 4 MHz indicating
that the coil is 90 degrees long. Measure the VF of the coil at
the 4 MHz self-resonant frequency. Remove those extra turns and
calculate the new electrical length. Hint: That electrical length
will be nowhere near a 3 nS delay (technically impossible).

"It is worth noting that, for a helical anisotropic wave guide, the
effective characteristic impedance is not merely a function of the
geometrical configuration of the conductors (as it would be for lossless
TEM coaxial cables and twin-lead transmission lines), but it is also a
function of the excitation frequency."

That's true - Z0 and VF change with frequency. The solution is
to measure or calculate the Z0 and VF at the chosen frequency
of operation. Problem solved!

I am suspicious of anyone's motives who says he believes in
an impossible 3 nS delay through a huge loading coil while
dismissing an IEEE white paper that suggests otherwise.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
Have you actually read and understood that article? Corum mentions
several times that everything he reduces to the simple formulas
applies only to quarter-wave resonance conditions.

Yes, a mobile 75m bugcatcher antenna is quarter-wave resonant.
It is clear that you have not taken time to understand the
paper. Figure 2 looks just like a loading-coil, stinger, and
top hat which is 1/4WL resonant. Note that the coil is conceptually
replaced with a length of transmission line and that's exactly
how mobile loaded antennas work. Here are the conditions:

At the feedpoint is a piece of transmission line with a Z0 of
4000 ohms and a VF of 0.02 - physical length to be determined.

Attached to that is a piece of transmission line with a Z0 of
400 ohms and a VF of 1.0. This element is 8 feet long.

The frequency of operation is 4.0 MHz. What physical length
of the 4000 ohm line will cause 1/4WL resonance?

If you can solve that problem, you will understand how loaded
mobile antennas work. Hint: the delay through the 4000 ohm
section is NOT 3 nS.

Look at the author's highlight between equations 31 and 32. Look at
the discussion near equation 47. Look at the discussion following
equation 60. Read the entire discussion in section 5.

I have done that, Gene. A 75m bugcatcher coil falls within
the specified test conditions and thus the VF equation should
be within ten percent accuracy.

Note that he does not say the characteristic impedance is a constant
that can be deduced from resonance conditions and then applied to
operating conditions. In fact, he says exactly the opposite.

Yes, and I have never stated otherwise. The approach that works
is to take a 1/4WL self-resonant coil and use only a percentage
*at the same frequency*. The VF and Z0 will remain approximately
the same as long as we don't change frequencies.

Here is what can be done. Take a 75m bugcatcher coil and extend
the number of turns until it is self-resonant at 4 MHz indicating
that the coil is 90 degrees long. Measure the VF of the coil at
the 4 MHz self-resonant frequency. Remove those extra turns and
calculate the new electrical length. Hint: That electrical length
will be nowhere near a 3 nS delay (technically impossible).

"It is worth noting that, for a helical anisotropic wave guide, the
effective characteristic impedance is not merely a function of the
geometrical configuration of the conductors (as it would be for
lossless TEM coaxial cables and twin-lead transmission lines), but it
is also a function of the excitation frequency."

That's true - Z0 and VF change with frequency. The solution is
to measure or calculate the Z0 and VF at the chosen frequency
of operation. Problem solved!

I am suspicious of anyone's motives who says he believes in
an impossible 3 nS delay through a huge loading coil while
dismissing an IEEE white paper that suggests otherwise.


Cecil,

First, this is NOT an IEEE white paper. It appears to be a simple
conference proceedings paper.

Second, your analysis is utter rot! Are you suggesting that if the coil
can be made resonant at some frequency, and then you cut it in half,
that it still behaves the same?

Corum does not say anything like that, and you shouldn't either.

Shame on you!

73,
Gene
W4SZ

Gene Fuller wrote:
Second, your analysis is utter rot! Are you suggesting that if the coil
can be made resonant at some frequency, and then you cut it in half,
that it still behaves the same?

No, it behaves approximately like half of the original
coil tending to have approximately the same Z0 and VF as
the original coil. The phase shift through the coil will
tend to be approximately 1/2 of the original phase shift -
not exact because of end effects.

Let's say we have a 1/4WL helical antenna with an obvious
phase shift of 90 degrees. If we cut that helical in half,
it is likely to have a phase shift of approximately 45
degrees, nowhere near the 4.5 degrees that W8JI has
"measured".

If we add a stinger to the above half-coil, we will have
a base-loaded antenna. The phase shift will be relatively
close to 45 degrees at the same frequency. The stinger
contributes another few degrees. The impedance discontinuity
between the coil and stinger contributes the rest of the
90 degrees of electrical length.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Gene Fuller wrote:
Second, your analysis is utter rot! Are you suggesting that if the
coil can be made resonant at some frequency, and then you cut it in
half, that it still behaves the same?

No, it behaves approximately like half of the original
coil tending to have approximately the same Z0 and VF as
the original coil. The phase shift through the coil will
tend to be approximately 1/2 of the original phase shift -
not exact because of end effects.

Let's say we have a 1/4WL helical antenna with an obvious
phase shift of 90 degrees. If we cut that helical in half,
it is likely to have a phase shift of approximately 45
degrees, nowhere near the 4.5 degrees that W8JI has
"measured".

If we add a stinger to the above half-coil, we will have
a base-loaded antenna. The phase shift will be relatively
close to 45 degrees at the same frequency. The stinger
contributes another few degrees. The impedance discontinuity
between the coil and stinger contributes the rest of the
90 degrees of electrical length.

"Utter rot" is a pretty good description of this. Your problem is
that you've become so enamored of your little reflection theory that
you insist that only a set of transmission lines 90 degrees in total
length can resonate. Too bad your education isn't complete or you'd know
this isn't so.
73,
Tom Donaly, KA6RUH

Cecil Moore wrote:
Gene Fuller wrote:
Second, your analysis is utter rot! Are you suggesting that if the
coil can be made resonant at some frequency, and then you cut it in
half, that it still behaves the same?

No, it behaves approximately like half of the original
coil tending to have approximately the same Z0 and VF as
the original coil. The phase shift through the coil will
tend to be approximately 1/2 of the original phase shift -
not exact because of end effects.

Let's say we have a 1/4WL helical antenna with an obvious
phase shift of 90 degrees. If we cut that helical in half,
it is likely to have a phase shift of approximately 45
degrees, nowhere near the 4.5 degrees that W8JI has
"measured".

If we add a stinger to the above half-coil, we will have
a base-loaded antenna. The phase shift will be relatively
close to 45 degrees at the same frequency. The stinger
contributes another few degrees. The impedance discontinuity
between the coil and stinger contributes the rest of the
90 degrees of electrical length.

Cecil,

It appears you missed the primary message of the Corum article. He is
completely denying the simple concept you wrote above. He argues that
there is a very special effect near resonance. You cannot simply cut the
coil in half and expect the same behavior.

Frankly, I have little interest in Tesla coils, and I don't know or care
if Corum is right or wrong. I do believe, however, that it is a bit
careless for you to pick and choose equations from the article, ignore
the caveats, and then go ahead and misuse those equations.

73,
Gene
W4SZ