Vincent antenna
 

art wrote:
W8JI is a competant engineer and well versed in "traditional"
antenna design but he is not without fault or error since
he is a human being.

He is absolutely wrong about the phase shift through
a 75m bugcatcher loading coil. Over on QRZ.com, he
tried to prove something using the lumped inductance
in EZNEC. :-)
--
73, Cecil http://www.w5dxp.com

Vincent antenna
 

On Tue, 27 Nov 2007 20:00:22 -0800 (PST), art
wrote:

Why not educate the masses with respect to waves versus particles,
everybody will be very interested as to what emanates from a
radiator or visa versa when on the receiving end.

How curious, Arthur, that I asked you for EXACTLY the same information
and you showed absolute repugnance towards the topic!

Already bored?

73's
Richard Clark, KB7QHC

Vincent antenna
 

Cecil Moore wrote:
art wrote:
W8JI is a competant engineer and well versed in "traditional"
antenna design but he is not without fault or error since
he is a human being.

He is absolutely wrong about the phase shift through
a 75m bugcatcher loading coil. Over on QRZ.com, he
tried to prove something using the lumped inductance
in EZNEC. :-)

People who want to know what W8JI actually believes, as
opposed to what Cecil says he believes, should go to W8JI's
website. And, no, Cecil, 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.
73,
Tom Donaly, KA6RUH

Loading Coils; was : Vincent antenna
 

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".
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

On Wed, 28 Nov 2007 13:25:34 -0600, Cecil Moore
wrote:

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".

Art probably had more pressing issues with the Patent Office.

Loading Coils; was : Vincent antenna
 

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.)

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

AI4QJ wrote:
That is his "obvious" explanation. He should remove that from his webpage as
it is rather embarassing.

W8JI made a gross error in his measurement and
then tried to rationalize the impossible result.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

On Thu, 29 Nov 2007 03:58:11 GMT, Cecil Moore
wrote:
W8JI made a gross error in his measurement and
then tried to rationalize the impossible result.

Given the volume of smoke generated here (over an issue that was long
ago laid in its coffin), did he violate your patented technique?

You and Art seem intent on collecting on a bet, or a debt, or
otherwise mooching validation, because if you two had such
dead-to-rights positions, they wouldn't require exhumation from the
grave to prop the corpses on soap box pedestals as resurrected proof.

Loading Coils; was : Vincent antenna
 

I see Cecil's temporarily run out of steam on his alternative theories
of transmission line operation and so has fallen back to his equally
imaginative pseudo-science of loading coils. I made and posted careful
measurements on this group long ago of a physically small coil to refute
some of the stranger claims being made. I can only describe as
disgusting the ducking, weaving, hemming, and hawing Cecil and Yuri went
through in trying to predict using their imaginative theories what the
results would be. Of course, like any competent fortune tellers, once
the results were given they claimed to have known all along. It's all
there in the archives for anybody who has the stomach for it. I don't.

Roy Lewallen, W7EL

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
AI4QJ wrote:
That is his "obvious" explanation. He should remove that from his
webpage as it is rather embarassing.

W8JI made a gross error in his measurement and
then tried to rationalize the impossible result.

Well h*ll, I like him better already--then he is human, huh? ;-)

Save us from keepin' on tryn' to walk on water. chuckle

Regards,
JS

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
AI4QJ wrote:
That is his "obvious" explanation. He should remove that from his
webpage as it is rather embarassing.

W8JI made a gross error in his measurement and
then tried to rationalize the impossible result.

Cecil:

How would you have like to be working at NASA, with this group; And, you
were the one responsible for not coverting kilometers to miles and
SMACKING that spacecraft we lost into Mars? ;-)

Crud, I've volunteered on serving on those soup-lines, would hate to
have seen ya' there. chuckle

Regards,
JS

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

Richard Clark wrote:
You and Art seem intent on collecting on a bet, or a debt, or
otherwise mooching validation, because if you two had such
dead-to-rights positions, they wouldn't require exhumation from the
grave to prop the corpses on soap box pedestals as resurrected proof.

On the contrary, Richard, old wives' tales sometimes
die hard. It's like water wearing away a stone.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

Roy Lewallen wrote:
I see Cecil's temporarily run out of steam on his alternative theories
of transmission line operation and so has fallen back to his equally
imaginative pseudo-science of loading coils. I made and posted careful
measurements on this group long ago of a physically small coil to refute
some of the stranger claims being made.

Well, the subject was 75m bugcatcher loading coils", so your
choice of a "physically small coil" was already somewhat of
a straw man.

And Roy, you made the same mental blunder in your measurements
that Tom made. I have explained it to you before and you have
so far refused to listen or even read my postings so here it
is once again. Everyone is invited to think about what I am
saying and agree or attempt to refute it. Point by point:

A 1/4WL monopole over ground is known to be 90 degrees long.
The phase of the current changes by only a few degrees from
feedpoint to tip. How much phase shift (delay) in the current
would we measure in 30 degrees of a monopole? Answer: Only
one or two degrees. Why is there only a small number of degrees
of phase shift (delay) in the current in 30 degrees of monopole?
Because it is *standing-wave current* that is being used for
the measurement and the phase barely changes over the entire
monopole length.

EZNEC agrees. A 1/4WL monopole has 5.67 degrees of phase shift
in the current from segment 1 to segment 33 even though the
antenna is 90 degrees long and therefore has an inherent delay
of 90 degrees from feedpoint to tip. Standing-wave current
cannot be used to measure the delay through a wire.

So can that same *standing-wave current* be used to measure
the phase shift (delay) through a coil? Answer: No, standing
wave current cannot be used to measure the phase shift (delay)
through a wire or through a coil because the phase hardly
changes no matter how long is the delay through the coil or
through the wire (assuming coil and wire are 1/2WL).

Roy and Tom both used standing-wave current to try to measure
the delay through a coil. Such an attempt is doomed to failure
for obvious reasons and is a violation of the scientific method.

STANDING WAVE CURRENT CANNOT BE USED TO MEASURE PHASE SHIFTS
IN A WIRE OR IN A COIL BECAUSE STANDING WAVE CURRENT HAS
ESSENTIALLY NO PHASE SHIFT! THERE IS NO PHASE INFORMATION
IN STANDING WAVES!

There is absolutely no correlation between the phase of
standing-wave current and the delay through a coil or
through a wire.

What is the phase shift through a coil at self-resonance?
Answer: It is known to be 90 degrees at the first self-
resonant frequency, i.e. 180 degrees end-to-end.

What is the measured phase shift through that self-resonant
coil at the self-resonant frequency using standing-wave
current? Answer: That measured phase shift will be very
close to zero, nowhere near the known 90 degrees.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

John Smith wrote:
Cecil Moore wrote:
AI4QJ wrote:
That is his "obvious" explanation. He should remove that from his
webpage as it is rather embarassing.

W8JI made a gross error in his measurement and
then tried to rationalize the impossible result.

Well h*ll, I like him better already--then he is human, huh? ;-)
Save us from keepin' on tryn' to walk on water. chuckle

99+% of W8JI's stuff is accurate and that's great. I'm
talking about the small portion he presents as fact that
is technically impossible. The theory of current jumping
from one end of a 75m bugcatcher loading coil to the other
is a rationalization based on a conceptual error during a
measurement. W8JI obviously doesn't understand the nature
of standing-wave current on a standing-wave antenna.

The trouble is that a guru cannot afford to admit a mistake
even though he is human.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:

...
The trouble is that a guru cannot afford to admit a mistake
even though he is human.

Although, perhaps, cryptic, that is exactly what I was inferring ...

I found it the same in institutions of higher learning--surest way to a
low grade was/is to recognize an instructors mistake(s) ...

A certain, and gifted, past instructor I had once said, "We are here to
teach you the laws and rules. It is your job, in the future, to
EFFECTIVELY break them ..." I liked him. :-)

Regards,
JS

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:

W8JI's mistake was using standing wave current to try
to measure that delay.

It's not at all apparent that that was his mistake.

Even though the delay changes with frequency,
it is highly unlikely to drop from 90 degrees to 4.5
degrees in a few MHz.

Any phase delay given in degrees would of course vary as function of
angular frequency independent of any systematic effect simply by
virtue of the fact that the amount of time per period varies with
frequency while the number of degrees per period obviously do not.

Over the range of a few octaves, propagation delay on the other hand
does not vary to any significant extent as a function of frequency.
Ostensibly, it should be equal to sqrt(LC) series L, shunt C.
e.g.

http://www.rhombus-ind.com/dlcat/app1_pas.pdf

In order to either validate or invalidate claims, one must do at least
two things. First make verifyable and repeatable measurements.
Second, show how those measurements are supported by the underlying
principles, and are predicted by the associated mathematics. Without
those things, you may as well go shout it at cars.

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.

The display on Tom's web page appears to be set for 100ns per
division. The delay between cursor 1 and cursor 2 is 486.43 nS, and
the position of cursor 1 appears to be arbitrarily set. The 3nS
measurement would be at ~0.3% of full scale - not normally the scale
one would employ to make such a measurement. Lacking any sort of
description of the stimulus or of the instrument, it's not clear to me
what W8JI's test unit is actually measuring. But at least he measured
something and isn't shouting at cars about it.

73, ac6xg

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

Gene Fuller wrote:
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

The Corum duo model their Tesla coil as "an isotropically conducting
cylindrical boundary." Later, they call it a "helically disposed surface
waveguide." Later, they write, "Further, the Tesla coil passes to a
conventional lumped element inductor as the helix is electrically
shortened." Do the first two quotes resemble a description of a
typical ham antenna loading coil? Has anybody here used a Tesla coil
to load an antenna? The Corums also state in one part of their paper
that their method of analysis is "fraught with danger." Indeed.
Cecil's misuse of the formulas certainly proves that.
Many people over the years have done just fine loading their antennas
with lumped inductors. There's no need to put a "helically disposed
surface waveguide" on a mobile antenna, and if someone thinks that
modeling a coil as "an isotropically conducting cylindrical boundary"
actually turns that coil into an isotropically conducting cylindrical
boundary, that someone should seek help.
73,
Tom Donaly, KA6RUH

Loading Coils; was : Vincent antenna
 

John Smith wrote:
I found it the same in institutions of higher learning--surest way to a
low grade was/is to recognize an instructors mistake(s) ...

The quickest way to get ploinked on this newsgroup
is to catch a guru in a severe technical blunder. The
guru gang then bands together to punish the technically
correct upstart who dares to question their authority.

Trouble is, those reincarnations of Galileo's judges
wind up hoodwinking the naive and uninitiated. "If
________ says it, it must be a fact."
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

On Thu, 29 Nov 2007 16:02:30 GMT, Cecil Moore
wrote:
You and Art seem intent on collecting on a bet, or a debt, or
otherwise mooching validation, because if you two had such
dead-to-rights positions, they wouldn't require exhumation from the
grave to prop the corpses on soap box pedestals as resurrected proof.

On the contrary, Richard, old wives' tales sometimes
die hard. It's like water wearing away a stone.

More mooching validation. You guys could collect more nickels if you
learned to doff your caps instead of engaging in your incessant
muttering.

Loading Coils; was : Vincent antenna
 

Jim Kelley wrote:
Cecil Moore wrote:
W8JI's mistake was using standing wave current to try
to measure that delay.

It's not at all apparent that that was his mistake.

The description of his test setup is on his web page.
Did he use standing-wave current to try to measure the
delay through a loading-coil? Yes, it is obvious that
he did. He should have loaded the circuit with the
characteristic impedance of his loading coil. That
would have reduced the reflections to the point that
the actual delay could be measured.

Lacking any sort of description of the stimulus or
of the instrument, it's not clear to me what W8JI's test unit is
actually measuring.

Second, show how those measurements are supported by the
underlying principles, and are predicted by the associated
mathematics. Without those things, you may as well go shout
it at cars.

But since W8JI's measurements are NOT "supported by the
underlying principles", by your own assertions, he indeed
seems to be "shouting it at cars" on his web page. I am
merely objecting to a technical absurdity, e.g. a 3 nS
delay through a foot long loading coil. The standing-
wave current phase shift through a coil bears no
relationship to the delay through a coil.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

Tom Donaly wrote:
Many people over the years have done just fine loading their antennas
with lumped inductors.

That's not the point of this discussion, Tom. The
only question that needs to be answered here is:
Can a 2" dia, 100 T, 10" long loading coil have
a delay of 3 nS through it at 4 MHz? Do you support
such a technical absurdity? The Corum IEEE white
paper suggests that delay is in error by a magnitude.

All of the boundary test conditions given in Corum's
IEEE white paper are satisfied by a 75m bugcatcher
loading coil. There is no reason to believe that
the underlying principles of physics do not apply.
In fact, the diagram of the 1/4WL resonant system
looks exactly like a base loading coil, stinger,
and top hat as is used for 75m mobile operation.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Richard Clark wrote:
More mooching validation. You guys could collect more nickels if you
learned to doff your caps instead of engaging in your incessant
muttering.

The same could have been said of Galileo. Do you
suggest that technical absurdities go unchallenged?
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:

The description of his test setup is on his web page.
Did he use standing-wave current to try to measure the
delay through a loading-coil? Yes, it is obvious that
he did.

From what is written there it's not possible to know exactly what he
measured. Why don't you take some measurements yourself if you feel
that strongly about it? And please stop shouting at cars. :-)

The standing-
wave current phase shift through a coil bears no
relationship to the delay through a coil.

I have no idea what 'standing wave current phase shift' is supposed to
mean. Standing waves obviously don't propagate, so naturally there
wouldn't be a propagation delay associated with them. Hopefully you
understand that radiating RF currents don't stand, they travel [1].

73, ac6xg


[1] Contrary to unpopular misconception, the reflected wave doesn't
actually affect the forward wave. Forward and reflected currents both
radiate equally well at every point along a radiator. What we see is
the net result of the fields that are present.

Loading Coils; was : Vincent antenna
 

On Thu, 29 Nov 2007 18:26:56 GMT, Cecil Moore
wrote:
More mooching validation. You guys could collect more nickels if you
learned to doff your caps instead of engaging in your incessant
muttering.
The same could have been said of Galileo.

OK, so you believe that Galileo was a muttering mooch and you desire
association with him in that context. Don't get singed.

Do you suggest that technical absurdities go unchallenged?

Has that challenge never occurred, or simply not in this week? You
are just blocking the sidewalk and mooching for validation.

While we are dropping the names of Italian notables, enjoy my Bonfire
of the Vanities as you have already brought your marshmallows.

73's
Girolamo Savonarola

Loading Coils; was : Vincent antenna
 

That is his "obvious" explanation. He should remove that from his webpage as
it is rather embarassing. Given that the magnetic field moves at the speed
of light, there will be no equipment in any hamshack that will measure the
delta between the field affecting coils spaced 1mm apart vs coils spaced
10mm apart or 1000mm apart.



I should think that many hams have things that can measure 3 ns (1000mm
light time), particularly in a repetitive system. That's one cycle at
300 MHz, or 36 degrees at 30 MHz.


Systems that rely on nulling or matching, with a variable line
stretcher, for instance, can do this fairly well.

For example of a measurement technique, say one put a LED in series with
the turn at one end, and another at the other end, along with enough DC
bias current to make sure they both stay lit, with the RF current
essentially modulating the brightness (Hmm. the LED has parasitic terms,
and you'd need a fast one.. but that's the general idea).

You could then observe the two LEDs with some system that compares the
modulated signal from the two in a nulling arrangement (for instance,
put an optical chopper wheel in front of one light path), then adjust
relative lengths of the optical paths (with a moving mirror).

Or, what about using a H field probe (i.e. something like a Rogowski
coil), fed back to a measurement system using resistive leads (377
ohms/square) that don't perturb the field.

If you have a LOT of RF power available for the test, you could use the
Faraday or Kerr effect to measure the magnetic field too.. Flint glass
has a Verdet constant of 0.11 radians/(Tesla*mm).
Rotation(radians) = V*B*l

Say your probe is 1mm long, and you can reliably measure a rotation of
0.11 radian (5-6 degrees), you'd need a field of 1 T, which is fairly high.
Biot-Savart is B=4piE-7*I/(2pi R) = 2E-7 *I/R
Say your probe is 1mm (1E-3m), to get 1T you'd need 1/2E-4 amps (5kA)..



Anyway... a sufficiently clever amateur probably does have equipment in
their shack that could be cobbled together to make this sort of
measurement, without needing exotic measurement gear.

(Mind you, having a fast sampling scope would make it easy).

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
Tom Donaly wrote:
Many people over the years have done just fine loading their antennas
with lumped inductors.

That's not the point of this discussion, Tom. The
only question that needs to be answered here is:
Can a 2" dia, 100 T, 10" long loading coil have
a delay of 3 nS through it at 4 MHz? Do you support
such a technical absurdity? The Corum IEEE white
paper suggests that delay is in error by a magnitude.

All of the boundary test conditions given in Corum's
IEEE white paper are satisfied by a 75m bugcatcher
loading coil. There is no reason to believe that
the underlying principles of physics do not apply.
In fact, the diagram of the 1/4WL resonant system
looks exactly like a base loading coil, stinger,
and top hat as is used for 75m mobile operation.

Do you really believe that an antenna + loading coil has
to be a quarter wave long to resonate?
73,
Tom Donaly, KA6RUH

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
Richard Clark wrote:
More mooching validation. You guys could collect more nickels if you
learned to doff your caps instead of engaging in your incessant
muttering.

The same could have been said of Galileo. Do you
suggest that technical absurdities go unchallenged?

You're not Galileo.
73,
Tom Donaly, KA6RUH

Loading Coils; was : Vincent antenna
 

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

Loading Coils; was : Vincent antenna
 

On 29 Nov, 08:36, Cecil Moore wrote:
Roy Lewallen wrote:
I see Cecil's temporarily run out of steam on his alternative theories
of transmission line operation and so has fallen back to his equally
imaginative pseudo-science of loading coils. I made and posted careful
measurements on this group long ago of a physically small coil to refute
some of the stranger claims being made.

Well, the subject was 75m bugcatcher loading coils", so your
choice of a "physically small coil" was already somewhat of
a straw man.

And Roy, you made the same mental blunder in your measurements
that Tom made. I have explained it to you before and you have
so far refused to listen or even read my postings so here it
is once again. Everyone is invited to think about what I am
saying and agree or attempt to refute it. Point by point:

A 1/4WL monopole over ground is known to be 90 degrees long.
The phase of the current changes by only a few degrees from
feedpoint to tip. How much phase shift (delay) in the current
would we measure in 30 degrees of a monopole? Answer: Only
one or two degrees. Why is there only a small number of degrees
of phase shift (delay) in the current in 30 degrees of monopole?
Because it is *standing-wave current* that is being used for
the measurement and the phase barely changes over the entire
monopole length.

EZNEC agrees. A 1/4WL monopole has 5.67 degrees of phase shift
in the current from segment 1 to segment 33 even though the
antenna is 90 degrees long and therefore has an inherent delay
of 90 degrees from feedpoint to tip. Standing-wave current
cannot be used to measure the delay through a wire.

So can that same *standing-wave current* be used to measure
the phase shift (delay) through a coil? Answer: No, standing
wave current cannot be used to measure the phase shift (delay)
through a wire or through a coil because the phase hardly
changes no matter how long is the delay through the coil or
through the wire (assuming coil and wire are 1/2WL).

Roy and Tom both used standing-wave current to try to measure
the delay through a coil. Such an attempt is doomed to failure
for obvious reasons and is a violation of the scientific method.

STANDING WAVE CURRENT CANNOT BE USED TO MEASURE PHASE SHIFTS
IN A WIRE OR IN A COIL BECAUSE STANDING WAVE CURRENT HAS
ESSENTIALLY NO PHASE SHIFT! THERE IS NO PHASE INFORMATION
IN STANDING WAVES!

There is absolutely no correlation between the phase of
standing-wave current and the delay through a coil or
through a wire.

What is the phase shift through a coil at self-resonance?
Answer: It is known to be 90 degrees at the first self-
resonant frequency, i.e. 180 degrees end-to-end.

What is the measured phase shift through that self-resonant
coil at the self-resonant frequency using standing-wave
current? Answer: That measured phase shift will be very
close to zero, nowhere near the known 90 degrees.
--
73, Cecil http://www.w5dxp.com

IF the coil windings are all exposed then I agree with you Cecil
But a dead horse will never get upregardless of the amount of
whipping.
Regards
Art

Loading Coils; was : Vincent antenna
 

Jim Kelley wrote:
From what is written there it's not possible to know exactly what he
measured.

Please read the rest of the material on his web site
concerning current flow through loading coils. He
made many more assertions and "measurements" using
standing-wave current.

I have no idea what 'standing wave current phase shift' is supposed to
mean. Standing waves obviously don't propagate, so naturally there
wouldn't be a propagation delay associated with them.

My point exactly yet standing-wave current is what
both W8JI and W7EL used to "measure" the phase shift
through a loading coil. It is exactly my point that
there is no phase shift associated with standing-
wave current in a coil or in a wire so it CANNOT
be used to "measure" phase shift. There is NO
phase information in the current used for the
W8JI and W7EL measurements. They both apparently
thought they were measuring traveling-wave currents
when the currents were actually overwhelmingly
standing-wave currents.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Jim Lux wrote:
I should think that many hams have things that can measure 3 ns (1000mm
light time), particularly in a repetitive system. That's one cycle at
300 MHz, or 36 degrees at 30 MHz.

The referenced W8JI 3 nS "measurement" was the delay
in a 2' dia, 100 T, 10" long loading coil on 4 MHz,
i.e. 4.5 degrees.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

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.


Ahem...I'm quite familiar with that paper from work with Tesla coils,
and I have had some conversations a few years ago with Jim Corum.

That's a conference paper, so I wouldn't vouch for it's extensive peer
review.

The Corum's analysis is an attempt to fit transmission line behavior to
what is essentially a lumped system (Tesla coils can be very well
modeled as lumped systems). While the model is certainly valid within
their stated limitations, the real question that arises is "why". A
useful model makes useful predictions, and simple lumped models make
adequate predictions of tesla coil performance.

However, their analysis might have value for higher frequencies, where
the coil is a bigger fraction of a freespace wavelength. A typical
tesla coil runs at a few hundred kHz (lambda= 10-20 km), and a
positively huge one might have a secondary perhaps 2-3 meters long (i.e.
the coil is 1/10,000th wavelength long.
Furthermore, people HAVE made current measurements at the top and bottom
of a large tesla coil and found very small phase differences, indicating
that there is little or no deviation from a lumped model. One might
want to look at
http://www.abelian.demon.co.uk/tssp/

Compare this to a loading coil that is 30 cm long on an antenna for
40m: 1:120th wavelength.

Loading Coils; was : Vincent antenna
 

John Smith wrote:
Cecil Moore wrote:

AI4QJ wrote:

That is his "obvious" explanation. He should remove that from his
webpage as it is rather embarassing.


W8JI made a gross error in his measurement and
then tried to rationalize the impossible result.


Cecil:

How would you have like to be working at NASA, with this group; And, you
were the one responsible for not coverting kilometers to miles and
SMACKING that spacecraft we lost into Mars? ;-)


It wasn't km and miles, it was pounds and newtons AND
the error was that Lockheed Martin supplied the thrust data in pounds,
unlike the contractual requirement to supply it in Newtons (which is
what we at JPL have used for decades). The error wasn't caught because
the absolute magnitude of the force is very small, so the differences
from predict to observation were on the order of the measurement
uncertainty. (We're talking measuring the velocity to mm/sec and range
to mm, when its at Mars.)
I'd venture that anyone would find measuring distances to 1 part in 1E12
challenging...





Crud, I've volunteered on serving on those soup-lines, would hate to
have seen ya' there. chuckle

Regards,
JS