Current through coils
 

Gene Fuller wrote:
Isw = 2Io cos (kz) cos (wt)

What can be seen immediately is that the standing wave current still has
exactly the same time dependence that the traveling waves had. The
magnitude of the current is now a function of z, unlike the constant
magnitude in the traveling waves. The "current" is still defined as
above, namely the charge that moves back-and-forth in the z-direction.

On the contrary, when kz is not linked by a plus or minus sign
to wt, the wave doesn't move anymore. Maybe you need a review?

Gene, you are a genius. Why didn't I think of that? I recognize
that equation from "Optics", by Hecht. Pick any point, 'z', and
see what you get. Hecht says, "It doesn't rotate at all, and the
resultant wave it represents *DOESN'T PROGRESS THROUGH SPACE* - it's
a standing wave." The RF equivalent of a standing wave of light that
doesn't progress through space is an RF standing wave that doesn't
progress through a wire. That's what I have been telling you guys.
Standing waves don't move. Standing wave current doesn't flow!
Even in empty space, a light standing wave doesn't progress
through space, i.e. IT DOESN'T MOVE!
That is on page 289 of "Optics", by Hecht, 4th edition.

From "Fields and Waves ...", by Ramo & Whinnery, in describing the
standing wave situation: "The total energy in any length of line
a multiple of a quarter wavelength long is constant, *merely
interchanging between energy in the electric field of the voltages
and energy in the magnetic field of the currents*." Again, proof
that standing wave energy doesn't flow. It just stands there
being exchanged between the E-fields and the H-fields.
That is from page 40 of "Fields and Waves in Communications
Electronics", by Ramo, Whinnery, and Van Duzer.

Now I did make a mistake in what I said earlier and I apologize for
that. I said the energy in the E-field and H-field exchanges at a
"point" on the line. Obviously, since a current maximum occurs at
a voltage zero, that can't be true so I mis-spoke. Since the voltage
maximum is 1/4 wavelength away from the current maximum, as Ramo &
Whinnery say, one has to consider 1/4WL of line, and not a point as
I said.

Consider a 1/4WL section of line with a voltage maximum at Z and
a current maximum at Z+(1/4WL). The current at Z is zero and the
voltage at Z+(1/4WL) is zero. The net energy in that 1/4WL of line
is constant. No net energy is flowing into or out of that 1/4WL
of line. At some point the E-field energy is strongest toward
the Z end and 1/4 cycle later, it is strongest toward the Z+(1/4WL)
end. Since there is no net energy flow into or out of the line,
there is no net current flow into or out of the line.

The current oscillation factor (wt) is now decoupled from "z", unlike
the traveling wave case. The "wave" is stationary. The current itself,
however, behaves exactly the same as in the case of the traveling waves.

Sorry, you are wrong there, Gene. On that same page, Hecht says, "The
standing wave does not move through space: it is clearly not of the
form f(x +/- vt). For your equations that statement would be: The
standing wave current does not move through the wi it is clearly
not of the form f(z +/- wt). When you separate the 'z' function from
the 'wt' function, the wave doesn't move anymore. It, well, it just
stands there, like a good little standing wave.

Of course there are important differences in radiation patterns for
traveling waves and standing waves. The magnitude of the current is
different along the wire. However, except at the standing wave nodes,
the standing wave current is very real and non-zero.

And stationary as Hecht says. Your own equation indicates that it
is stationary, i.e. not moving.

I am almost embarrassed to write this, ...

As you should be for not realizing that [Isw = 2Io cos (kz) cos (wt)]
is "clearly not of the form f(z +/- wt)", i.e. of the form of a current
traveling wave that moves. Time to refresh you memory on that subject.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

John Popelish wrote:
the net charge movement is zero and therefore
the standing wave current is not "going" anywhere?

Sorry, no.

Gene just posted the equation for standing wave current.

Isw = 2Io cos (kz) cos (wt)

This is definitely not in the form of a traveling wave.
Hecht, in "Optics" says the standing wave does not move
through space. Presumably, for the same reason, a
standing wave does not move through a wire.

Looking
just at just current, and at only a single point, a traveling current
wave and a standing current wave are indistinguishable.

True but if you know the equation above, then they are distinguishable.

The only way to understand a standing wave having a phase of zero
degrees, that makes sense to me, is that it applies to all points
between one current node and the next.

Yes, the subject in context is 1/4WL monopoles or 1/2WL dipoles.

That's unclear to me. Why can't the E-field and H-field simply be
exchanging energy at a point rather than any net charge moving
laterally?

In an isolated EM plane wave, I think this is the case, and displacement
charge in space takes the place of conductor current. But when a wave is
guided by a conductor, we can measure the charge sloshing back and forth
in the conductor in response to those fields.

Yes, I was confused about that. If the question is changed to: "Why
can't the E-field and H-field simply be exchanging energy within each
1/4WL rather than any net charge moving out of that 1/4WL?", it would
make sense.

Thanks John, for the refresher course.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil,

Good grief!!!!

I said several times that the standing wave does not move. I also said
the "wave" is not the same thing as the "current". The current is
nonzero even though the wave is stationary.

At this point it is obvious that you are just interested in causing a
fuss, and not the slightest bit interested in reaching any sort of
resolution of this item.

Bye.

73,
Gene
W4SZ

Cecil Moore wrote:
Gene Fuller wrote:

Isw = 2Io cos (kz) cos (wt)

What can be seen immediately is that the standing wave current still
has exactly the same time dependence that the traveling waves had. The
magnitude of the current is now a function of z, unlike the constant
magnitude in the traveling waves. The "current" is still defined as
above, namely the charge that moves back-and-forth in the z-direction.


On the contrary, when kz is not linked by a plus or minus sign
to wt, the wave doesn't move anymore. Maybe you need a review?

Gene, you are a genius. Why didn't I think of that? I recognize
that equation from "Optics", by Hecht. Pick any point, 'z', and
see what you get. Hecht says, "It doesn't rotate at all, and the
resultant wave it represents *DOESN'T PROGRESS THROUGH SPACE* - it's
a standing wave." The RF equivalent of a standing wave of light that
doesn't progress through space is an RF standing wave that doesn't
progress through a wire. That's what I have been telling you guys.
Standing waves don't move. Standing wave current doesn't flow!
Even in empty space, a light standing wave doesn't progress
through space, i.e. IT DOESN'T MOVE!
That is on page 289 of "Optics", by Hecht, 4th edition.

From "Fields and Waves ...", by Ramo & Whinnery, in describing the
standing wave situation: "The total energy in any length of line
a multiple of a quarter wavelength long is constant, *merely
interchanging between energy in the electric field of the voltages
and energy in the magnetic field of the currents*." Again, proof
that standing wave energy doesn't flow. It just stands there
being exchanged between the E-fields and the H-fields.
That is from page 40 of "Fields and Waves in Communications
Electronics", by Ramo, Whinnery, and Van Duzer.

Now I did make a mistake in what I said earlier and I apologize for
that. I said the energy in the E-field and H-field exchanges at a
"point" on the line. Obviously, since a current maximum occurs at
a voltage zero, that can't be true so I mis-spoke. Since the voltage
maximum is 1/4 wavelength away from the current maximum, as Ramo &
Whinnery say, one has to consider 1/4WL of line, and not a point as
I said.

Consider a 1/4WL section of line with a voltage maximum at Z and
a current maximum at Z+(1/4WL). The current at Z is zero and the
voltage at Z+(1/4WL) is zero. The net energy in that 1/4WL of line
is constant. No net energy is flowing into or out of that 1/4WL
of line. At some point the E-field energy is strongest toward
the Z end and 1/4 cycle later, it is strongest toward the Z+(1/4WL)
end. Since there is no net energy flow into or out of the line,
there is no net current flow into or out of the line.

The current oscillation factor (wt) is now decoupled from "z", unlike
the traveling wave case. The "wave" is stationary. The current itself,
however, behaves exactly the same as in the case of the traveling waves.


Sorry, you are wrong there, Gene. On that same page, Hecht says, "The
standing wave does not move through space: it is clearly not of the
form f(x +/- vt). For your equations that statement would be: The
standing wave current does not move through the wi it is clearly
not of the form f(z +/- wt). When you separate the 'z' function from
the 'wt' function, the wave doesn't move anymore. It, well, it just
stands there, like a good little standing wave.

Of course there are important differences in radiation patterns for
traveling waves and standing waves. The magnitude of the current is
different along the wire. However, except at the standing wave nodes,
the standing wave current is very real and non-zero.


And stationary as Hecht says. Your own equation indicates that it
is stationary, i.e. not moving.

I am almost embarrassed to write this, ...


As you should be for not realizing that [Isw = 2Io cos (kz) cos (wt)]
is "clearly not of the form f(z +/- wt)", i.e. of the form of a current
traveling wave that moves. Time to refresh you memory on that subject.

Current through coils
 

wrote:

I have a 100 turn 2" diameter #18 gauge wire air core inductor. There
are 100 turns, so there is about 630 inches or 32 feet of wire in the
coil.

I have a Network Analyzer with port to port time delay measurement
capability. It measures coaxial cables very well, and even clip leads.

Cecil, please predict or guess the group delay of this inductor at 3.8
MHz. Tell us all what that group delay means for your wave theory.

Tom, I have no idea since you chose not to post the length of
the coil or the inductance of the coil or the Q of the coil
or even the turns/inch of the coil.

Is your Network Analyzer equipped with current probes? If not,
you are wasting your time.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil warned me that if I posted, the posting would be nit picked to
pieces. I`ve read correct postings describing the incident and reflected
waves on a transmission line, and Maxwell`s secret of radiation
(displacement current produces a magnetic field same as conduction
current). All this may be relevant or not to some extent, but they don`t
seem to resolve the current through a coil.

Tom, W8JI wrote:
"You have consistently disagreed with me when I said the time delay
through an inductor with tight mutual coupling from turn to turn is
somewhat close to light speed over the physical length of the inductor,
rather than the time it rakes to wind its way around the copper."

That contradicts established experience.

The property of reactance is to limit current flow. Inductive reactance
limits by means of counter-emf which depends upon the rate at which
current is changing in the coil. A-C current changes most rapidly at
zero time (the axis crossings of the sine waveform). Lenz`s law says the
counter-emf must oppose the growth of current in this case. Opposotion
of the counter-emf causes the current to reach its maximum 1/4-cycle
after the emf applied to the coil reaches its maximum. As almost
everyone knows, the current lags by 90-degrees in a pure inductor. Make
the turns coupling as tight as you can, the current is still delayed by
90-degrees.

Now, it surely is possible to bypass a perfect inductor with a capacitor
to mitigate a delay.

I can`t repeat without retyping text on my screen, so the fact that I
don`t retype everything only means I`m lazy.

Right or wrong, W8JI may never lose an argument, but when he is clearly
wrong it should be pointed out.

Best regards, Richard Harrison, KB5WZI

Current through coils
 

wrote:

Cecil,
You have consistently disagreed with me when I said time delay through
an inductor with tight mutual coupling from turn-to-turn is somewhat
close to light speed over the physical length of the inductor,

No, I haven't, Tom. What you are describing is the voltage delay.
I have never argued with you about the voltage delay through a
coil. It occurs at the speed of light adjusted for VF. In EE101
everybody learns that the voltage leads the current through a
coil. The question is by how much in a 75m bugcatcher coil?

Have you ever seen a graph of the voltage vs current at the
output of a series coil? It shows the current lagging the
voltage by 90 degrees. It takes a series resonant capacitor
to align the current with the voltage again.

rather
than the time it takes current to wind its way around through the
copper.

If you can find a posting of mine like that, I'll give you $100.
If you can't find it, please admit you are fibbing again about
what I have said.

You didn't like my measurement of a small 100uH choke,

I didn't say I didn't like it. You posted some results and then
described those same results differently as time passed. At the
moment, I have no idea what those results were. Was the -60 to
-70 degree delay a voltage delay or a current delay?

and said
a large inductor like a bug catcher coil is different. You predicted
standing waves in that inductor.

Now we are getting to the truth. A 75m bugcatcher is closer to
being a Tesla coil than it is to being a lumped-inductor. It
satisfies R.W.P. King's advice that if the wire length used
to make the coil exceeds 1/6 wavelength then, "an adequate
representation of the reactance of a coil with a nonuniformly
distributed current is NOT POSSIBLE in terms of a coil with
a uniform current". The 75m bugcatcher uses very close to
1/6 wavelength of wire.

And yes, standing wave antennas have standing waves so a 75m
bugcatcher coil is emersed in a standing wave environment.
Quoting Dr. Corum: "Lumped element representations for coils
REQUIRE that the current is uniformly distributed along the
coil - no wave interference and no standing waves can be
present on lumped elements."

I have a 100 turn 2 inch diameter air wound inductor of pretty good
quality. It is 10 inches long.

What is the inductance? What is the Q?

Please tell all of us the time delay you expect in that inductor on 3.8
MHz. Please tell all of us what that delay means for your various
changing theories about waves standing in that coil.

First please describe the circuit used to drive the coil, what other
components are in the loop, and how you are picking off the two currents
at the ends of the coil. Is your Network Analyzer equipped with current
probes? If not, you are wasting your time. We already know the delay for
the voltage will approximate the speed of light adjusted for VF.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Gene Fuller wrote:
Good grief!!!!

Good grief!!! I've already posted in another posting that I
was mistaken about that. There is standing wave charge
migrating from end to end in a 1/4WL monopole. Next time
I have spaghetti, I'll give myself 20 licks with a wet
noodle.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Richard Harrison wrote:

Tom, W8JI wrote:
"You have consistently disagreed with me when I said the time delay
through an inductor with tight mutual coupling from turn to turn is
somewhat close to light speed over the physical length of the inductor,
rather than the time it rakes to wind its way around the copper."

That contradicts established experience.

Tom seems to be confusing the effects of the E-field with the
effects of the H-field. The E-field propagates at the speed
of light through a coil. The H-field propagates at the
speed of light through a capacitor.

Make
the turns coupling as tight as you can, the current is still delayed by
90-degrees.

Can the actual current phase delay be estimated knowing the Q
of the coil? I don't recall a formula for that.

Now, it surely is possible to bypass a perfect inductor with a capacitor
to mitigate a delay.

Dang Richard, now you've told Tom how to run his experiment
in order to obtain the results he predicts. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:
Now, it surely is possible to bypass a perfect inductor with a capacitor
to mitigate a delay.

Dang Richard, now you've told Tom how to run his experiment
in order to obtain the results he predicts. :-)

You say you will accept something, you ask for something to be done,
and when it is offered you back up and stall, preparing advance excuses
why it won't be done correctly and refusing to make a prediction.

You've eaten up hours of my time and the only thing I've learned is you
don't want to learn, and you are so unsure of yourself you'll avoid any
prediction of how something will work any way you can.

I'm just amazed you have to fall back on name calling, mubo-jumbo, and
inuendo when someone offers to help you understand something. I'm all
done with this too.

73 Tom

Current through coils
 

Gene Fuller wrote:
Cecil,

Good grief!!!!

I said several times that the standing wave does not move. I also said
the "wave" is not the same thing as the "current". The current is
nonzero even though the wave is stationary.

At this point it is obvious that you are just interested in causing a
fuss, and not the slightest bit interested in reaching any sort of
resolution of this item.

Bye.

73,
Gene
W4SZ


Cecil also said he wanted a measurement. When I asked him to make a
prediction, he made excuses why any result would be wrong and avoided
any prediction.

Like you, I now am sure there is no reason to get caught up in any
further exchange with him. Whatever he is trying to do, it certainly
isn't teaching or learning.

73 Tom

Current through coils
 

Current through coils
 

wrote:
Cecil Moore wrote:
Dang Richard, now you've told Tom how to run his experiment
in order to obtain the results he predicts. :-)

You say you will accept something, you ask for something to be done,
and when it is offered you back up and stall, preparing advance excuses
why it won't be done correctly and refusing to make a prediction.

It was a joke, Tom. I am still trying to work out the measurement
details in my mind. It certainly won't do any good to measure
a parameter other than the one we want to measure.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

wrote:
Cecil also said he wanted a measurement. When I asked him to make a
prediction, he made excuses why any result would be wrong and avoided
any prediction.

The concept is easy. The measurement it tricky. It won't do
a bit of good to measure the voltage delay and call it the
current delay. I asked you pointed questions about your
coil and measurement setup. Instead of responding with
answers to my questions, you respond with more ad hominem
attacks. One wonders what your motive really is. Did your
measurements support my side of the argument and now you
are ashamed to report those results?

If you refuse to make the measurements, I'll just find
someone else willing to do it or do it myself.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Roy Lewallen wrote:
That's exactly what he did back in November 2003. I see he hasn't
changed any. Wonder who the next person will be to get sucked in, jerked
around, and disgusted.

Here comes the junk yard dog guru gang. Tom has refused
to give me the necessary needed information about his
coil and his measurement configuration and you are blaming
me for that? With the information that he has provided
so far, I might as well be trying to guess how much
loose change he has in his pocket.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:

wrote:
You say you will accept something, you ask for something to be done,
and when it is offered you back up and stall, preparing advance excuses
why it won't be done correctly and refusing to make a prediction.

I'm not stalling, Tom, I'm waiting for you to provide the
information I requested. Why are you avoiding providing
that information? It's pretty simple stuff that anyone
would need to make a prediction.

1. What is the inductance of the coil? What is the
Q of the coil?

2. What kind of current probes are you using with your
Network Analyzer? What are the characteristics of the
driving source signal?

3. What is the schematic configuration of your test setup?
How can I possibly make a prediction without that schematic?

That is certainly a reasonable request. Without that
information, a prediction is impossible, not just for
me but for anyone else.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

I wrote and all can read:

Fri, Mar 10 2006 9:13 pm
Email:
Groups: rec.radio.amateur.antenna
Cecil,


I have a 100 turn 2 inch diameter air wound inductor of pretty good
quality. It is 10 inches long.

To which Cecil Moore replied:
Tom, I have no idea since you chose not to post the length of
the coil or the inductance of the coil or the Q of the coil
or even the turns/inch of the coil.

Cecil: "I have no idea since you CHOSE to not post...blah blah blah"

Fact: I already had posted coil length, number of turns, diameter, and
I said the inductor has "pretty good quality".

Current through coils
 

wrote:
I wrote and all can read:

Everyone please take a close look at the lengths to which
Tom will go to to deceive the readers. He has falsified
the following postings. He mixed and matched, cut and
pasted, from multiple postings made at different times
for the sole purpose of deceiving. That cannot happen
accidentally. That is a deliberately unethical act, a
lie about what I posted, and is probably criminal.

Please observe to what lengths Tom is willing to go to
divert the technical issues and hide the technical truth
in order to protect his lumped-circuit myths.

Here's is the entire posting: Where did Tom give the coil length?
************************************************** ****************
wrote:

I have a 100 turn 2" diameter #18 gauge wire air core inductor. There
are 100 turns, so there is about 630 inches or 32 feet of wire in the
coil.

I have a Network Analyzer with port to port time delay measurement
capability. It measures coaxial cables very well, and even clip leads.

Cecil, please predict or guess the group delay of this inductor at 3.8
MHz. Tell us all what that group delay means for your wave theory.

Tom, I have no idea since you chose not to post the length of
the coil or the inductance of the coil or the Q of the coil
or even the turns/inch of the coil.

Is your Network Analyzer equipped with current probes? If not,
you are wasting your time.
--
73, Cecil http://www.qsl.net/w5dxp
************************************************** **************************
Fri, Mar 10 2006 9:13 pm
Email:
Groups: rec.radio.amateur.antenna
Cecil,

The posting I replied to was the following made at 7:34pm which
did not contain the length of the coil. I read this one first and
replied to it. It is absolutely true that Tom chose not to post
the length of the coil in the 7:34pm posting to which I replied.

Tom wrote at 7:34pm:
I have a 100 turn 2" diameter #18 gauge wire air core inductor. There
are 100 turns, so there is about 630 inches or 32 feet of wire in the
coil.

See? The length of the coil is NOT there.

The following quote is from Tom's *second* posting made at 8:13pm,
almost half an hour later. His *first* posting didn't say how
long the coil was. I read Tom's *first* posting first and replied
to it before I read his second posting.

Tom wrote at 8:13pm:
I have a 100 turn 2 inch diameter air wound inductor of pretty good
quality. It is 10 inches long.

To which Cecil Moore replied:

Tom, I have no idea since you chose not to post the length of
the coil or the inductance of the coil or the Q of the coil
or even the turns/inch of the coil.

That quote is my reply to Tom's *first* posting. I had
not read your *second* posting yet. Everything I said was
absolutely true about his first posting.

How unethical can one get? Tom cut and pasted multiple postings
from different times to try to deceive the readers. Not only is
it unethical but it is probably also illegal.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Now, now, gentlemen, there's no need to re-start the Civil War. Put
away your literary weapons.

The slaves have all been freed and we now have computers.

A 100 turn coil, 10 inches long, 2 inches in diameter, has an
inductance of 102 microhenrys, a Q of aproximately 380 at F = 1.9 MHz,
and the self-resonant frequency is 12.0 MHz.

Its radiation resistance at 1.9 MHz is negligible.

It is near enough to being exactly 100 microhenrys to justify it being
called an Inductance Standard.
----
Reg.

Current through coils
 

Reg Edwards wrote:
A 100 turn coil, 10 inches long, 2 inches in diameter, has an
inductance of 102 microhenrys, a Q of aproximately 380 at F = 1.9 MHz,
and the self-resonant frequency is 12.0 MHz. Its radiation resistance
at 1.9 MHz is negligible.

Good stuff Reg. Modeling it as a transmission line, what would
be its Z0 and VF?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Roy Lewallen, W7EL wrote:
"The mathematical treatment in King is quite complex. But nowhere does
he mention any traveling, reflected, or standing current, power, or
energy waves, or that inductance behaves any differently in an antenna
than in a lumped circuit.."

Maybe something was overlooked. The above is just more squid ink.

Kraus characterizes inductors as helices. At one extreme they are
stretched into straifht wires. At the other they collapse into single
loops.

After years of wrangling it is time to admit that the old authors are
right.

King and Wing were associates at Harvard.

Alexander H. Wing wrote on page 3 of "Transmission Lines, Antennas, and
Wave Guides":
"5. Distributed constants - The Transmission line cannot be analyzed as
a simple series circuit, because the current in the wires is not
everywhere the same."

J.D. Kraus wrote on page 185 of his 1950 edition of "Antennas":
"Thus, a helix with circumference too small for the axial mode of
radiation (circumferennce less than 2/3 wavelength) has a nearly
sinusoidal current distribution, caused by alternate reinforcement and
cancellation of two oppositely directed traveling waves on the helix of
nearly equal amplitude Izero as suggested in Fig. 7-13c. Both traveling
waves are of the Tzero transmission mode type."

I expedct no one will throw in the towel, but do expect more squirts of
squid ink.

Best regards, Richard Harrison, KB5WZI

Current through coils
 

Current through coils
 

Reg Edwards wrote:
A 100 turn coil, 10 inches long, 2 inches in diameter, has an
inductance of 102 microhenrys, a Q of aproximately 380 at F = 1.9 MHz,
and the self-resonant frequency is 12.0 MHz.

I'll bet the measured self-resonant frequency would be lower
if mounted as a base-loading coil on my pickup.

Seems the VF of the coil is 0.041 based on 10" being 1/4WL
at 12 MHz. Assuming that VF holds down to 1.9 MHz we
can calculate the electrical length of the coil on 1.9 MHz
which will be the same as the phase shift through the coil.

So I get about ~14 degrees of phase shift through that coil
at 1.9 MHz assuming the self-resonant frequency really
is 12 MHz at the spot where the coil is mounted.

If the coil were used on 3.8 MHz, the phase shift would
be ~28 degrees.

But my 75m bugcatcher coil shows to be self-resonant at
6.6 MHz while sitting there on my pickup being driven
by an MFJ-259B. It is 6.5" long. When 6.5" is 1/4WL
at 6.6 MHz, the VF = 0.0145, considerably lower than
the coil above and operating much closer to its self-
resonant frequency.

A length of 6.5" coil with a VF of 0.145 on 4 MHz is
~55 degrees of phase shift. And indeed the net current
at the top of the coil drops to about 2/3 of what it
is at the bottom.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

John Popelish wrote:
Dang! I was looking forward to your test results, and a description of
your test method. I think your 2" diameter coil is a good example of an
inductor that is neither a perfect "lump" nor a pure transmission line.

That's what my back of the napkin calculations would indicate.
I get ~14 degrees at 1.9 MHz or ~28 degrees at 3.8 MHz based
on 90 degrees at 12 MHz.

But based on what these guys measured before, anyone would be
a fool to predict the results without knowing what the test
setup looks like. In fact, the prediction challenge was a
blatently obvious attempt to lead the unsuspecting down
a primrose path without a roadmap. Do you think W7EL would
ever make a prediction based on the meager amount of
information provided? :-) A few years ago he provided some
information but kept changing parameters daily until I got
tired and withdrew my estimate. But it turned out in the
end that I was pretty close.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Reg wrote:
"Now, now gentlemen, there is no need to re-start the Civil War."

In Texas we call it the War Between the States!

The following is from my daughter Linda Edwards (not related to Reg) who
lives in London:
The scene is on a mexican golf course and the "Federales" are
investigating an apparent homicide. Investigator asks: "What was the
murder weapon?" Reply is: "A golf gun." Investigator asks "What`s a golf
gun?" Reply is:
"Don`t know but it sure made a hole in Juan!"

best regards, Richard Harrison, KB5WZI

Current through coils
 

Richard Harrison wrote:
J.D. Kraus wrote on page 185 of his 1950 edition of "Antennas":
"Thus, a helix with circumference too small for the axial mode of
radiation (circumferennce less than 2/3 wavelength) has a nearly
sinusoidal current distribution, caused by alternate reinforcement and
cancellation of two oppositely directed traveling waves on the helix of
nearly equal amplitude Izero as suggested in Fig. 7-13c. Both traveling
waves are of the Tzero transmission mode type."

Over on qrz.com, Tom was trying to prove Kraus wrong when he said in
"Antennas for All Applications", 3rd edition: "A coil (or trap) can
also act as a 180 degree phase shifter as in the collinear array
of 4 in-phase 1/2WL elements in Fig. 23-21B. Here the elements
present a high impedance to the coil which may be resonated without
an external capacitor due to its distributed capacitance. The coil
may also be thought of as a coiled-up 1/2WL element."

In trying to prove one could not obtain Kraus' 180 degree phase shift
with a coil [because everyone knows the phase shift is always zero],
Tom accidentally let slip the following - quoted from qrz.com:

W8JI wrote:
"By the way, I swept S12 phase with my network analyzer on a
100uH inductor a few hours ago while working on a phasing
system. The phase shift through that series inductor was about
-60 or -70 degrees on 1 MHz, ... "

Say what? Tom reporting a phase shift through an inductor? Will
miracles never cease?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

I think Reg's estimate of both inductance and first self-resonance (or
is that self-anti-resonance?? ;-) are a bit high. Methods I trust all
predict about 97uH and self-resonance at very close to 8MHz, for a coil
wound with 16AWG to a 2-inch inner diameter. (Inductance would be a
bit lower if that's the wire center-to-center diameter.) Winding and
measuring one to see which estimate is closer is left as an exercise
for the reader, but I wouldn't trust either Reg's or my estimates on
this for building an inductance standard (and besides, I'd build such a
standard with a lower L/D).

A transmission line model shows 13.5 electrical degrees of line at
1.9MHz, at about 6140 ohms. You should probably look up an article by
John Mezak that appeared in "RF Design" some years ago before you to
applying that info willy-nilly, but I don't really expect you will.
Have fun.


Cecil Moore wrote:
Reg Edwards wrote:
A 100 turn coil, 10 inches long, 2 inches in diameter, has an
inductance of 102 microhenrys, a Q of aproximately 380 at F = 1.9 MHz,
and the self-resonant frequency is 12.0 MHz. Its radiation resistance
at 1.9 MHz is negligible.

Good stuff Reg. Modeling it as a transmission line, what would
be its Z0 and VF?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:
John Popelish wrote:

Dang! I was looking forward to your test results, and a description
of your test method. I think your 2" diameter coil is a good example
of an inductor that is neither a perfect "lump" nor a pure
transmission line.


That's what my back of the napkin calculations would indicate.
I get ~14 degrees at 1.9 MHz or ~28 degrees at 3.8 MHz based
on 90 degrees at 12 MHz.

But based on what these guys measured before, anyone would be
a fool to predict the results without knowing what the test
setup looks like. In fact, the prediction challenge was a
blatently obvious attempt to lead the unsuspecting down
a primrose path without a roadmap. Do you think W7EL would
ever make a prediction based on the meager amount of
information provided? :-) A few years ago he provided some
information but kept changing parameters daily until I got
tired and withdrew my estimate. But it turned out in the
end that I was pretty close.

Predictions are little more than an ego trip, unless they are a test
of a specific calculation method used for the prediction. But I was
willing to wait for the test result and an after the fact description
of the test method, to see what understanding might be teased out that
combination of facts. The discussion might also have lead to a better
way to perform such a test.

Baby steps.

Current through coils
 

"Richard Harrison" wrote
Kraus characterizes inductors as helices. At one extreme they are
stretched into straifht wires. At the other they collapse into
single
loops.

=====================================

See program SOLNOID3 which calculates inductance of 1-turn loops, via
multi-turn solenoids, to straight wires. With many other parameters
of interest such as temperature rise for a given applied voltage, as
in tank circuits and antenna loading coils.

So far as the author is aware there are no bugs in it. It's been
around and much used for a few years.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Current through coils
 

John Popelish wrote:
Predictions are little more than an ego trip, unless they are a test of
a specific calculation method used for the prediction. But I was
willing to wait for the test result and an after the fact description of
the test method, to see what understanding might be teased out that
combination of facts. The discussion might also have lead to a better
way to perform such a test.

Still might. But I suspect the test results are already available
and just being withheld because someone doesn't like the results.
I'm a skeptical, suspicious type. I'm sure Tom wishes he had not
published his "-60 to -70 degree phase shift" results.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Reg Edwards wrote:
See program SOLNOID3 which calculates inductance of 1-turn loops, via
multi-turn solenoids, to straight wires.

Reg, at http://www.ttr.com/TELSIKS2001-MASTER-1.pdf equation (43)
gives the helical wave guide effective characteristic impedance.
Unfortunately, that web site is not responding at the moment (probably
because all the gurus here are accessing it wondering what they did
wrong.) :-) But, when the page becomes available would you take a look
at that equation? It goes something like this:

Zc = 60/Vf[I0(tau*alpha)*K0(tau*alpha)]

Is tau the transmission coefficient and alpha the attenuation constant?
Are I0 and K0 functions? Have you ever seen this equation before?

Also, Fig. 1 is a graph of velocity factor vs the diameter of the helix
divided by the wavelength for 10k, 5k, 2.5k, 1k, 500, 250, 100, and 50
turns per wavelength. It says: "Tightly wound coils are slow wave
structures." My 75m bugcatcher coil appears to fall nicely into the
catagory of a "tightly wound slow wave structure".
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

The phase shift along a coil, an inductor, considered as a
transmission line, obviously depends on what it is terminated with.
It much depends on frequency.

In the present context, the termination of the coil is the input
impedance of another transmission line consisting of a rod or length
of wire, or a capacitance hat, forming the remainder of the antenna.

To the participants to this discussion, just think about it. The
behaviour of the coil depends on the behaviour of the rest of the
system.

On the other hand, a coil has certain fixed parameters which are
independent of the rest of the system.

It is a good idea to restrict analysis to the resonant frequency of
the system. It assists with simpification and understanding of it.

Tonight, I've switched to Western Austalian dry white.
----
Reg.

Current through coils
 

wrote:

Cecil,
You have consistently disagreed with me when I said time delay through
an inductor with tight mutual coupling from turn-to-turn is somewhat
close to light speed over the physical length of the inductor, rather
than the time it takes current to wind its way around through the
copper.

I think I have figured out your misunderstanding here, Tom.
I *never* said the current winds its way around through the
copper. That was just another one of your strawmen that
I don't believe and have never believed. I have offered you
$100 if you can find where I ever said that. Would it make
any difference if I offered you $1000?

The effect of a velocity factor of 0.015 may seem to you
to be the same as "current winds its way around through
the copper" but I assure you, if you understood the wave
model of distributed network analysis, you would understand
why that is not the case.

I can fully understand why someone so emotionally
attached to the lumped-circuit model would assume
"current winding its way around through the copper"
but that is simply a misconception of yours.
Distributed networks are not nearly as simple-minded
as your lumped-circuits.

A helical coil structure with a VF of 0.015 *is what it
is*. Waves propagate at 0.015 the speed of light and
that's quite a delay through a relatively physically
short coil. If the coil is 6.5 inches long, as is my
75m bugcatcher coil, it occupies an electrical length
of 6.5"/.015 = 433" = 36 feet. The fact that it consumes
42 feet of wire is just a coincidence. The 6.5" coil
replaces aabout 36' of straight wire. From those facts,
you can calculate the number of degrees or percentage
of a wavelength.

Shirley, you understand that 1/4WL of a transmission
line with a 0.9 velocity factor is longer than 1/4WL
of line with a 0.66 velocity factor. That's why coax
stubs are shorter than 450 ohm ladder-line stubs. (I
feel like I'm doing a EE323 tutorial here).

What is it about a VF of 0.015 that you don't understand?
All it means is that RF through the coil is traveling
at 1/67 the speed of light. If you understand that
RF through RG-8 is traveling at 2/3 the speed of light,
why can't you understand "slow wave coils"?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Reg Edwards wrote:
To the participants to this discussion, just think about it. The
behaviour of the coil depends on the behaviour of the rest of the
system.

i.e. the behavior of the coil depends upon the reflected
energy in the system delivered back to the coil by other
elements in the system. That's basically why the lumped-
constant model fails.

Tonight, I've switched to Western Austalian dry white.

"Austalian"? You've got two choices, Reg. Sober up or
have another. I would have another. :-) But please note,
you have given up a lot of antioxidants from the reds.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

John Popelish wrote:
Cecil Moore wrote:

. . . Do you think W7EL would
ever make a prediction based on the meager amount of
information provided? :-) A few years ago he provided some
information but kept changing parameters daily until I got
tired and withdrew my estimate. But it turned out in the
end that I was pretty close.

That's entirely untrue. The record is readily available via
groups.google.com for anyone interested in seeing what really happened.
The thread was "Current in antenna loading coils controversy (long)", in
November 2003.

. . .

Roy Lewallen, W7EL

Current through coils
 

Roy Lewallen wrote:
John Popelish wrote:

Cecil Moore wrote:
. . . Do you think W7EL would
ever make a prediction based on the meager amount of
information provided? :-) A few years ago he provided some
information but kept changing parameters daily until I got
tired and withdrew my estimate. But it turned out in the
end that I was pretty close.

The record is readily available via
groups.google.com for anyone interested in seeing what really happened.
The thread was "Current in antenna loading coils controversy (long)", in
November 2003.

Yes, indeed, it is, Roy. That's also my reference. And I have
learned a lot of the details underlying your myths since then.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Roy Lewallen wrote:
The record is readily available via
groups.google.com for anyone interested in seeing what really happened.
The thread was "Current in antenna loading coils controversy (long)", in
November 2003.

At that time in 2003, I was as naive as Galileo in front
of the court run by religious priests.

Any time you feel like apologizing for your questionable
behavior, all I ask is that you retract that single
"gobbledygook" statement that you made against my use of
the rules of the distributed-network model and laws of
reflection physics which are both a subset of Maxwell's
equations.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil Moore wrote:

. . . Do you think W7EL would
ever make a prediction based on the meager amount of
information provided? :-) A few years ago he provided some
information but kept changing parameters daily until I got
tired and withdrew my estimate. But it turned out in the
end that I was pretty close.

W7EL wrote:

That's entirely untrue. The record is readily available via
groups.google.com for anyone interested in seeing what really happened.
The thread was "Current in antenna loading coils controversy (long)", in
November 2003.
Roy Lewallen, W7EL

Roy,

I'm also a victim of Cecil's twicted reality now.

I offered to make a measurement if he would even loosely predict
results and tell us in advance what they would mean. When he didn't
respond, I made the measurements anyway.

Time delay measurements of current at each terminal of a "bug-catcher
syle" loading coil are now at:

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

Cecils is also writing what I said on QRZ. If anyone reads back through
his dozens and dozens of waffling posts, eventually they will find a
post where he acknowledges a phase delay I posed on QRZ was in voltage
across the source compared to voltage across a load resistance.

When I measured CURRENT at each end of the inductor (in that case the
inductor was a 1-1/4" long iron core 100uH choke), current had no
detectable amplitude or phase shift. Voltage from the generator was not
in phase with current because of the inductive reactance, but current
had the same relationship at each end of the choke.

Of course Cecil wrote that off as "measuring standing wave current that
is current that doesn't flow", and then suceeded in driving off
someone who was trying to straighten him out on that. All of that is
also in this thread for anyone to read.

There really isn't anything anyone can do to resolve any disagreement
with Cecil, because as soon as he frustrates them into giving up he
will rewrite everything that was said. My only hope is that people who
want to learn will look at the data and understand how an inductor
really works.

It would be comical to watch Cecil twist reality if it wasn't sad. The
sad part is there will be some people out there who will accept his
twisted logic. They won't take the time to read or ask hard questions.
The good part is my understanding of what goes on in a loading coil has
been improved, and I have more data for my web pages.

Fortunately the very high traffic volume into that site keeps it at the
top of search engines.

If you or anyone else finds anything that will clarify inductor
behavior, please let me know. I don't learn much from arguing with
Cecil, but I do learn from other contributors to this thread. I'd like
to thank everyone who has contributed. Even if it doesn't help
everyone, it helps some people.

73 Tom W8JI

Current through coils
 

On Sat, 11 Mar 2006 22:22:47 GMT, Cecil Moore wrote:
I was as naive as Galileo in front of the court run by religious priests.
Has Cecileo been dropping his balls off of the Tower of Pisa again?

Current through coils
 

Cecil Moore wrote:
. . . Do you think W7EL would
ever make a prediction based on the meager amount of
information provided? :-) A few years ago he provided some
information but kept changing parameters daily until I got
tired and withdrew my estimate. But it turned out in the
end that I was pretty close.
W7EL wrote:
That's entirely untrue. The record is readily available via
groups.google.com for anyone interested in seeing what really happened.
The thread was "Current in antenna loading coils controversy (long)", in
November 2003.
Roy Lewallen, W7EL
I'm also a victim of Cecil's twisted reality Roy.
I offered to make a measurement if Cecil would even loosely predict
results and tell everyone in advance what they would mean. When he
didn't
respond, I made the measurements anyway.
Time delay measurements of current at each terminal of a "bug-catcher
style" loading coil are now at:
http://www.w8ji.com/inductor_current_time_delay.htm
Cecil is also re-writing what I said on QRZ. If anyone reads back
through
his posts on this list, they will eventually find a post where he
acknowledges a phase measurement I posted on QRZ was in voltage
across the source compared to voltage across a load resistance.
My response was on Mar 9 2006 at 10:03 PM
When I measured CURRENT at each end of the inductor (in that case the
inductor was a 1-1/4" long iron core 100uH choke), current had no
detectable amplitude or phase shift. Voltage from the generator was not

in phase with current because of the inductive reactance, but current
had the same relationship at each end of the choke.
Of course Cecil wrote that off as "measuring standing wave current that

is current that doesn't flow", and then succeeded in driving off
someone who was trying to straighten him out on that. All of that is
also in this thread for anyone to read. The exact text is:
Cecil,
Good grief!!!!
I said several times that the standing wave does not move. I also said

the "wave" is not the same thing as the "current". The current is
nonzero even though the wave is stationary.
At this point it is obvious that you are just interested in causing a
fuss, and not the slightest bit interested in reaching any sort of
resolution of this item.
Bye.
73,
Gene
W4SZ
There really isn't anything anyone can do to resolve any disagreement
with Cecil, because as soon as he frustrates them into giving up he
will rewrite everything that was said. My only hope is that people who
want to learn will look at the data and understand how an inductor
really works.
It would be comical to watch Cecil twist reality if it wasn't sad. The
sad part is there will be some people out there who will accept his
twisted logic. They won't take the time to read or ask hard questions.
The good part is my understanding of what goes on in a loading coil has

been improved, and I have more data for my web pages.
Fortunately the very high traffic volume into that site keeps it at the

top of search engines.
If you or anyone else finds anything that will clarify inductor
behavior, please let me know. I don't learn much from arguing with
Cecil, but I do learn from other contributors to this thread. I'd like
to thank everyone who has contributed. Even if it doesn't help
everyone, it helps some people.
73 Tom W8JI

Current through coils
 

Cecil Moore wrote:
Roy Lewallen wrote:

The record is readily available via groups.google.com for anyone
interested in seeing what really happened. The thread was "Current in
antenna loading coils controversy (long)", in November 2003.


At that time in 2003, I was as naive as Galileo in front
of the court run by religious priests.

Any time you feel like apologizing for your questionable
behavior, all I ask is that you retract that single
"gobbledygook" statement that you made against my use of
the rules of the distributed-network model and laws of
reflection physics which are both a subset of Maxwell's
equations.

Cecil, have you ever read the book _Don Quixote_, by Cervantes?
There's a character in there you remind me of.
73,
Tom Donaly, KA6RUH