Current through coils
 

Cecil Moore wrote:

[snip]


I apologize for missing the small detail that S12 was a voltage
measurement rather than a current measurement but I'm sure you can
see how that was an honest mistake and easy to make. You didn't
mention "voltage" at all in your posting and the context was current.
I didn't recall until your objection here today that S12 is a voltage
parameter measurement.

But that leads to a question. Why were you using voltage measurements
to try to disprove Kraus' statement about 180 degree current phase
shifting coils. Quoting from: "Antennas for All Applications", Kraus
and Marhefka, 3rd edition, page 824: "A coil (or trap) can also act
as a 180 deg (current) phase shifter as in the collinear array ...
The coil may also be thought of as a coiled-up 1/2WL element."

Cecil,

Interesting,

The complete quote from Kraus on page 744 in my copy of his 2nd edition is:

"A coil (or trap) can also act as a 180 degree phase shifter as in the
collinear array of 4 in-phase lambda/2 elements in Fig. 16.30b. Here the
elements present a high impedance to the coil which may be resonated
without an external capacitance due to its distributed capacitance. The
coil may also be though of as a coiled-up lambda/2 element."


* It is possible that Kraus edited the comment in the 3rd edition, but I
don't see the word "current" in this quote. It is considered good
editorial form to indicate clearly when you have altered the original
wording, unless you are trying to make a point, I suppose.

* The coil in this case is self-resonant at the frequency of use. Do you
use a self-resonant coil for your 80 meter bugcatcher? (Such a coil
might be more appropriate for a pterodactyl catcher.) In any case, this
has little to do with all of your rantings about loading coils. I
suspect even at A&M they must have mentioned something about the
characteristics of resonant circuits.

* You might have noticed the prominent role of capacitance. I believe
that was the item that spurred this thread.

73,
Gene
W4SZ

Current through coils
 

Gene Fuller wrote:
Cecil Moore wrote:
I apologize for missing the small detail that S12 was a voltage
measurement rather than a current measurement but I'm sure you can
see how that was an honest mistake and easy to make. You didn't
mention "voltage" at all in your posting and the context was current.
I didn't recall until your objection here today that S12 is a voltage
parameter measurement.

But that leads to a question. Why were you using voltage measurements
to try to disprove Kraus' statement about 180 degree current phase
shifting coils. Quoting from: "Antennas for All Applications", Kraus
and Marhefka, 3rd edition, page 824: "A coil (or trap) can also act
as a 180 deg (current) phase shifter as in the collinear array ...
The coil may also be thought of as a coiled-up 1/2WL element."

The complete quote from Kraus on page 744 in my copy of his 2nd edition is:

"A coil (or trap) can also act as a 180 degree phase shifter as in the
collinear array of 4 in-phase lambda/2 elements in Fig. 16.30b. Here the
elements present a high impedance to the coil which may be resonated
without an external capacitance due to its distributed capacitance. The
coil may also be though of as a coiled-up lambda/2 element."

* It is possible that Kraus edited the comment in the 3rd edition, but I
don't see the word "current" in this quote. It is considered good
editorial form to indicate clearly when you have altered the original
wording, unless you are trying to make a point, I suppose.

Gene, I assume you know it is common practice to insert words in
parentheses in a quotation to make the meaning clear. Such words
are understood not to be part of the quote. Since Kraus illustrated
the current, not the voltage in Figure 23-21 and earlier in figures
14-2, 14-3, and 14-4, it is rather obvious that he was talking about
a 180 degree current shift. Nowhere that I have seen does Kraus
illustrate the voltage on a standing wave antenna or talk much about
that voltage. Do you see the arrows drawn on the antenna in question?
Do you not know that an arrow drawn on a line denotes current? And
note that since all the current arrows are pointing to the right,
there is a 180 degree current phase shift in each of those phase-
shifting coils.

However, I see I should have used brackets because Kraus was already
using parentheses. I promise to do better next time.

Again, there is hardly any technical content in your reply. You have
refused to respond to the questions I listed for you in an earlier
posting. One wonders why you are avoiding the technical issues.

So I'll ask again. At http://www.qsl.net/w5dxp/qrzgif35.gif

is an EZNEC simulation. How do you explain the 0.1+ amp of current
'flowing' into the bottom of the coil and 0.7+ amp of current
'flowing' out of the top of the coil. How, exactly, is the coil
manufacturing extra current? Hint: such a thing happens all the
time in a standing wave environment because standing wave current
doesn't flow. How could it possibly flow with a constant fixed zero
degree phase angle?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil,

What you are missing is the flux inside the coil links all the turns at
light speed. When it does that, current appears at nearly the same
instant of time (light speed over the spatial distance of the inductor)
in all areas that are linked by flux.

The flux coupling also tries to equalize currents throughout every area
of the coil.

Charge conservation also dictates that any current flowing into the
coil has to be equalled by a like current flowing out the other
terminal, less any displacement currents caused by stray capacitance
(electric fields) to the outside world.

We cannot have a two terminal "black box" with confined fields that
behaves any other way, standing waves or not.

The only flaws in having zero current phase shift and zero current
difference are the less-than-perfect flux coupling and
less-than-perfect confinement of the electric field. Any deviation from
following perfect two-terminal rules are directly tied to the ratio of
load impedance on the inductor to the stray capacitance to the outside
world, and of course less than perfect flux linkage from end-to-end in
the coil.

People can often better understand the limits when things are taken to
an extreme.

Imagine a helical whip antenna. It is a very poorly constructed
"loading coil". It has nearly infinite termination impedance at the
open end, and very poor mutual coupling from turn to turn. The form
factor is very distorted, far from being equal in diameter and length.
The ratio of distributed capacitance to termination capacitance is very
large, it can be nearly infinite.

A loading inductor or helical whip like this behaves nearly like an
antenna.

The opposite would be a toroid, with a very compact form and almost
total confinement of fields. Standing waves or not, as long as it is
not near self-resonance it has evenly distributed current inside and at
each terminal.

Most well-designed efficient short antennas use a loading coil having
very nearly equal currents at each terminal. Current equality actually
is a good way to determine a properly designed loading coil.

If you can stay on topic and we process only one point at a tme, I'm
sure you will be able to learn how this works. If you see any flaw in
how I just described inductor behavior, please point it out. Once we
agree how an inductor works everything else will fall into place.

73 Tom

Current through coils
 

wrote:


W8JI:
I think it would be better if Walt represented himself, unless he ASKED
you to post that Cecil.

Cecil Moo
Walt isn't presently posting for reasons of his own.
He certainly gave me permission to quote his email. I
will ask him if he wants to defend his statements here.

Odd you say that because Walt sent me this:


Hi Tom, it's been a long time since we've talked. I'm sorry if you feel
put
upon.

I had no idea that Cecil was going to put my response on QRZ, and my
only intent
in my comment to him was that with your broad knowledge in the area of
this
issue, I found it hard to believe you didn't understand it. I was
simply
incredulous, not critical. I'm sorry you perceived it as critical, as
it
certainly wasn't intended. In addition, Cecil should not have included
that
portion which was personal in his post to QRZ.

Walt

That doesn't sound like Walter gave you permission to me.

73 Tom

Current through coils
 

Richard Harrison wrote:
A transmission line can`t be analyzed as a simple series circuit,
because the current in the wires is not everywhere the same. Neither is
the voltage. To analyze the line, each unit length must be examined.

Each unit length produces a phase lag in the current on its wires. The
voltage lags too. This can be totaled and the interference between the
incident and reflected waves deternined to find the voltage and current
at any point on the transmission line,

Yes, and that also applies to a real-world loading coil installed
in an environment of incident (forward) and reflected (backward)
waves. Why this is so difficult for some people to understand
is puzzling. All one has to do is use the superposition principle.
Analyze the forward wave, analyze the reflected wave, and superpose
the results.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

wrote:
What you are missing is the flux inside the coil links all the turns at
light speed. When it does that, current appears at nearly the same
instant of time (light speed over the spatial distance of the inductor)
in all areas that are linked by flux.

I am not missing the flux linkage. What you are missing is the known
phase lag that the current undergoes compared to the voltage. Whatever
voltage phase shift you measured (60 degrees), the lagging current
phase shift is likely to be more than double that value. Hint: an
ideal inductor forces the current to lag the voltage by 90 degrees.
If the current propagates at the speed of light, the voltage propagates
much faster than the speed of light so it can lead the current. Please
explain that one to us.

The flux coupling also tries to equalize currents throughout every area
of the coil.

A well known fact. It applies to the forward current and reflected
current, not to the standing wave current which is not flowing
into or out of the coil at all. There is no net charge flow in
a standing wave and therefore, no net current flow. At any point
on a 1/2WL thin wire dipole, the only thing happening is that the
energy is migrating between the H-field and the E-field. There is
zero energy flow away from that point in either direction. That's
why the phase angle of the reflected current is constant and fixed
at zero degrees. It is simply not flowing. What is flowing is the
forward and reflected component currents which indeed to obey all
the rules you have listed here.

Charge conservation also dictates that any current flowing into the
coil has to be equalled by a like current flowing out the other
terminal, less any displacement currents caused by stray capacitance
(electric fields) to the outside world.

Absolutely no argument here. Even assuming the coil is lossless, the
magnitude of the forward current flowing into the coil is equal to
the magnitude of the forward current flowing out of the coil. Likewise
for the reflected current. So this part of your argument is somewhat
irrelevant. What you seem to be missing is the phase shift in those
component currents.

We cannot have a two terminal "black box" with confined fields that
behaves any other way, standing waves or not.

If a piece of transmission that is an appreciable percentage of a
wavelength is coiled into a coil that is an appreciable percentage
of a wavelength, why is it surprising to you that the coil responds
somewhat like the piece of wire that it replaces? The answer is that
you assumed the proof in your argument. It goes something like this:

A lumped inductance doesn't have any magnitude change or phase shift
through the coil. A bugcatcher loading coil is a lumped inductance.
Therefore, a bugcatcher loading coil doesn't have any magnitude change
or phase shift through the coil. The first proof that you offered some
months ago was that the lumped inductance modeled in EZNEC didn't show
any magnitude change or phase shift. Do you see the fallacy in your
thought processes? You assumed the proof in your argument and you
are still falling into that logical trap. Is it any surprise that
a software program shows no magnitude change or phase shift? Please
open up your mind and think the unthinkable. You will be rewarded.

The only flaws in having zero current phase shift and zero current
difference are the less-than-perfect flux coupling and
less-than-perfect confinement of the electric field.

There you go, assuming the proof in your argument. A lossless non-
radiating transmission line doesn't even obey those rules. Why should
you expect a real-world coil made from that transmission line wire to
obey those rules? Before you respond with the 2-terminal Vs 4-terminal
argument, please realize that a horizontal #14 wire 30 ft. above ground
is considered to be a single-wire transmission line with a Z0 of around
600 ohms. Thus, a horizontal dipole is simply a lossy transmission line.

If you would like, I can quote Balanis on all of this.

Any deviation from
following perfect two-terminal rules are directly tied to the ratio of
load impedance on the inductor to the stray capacitance to the outside
world, and of course less than perfect flux linkage from end-to-end in
the coil.

Assuming the proof again. 1/4WL apart in a lossless, non-radiating
transmission line, the standing wave currents are wildly different.
Why are you surprised when we take that 1/4WL of wire, wind it into
a coil, and achieve a lot of the same conditions?

If you can stay on topic and we process only one point at a tme, I'm
sure you will be able to learn how this works.

I'm certainly game for that. We can start by agreeing that the forward
current through a loading coil has the same magnitude at each end of
the coil but suffers a phase shift through the coil. You measured a
voltage phase shift of 60 degrees through a 100uH coil at 1 MHz. Since
the current lags the voltage in a coil, the current phase shift has to
have been greater than 60 degrees, maybe even 120+ degrees depending
upon the Q of the coil. Tom, even I can measure the traveling wave
current phase shift in a 75m bugcatcher coil so please don't insult
my intelligence by asserting that a phase shift doesn't exist.

If a coil could eliminate phase shifts, Intel would be using them in
their computer busses. The truth is, a coil in a computer bus
increases the phase shift, not decreases it. So please give us a
break on that irrational concept. You have been fooled by your model.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

wrote:
That doesn't sound like Walter gave you permission to me.

Tom, I can't believe you have the balls to lie about such a thing
when it is so easy to prove otherwise. Your behavior is unbelievably
unethical. I simply cannot believe you are willing to go to these
lengths to satisfy that insatiable ego of yours.

W5DXP asks Walt:
And Walt, would you mind if I add just your following comments
to the thread on qrz.com and credit them to you? I trimmed out
any reference to me or Tom.

Walter Maxwell earlier wrote:
If an inductance is in series with a line that has no reflections,
the current will be the same at both ends of the inductor.

If an inductance is in series with a line that has reflections,
the current will NOT be the same at both ends of the inductor.

Consequently, circuit analysis will not work when both forward
and reflected currents are present in a lumped circuit.

Walter Maxwell replied to the request:
Fine with me, Cecil, but you might also add the point about the loop
and node appearing simultanously when reflections are present--sorta
puts the icing on the cake.

Walt

Tom, not only did Walt give me permission, he pointed out something
that I had left out.

You are being unbelievably unethical. You could have handled this
in a private email to me but you are apparently willing to drag
Walter Maxwell through the mud in order to spread your old wives'
tales. Good grief, will you stop at nothing? I'm going to have to
sign off and cool down.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Cecil,

All personal issues and insults aside, before anyone does anything with
any of this they would have to have a good feel for how an inductor
behaves.

Do you agree or disagree with my post about how an inductor behaves?

73 Tom

Current through coils
 

wrote:
That doesn't sound like Walter gave you permission to me.

He did give me permission. In a fit of anger, I made a posting
that proves that fact. Upon reflection, after cooling down by
taking a walk, I should not have made that posting and I have
canceled it. Walter Maxwell is my friend and I don't want to
drag the great man into your junk yard dog war. I respect
him too much for that and regret making that posting. I just
hope it didn't make it off my news-server before I canceled it.
It is gone from my news-server.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

wrote:
All personal issues and insults aside, before anyone does anything with
any of this they would have to have a good feel for how an inductor
behaves.

I just asked my dog if she has a good feeling about how an inductor
behaves. She wagged her tail in affirmation. Now please explain why
feelings are important to this discussion.

Do you agree or disagree with my post about how an inductor behaves?

I disagree with you about how an inductor behaves in a standing
wave environment. I agree with Walter Maxwell who said:

"If an inductance is in series with a line that has reflections, the
current will NOT be the same at both ends of the inductor."

Sorry about that, but Walt gave me permission to quote him. Note the
emphasis on 'NOT' in his statement. A 75m bugcatcher mobile system
is a *STANDING WAVE ANTENNA*, so no, I don't agree with you at all
as enumerated in my previous posting. Please don't ask me the same
question over and over. I am not going to change my mind until
you provid valid evidence to the contrary and so far, all you have
done is prove your ethics leave something to be desired.
--
73, Cecil http://www.qsl.net/w5dxp