Cecil Moore wrote:

Tom Donaly wrote:

Hecht was talking about two opposing waves of the same phase and
amplitude interfering with each other. You can't guarantee, in a real
antenna, that the two waves do have the same phase and magnitude.


:-) Hecht was talking about two coherent EM waves traveling in
opposite directions. We are talking about two coherent EM waves
traveling in opposite directions. There is a small traveling
wave component but it doesn't affect the standing wave. It is
what is left over from the standing wave.

This discussion has not been about coils. We need to discuss
an unterminated lossless transmission line and then move on
to 1/2 wavelength thin-wire standing wave antennas.

Has it ever occurred to you, Cecil, that a half wave dipole with
equal current and voltage waves traveling in opposite directions
wouldn't accept power?
73,
Tom Donaly, KA6RUH

John Popelish wrote:
. . .
It is obvious to me that you are one of them. Every point on a line
carrying a standing wave (except the node points) has AC voltage on it,
and AC current through it. The amplitude and phase of those voltages
and currents can be described as a phasor, with respect to some
reference phase of the same frequency. As you move along the line, the
amplitude changes and when you pass through a node the phase reverses.
So the phasor does not rotate with position change, except for a step
change of 180 degrees at nodes, rather than smooth rotation with respect
to position.

For a traveling wave, every point on the line has an AC voltage on it,
and an AC current passing through it. The amplitude is constant along
the line, but the phasor rotates as you move along the line (the phase
is linearly dependent on position). But at any single point on the
line, a non rotating phasor describes the amplitude and phase with
respect to a reference phase of the same frequency.

There's a potential for ambiguity here, and that ambiguity has been used
a number of times in this thread to cause confusion. So let me try to
clarify things.

All phasors "rotate", in that every one contains an implicit term e^jwt.
That term describes a rotation of the complex phasor quantity at the
rotational frequency w (omega), but no change in amplitude. If a
quantity doesn't include this implicit term, it's not a phasor, by
definition. We can look at any phasor quantity in a system and compare
the phase of its rotation with the phase of a reference, and from this
assign a phase angle to it. In steady state, the phase angle doesn't
change with time -- it's the phase difference between the w - rotating
phasor and the w - rotating reference. Phasors of different rotational
rates (that is, of different frequencies) can't be combined in the same
analysis, unless the implicit term is made explicit, in which case
they're no longer phasors.

The use of "rotation" in John's posting is talking about a change of
phase with physical position. This usage has been confused with the time
rotation of the phasor which comes from the implicit e^jwt term. I'd
prefer to use the term "phase", which doesn't change with time in a
steady state system, directly rather than "rotation" to describe a
change in phase with position.

With that convention, we see that the phase of a pure traveling wave
changes linearly with position. But when we sum forward and reverse
traveling waves together to get a total current (or voltage), the phase
of the total current (or voltage) is no longer a linear function of
position. In the special case of an open or short circuited transmission
line, where the forward and reverse traveling waves are equal in
amplitude, the phase doesn't change with position at all (except for a
periodic reversal in current and voltage direction, which can be
interpreted as a 180 degree phase change). But the phasor representing
total voltage or current (which Cecil refers to as "standing wave
current") at any point, which is the sum of two phasors representing
forward and reverse traveling waves, does indeed rotate at w (omega)
radians/second rate, just like its constituent phasors. The constant
phase with position (of an open or shorted line) simply means that if
you froze time at some instant and looked at the angles of the rotating
phasors representing the total current at each point along the line,
you'd find them all to be at the same angle. They're all rotating.

This isn't revolutionary or controversial -- you can find phasors
discussed in any elementary circuit analysis text.[*] And it's not
difficult to do the summation of forward and reverse traveling waves to
see the result, but if you'd like to see how someone else did it, one of
the clearest discussions I've found is in Chipman's _Transmission
Lines_, a Schaum's Outline book.
[*] You have to be a little careful, though. In most introductions to
phasors, the author introduces the e^jwt term early on, and quickly
drops it from the phasor notation as is customary. So it's easy to
forget it's there. But remembering that it is there is vital to
understanding this topic, and to keep from being misled by misdirection
which takes advantage of confusion and abbreviated notation.

Roy Lewallen, W7EL

Cecil Moore wrote:
John Popelish wrote:

Of course. no one is talking about the red herring of charge stored
over a whole cycle.


Of course, *everyone* except you and Tom Donaly are talking about
charge stored over a whole cycle.

Bull.

That's the entire base of their
arguments. The unbalance in the *RMS* current at the bottom of the
coil and the *RMS* current at the top of the coil is what the entire
discussion is all about.

The currents measured by W8JI and W7EL were *RMS* currents. The
currents reported by EZNEC are *RMS* currents.

And the capacitive currents can also be measured in RMS terms. So what?

And no one but you brings up "net storage". We are all talking about
ordinary capacitive charge storage within a cycle.

If so, that is completely irrelevant to the discussion since
W8JI and W7EL are using *RMS* currents for their measurements
and EZNEC is reporting *RMS* currents.

Let me summarize it for you. W8JI and W7EL apparently think
that the RMS current value of zero at the bottom of the coil
Vs the RMS current value of one amp at the top of the coil
means energy is being sucked into the coil from some external
source.

I don't read their responses that way. I read their responses as
saying that the current leaving or entering an end of an inductor
includes a capacitive component and an inductive component. The
capacitive current branches out of the coil to the surrounding space,
and is what allows a measured difference in the currents passing
through its two ends. The path through the wire to the other end is
not the only path for current.

How about assisting in a tutorial on standing waves rather
than diverting and obfuscating the issues?

I'm trying.

Roy Lewallen wrote:
John Popelish wrote:

. . .
It is obvious to me that you are one of them. Every point on a line
carrying a standing wave (except the node points) has AC voltage on
it, and AC current through it. The amplitude and phase of those
voltages and currents can be described as a phasor, with respect to
some reference phase of the same frequency. As you move along the
line, the amplitude changes and when you pass through a node the phase
reverses. So the phasor does not rotate with position change, except
for a step change of 180 degrees at nodes, rather than smooth rotation
with respect to position.

For a traveling wave, every point on the line has an AC voltage on it,
and an AC current passing through it. The amplitude is constant along
the line, but the phasor rotates as you move along the line (the phase
is linearly dependent on position). But at any single point on the
line, a non rotating phasor describes the amplitude and phase with
respect to a reference phase of the same frequency.


There's a potential for ambiguity here, and that ambiguity has been used
a number of times in this thread to cause confusion. So let me try to
clarify things.

All phasors "rotate", in that every one contains an implicit term e^jwt.
That term describes a rotation of the complex phasor quantity at the
rotational frequency w (omega), but no change in amplitude. If a
quantity doesn't include this implicit term, it's not a phasor, by
definition. We can look at any phasor quantity in a system and compare
the phase of its rotation with the phase of a reference, and from this
assign a phase angle to it. In steady state, the phase angle doesn't
change with time -- it's the phase difference between the w - rotating
phasor and the w - rotating reference. Phasors of different rotational
rates (that is, of different frequencies) can't be combined in the same
analysis, unless the implicit term is made explicit, in which case
they're no longer phasors.

The use of "rotation" in John's posting is talking about a change of
phase with physical position. This usage has been confused with the time
rotation of the phasor which comes from the implicit e^jwt term. I'd
prefer to use the term "phase", which doesn't change with time in a
steady state system, directly rather than "rotation" to describe a
change in phase with position.

With that convention, we see that the phase of a pure traveling wave
changes linearly with position. But when we sum forward and reverse
traveling waves together to get a total current (or voltage), the phase
of the total current (or voltage) is no longer a linear function of
position. In the special case of an open or short circuited transmission
line, where the forward and reverse traveling waves are equal in
amplitude, the phase doesn't change with position at all (except for a
periodic reversal in current and voltage direction, which can be
interpreted as a 180 degree phase change). But the phasor representing
total voltage or current (which Cecil refers to as "standing wave
current") at any point, which is the sum of two phasors representing
forward and reverse traveling waves, does indeed rotate at w (omega)
radians/second rate, just like its constituent phasors. The constant
phase with position (of an open or shorted line) simply means that if
you froze time at some instant and looked at the angles of the rotating
phasors representing the total current at each point along the line,
you'd find them all to be at the same angle. They're all rotating.

This isn't revolutionary or controversial -- you can find phasors
discussed in any elementary circuit analysis text.[*] And it's not
difficult to do the summation of forward and reverse traveling waves to
see the result, but if you'd like to see how someone else did it, one of
the clearest discussions I've found is in Chipman's _Transmission
Lines_, a Schaum's Outline book.

[*] You have to be a little careful, though. In most introductions to
phasors, the author introduces the e^jwt term early on, and quickly
drops it from the phasor notation as is customary. So it's easy to
forget it's there. But remembering that it is there is vital to
understanding this topic, and to keep from being misled by misdirection
which takes advantage of confusion and abbreviated notation.

Excellent!

Cecil Moore wrote:
Let me summarize it for you. W8JI and W7EL apparently think
that the RMS current value of zero at the bottom of the coil
Vs the RMS current value of one amp at the top of the coil
means energy is being sucked into the coil from some external
source.

John Popelish wrote:
I don't read their responses that way. I read their responses as
saying that the current leaving or entering an end of an inductor
includes a capacitive component and an inductive component. The
capacitive current branches out of the coil to the surrounding space,
and is what allows a measured difference in the currents passing
through its two ends. The path through the wire to the other end is
not the only path for current.

You read what I wrote and what Roy wrote correctly John.

Cecil changes what other people write to suit his own needs. He changes
what other people say, and then points out why the creatively edited
text he invented is wrong. That's his debating style. Watch out for it!

73 Tom

wrote:
Cecil Moore wrote:
Let me summarize it for you. W8JI and W7EL apparently think
that the RMS current value of zero at the bottom of the coil
Vs the RMS current value of one amp at the top of the coil
means energy is being sucked into the coil from some external
source.

John Popelish wrote:
I don't read their responses that way. I read their responses as
saying that the current leaving or entering an end of an inductor
includes a capacitive component and an inductive component. The
capacitive current branches out of the coil to the surrounding space,
and is what allows a measured difference in the currents passing
through its two ends. The path through the wire to the other end is
not the only path for current.

You read what I wrote and what Roy wrote correctly John.

Cecil changes what other people write to suit his own needs. He changes
what other people say, and then points out why the creatively edited
text he invented is wrong. That's his debating style. Watch out for it!

Absolutely true. Cecil complains that people won't engage in a technical
discussion with him. Many have tried, and all we get in response is
evasion, misquotes, diversion, and brushing off of any evidence contrary
to his preconceived notions.

Anyone who wants to know what I said or what I think should read what
I've posted. If it's not clear, ask. But don't trust Cecil to tell you.

Roy Lewallen, W7EL

Tom Donaly wrote:
Has it ever occurred to you, Cecil, that a half wave dipole with
equal current and voltage waves traveling in opposite directions
wouldn't accept power?

It is an approximation, Tom, like a lossless line. For real world
dipoles, the voltage and current decay by about 10% between the
forward wave and the arrival of the reflected wave. Kraus and
Terman both use that approximation in their examples.

We aren't saying anything about the traveling wave part of the
waves. The discussion is about the standing wave portion of
the wave which, by definition, requires equal magnitudes.
--
73, Cecil http://www.qsl.net/w5dxp

Roy Lewallen wrote:
The constant
phase with position (of an open or shorted line) simply means that if
you froze time at some instant and looked at the angles of the rotating
phasors representing the total current at each point along the line,
you'd find them all to be at the same angle. They're all rotating.

Yes, when I said standing wave current phase doesn't rotate, I meant
with respect to the source current phase. At any instant in time,
the phase of the standing wave current is unchanging up and down
the line.

Assume the standing wave current all up and down the dipole is of
constant phase with no variation with 'x'. Roy, you used that
current to try to measure the delay through a coil. How did you
plan to measure that delay with a signal known to be the same
phase not only at both ends of the coil but all up and down
the antenna?
--
73, Cecil http://www.qsl.net/w5dxp

John Popelish wrote:

Cecil Moore wrote:
Of course, *everyone* except you and Tom Donaly are talking about
charge stored over a whole cycle.

Bull.

If that's what you think and you can find someone to discuss
energy exchange within a cycle, be my guest. As far as I know,
Tom Donaly introduced the subject as a diversion.

I don't read their responses that way.

I couldn't believe it either but after years of arguing with them,
it is apparent that many of the gurus here on r.r.a.a are simply
ignorant of the nature of standing waves.

I really expected them to shout, "April Fool, we have been pulling
your leg!" But, sad to say, they are serious about standing wave
current "flowing" into the bottom of the coil and out the top.
They apparently haven't read "Optics", by Hecht where he says:
"E(x,t) = 2Eo*sin(kx)*cos(wt) This is the equation for a standing
wave, as opposed to a traveling wave. Its profile does not move
through space. ... [The standing wave] phasor doesn't rotate at
all, and the resultant wave it represents doesn't progress through
space - its a standing wave." If standing waves of light don't move
through space, standing waves of RF don't move through a wire.

I read their responses as saying
that the current leaving or entering an end of an inductor includes a
capacitive component and an inductive component. The capacitive current
branches out of the coil to the surrounding space, and is what allows a
measured difference in the currents passing through its two ends.

That is a secondary effect. The primary effect is the phasor addition
of the forward current and reflected current which you provided.

Compared to zero amps of standing wave current when the forward current
phasor and the reflected current phasor are 180 degrees out of phase,
just how much effect can capacitance have?
--
73, Cecil http://www.qsl.net/w5dxp

wrote:
Cecil changes what other people write to suit his own needs. He changes
what other people say, and then points out why the creatively edited
text he invented is wrong. That's his debating style. Watch out for it!

Tom, do you or do you not believe that standing wave current flows
into the bottom of the coil and out the top? It's a simple yes/no
question. You have earlier stated that "current is current" and
that, in spite of the different equations for for the two currents,
standing wave current moves like traveling wave current in spite
of what Hecht had to say in "Optics".

"E(x,t) = 2*Eo*sin(kx)*cos(wt) This is the equation for a STANDING
or STATIONARY WAVE, as opposed to a traveling wave. Its profile does
not move through space; it is clearly not of the form Func(x +/- vt).
.... [Standing wave phase] doesn't rotate at all, and the resultant
wave it represents doesn't progress through space - its a standing
wave."

If standing waves of light don't move through space, standing waves
of RF don't move through wires.

Time to stop the ad hominem attacks and address this technical issue.
--
73, Cecil http://www.qsl.net/w5dxp