On Jan 1, 9:03*pm, Cecil Moore wrote:
Roger wrote:
The principles of superposition are mathematically usable, not too hard,
*and I think very revealing. *Yes, if we use part of the model, we must
use it all the way. *To do otherwise would be error, or worse.

Roy and Keith don't seem to realize that the zero source
impedance for the ideal voltage source is only when the
source is turned off for purposes of superposition.

I am not sure you have the methodology quite correct.
The source is not turned off; its output is set to 0.

It does what every ideal voltage source will do when
set to a voltage; maintain that voltage. Through all
of this, the impedance of the ideal source remains 0.

Now it turns out that an ideal voltage source set
to zero volts can be replaced by a short which also
has an impedance of 0 and produces no volts. But this
does not alter that the ideal source always has an
impedance of 0.

Analogously, an ideal current source always has an
infinite impedance. When set to 0 amps, it behaves
exactly like an open circuit.

They
conveniently avoid turning the source voltage on to complete
the other half of the superposition process. When the
source signal and the reflected wave are superposed at
the series source resistor, where the energy goes becomes
obvious. Total destructive interference in the source
results in total constructive interference toward the load.
See below.

You have been a supporter of this theory for a long time.

Yes, I have. I am a supporter of the principles and laws of
physics. Others believe they can violate the principle of
conservation of energy anytime they choose because the
principle of conservation of energy cannot be violated -
go figure.

You should really stop repeating this to yourself. No
one is attempting to violate the principle of conservation
of energy.

By continually repeating this mantra, you convince
yourself that you do not need to examine the claims
of those who disagree with you. So you do not
examine and understand their claims. This seriously
limits your capability to learn.

If you truly wish to demolish the claims, you should
study them in great detail, then write an even better
and more persuasive description of the claim than did
the original author. Then identify and point out the
flaws.

As it stands, you do not examine the claims, but
immediately coat them with the tar of "violates
conservation of energy" or some other mantra and
walk away.

It does not lead to learning.

...Keith

Keith Dysart wrote:
I am not sure you have the methodology quite correct.
The source is not turned off; its output is set to 0.

That's exactly the same thing - turning a source off
and setting it to zero. I suggest you go back and
study the rules for superposition and get back to us.
Exactly the same concepts apply for an s-parameter
analysis. Please learn how s11 and s22 are measured
and get back to us.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
On Jan 1, 9:03 pm, Cecil Moore wrote:
Roger wrote:
The principles of superposition are mathematically usable, not too hard,
and I think very revealing. Yes, if we use part of the model, we must
use it all the way. To do otherwise would be error, or worse.
Roy and Keith don't seem to realize that the zero source
impedance for the ideal voltage source is only when the
source is turned off for purposes of superposition.

I am not sure you have the methodology quite correct.
The source is not turned off; its output is set to 0.

It does what every ideal voltage source will do when
set to a voltage; maintain that voltage. Through all
of this, the impedance of the ideal source remains 0.

Now it turns out that an ideal voltage source set
to zero volts can be replaced by a short which also
has an impedance of 0 and produces no volts. But this
does not alter that the ideal source always has an
impedance of 0.

Analogously, an ideal current source always has an
infinite impedance. When set to 0 amps, it behaves
exactly like an open circuit.

They
conveniently avoid turning the source voltage on to complete
the other half of the superposition process. When the
source signal and the reflected wave are superposed at
the series source resistor, where the energy goes becomes
obvious. Total destructive interference in the source
results in total constructive interference toward the load.
See below.

You have been a supporter of this theory for a long time.
Yes, I have. I am a supporter of the principles and laws of
physics. Others believe they can violate the principle of
conservation of energy anytime they choose because the
principle of conservation of energy cannot be violated -
go figure.

You should really stop repeating this to yourself. No
one is attempting to violate the principle of conservation
of energy.

By continually repeating this mantra, you convince
yourself that you do not need to examine the claims
of those who disagree with you. So you do not
examine and understand their claims. This seriously
limits your capability to learn.

If you truly wish to demolish the claims, you should
study them in great detail, then write an even better
and more persuasive description of the claim than did
the original author. Then identify and point out the
flaws.

As it stands, you do not examine the claims, but
immediately coat them with the tar of "violates
conservation of energy" or some other mantra and
walk away.

It does not lead to learning.

...Keith
I fully agree with the philosophy you express here Keith. But I can see
how you would doubt that I am practicing what I just agreed with.

You have posted several times on the subject of impedance of an ideal
source, and I have learned from your words. You may find however, that
I have still not completely grasped an important component of the
concept. If that happens, please try again, using a different argument.

Learning is a meshing of words, ideas, concepts, experience, and more.
You can see that I am inexperienced. I can see that many of the posters
are very experienced. Experience is not necessary for presenting an
argument, but it certainly helps in presenting the argument wisely,
coherently, and convincingly. Correctness is always a judgment by the
reader.

73, Roger, W7WKB

On Jan 3, 7:22*am, Roger wrote:
Keith Dysart wrote:
On Jan 1, 9:03 pm, Cecil Moore wrote:
Roger wrote:
The principles of superposition are mathematically usable, not too hard,
*and I think very revealing. *Yes, if we use part of the model, we must
use it all the way. *To do otherwise would be error, or worse.
Roy and Keith don't seem to realize that the zero source
impedance for the ideal voltage source is only when the
source is turned off for purposes of superposition.

I am not sure you have the methodology quite correct.
The source is not turned off; its output is set to 0.

It does what every ideal voltage source will do when
set to a voltage; maintain that voltage. Through all
of this, the impedance of the ideal source remains 0.

Now it turns out that an ideal voltage source set
to zero volts can be replaced by a short which also
has an impedance of 0 and produces no volts. But this
does not alter that the ideal source always has an
impedance of 0.

Analogously, an ideal current source always has an
infinite impedance. When set to 0 amps, it behaves
exactly like an open circuit.

They
conveniently avoid turning the source voltage on to complete
the other half of the superposition process. When the
source signal and the reflected wave are superposed at
the series source resistor, where the energy goes becomes
obvious. Total destructive interference in the source
results in total constructive interference toward the load.
See below.

You have been a supporter of this theory for a long time.
Yes, I have. I am a supporter of the principles and laws of
physics. Others believe they can violate the principle of
conservation of energy anytime they choose because the
principle of conservation of energy cannot be violated -
go figure.

You should really stop repeating this to yourself. No
one is attempting to violate the principle of conservation
of energy.

By continually repeating this mantra, you convince
yourself that you do not need to examine the claims
of those who disagree with you. So you do not
examine and understand their claims. This seriously
limits your capability to learn.

If you truly wish to demolish the claims, you should
study them in great detail, then write an even better
and more persuasive description of the claim than did
the original author. Then identify and point out the
flaws.

As it stands, you do not examine the claims, but
immediately coat them with the tar of "violates
conservation of energy" or some other mantra and
walk away.

It does not lead to learning.

...Keith

I fully agree with the philosophy you express here Keith. *But I can see
* how you would doubt that I am practicing what I just agreed with.

You may have mis-interpreted my comments. I have NOT
seen evidenace of the behaviour I describe above in
your writings.

The comments mostly apply to a single poster who has
been posting on this group for many years, at least
since when I first started viewing this group in the
mid 90s and began to really gain an understanding of
transmission lines.

The presence of this poster providing misleading
information makes this group a rather unique learning
environment.

In most learning environments, the information is
neatly packaged and presented from a consistent
point of view with no challenge.

Here, a lot of chaff is mixed with the wheat. This
has the "benefit" of forcing the learner to
understand well enough to make decisions between
competing explanations. The learner who makes the
right choices comes out with a much more solid
understanding than one who has just been (spoon)
fed the story. On the other hand, some have
probably been lead seriously astray.

For sure, I have a better understanding than
I would have had without the challenging
misleading information.

So for sure it would be better for the poster
in question were he to let go of some of his
incorrect beliefs, it would also reduce some of
the opportunities for learning provided to
others lurking or partaking in the discussions.

...Keith

Keith Dysart wrote:
The presence of this poster providing misleading
information makes this group a rather unique learning
environment.

But a learning experience nonetheless. All one has
to do regarding false information is to produce
valid technical references to the contrary.

Ad hominem attacks are not technical references
and the mere assertion that the information is
misleading implies some level of omniscience in
the asserter that is not in evidence.

For the record: The only controversial assertion
that I have ever made is that coherent EM wave
cancellation can cause a redistribution of the
EM energy in the opposite direction in a transmission
line. No one has proved that assertion to be wrong.

A couple of technical web pages assert that wave
cancellation can be the cause of a redistribution
of photonic energy to areas that allow constructive
interference.

Since there is only one other direction available
in a transmission line, the constructive interference
must occur in the opposite direction from the
direction of wave cancellation.

That seems like a no-brainer to me.
--
73, Cecil http://www.w5dxp.com

On Thu, 03 Jan 2008 12:25:59 -0600, Cecil Moore
wrote:

The presence of this poster providing misleading
information makes this group a rather unique learning
environment.

For the record: The only controversial assertion
that I have ever made is that coherent EM wave
cancellation can cause a redistribution of the
EM energy in the opposite direction in a transmission
line. No one has proved that assertion to be wrong.

What an ego to rush to slip into a TNT vest in the hope of being
associated with Nobel.

As usual, Cecil's arguments are so script driven, that I cannot pass
up this mocking opportunity:

I shall assert that coherent EM wave cancellation can not cause a
redistribution of the EM energy in the opposite direction in a
transmission line.

No one has proved that assertion to be wrong.

Does that misleading statement qualify me for Keith's anointed villain
of the group? Cecil certainly has described me as being scurrilous
enough to so qualify! ;-)

Besides, I think I look better in that vest than he does.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
I shall assert that coherent EM wave cancellation can not cause a
redistribution of the EM energy in the opposite direction in a
transmission line.

No one has proved that assertion to be wrong.

The Melles-Groit and FSU web pages certainly seem to
disagree with you. To the best of my knowledge, they
prove your assertion to be wrong and support my
contention of redistribution of energy after wave
cancellation.

http://www.mellesgriot.com/products/optics/oc_2_1.htm

"Clearly, if the wavelength of the incident light and
the thickness of the film are such that a phase difference
exists between reflections of p, then reflected wavefronts
interfere destructively, and overall reflected intensity is
a minimum. If the two reflections are of equal amplitude,
then this amplitude (and hence intensity) minimum will be
zero." (Referring to 1/4 wavelength thin films.)

"In the absence of absorption or scatter, the principle of
conservation of energy indicates all 'lost' reflected intensity
will appear as enhanced intensity in the transmitted beam.
The sum of the reflected and transmitted beam intensities is
always equal to the incident intensity. This important fact
has been confirmed experimentally."

http://micro.magnet.fsu.edu/primer/j...ons/index.html

"... when two waves of equal amplitude and wavelength that are
180-degrees ... out of phase with each other meet, they are not
actually annihilated, ... All of the photon energy present in
these waves must somehow be recovered or redistributed in a new
direction, according to the law of energy conservation ... Instead,
upon meeting, the photons are redistributed to regions that permit

constructive interference, so the effect should be considered as
a redistribution of light waves and photon energy rather than
the spontaneous construction or destruction of light."

In an RF transmission line, since there are only two possible
directions, the only "regions that permit constructive interference"
at an impedance discontinuity is the opposite direction from the
direction of destructive interference.
--
73, Cecil http://www.w5dxp.com

On Thu, 03 Jan 2008 14:17:11 -0600, Cecil Moore
wrote:

No one has proved that assertion to be wrong.

The Melles-Groit and FSU web pages certainly seem to
disagree with you.

There is a vast gulf between seeming and proving.

My assertion stands unassailed! [except for a few pecks by a duck]

On Jan 3, 1:25*pm, Cecil Moore wrote:
For the record: The only controversial assertion
that I have ever made is that coherent EM wave
cancellation can cause a redistribution of the
EM energy in the opposite direction in a transmission
line.

Don't be so modest.

You have also claimed that for an amplifier which can
be modelled as a Thevenin or Norton equivalent circuit,
the output impedance can not be used to derive the
reflection coefficient.

You have claimed that the only way to prevent a
re-reflection at a generator is to use a circulator;
a 10 cent resistor will never do.

You have claimed that energy can cross a point on
the line where V or I is always 0.

You have claimed that there is great importance
to the terms "Traveling-Wave Current" and
"Standing-Wave Current" (the title of this thread).

And there were more that escape my memory.

...Keith

"Keith Dysart" wrote in message
...

Sorry i have been absent for a while, been too busy with other work and had
to turn this off to keep from spending all my time laughing at the postings.
Are we going for another 1000 post thread? almost 2/3's of the way there
now... here is a kick to keep it going.

You have claimed that energy can cross a point on
the line where V or I is always 0.

ah, so once you have a standing wave on a line then no energy can cross the
voltage or current nodes?? thats interesting. so at the place where
current is 'always' 0 the voltage is a max right? so what happens to the
V^2/Z power at that point? is that not flowing past that point?
conversely, at the point where voltage is always zero, what happens to the
large I^2*R power at that point??? where does that go? then try this
thought experiment... take a long coax with an open circuit end, feed it
with sinusoidal ac so it has nice standing waves, keep it lossless just
because that irritates some of the writers on here. then attach a pure
resistance equal to Z0 at the open end. now, if energy can't pass the
points where V or I is zero, and I is obviously zero at the open circuit at
the end of the line there should be no power to flow into that resistor???
Oh, but wait, the voltage is a max there so the resistor could draw power
from the voltage standing wave, but then what happens to the current
standing wave? once the resistor drains the last half wave voltage wave how
does energy get from the next standing wave into the far end one to
replenish it if it can't flow across the voltage node?? sorry, i have to
stop, about to start another laughing fit.

all of the above obvious contradictions become intuitively obvious once you
completely forget the standing waves and think only in terms of the
traveling waves. and remember, again just because it tweaks some
correspondents on here, you only need the voltage OR the current traveling
wave, either one is sufficient to completely describe the conditions on the
line in either steady state or transient conditions. (as long as the line
and components are all linear and time invarient, loss is not a problem for
this statement to be true)