Richard Harrison wrote:
Those are the necessary and sufficient conditions to reverse the
direction of some of the energy in an incident wave on a transmission
line. For a complete reversal, a short or an open is required.

What you say happens at a load is entirely correct. At a
load, there is only one EM wave incident upon the load.
But at an impedance discontinuity in a transmission line
with reflections, there are two EM waves incident upon
the impedance discontinuity, one from each direction.
There's a forward wave coming from the source and a
reflected wave coming from the load.

It might stand to reason that twice as many incident
waves might complicate things beyond what happens at
a load. And things are more complicated as can be
observed from the s-parameter equations. For a single
load, the s-parameter reflected voltage/power equations
reduce to:

b1 = s11*a1 for normalized reflected voltage, and

b1^2 = (s11*a1)^2 for reflected power where s11^2
is the power reflection coefficient

For an impedance discontinuity in the middle of a
transmission line with reflections, the s-parameter
equation for normalized reflected voltage is:

b1 = s11*a1 + s12*a2 for normalized voltage, and

b1^2 = (s11*a1 + s12*a2)^2 for reflected power

It's pretty obvious that the reflected power equation at
the impedance discontinuity is more complicated than the
reflected power equation at the load. In fact, if you
do the squaring of the right hand side of the equation
just above, you get the interference term.

2*s11*s12*a1*a2*cos(phi) where phi is the phase angle
between phasors a1 and a2.

The interference term, in watts, represents the amount
of interference present and affects the magnitude of
the reflected power. Since the amount of interference
affects the total reflected power, it must also affect
the total forward power so as to satisfy the conservation
of energy principle. Since interference affects the
magnitudes of both the reflected power and forward power,
the conclusion is inescapable that interference can also
cause reflections and this is verified by a couple of
technical web pages pertaining to light waves.

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

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

Walter Maxwell wrote about such back in the 70's. From
Sec 4.3 of "Reflections" speaking of match points:

"The destructive wave interference between these two
complementary waves ... causes a complete cancellation
of energy flow in the direction toward the generator.
Conversely, the constructive wave interference produces
an energy maximum in the direction toward the load, ..."

In a transmission line with only two directions, when the
energy flow is canceled in one direction, that energy must
necessarily flow in the only other direction available, i.e.
an energy reflection must take place.

So to your list of three things that can cause 100% reflection,
you can add wave cancellation in the form of total destructive
interference between two EM waves traveling in the same direction
in a thansmission line, having equal magnitudes and opposite
phases.
--
73, Cecil, http://www.qsl.net/w5dxp


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Cecil Moore wrote:
Jim Kelley wrote:

Cecil Moore wrote:
Exactly! So what does cause the reflection of reflected energy
at the match point? We know it happens and you have given us
no clue as to why it happens.

I assumed you knew. Reflection is caused when a wave encounters a
change in media of some kind.

What I am asserting and you haven't even come close to disproving is
that wave cancellation of RF waves can cause reflections in exactly
the same way as wave cancellation of light waves has been proven
to cause reflections.

Since you're the only person in history to have ever claimed such a
phenomenon occurs, the responsibility rests squarely with you to prove
it exists. As I just got done saying, the only way for electromagnetic
energy to change direction is by reflection. It seemed you understood
that.

What is it about the two following two
technical reference quotes that you don't understand?

I understand them perfectly. You may recall that I introduced you to
the Melles-Griot site. You on the other hand, misunderstand them.

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."

That's as clear as it can possibly be, Jim. Wave cancellation redistributes
the energy.

And you are clearly reading more into it than it clearly says (as
evidenced by the fact that what you wrote and what it says are clearly
not the same thing). Your interpretation is totally incorrect.
Interference is an effect not a cause. The text desribes the actual
end result, but you're interpretting it to be a allusion to some sort
of bizzarre supernatural phenomenon. You're better off doing what I
have done. Figure out how it works by relying upon natural phenomena
for the explanation. It works out beautifully if you'd at least give
it a try. True, you won't be able to claim to have invented it. But
claiming to have invented the other thing would probably only have
earned you a "Cranky" on crank.net anyway.

73, ac6xg

ps Your article did not appear on my news service, so I'm responding
via Google.

On Fri, 05 Aug 2005 12:33:44 -0500, Cecil Moore
wrote:
What you say happens at a load is entirely correct. At a
load, there is only one EM wave incident upon the load.
But at an impedance discontinuity in a transmission line
with reflections, there are two EM waves incident upon
the impedance discontinuity, one from each direction.
There's a forward wave coming from the source and a
reflected wave coming from the load.
snip

There's another way of viewing the manner in which energy reflected
from a mismatch load. That is 'motor generator action'. Lest you think
I'm joking, please let me quote from my own writing in QST August
1973, 32 years ago, repeated in Chapter 3 of Reflections 1 and 2:

"... Now we'll proceed to the generation of reflections. When the
electromagnetic field reaches the end of the line, if the load
terminating the line is an open circuit, the magnetic field collapses
because the current goes to zero due to the infinite impedance of the
open-circuit. The changing magnetic field at the open circuit
produces a new electric field equal in energy to the magnetic field,
which induces a new voltage into the load circuit that is equal to,
and in phase with the voltage in the forward wave. (Keep in mind that
a voltage is induced, or generated, by mutual motion between a
magnetic field and a conductor, a phenomenon generally known as
motor-generator action. Thus, it can be said that the reflected
voltage was developed and delivered by a generator, a reflection
generator. Although in this case the field is changing while the
conductor is stationary, as in a transformer, it is motor-generator
action nonetheless.) The new electric field induced by the changing
magnetic field adds in phase to the existing electric field, and the
new induced voltage (delivered by the reflection generator) adds in
phase to the voltage in the forward wave, resulting in an increase of
voltage at the open circuit to twice the voltage of the forward wave.
At this instant, a standing wave is developing, because now there is a
current minimum and a voltage maximum at the open-circuit termination,
where an instant before, current and voltage were constant all along
the line.
The new voltage at the open-circuit termination, along with its
new electric field, starts a voltage wave traveling in the rearward
direction, as if it had been launched by a separate generator at the
open-circuit point. (It has---remember the induced voltage, generated
by the changing magnetic field?) Since no energy was absorbed by the
open-circuit load, the new rearward-traveling voltage wave has the
same magnitude as the original forward wave, which is why rho = 1,
indicating total reflection. As the new electric field starts its
rearward travel, it produces a new magnetic field, which in turn
produces a new current, launched into the line as the reflected
current wave with the same magnitude as the forward current wave, but
with opposite polarity and direction. The new electric and magnetic
fields combine to form the reflected electromagnetic field and, as in
the forward electromagnetic-field wave, the energy in the reflected
electromagnetic-field wave also divides equally between its electric
and magnetic fields."

Walt, W2DU

Jim Kelley wrote:
Since you're the only person in history to have ever claimed such a
phenomenon occurs, the responsibility rests squarely with you to prove
it exists.

I have quoted many references. That you choose to ignore them is
not my problem. Of course, they are not going to use identical
words to mine. Ham radio lingo has a flavor all it's own,
"reflections" being one of them. I am expecting any moment for
you to say a reversal of energy flow in a transmission line is
not always a reflection. That's how you resolve arguments - by
redefining words until your opponent is wrong, by definition.

As I just got done saying, the only way for electromagnetic
energy to change direction is by reflection. It seemed you understood
that.

I certainly do and wave cancellation can cause a reflection,
i.e. a reversal of energy flow in a transmission line. It's
as simple as that. The "redistribution of energy in a different
direction" caused by wave cancellation can only occur in one
direction in a transmission line. If wave cancellation occurs
in one direction, the energy existing in the waves before they
were canceled must necessarily be distributed in the only other
direction possible. It's all explained on the optics web pages
that I previously posted.

I understand them perfectly. You may recall that I introduced you to
the Melles-Griot site. You on the other hand, misunderstand them.

When you introduced me to the Melles-Groit web page, you told
me what it said and I still think you were right. You were happy
for me because you had found something to support my concepts. After
a few days, you changed your mind and informed me that it didn't
say what you first thought it said. Maybe you should question what
caused your mind to change? Quite often, the first conclusion is the
correct one. So does it say what it says, or not?

And you are clearly reading more into it than it clearly says (as
evidenced by the fact that what you wrote and what it says are clearly
not the same thing).

Clearly not identical but clearly meaning the same thing as
you said it meant when you first introduced me to that web page.
Why did you change your mind about what it said?

Your interpretation is totally incorrect.

Then your initial interpretation of the Melles-Groit web page
information was totally incorrect. Why did you do a 180?

Interference is an effect not a cause.

Interference is not an end effect. Interference can cause the
perception of light and dark rings on the human retina. Lots
of effects which have a cause, cause additional effects in
a chain of cause and effect events. Haven't you ever seen
the TV series "Connections" where one effect caused another
effect which caused another effect ...? So the spacing of the
wheels on a Roman chariot eventually dictated the maximum size
of the boosters on the Space Shuttle?

Interference in transmission lines can cause reflections which
is simply a redistribution of energy in the only other direction
possible. What is it about the "redistribution of energy caused
by interference" that you don't understand? It is explained on
those web pages. In a transmission line, dispersion and refraction
are mostly absent, so reflection is the only thing that can
possibly "redistribute the energy". We know the reflected energy
stops flowing toward the source in the transmission line at a
match point. Wonder what other possible direction it can take next?
That's a really tough question. ... I like you, Jim, because you
make me laugh.
--
73, Cecil http://www.qsl.net/w5dxp

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On Fri, 05 Aug 2005 14:24:43 -0500, Cecil Moore
wrote:

We know the reflected energy
stops flowing toward the source in the transmission line at a
match point.

And this has been proven to the precision of 1 place! If you leave
your thumb on the scale of the energy balance, you can say anything.

Jim's legacy (and those who silently share in it) is bountiful. :-)

Cecil Moore wrote:
Jim Kelley wrote:
I understand them perfectly. You may recall that I introduced you to
the Melles-Griot site. You on the other hand, misunderstand them.


When you introduced me to the Melles-Groit web page, you told
me what it said and I still think you were right. You were happy
for me because you had found something to support my concepts. After
a few days, you changed your mind and informed me that it didn't
say what you first thought it said. Maybe you should question what
caused your mind to change?

I know intimately well what caused me to change my mind. It doesn't
make sense! It's insupportable by the underlying physics. I work in
the field; I've asked E&M people about it. I didn't make up an
explanation for this - YOU DID! Then you looked around to see if it was
true. And you want to think that Melles-Griot confirms it. But it
doesn't.

Quite often, the first conclusion is the
correct one. So does it say what it says, or not?

My second conclusion enjoyed the benefit of actually working through the
problem. That's certainly not true in your case.

Interference is an effect not a cause.


Interference is not an end effect.

You have no idea what you are talking about. You are making a fool of
yourself. Since you don't believe me, try to get Melles-Griot or Eugene
Hecht to confirm your theory that interference causes waves to reflect.
Good luck with that OM.

ac6xg

Richard Clark wrote:
Jim's legacy (and those who silently share in it) is bountiful. :-)

Richard, I wish I could share my email with you.
There is only agreement and encouragement. The
only negative comment is that I stick with a
thread longer than I probably should.
--
73, Cecil http://www.qsl.net/w5dxp

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Jim Kelley wrote:
I know intimately well what caused me to change my mind. It doesn't
make sense! It's insupportable by the underlying physics. I work in
the field; I've asked E&M people about it. I didn't make up an
explanation for this - YOU DID! Then you looked around to see if it was
true. And you want to think that Melles-Griot confirms it. But it
doesn't.

That's just your opinion, worth exactly what it costs. You have
presented no technical argument to prove your case. All you have
presented are logical diversions, personal opinions, and gut feelings.

Why do you refuse to answer the question: Given reflected energy
rejected by a mismatched load, what causes the reversal of direction
of the energy flow and momentum at the match point? It is a simple
question that you have avoided answering for months. One wonders why.

You have no idea what you are talking about. You are making a fool of
yourself.

Asserting that there is no before and after is foolish. Asserting
that a redistribution of energy in a transmission line must have
more than one choice is foolish. Implying that cause and effect
doesn't exist is foolish. Asserting that the waves involved
in wave cancellation don't exist is foolish.

If the waves involved in wave cancellation don't exist, then
wave cancellation is impossible. That's simple logic. If wave
cancellation doesn't exist, it follows that the energy flowing
toward the source is not zero even though we measure it at zero.
This is the logical hole that Dr. Best dug for himself and you
crawled right in after him. Dr. Best asserted that the two waves
keep flowing toward the load, canceling each other all the way
to somewhere (or nowhere). The concepts that you hold concerning
this subject are proven to be logically contradictory. You may
disagree, but I don't believe contradictions can exist in reality.
I believe they can only exist in human minds and yours obviously
contains a multitude. When I encounter a contradiction, I change
my mind. You obviously tolerate (and seem to enjoy) contradictions.
You even use contradictions as part of your arguments.
--
73, Cecil http://www.qsl.net/w5dxp

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I have only found infallibility in Terman, Kraus, Maxwell, The Pope, and
now Cecil!

"Cecil Moore" wrote in message
...
Richard Clark wrote:
Jim's legacy (and those who silently share in it) is bountiful. :-)

Richard, I wish I could share my email with you.
There is only agreement and encouragement. The
only negative comment is that I stick with a
thread longer than I probably should.
--
73, Cecil http://www.qsl.net/w5dxp

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Fred W4JLE wrote:
I have only found infallibility in Terman, Kraus, Maxwell, The Pope, and
now Cecil!

I apologize profusely, Fred, and will strive for infallibility.
--
73, Cecil http://www.qsl.net/w5dxp

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