Cecil Moore wrote:
Gene Fuller wrote:

Cecil, You can't be serious!
This is basic stuff found in virtually any intermediate level E&M
textbook.


If you can provide me with a reference that says, wave cancellation can
cause reflection of the canceled waves, I will be eternally grateful.
I have been able to find references that imply such for light waves,
but I have not found one that comes right out and says it for either
light waves or RF waves.
. . .

I'm afraid that your difficulty in finding a reference is simply due to
its not being so.

If it is indeed so, it appears that your forthcoming QEX article will be
a seminal work, as the first published work to explicitly state that
this phenomenon indeed happens (outside of countless newsgroup postings
to that effect). Assuming you understand the physics which causes it to
happen, I'd think that a professional publication would be a much more
appropriate forum than QEX for such an important work. Have you tried
any of the IEEE publications?

Roy Lewallen, W7EL

Roy Lewallen wrote:
Does your analysis produce the result of 2.3 dB loss claimed by H.
for a 1.7:1 SWR?

Cheap friggin' damn shot, Roy, after my posting where I disagreed
with H. and agreed with your calculations.
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil Moore wrote:
. . .
What is happening in your "food for thought" assertions is that you
are neglecting the ability of the phenomenon of wave cancellation to
cause 100% reflection of the energy components in the two canceled
waves, something that is well understood in the field of optics.
Dr. Best also neglected to take interference energy into account in
his QEX article on transmission lines.
. . .

If I'm neglecting an important phenomenon, then surely some of my
numerical results showing voltages, currents, forward, reverse, and
total powers, and power dissipation must be incorrect. And an experiment
can be set up to demonstrate their incorrectness and the validity of the
alleged phenomenon.

I'd appreciate it very much if you or anyone else who finds any
incorrect results in that series of essays, or anything else I've
written or posted, bring it to my attention so it can be corrected.

Roy Lewallen, W7EL

Roy Lewallen wrote:

Cecil Moore wrote:

Gene Fuller wrote:
Cecil, You can't be serious!
This is basic stuff found in virtually any intermediate level E&M
textbook.

If you can provide me with a reference that says, wave cancellation can
cause reflection of the canceled waves, I will be eternally grateful.
I have been able to find references that imply such for light waves,
but I have not found one that comes right out and says it for either
light waves or RF waves.

I'm afraid that your difficulty in finding a reference is simply due to
its not being so.

Well, Gene says it is really basic stuff (not worthy of a second
thought). Which is it? - Not worthy of a second thought or seminal
work?

If it is indeed so, it appears that your forthcoming QEX article will be
a seminal work, as the first published work to explicitly state that
this phenomenon indeed happens (outside of countless newsgroup postings
to that effect). Assuming you understand the physics which causes it to
happen, I'd think that a professional publication would be a much more
appropriate forum than QEX for such an important work. Have you tried
any of the IEEE publications?

Nope, I haven't. I've retired from being a pro. Now I am just
an amateur.

When two coherent waves traveling in the same path and direction are
180 degrees out of phase, they disappear from existence in that
original direction of travel, i.e. they undergo wave cancellation.
When they are confined to a transmission line with only two directions,
the flow of energy in the original direction ceases. There is no other
choice but for the energy in the two cancelled waves to be conserved
and to reverse direction and start flowing in the opposite direction.
That, my friend, is a reflection. How can you possibly believe that
the energy in cancelled waves is not conserved?

So to your list of shorts, opens, and pure reactances being able to
cause 100% reflection, you can add wave cancellation. Note that wave
cancellation cannot happen at a single load with a single incident
wave. It can only happen at points where there are waves flowing
in opposite directions, e.g. match points on transmission lines with
reflections and at sources subjected to reflections.

Please don't argue that you have never seen such. Anyone who has
looked at an oil film on water has witnessed reflections caused
by interference and wave cancellation.
--
73, Cecil http://www.qsl.net/w5dxp

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Jim Kelley wrote:

Cecil Moore wrote:
It can easily be shown that 300 joules of energy have been
generated that have not been delivered to the load, i.e.
those 300 joules of energy are stored in the feedline.

Not easy if t 2 sec. :-)

Of course, my statement is related to steady-state. I don't
see anything worth responding to, Jim. Where's the beef?
--
73, Cecil http://www.qsl.net/w5dxp

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Roy Lewallen wrote:

If I'm neglecting an important phenomenon, then surely some of my
numerical results showing voltages, currents, forward, reverse, and
total powers, and power dissipation must be incorrect.

No, they are not incorrect. They are net values and, as
such, are simply incomplete. Dr. Best had the same problem
in his article which was accurate but incomplete. The
problem with incomplete information is that erroneous
conclusions are likely to occur. In addition to a closed
mind, that's your present problem and Dr. Best's problem
with his QEX article.

Valid data being incomplete can sometimes be just as bad
or worse than data being wrong.
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil,

I do not expect that the reference you seek can be found.

There is no need to invoke interference or wave cancellation to explain
anything, and it is unlikely there is any mathematical formulation that
uses interference as one of the input variables.

It is totally unnecessary. Maxwell's equations contain everything needed
to accurately describe electromagnetic interactions, including wave
reflections, cancellations, and interference.

Any serious treatment of the subject of electromagnetic interactions
begins with the field equations, not with the resulting interference.
The sort of description found on the Melles-Griot web site and on their
CD-ROM is a handwaving, but comforting, description meant for general
understanding, not for detailed analysis.

73,
Gene
W4SZ

Cecil Moore wrote:
Gene Fuller wrote:

Cecil, You can't be serious!
This is basic stuff found in virtually any intermediate level E&M
textbook.


If you can provide me with a reference that says, wave cancellation can
cause reflection of the canceled waves, I will be eternally grateful.
I have been able to find references that imply such for light waves,
but I have not found one that comes right out and says it for either
light waves or RF waves.

I agree with you 100%. I had this "basic stuff" taught to me at Texas
A&M half a century ago. But Roy's "food for thought" stuff completely
ignores exactly that "basic stuff" concerning constructive/destructive
interference. Nowhere in his arguments is "interference" even mentioned.
I expect him to respond that interference is irrelevant. Dr. Best
went so far as to deny that interference is necessary for a Z0-match to
occur in a system with reflections. That was around May/June 2001 on
this very newsgroup for anyone who wants to Google it.

I have been fighting this battle for three years on this newsgroup.
Now you say it's "basic stuff". I've agreed for three years, but
where have you been all this time?

The treatment is generally the same; start with the field equations
describing the waves, add the material conditions and the boundary
conditions, plug and crank. The answers pop right out. No need to
invoke any magic incantations about interfering waves or wave
cancellation. The interference is the result of the analysis, not the
cause.


Some people have forgotten what they learned in college. Their net/
steady-state shortcuts have become reality and scrambled their brains.
You are obviously not one of the people at whom I aimed my remarks.
I am glad to see that not everyone has been seduced into thinking
that interference is irrelevant.

In the classical case, there is absolutely no difference in behavior
between "RF" and "optical". The material properties for every
situation can vary, but the physical principles do not.


I know that. You know that. We are on the same side. Now convince the
RF gurus of that. Roy calculated the net power at the source and
assumed from that figure that there was not enough energy available
to support the energy in reflected waves.

Sooo, rather than introducing a new concept, you are perhaps the last
person to finally understand the old one.


No, not the last one. What you say is exactly what is wrong with
Roy's arguments that reflected energy doesn't flow from the load
back toward the source. I am NOT introducing a new concept. I am
introducing a new (or forgotten) concept to some of the RF gurus
on this newsgroup. I am (re)introducing destructive/constructive
interference concepts to Roy, Dr. Best, and others.

Roy Lewallen wrote:
In my third example, where does the other 10 watts of reflected power
go? If it goes to the load and back, why does it reflect off the source
resistor?

I have read the third example, which is NOT steady-state,
and I don't understand the question. Give me some steady-
state values and I will discuss it.

************************************************** *************
However, a reflected wave approaching a source resistor doesn't
encounter the source resistor as an isolated load. The source
voltage superposes with the reflected voltage at that point
which may, in reality, actually turn out to be an impedance
discontinuity.
************************************************** *************

Quoting Ramo and Whinnery: "It must be emphasized, as in any
Thevenin equivalent cirsuit, that the equivalent circuit was
derived to tell what happens in the ***LOAD*** under different
load conditions, and significance cannot be automatically
attached to a calculation of power loss in the internal
impedance of the equivalent circuit."
--
73, Cecil http://www.qsl.net/w5dxp

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Gene Fuller wrote:
There is no need to invoke interference or wave cancellation to explain
anything, ...

But there is, Gene. It's the only way to correct the present
misinformation and old wives' tales being promoted on this
newsgroup. It is obvious that the r.r.a.a poster who
understands the role that interference plays in the
conservation of RF energy is very rare.

There is a conspiracy to keep this information from
surfacing - "Nothing new", "no need", "irrelevant",
"who cares?" Why are you guys afraid to discuss the
technical details?

This should be an easy question to answer. If two coherent
waves of 50 joules/sec each, are traveling in the same
path in the same direction and are 180 degrees out of
phase, they cancel in that direction of travel. What
happens to their 50+50 joules/sec? Hint: energy doesn't
cancel and there are only two possible directions. Can
you spell R-E-F-L-E-C-T-I-O-N?
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil Moore wrote:
Roy Lewallen wrote:

Does your analysis produce the result of 2.3 dB loss claimed by H.
for a 1.7:1 SWR?


Cheap friggin' damn shot, Roy, after my posting where I disagreed
with H. and agreed with your calculations.

Sorry, it was an honest question. I saw your posting re the SWR
calculations, but guess I missed the one you mention. H's calculations
remain a mystery to me, as apparently they do to you.

Roy Lewallen, W7EL