On Jun 12, 8:16*pm, walt wrote:
Thank you for the insightful response, Cecil. However, when you go to
the 2-port version I’m unable to correlate that configuration with my
stubbing problem.

The reason that I didn't say anything about the stub example is
because I cannot comprehend it without a schematic. That's why I
changed examples. Do you agree with what I said about my example?
Could you post a schematic of your first example? It is the "series
stub" part that I don't understand. Such is usually called a "series
section" because a stub is usually a parallel dead end open or short
circuit. It is also difficult to comprehend how a two-port analysis
could be done at the stub connection point. Wouldn't that require a
three-port analysis?

We’re considering the source to be an RF power amp, where we know the
output source resistance is non-dissipative, thus re-reflects all
reflected power incident on it. I maintain that the reflection
coefficient at the source is 1.0 because of the total re-reflection
there.

How's about we limit the *initial* discussion and examples to a source
with zero incident reflected power so the source impedance doesn't
matter? IMO, a two-port analysis of a Z0-match point will reveal the
main ingredients of the energy flow.

However, mathematical experts say that the equation is correct, saying
that rho_¬’s’ cannot be equal to 1.0, because the virtual open circuit
was established by wave interference, not a physical open circuit.

A one-port analysis cannot tell the difference between wave
interference and reflections. You are correct that the reflection
coefficients are not necessarily the same between a one-port analysis
and a two-port analysis. Your "mathematical experts" don't seem to
understand the limitations of a one-port analysis. It's akin to not
knowing what is inside a black box, i.e. one cannot tell the
difference between a resistor and a virtual resistance. However, with
a two-port analysis, one can tell the difference. It appears that your
"mathematical experts" are insisting on a two-port analysis such as
provided by the s-parameter equations:

b1 = s11*a1 + s12*a2

b2 = s21*a1 + s22*a2

http://www.sss-mag.com/pdf/an-95-1.pdf
--
73, Cecil, w5dxp.com

On Jun 12, 9:45*pm, Cecil Moore wrote:
On Jun 12, 8:16*pm, walt wrote:

Thank you for the insightful response, Cecil. However, when you go to
the 2-port version I’m unable to correlate that configuration with my
stubbing problem.

The reason that I didn't say anything about the stub example is
because I cannot comprehend it without a schematic. That's why I
changed examples. Do you agree with what I said about my example?
Could you post a schematic of your first example? It is the "series
stub" part that I don't understand. Such is usually called a "series
section" because a stub is usually a parallel dead end open or short
circuit. It is also difficult to comprehend how a two-port analysis
could be done at the stub connection point. Wouldn't that require a
three-port analysis?

We’re considering the source to be an RF power amp, where we know the
output source resistance is non-dissipative, thus re-reflects all
reflected power incident on it. I maintain that the reflection
coefficient at the source is 1.0 because of the total re-reflection
there.

How's about we limit the *initial* discussion and examples to a source
with zero incident reflected power so the source impedance doesn't
matter? IMO, a two-port analysis of a Z0-match point will reveal the
main ingredients of the energy flow.

However, mathematical experts say that the equation is correct, saying
that rho_¬’s’ cannot be equal to 1.0, because the virtual open circuit
was established by wave interference, not a physical open circuit.

A one-port analysis cannot tell the difference between wave
interference and reflections. You are correct that the reflection
coefficients are not necessarily the same between a one-port analysis
and a two-port analysis. Your "mathematical experts" don't seem to
understand the limitations of a one-port analysis. It's akin to not
knowing what is inside a black box, i.e. one cannot tell the
difference between a resistor and a virtual resistance. However, with
a two-port analysis, one can tell the difference. It appears that your
"mathematical experts" are insisting on a two-port analysis such as
provided by the s-parameter equations:

b1 = s11*a1 + s12*a2

b2 = s21*a1 + s22*a2

http://www.sss-mag.com/pdf/an-95-1.pdf
--
73, Cecil, w5dxp.com


Cecil, the series stubbing appears in Reflections, Chapter 23, with
the same values as I presented above, with detailed diagrams shown in
each step in the progression of the explanation. I hope these diagrams
can help.

As I said in the previous post, the experts were referring to the
output of the RF amp as not establishing a reflection coefficient rho
= 1.0, which has put me in a corner.

Sorry Cecil, I can't correlate a two-port configuration using S
parameters with the problem I have. Thanks a million for the
discourse.

Walt

On Sun, 12 Jun 2011 19:09:29 -0700 (PDT), walt wrote:

the series stubbing appears in Reflections, Chapter 23, with
the same values as I presented above, with detailed diagrams shown in
each step in the progression of the explanation. I hope these diagrams
can help.

In other words, consult:
http://www.w2du.com/Chapter%2023.pdf
Figures 1 through 5

As I said in the previous post, the experts were referring to the
output of the RF amp as not establishing a reflection coefficient rho
= 1.0, which has put me in a corner.

Hi Walt,

How so? (What is the corner?)

73's
Richard Clark, KB7QHC

On Jun 12, 11:14*pm, Richard Clark wrote:
On Sun, 12 Jun 2011 19:09:29 -0700 (PDT), walt wrote:
the series stubbing appears in Reflections, Chapter 23, with
the same values as I presented above, with detailed diagrams shown in
each step in the progression of the explanation. I hope these diagrams
can help.

In other words, consult:http://www.w2du.com/Chapter%2023.pdf
Figures 1 through 5

As I said in the previous post, the experts were referring to the
output of the RF amp as not establishing a reflection coefficient rho
= 1.0, which has put me in a corner.

Hi Walt,

How so? *(What is the corner?)

73's
Richard Clark, KB7QHC


The corner I'm in, Richard, is that In Reflections 3, Chapter 25, I
assert that Steve Best's Eq 8 in the first part of his three-part
article appearing in QEX is invalid, because it gives incorrect
answers when I plug in what I believe are correct values of reflection
coefficients. Yet his equation agrees with that of Johnson on Page 100
of his "Transmission Lines" text book. In addition, a mathematics
expert whom I respect says Best's equation is correct. So I've got to
make the decision whether to delete my criticism of his equation or
leave it in and be accused of criticizing him incorrectly. What to do!

Walt

On Sun, 12 Jun 2011 20:31:42 -0700 (PDT), walt wrote:

On Jun 12, 11:14*pm, Richard Clark wrote:
On Sun, 12 Jun 2011 19:09:29 -0700 (PDT), walt wrote:
the series stubbing appears in Reflections, Chapter 23, with
the same values as I presented above, with detailed diagrams shown in
each step in the progression of the explanation. I hope these diagrams
can help.

In other words, consult:http://www.w2du.com/Chapter%2023.pdf
Figures 1 through 5

As I said in the previous post, the experts were referring to the
output of the RF amp as not establishing a reflection coefficient rho
= 1.0, which has put me in a corner.

Hi Walt,

How so? *(What is the corner?)

73's
Richard Clark, KB7QHC


The corner I'm in, Richard, is that In Reflections 3, Chapter 25,

In other words, consult:
http://www.w2du.com/r3ch25.pdf

I assert that Steve Best's Eq 8 in the first part of his three-part
article appearing in QEX is invalid, because it gives incorrect
answers when I plug in what I believe are correct values of reflection
coefficients. Yet his equation agrees with that of Johnson on Page 100
of his "Transmission Lines" text book. In addition, a mathematics
expert whom I respect says Best's equation is correct. So I've got to
make the decision whether to delete my criticism of his equation or
leave it in and be accused of criticizing him incorrectly. What to do!

Walt

Hi Walt,

So this is not only double-deep, through your work to Steve's, but
triple deep then through Steve to Johnson.

Lacking the necessary, culminating edition of Johnson's, I still don't
know what the corner is.

Lacking the complete math from all sides of the argument (not
somewhere I would like to go), and noting that many authors (not
making attributions here) frequently ignore some relatively basic
mandates where they don't matter, to then expand into situations where
they do matter; then I don't really trust heavily editorialized math
analysis.

I note your summary statement for Steve that you find contentious,
viz.
"A total re-reflection of power at the match
point is not necessary for the impedance
match to occur."
is one where I would agree with Steve; but not necessarily for reasons
brought forward. What is worse, this simple statement may mean three
things to two people.

73's
Richard Clark, KB7QHC

On Jun 12, 10:31*pm, walt wrote:
So I've got to
make the decision whether to delete my criticism of his equation or
leave it in and be accused of criticizing him incorrectly. What to do!

Personally, I didn't find anything wrong with parts 1 and 2. It's in
part 3 where Dr. Best gets lost. In an exchange on this newsgroup
before the article was published, he asserted that there was no
interference occurring at an impedance discontinuity on a transmission
line. When he published his component powers, he took into account
P1and P2 while completely ignoring (what I have dubbed) the component
powers, P3 and P4 in the opposite direction. He even invented
something like two phantom waves traveling forever in the direction of
total destructive interference while transporting energy but
completely canceling each other in the process, obviously a physical
impossibility.
--
73, Cecil, w5dxp.com

Thoughts on voltage vs power, reflection vs interference:

What most RF people do is deal exclusively with voltages. Power is
considered only at the beginning and end of a voltage analysis, NOT
during the voltage analysis. If joules/second are to be tracked
seamlessly throughout the analysis, a working knowledge of the effects
of superposition/interference is absolutely necessary. Optical
physicists do not have the luxury of working exclusively with
voltages, as we do in RF, so they must necessarily understand
superposition/interference and be able to track every component of
irradiance (power density).

I took a look at Johnson and he is dealing with voltage, not power,
and certainly not with dissipationless resistances as part of the
generator source impedance. He uses 'k' sub-script 'g' as the symbol
for the voltage reflection coefficient. I'm going to use 'rho' for his
'k' with braces {g} indicating subscripts. His *voltage* reflection
coefficient at the generator is:

rho{g} = (Zg-Z0)/(Zg+Z0)

which is just standard *voltage* wave reflection mechanics. What
happens to the energy (power) in superposed waves is completely
transparent when superposing voltages. For instance, let's say we have
two 200 watt waves in a 50 ohm environment which makes each of their
voltage magnitudes equal to 100 volts RMS. The electric fields of the
two waves are 120 degrees apart. What happens when we superpose 100
volts at +60 degrees with 100 volts at -60 degrees?

Every student of three-phase power systems knows the result will be
100 volts at zero degrees. All is well until we take a look at the
energy in those two superposed waves. Each wave is associated with an
ExH amount of power, V^2/Z0=200w, for a total of 400 watts in the two
waves. The resultant (total?) superposed wave contains 200 watts of
ExH power. Most people don't give this idea a second thought but where
did the other 200 watts go? To answer the question, one must
understand destructive/constructive interference. In the above
example, there is 200 watts of destructive interference present so the
resulting "total" voltage is not the only component of superposition.

If the above occurs in a transmission line, the amount of destructive
interference energy that is lost in the direction of superposition,
e.g. toward the load, is redistributed in the only other direction
possible, i.e. toward the source. There is a second 200w wave
generated that travels toward the source but that fact is not covered
when voltage superposition is involved. Note that it is a reverse-
traveling wave but it is technically not a reflection of a single wave
as it is the result of superposition of two waves.

Voltage superposition takes care of itself and everyone believes in
the conservation of energy principle which is probably why very few
people ask, "Where does the power go?" It is only when we are trying
to track energy throughout the system that we are forced to understand
the effects associated with interference.

Thoughts on one-port analysis vs two-port analysis.

Sources are necessarily treated as single-port devices. We know we
often get completely different reflection coefficients when treating
something as a single-port device vs as a dual-port device. For
instance, most of us treat a dipole feedpoint as a single-port device
when it is actually far from being a single-port device. In reality,
many other things besides a single reflection, are happening at a
dipole's feedpoint. The actual physical reflection coefficient at the
feedpoint of a "50 ohm" dipole fed with 50 ohm coax is around 0.845
because the characteristic impedance of a #14 wire 30 feet above
ground is around 600 ohms. Proof: Eliminate the reflections from the
ends of the dipole by terminating the ends of the inv-V dipole to
ground through 600 ohm resistors and the SWR on the 50 ohm feedline
goes to 12:1.

Because of reflections from the ends of the dipole, a lot of
interference is happening at the feedpoint which results in a
*virtual* reflection coefficient of 0.0 only because of the single-
port analysis that is ordinarily used. IMO, a virtual reflection
coefficient is a *result* and cannot cause anything including
reflections. IMO, only physical reflection coefficients, i.e. physical
impedance discontinuities, can *cause* reflections. Much of what we
consider to be reflections are the result of interference.

Seems that something similar, but more complicated, is happening
inside a source where there is an active-source component in the mix.
IMO, what is happening to the energy inside a source cannot possibly
be understood without taking the effects associated with interference
into account.
--
73, Cecil, w5dxp.com

On Jun 12, 9:09*pm, walt wrote:
Sorry Cecil, I can't correlate a two-port configuration using S
parameters with the problem I have.

In a one-port analysis, virtual impedances cause reflections. In a two-
port analysis, only physical impedance discontinuities cause
reflections. As I see it, that is the entire problem in a nutshell.
You are using a one-port analysis for virtually :-) all of your
analyses, including your source analysis. Your detractors are trying
to talk you into using a two-port analysis.
--
73, Cecil, w5dxp.com

On Jun 13, 6:17*pm, Cecil Moore wrote:
On Jun 12, 9:09*pm, walt wrote:

Sorry Cecil, I can't correlate a two-port configuration using S
parameters with the problem I have.

In a one-port analysis, virtual impedances cause reflections. In a two-
port analysis, only physical impedance discontinuities cause
reflections. As I see it, that is the entire problem in a nutshell.
You are using a one-port analysis for virtually :-) all of your
analyses, including your source analysis. Your detractors are trying
to talk you into using a two-port analysis.
--
73, Cecil, w5dxp.com


Cecil, as I said earlier, I can't see any relation between a two-port
configuration and the tank circuit of an RF power amp. Why are you
pushing it? Can't you just tell me whether you agree that the
reflection coefficient at the output of the tank circuit is rho = 1.0
or not. If you don't believe it does, even though it re-reflects all
the reflected power incident on it, then please explain what you
believe the reflection coefficient is at this point.

Walt, W2DU