Cecil Moore wrote:
Roy Lewallen wrote:

I didn't, and don't, claim to have derived a "power reflection
coefficient". What I calculated was the ratio of reflected voltage to
forward voltage at the load, and called its magnitude rho. If there's
any step in the analysis that's unclear, I'll be happy to explain it
in more detail.


What you apparently calculated is s11 which is not always equal to rho.

I calculated the ratio of the reflected to forward voltage at the load,
and called its magnitude rho. If you have some other "rho" you want to
argue about, please call it something else.


What I have calculated is the ratio of reflected voltage to forward
voltage at the load, no more and no less.


No, you have calculated the ratio of one of the reflected voltages to
one of the forward voltages. I believe you have calculated the ratio
of s21*a1 to s12*a2 when you should be calculating the ratio of
(s11*a1+s12*a2) to (s21*a1+s22*a2). You simply omitted half the terms.


Please repeat my analysis, including the voltages or currents which were
omitted, and explain why they should be included. I used standard steady
state analysis, which infers one forward traveling voltage and current
wave, and one reverse traveling voltage and current wave. Although the
physical meaning of multiple traveling forward and reverse waves in
steady state gets a little hazy to me, I don't think there's anything in
principal that prevents you from assuming any number of forward and
reverse voltage an current waves you'd like, calculating reflection
coefficients for each pair, and adding them all up to get the total.
It'll be interesting to see how you choose to do it.

Of course, by choosing the pairs carefully, you can probably assure that
the magnitude of the reflection coefficient for any pair doesn't exceed
one. I'm not sure what that means or proves, but by all means have at it.

. . .

I'm sure that with enough s parameter and optics references, the facts
of the matter can be satisfactorily obscured.


It is you who is using an s-, h-, y-, z-, or other-parameter analysis
and are inadvertently obscuring the facts. You left out half the voltage
terms that should be included in the forward voltage and reflected
voltage. Add all the reflected voltages together. Add all the forward
voltages together. Divide the total reflected voltage by the total
forward voltage.

What the heck are you talking about? Just where in the analysis do you
see any s, h, y, or z parameter? I did calculate an impedance here and
there from voltages and currents -- is that some kind of a no-no in your
eyes?

Again, please show your analysis with the "missing" terms (that is,
voltages and currents) included.

Your view of how average powers add and travel do force that
restriction. I'm looking forward to your alternative analysis, which
shows the voltages, currents, and powers at both ends of the line
while simultaneously satisfying your notion of how average powers
interact.


I think all that is built into your analysis. When you include all the
necessary terms, I will be surprised if everything doesn't fall out
consistently.

Well, good. So show us.

Roy Lewallen, W7EL

Yuck.

That should, of course, be "principle", not "principal". Sorry, I really
do know better!

Roy Lewallen, W7EL

Roy Lewallen wrote:
. . .
steady state gets a little hazy to me, I don't think there's anything in
principal that prevents you from assuming any number of forward and
reverse voltage an current waves you'd like, . .

Roy Lewallen wrote:
I calculated the ratio of the reflected to forward voltage at the load,
and called its magnitude rho.

No you didn't. The voltage that you think is the reflected voltage
is only one term of two. The voltage that you think is the forward
voltage is only one term of two.

Please repeat my analysis, including the voltages or currents which were
omitted, and explain why they should be included.

I have already done that, Roy. There are four waves. You must combine
the four waves to get the forward wave and the reflected wave. You
didn't do that. You declared one of the four waves to be the forward
wave and one to be the reflected wave and added the other two to get
a "third wave". That is an error.

What the heck are you talking about? Just where in the analysis do you
see any s, h, y, or z parameter? I did calculate an impedance here and
there from voltages and currents -- is that some kind of a no-no in your
eyes?

OK, let me do it in a way that you can understand. When you introduced
'x', you introduced a 2-port analysis whether you realize it or not.
In a 2-port analysis, there are four waves, two forward and two reflected.
The four power waves are proof that you are inadvertently using a 2-port
analysis. There are forward and reflected waves on the left side of 'x'
and there are forward and reflected waves on the right side of 'x'.
Let's look at only the voltages for now where rho is a reflection
coefficient and tau is a transmission coefficient.

V1 = Vfwd1*tau1 similar to s21*a1

V2 = Vref2*rho2 similar to s22*a2

V3 = Vfwd1*rho1 similar to s11*a1

V4 = Vref2*tau2 similar to s12*a2

You are saying that one of these voltages is the forward voltage.
That's just not true.

V1+V2 = forward voltage similar to b2=s21*a1+s22*a2

V3+V4 = reflected voltage similar to b1 = s11*a1+s12*a2

Again, please show your analysis with the "missing" terms (that is,
voltages and currents) included.

Please publish your raw four term power equation, omitting the rP
and fP terms which you are wrong about. If you have already published
that equation, please tell me the date so I can go look it up.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy wrote -
If you have some other "rho" you want to
argue about, please call it something else.

===========================

- - - and while you are about it change the name of
the SWR meter.

Reg Edwards wrote:

Roy wrote -
If you have some other "rho" you want to
argue about, please call it something else.

- - - and while you are about it change the name of
the SWR meter.

Trouble is, (Z2-Z1)/(Z2+Z1) is not always equal to Sqrt(Pref/Pfwd)
What then?
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Reg Edwards wrote:

Roy wrote -
If you have some other "rho" you want to
argue about, please call it something else.

- - - and while you are about it change the name of
the SWR meter.

Trouble is, (Z2-Z1)/(Z2+Z1) is not always equal to Sqrt(Pref/Pfwd)
What then?

The equality was always iffy when you don't take the absolute value.
But once you do, the equality may hold depending on the equations
you use to derive Pref and Pfwd.

Whether Pref or Pfwd represent something physically meaningful is
another question, also dependent on how you derive them.

....Keith

wrote in message ...

Trouble is, (Z2-Z1)/(Z2+Z1) is not always equal to Sqrt(Pref/Pfwd)
What then?

The equality was always iffy when you don't take the absolute value.
But once you do, the equality may hold depending on the equations
you use to derive Pref and Pfwd.

Whether Pref or Pfwd represent something physically meaningful is
another question, also dependent on how you derive them.

...Keith

Cecil,

The ratio Pref/Pfwd is directly related to the ratio [rho].

Pref/Pfwd = [rho]**2 Absolute value brackets are a must!


Consider that after the absolute value brackets, the phase information
is gone. But since we are going to a ratio of average (RMS)
values OR peak values of power, it doesn't matter.

In other words, if you use V**2/R, the "V" can be either peak or
RMS, it doesn't matter, because it is a ratio. And of course, the "R"
doesn't matter either. And of course, the phase information is gone
with
the absolute value brackets.

If you agree that the Pref/Pfwd ratio cannot be greater than 1
for a passive network, then neither can the [Vref/Vfwd]= rho be
greater
than 1 either.

Some people wanna rewrite some books here.


Slick

Dr. Slick wrote:
If you agree that the Pref/Pfwd ratio cannot be greater than 1
for a passive network, then neither can the [Vref/Vfwd]= rho be
greater
than 1 either.

Sqrt(Pref/Pfwd) cannot be greater than one. (Z2-Z1)/(Z2+Z1) can be
greater than one. Both are defined as 'rho' but they are not
always equal. (Z2-Z1)/(Z2+Z1) is a physical reflection coefficient.
Sqrt(Pref/Pfwd) is an image reflection coefficient.
--
73, Cecil http://www.qsl.net/w5dxp



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