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

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 13, 1:55*pm, K7ITM wrote:
*It doesn't make any sense to me to put a shorted
section of line in series with another line, so my confusion starts.

Tom, I didn't know initially that the example was in "Reflections
III". A series stub can be used instead of a loading coil on a wire
antenna. I had never seen a series stub used in such a manner on a
transmission line and that's why I was confused. I'm assuming that the
center conductor is broken and one side is connected to the inner
conductor and one side is connected to the braid on a stub, but I am
not sure that is correct. There's got to be a less complicated example
that we can use.
--
73, Cecil, w5dxp.com

On 6/13/2011 12:34 PM, Cecil Moore wrote:
On Jun 13, 1:55 pm, wrote:
It doesn't make any sense to me to put a shorted
section of line in series with another line, so my confusion starts.

Tom, I didn't know initially that the example was in "Reflections
III". A series stub can be used instead of a loading coil on a wire
antenna. I had never seen a series stub used in such a manner on a
transmission line and that's why I was confused. I'm assuming that the
center conductor is broken and one side is connected to the inner
conductor and one side is connected to the braid on a stub, but I am
not sure that is correct. There's got to be a less complicated example
that we can use.
--
73, Cecil, w5dxp.com

Here is a small handout, with a smith chart example!

--

Regards,
JS
“The Constitution is not an instrument for the government to restrain
the people, it’s an instrument for the people to restrain the
government.” -- Patrick Henry

On 6/13/2011 12:34 PM, Cecil Moore wrote:
On Jun 13, 1:55 pm, wrote:
It doesn't make any sense to me to put a shorted
section of line in series with another line, so my confusion starts.

Tom, I didn't know initially that the example was in "Reflections
III". A series stub can be used instead of a loading coil on a wire
antenna. I had never seen a series stub used in such a manner on a
transmission line and that's why I was confused. I'm assuming that the
center conductor is broken and one side is connected to the inner
conductor and one side is connected to the braid on a stub, but I am
not sure that is correct. There's got to be a less complicated example
that we can use.
--
73, Cecil, w5dxp.com

Larger example:

http://personal.ee.surrey.ac.uk/Pers...ries-stub.html

--

Regards,
JS
“The Constitution is not an instrument for the government to restrain
the people, it’s an instrument for the people to restrain the
government.” -- Patrick Henry

On 6/13/2011 12:34 PM, Cecil Moore wrote:
On Jun 13, 1:55 pm, wrote:
It doesn't make any sense to me to put a shorted
section of line in series with another line, so my confusion starts.

Tom, I didn't know initially that the example was in "Reflections
III". A series stub can be used instead of a loading coil on a wire
antenna. I had never seen a series stub used in such a manner on a
transmission line and that's why I was confused. I'm assuming that the
center conductor is broken and one side is connected to the inner
conductor and one side is connected to the braid on a stub, but I am
not sure that is correct. There's got to be a less complicated example
that we can use.
--
73, Cecil, w5dxp.com

Small handout with example and smith chart:

http://www.ittc.ku.edu/~jstiles/723/...b%20Tuning.pdf

--

Regards,
JS
“The Constitution is not an instrument for the government to restrain
the people, it’s an instrument for the people to restrain the
government.” -- Patrick Henry

On Jun 13, 2:46*pm, John Smith wrote:
http://personal.ee.surrey.ac.uk/Pers...ries-stub.html

Thanks John, I can't help but point out that such a "series stub"
unbalances the transmission line currents resulting in common-mode
currents on the outside braid and is probably a deviation from the
original design specifications. There has got to be a simpler example
that illustrates the question/answer. I thought I had it with my Z0-
match example but maybe not.
--
73, Cecil, w5dxp.com

On 6/13/2011 1:22 PM, Cecil Moore wrote:
On Jun 13, 2:46 pm, John wrote:
http://personal.ee.surrey.ac.uk/Pers...ries-stub.html

Thanks John, I can't help but point out that such a "series stub"
unbalances the transmission line currents resulting in common-mode
currents on the outside braid and is probably a deviation from the
original design specifications. There has got to be a simpler example
that illustrates the question/answer. I thought I had it with my Z0-
match example but maybe not.
--
73, Cecil, w5dxp.com

Quite possible ...

--

Regards,
JS
“The Constitution is not an instrument for the government to restrain
the people, it’s an instrument for the people to restrain the
government.” -- Patrick Henry

On Jun 13, 3:08*pm, John Smith wrote:
http://www.ittc.ku.edu/~jstiles/723/...b%20Tuning.pdf

Thanks John, but I would like to see the schematic for coax. Shirley,
one doesn't cut the braid and add a stub?
--
73, Cecil, w5dxp.com