Analyzing Stub Matching with Reflection Coefficients
 

Jim Kelley wrote:
It certainly is an interesting way of looking at things, Cecil. It's
certainly true that equal and opposite fields cancel. When that's the
case though it becomes problematic arguing that there are waves there.

The waves are certainly there and are measured in
the process of determining the values of the
s-parameters. That's enough proof of their
existence for me. If you deny their existence,
you are denying that the s-parameter measurement
procedure is valid.

Jim, what happens to the ExB power density in the
equal and opposite fields that cancel?
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 18, 9:19 pm, Cecil Moore wrote:
Dr. Honeydew wrote:
Cecil Moore wrote:
A Bird wattmeter reads 100 watts forward and 100w reflected. The
current in the source is zero. The source is not only not sourcing any
forward power, it is also not sinking any reflected power.

What complete and utter Texas-size bullsh*t. It's obvious that the
source is sourcing the forward voltage wave, and it's sucking up
entire reverse voltage wave from the line.

And doing it while magically expending zero energy.
Perpetual motion is possible, after all.

If zero power is being dissipated in the source, it cannot
be sourcing the forward voltage wave and it cannot be
sucking up the reverse voltage wave.
--
73, Cecil http://www.w5dxp.com


Ah, I can see you didn't take me seriously. But I was dead serious.
It is absolutely not necessary for the source to be dissipating the
reverse wave it sucks up as heat.

A challenge: given a linear system consisting of a source of
impedance Z1, connected to a line (any length you want; any loss you
want) of impedance Z2, and the far end of the line connected to a load
of impedance Z3, or even to a different source of impedance Z3
(possibly different frequency, phase, and/or amplitude from the first
source). Give us one example, even one, that's not accurately
described by source Z1 launching waves into impedance Z2 in the
"forward" direction, plus whatever "reverse" wave is on the line doing
exactly the expected things at the Z2:Z1 boundary. In other words,
viewed from both sides, show us even one instance where the system is
not correctly analyzed with your S11--S12 equations for the Z1--Z2
interface. Show us even one instance where those equations will not
tell you exactly what happens to waves coming into that interface from
either direction, and in fact from both directions at once.

What the source does with the incoming wave is another matter,
independent of the Z1--Z2 interface. Whether it causes increased or
decreased dissipation of heat in the source depends on how the source
is made, and the characteristics (phase, amplitude, frequency, ...) of
the incoming wave.

From the labs,

Bunsen

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:

Gene Fuller wrote:

Do you see the common factor in your response about "wave
interaction"? In all of your examples there is an interface or some
sort of discontinuity. Nobody argues that waves are forever
unchanging. However, those changes take place only through interaction
with interfaces or other discontinuities.


I don't disagree and I have gone on record as saying that
reflections only occur at physical impedance discontinuities.

You have also gone on record as saying is this:

4/19/07 6:12 AM
"The only thing s11(a1) and s12(a2) encounter are each other and that
interaction completely changes those two waves. The two waves cancel
and their energy components are re-distributed in the opposite
direction. s11(a1) and s12(a2) never encounter an impedance
discontinuity."

73, ac6xg

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:

Jim, what happens to the ExB power density in the
equal and opposite fields that cancel?

Let's see E=0, and B=0; what power density, Cecil?

73, Jim AC6XG

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:

That is the nature of EM waves, Gene. EM waves flowing
in opposite directions do NOT interact. However, their
reflected and transmitted components traveling in the
same direction can and do interact at an impedance
discontinuity.

Actually it's even more straightforward than that. They do interact
with a physical impedance discontinuity, and don't interact with each
other no matter which way they are traveling.

73, Jim AC6XG

Analyzing Stub Matching with Reflection Coefficients
 

Richard Clark wrote:
On Thu, 19 Apr 2007 14:56:33 GMT, Gene Fuller
wrote:

Do you have any connection with "optical physicists" beyond your reading
of Hecht and the Melles Griot website?

Hi Gene,

Aside from the number of us that have experience in the practice?

73's
Richard Clark, KB7QHC

Hi Richard,

I have not seen an optical physicist since I looked in the mirror this
morning.

8-)

73,
Gene
W4SZ

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:
Gene Fuller wrote:
Help me out. How can we have scalars flowing in opposite directions?
If the waves can interact, as you claim, why does the associated
energy fail to interact and merely pass like ships in the night?

That is the nature of EM waves, Gene. EM waves flowing
in opposite directions do NOT interact. However, their
reflected and transmitted components traveling in the
same direction can and do interact at an impedance
discontinuity.



Cecil,

Progress!

All we need now is that you also understand that waves flowing in the
SAME direction do NOT interact unless there is an interface or other
discontinuity.

All sorts of things can happen at discontinuities. The detailed physical
mechanisms and the models are well understood.

73,
Gene
W4SZ

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 12:27 pm, Cecil Moore wrote:
Richard Harrison wrote:
How much energy will continue to enter the stub? Practically none
because there is no difference of potential between the source and the
reflection.

In a lossless stub, zero energy will continue to enter the stub.
In fact, in a lossless stub, the source can theoretically be
completely disconnected and everything remains the same
including 100% re-reflection of reflected waves by the new
open circuit.

I've always liked this example. By extension, on a line multiple
quarter wavelengths long, you can disconnect the line at ANY
of the voltage maxima and see exactly the same result as you
describe above. Are those travelling waves really crossing the
voltage maxima? Or are they being reflected? Or are they just
reflected at the maxima that actually occur at a discontinuity?
But there is no discontinuity at the source, so why would they
be reflected there? But if they are reflected at the
non-discontinuity at the source, then they should be reflected
at the non-discontinuities in the line as well. But wait, those
non-discontinuities are virtual opens and shorts, so maybe
they reflect at virtual ones as well. But no, it has been agreed
that reflections only happen at physical discontinuities.

And what if the stub is not a quarter (or multiple) wavelength
long? Then where does the reflection at the source occur?
At the last maximum or minimum along the line? Inside the
generator? It works for any length of line. Somehow the
generator knows exactly what reactance to supply?

It is definitely best to recognize that when the source impedance
is equal to the line impedance, there is no reflection at the
source. And it does not matter if the source impedance is
achieved with a circulator, a resistor, a multiplicity of resistors,
feedback, or what have you; there is no reflection if the
impedance is the same as the line. No discontinuity, no
reflection. A simple rule. Works at a load. Works at a
generator. Works along the line. Always works.

....Keith

Analyzing Stub Matching with Reflection Coefficients
 

Dr. Honeydew wrote:
Ah, I can see you didn't take me seriously. But I was dead serious.
It is absolutely not necessary for the source to be dissipating the
reverse wave it sucks up as heat.

Can a wave exist without energy? Where does the energy in the
sucked up wave go since it doesn't go into the source.

In other words,
viewed from both sides, show us even one instance where the system is
not correctly analyzed with your S11--S12 equations for the Z1--Z2
interface. Show us even one instance where those equations will not
tell you exactly what happens to waves coming into that interface from
either direction, and in fact from both directions at once.

You must have me confused with someone else. I'm a supporter
of the s-parameter analysis. It's others who have called
it "Gobbledegook" (sic).
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Jim Kelley wrote:


Cecil Moore wrote:
... I have gone on record as saying that
reflections only occur at physical impedance discontinuities.

You have also gone on record as saying is this:

4/19/07 6:12 AM
"The only thing s11(a1) and s12(a2) encounter are each other and that
interaction completely changes those two waves. The two waves cancel
and their energy components are re-distributed in the opposite
direction. s11(a1) and s12(a2) never encounter an impedance
discontinuity."

There's no conflict between those two statements. s11(a1) and
s12(a2) indeed *NEVER* encounter an impedance discontinuity
since they originate already flowing *away from* the impedance
discontinuity. Any interference between two coherent collinear
EM waves traveling in the same path is a permanent interaction.
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Jim Kelley wrote:

Cecil Moore wrote:
Jim, what happens to the ExB power density in the
equal and opposite fields that cancel?

Let's see E=0, and B=0; what power density, Cecil?

Play your silly word games if you will. Fields cannot
cancel unless those fields first exist. Assume E1xB1
joules/sec associated with the first field and E2xB2
joules/sec associated with the second field. The fields
cancel. What happens to the E1xB1 joules/sec and the
E2xB2 joules/sec? Hint: Their energy components are
redistributed in a direction that allows constructive
interference. In a transmission line, there is only
one other direction available.
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Jim Kelley wrote:
Cecil Moore wrote:
That is the nature of EM waves, Gene. EM waves flowing
in opposite directions do NOT interact. However, their
reflected and transmitted components traveling in the
same direction can and do interact at an impedance
discontinuity.

Actually it's even more straightforward than that. They do interact
with a physical impedance discontinuity, and don't interact with each
other no matter which way they are traveling.

Sorry Jim, the s11(a1) wave and s12(a2) wave are *NEVER*
incident upon an impedance discontinuity yet they cancel.
How do two waves cancel without interacting?
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 3:44 pm, Cecil Moore wrote:
Dr. Honeydew wrote:
Ah, I can see you didn't take me seriously. But I was dead serious.
It is absolutely not necessary for the source to be dissipating the
reverse wave it sucks up as heat.

Can a wave exist without energy? Where does the energy in the
sucked up wave go since it doesn't go into the source.

You are getting close to the truth. Yes, the forward and reverse
travelling waves are not necessarily moving energy. The Bird
wattmeter, despite its name, is computing a number with the
dimension of watts, but which does not necessarily represent
energy flowing (it represents flowing energy when the indicated
value is 0 in one direction or the other).

This will probably (I understate) be hard to accept but is the
only reasonable conclusion after examining a large number
of experiments and trying to rationalize the answer
to "Where does the energy in the reflected wave go?" Once
it becomes clear that there is no good answer to that
question, the only possible conclusion is that the question
is invalid and the roots of its invalidity lie in the assumption
of energy in the reflected wave.

....Keith

Analyzing Stub Matching with Reflection Coefficients
 

Gene Fuller wrote:
All we need now is that you also understand that waves flowing in the
SAME direction do NOT interact unless there is an interface or other
discontinuity.

Please stop implying things that I have never said. When I
asserted that reflections only happen at a physical impedance
discontinuity, that implies that interaction can only happen
at a physical impedance discontinuity. It is impossible to
get two coherent waves flowing in the same direction except
at a physical impedance discontinuity.

Assume b1 = s11(a1) + a12(s2) = 0

What I have said is that s11(a1) and s12(a2) are wave components
that cancel without ever being incident upon an impedance discontinuity.
Those two wave components originate at the impedance discontinuity
flowing *AWAY FROM* the impedance discontinuity. They are canceled
in a delta-t, i.e. a very short time. Those two waves are the result
of interaction at the impedance discontinuity but neither of them
ever interacted with the impedance discontinuity because they
originated at the impedance discontinuity.
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Keith Dysart wrote:
Are those travelling waves really crossing the
voltage maxima? Or are they being reflected?

There is no impedance discontinuity - therefore no
reflections.

But there is no discontinuity at the source, ...

You are still making the same mistake as you have from
the beginning. There is a discontinuity at the source.
In your example, it is called the load-line. The load-
line in the previous example is source voltage divided
by zero, i.e. infinity. That's what the reflected wave
sees.

It is definitely best to recognize that when the source impedance
is equal to the line impedance, there is no reflection at the
source.

You have been asserting that since your first posting and it
is a *FALSE STATEMENT* as proved by the latest example.
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:

Fields cannot
cancel unless those fields first exist.

Please clarify for us the distinction between canceled fields, and
fields which don't exist.

There is no energy traveling in the direction of fields that cancel;
E1xB1 and E2xB2 in this example.

Assume E1xB1
joules/sec associated with the first field and E2xB2
joules/sec associated with the second field. The fields
cancel. What happens to the E1xB1 joules/sec and the
E2xB2 joules/sec?

Since the fields cancel, and energy does not travel in the company of
nonexistent fields, there is no energy here with which to concern
ourselves.

Hint: Their energy components are
redistributed in a direction that allows constructive
interference. In a transmission line, there is only
one other direction available.

Producing a result which can only occur when there is no energy
traveling in the direction of E1xB1 and E2xB2.

73, Jim AC6XG

Analyzing Stub Matching with Reflection Coefficients
 

Keith Dysart wrote:
You are getting close to the truth. Yes, the forward and reverse
travelling waves are not necessarily moving energy.


How in the world is EM traveling waves existing without
energy getting close to the truth? Seems it is getting
closer to fantasy than anything else.

The Bird
wattmeter, despite its name, is computing a number with the
dimension of watts, but which does not necessarily represent
energy flowing (it represents flowing energy when the indicated
value is 0 in one direction or the other).

If the Bird is properly used, it indicates joules flowing
past a point in one second in the environment for which it
is calibrated. If EM energy waves ever stop flowing, they
cease to be EM waves. The boundary conditions for EM waves
will not permit them to travel at any other speed than
d(VF) nor exist devoid of energy.

This will probably (I understate) be hard to accept but is the
only reasonable conclusion after examining a large number
of experiments and trying to rationalize the answer
to "Where does the energy in the reflected wave go?" Once
it becomes clear that there is no good answer to that
question, the only possible conclusion is that the question
is invalid and the roots of its invalidity lie in the assumption
of energy in the reflected wave.

False, false, and false. *Every* EM wave is associated with ExB
joules/sec. The energy supporting a reflected EM wave is either
reflected or transmitted or dissipated. Those EM waves do not
care a whit if you never figure them out.
--
73, Cecil, w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:

How do two waves cancel without interacting?

No interaction is required in order for fields to cancel. Only that
they occupy the same space at the same time and be of the correct
amplitude and phase.

73, Jim AC6XG

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 12:44 pm, Cecil Moore wrote:
Dr. Honeydew wrote:

In other words,
viewed from both sides, show us even one instance where the system is
not correctly analyzed with your S11--S12 equations for the Z1--Z2
interface. Show us even one instance where those equations will not
tell you exactly what happens to waves coming into that interface from
either direction, and in fact from both directions at once.

You must have me confused with someone else. I'm a supporter
of the s-parameter analysis. It's others who have called
it "Gobbledegook" (sic).
--
73, Cecil, w5dxp.com

Ah, thank you. Then it follows directly from that, that when you
wrote,
A Bird wattmeter reads 100 watts forward and 100w reflected. The
current in the source is zero. The source is not only not sourcing any
forward power, it is also not sinking any reflected power.
you were not disallowing the fact that the source, which is matched to
the line, sucks up the entire reverse wave from the line. I'm happy
to see we agree on that little point after all.

Fallacies of the, "if the source absorbs the reverse wave, it must be
dissipated as heat," school: Start with a source which is a voltage
generator, 141.4Vrms sinewave, in series with a 50 ohm resistor.
Connect it to a 50 ohm load, and you have 100 watts dissipated inside
the source and 100 watts dissipated in the load. Put a 50 ohm
lossless line between the source and the load. We now have a
70.71Vrms wave from the source to the load, and no reflected. Assume
the line is 1/4 wave long; replace the load with a short. A moment
later, steady state is reached and the dissipation in the source's 50
ohm resistor dropped from 100W to 0W. We may be tempted to say that
source did not absorb the return wave and is no longer supplying the
forward wave. But that requires complete reflection of the return
wave at the interface between the source and the line. Ah, but there
is an infinite set of conditions under which the same should be
true. What if we make the line 1/2 wave long, still shorted at the
far end? In steady state, the source is still apparently delivering
no power to the line, but now, instead of it dissipating NO power,
it's suddenly dissipating 400 watts! In the line, though, we still
see 100 watts of forward power, and 100 watts of reverse power.

Ooops. The "if the source absorbs the reverse wave, it must be
dissipated as heat" school ... better go back to school. Or to the
lab. Or SOMEwhere else, till they get it figured out. It didn't hold
water when Dr. Slick (remember him?) tried to push it on us, and it
doesn't hold water now.

More fun: the guts of my source are now a 282.8V source and the 50
ohm resistor, feeding a fairly long piece of 50 ohm transmission line
to the front panel connector. The line has 6.02dB loss. Now back to
the original situation with 1/4 wave of 50 ohm line, shorted at the
far end, connected to the generator's output connector. NOW are you
going to say that the reverse wave on the 1/4 wave line stops when it
gets back to the generator? What if I put even a couple inches of
line between the guts of the source and the front panel connector,
does the reverse wave on the external line stop when it gets to the
front panel connector?

I repeat: [In the case of a line connected to a source, with the
impedance of the two matched--not conjugate] It's obvious that the
source is sourcing the forward voltage wave, and it's sucking up the
entire reverse voltage wave from the line.

What happens to that reverse voltage wave inside the source depends on
what's in the guts of the source.

From the lab,

Bunsen

Analyzing Stub Matching with Reflection Coefficients
 

On Thu, 19 Apr 2007 14:11:21 -0700, Jim Kelley
wrote:

Cecil Moore wrote:

How do two waves cancel without interacting?

No interaction is required in order for fields to cancel. Only that
they occupy the same space at the same time and be of the correct
amplitude and phase.

And are put into a load.

As waves are completely independant, then they never interact. A load
is required to reveal the cancellation. No load, and any issue of
cancelling fields is strictly limited to what goes on between the
ears.

73's
Richard Clark, KB7QHC

Analyzing Stub Matching with Reflection Coefficients
 

Jim Kelley wrote:
Cecil Moore wrote:

How do two waves cancel without interacting?

No interaction is required in order for fields to cancel. Only that
they occupy the same space at the same time and be of the correct
amplitude and phase.

Interaction is certainly required for them to cancel forever.
Otherwise, we have all these energyless phantom ghost waves
existing forever.
--
73, Cecil http://www.w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 2:59 pm, Richard Clark wrote:
On Thu, 19 Apr 2007 14:11:21 -0700, Jim Kelley
wrote:

Cecil Moore wrote:

How do two waves cancel without interacting?

No interaction is required in order for fields to cancel. Only that
they occupy the same space at the same time and be of the correct
amplitude and phase.

And are put into a load.

As waves are completely independant, then they never interact. A load
is required to reveal the cancellation. No load, and any issue of
cancelling fields is strictly limited to what goes on between the
ears.

73's
Richard Clark, KB7QHC


If nobody is there to hear it, does a tree that falls in the middle of
the forest (or anywhere else) make a noise? If there's a field and
nobody is there to measure it, is it there? If there's a summation to
zero and there's nobody there to verify that the summation really
occured, did it occur? Wheeee! Where will this take us next? Beaker
is soooo excited by the possibilities.

From the labs,
Bunsen

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 4:47 pm, Cecil Moore wrote:
Keith Dysart wrote:
Are those travelling waves really crossing the
voltage maxima? Or are they being reflected?

There is no impedance discontinuity - therefore no
reflections.

But there is no discontinuity at the source, ...

You are still making the same mistake as you have from
the beginning. There is a discontinuity at the source.
In your example, it is called the load-line. The load-
line in the previous example is source voltage divided
by zero, i.e. infinity. That's what the reflected wave
sees.

But the load line is the same for the generator equipped
with a circulator so it too must reflect the wave. If this is
the case, what heats the circulator load resistor?

I notice you skipped the tougher questions related to a
transmission line that is 3/8 wavelength long? Is there a
zero to divide by in this case? Apply analysis equally
to Experiment A and B.

....Keith

Analyzing Stub Matching with Reflection Coefficients
 

Dr. Honeydew wrote:
you were not disallowing the fact that the source, which is matched to
the line, sucks up the entire reverse wave from the line. I'm happy
to see we agree on that little point after all.

Old diversionary trick - doesn't work. We do NOT agree on "that
little point". Agreeing on that little point requires negative
energy which doesn't exist. The reflected energy is 100% re-
reflected. Nothing is coming out of the source and nothing
is going into the source.

But that requires complete reflection of the return
wave at the interface between the source and the line.

Yes, reality requires that. However, wet dreams do not
so be my guest.

I repeat: [In the case of a line connected to a source, with the
impedance of the two matched--not conjugate] It's obvious that the
source is sourcing the forward voltage wave, and it's sucking up the
entire reverse voltage wave from the line.

All with the voltage waves being completely devoid of energy.
Will wet dreams never cease?
--
73, Cecil http://www.w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Richard Clark wrote:
A load is required to reveal the cancellation.

What's the load for b1 = s11(a1) + s12(a2) = 0 ?
--
73, Cecil http://www.w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Keith Dysart wrote:
But the load line is the same for the generator equipped
with a circulator so it too must reflect the wave.

ABSOLUTELY NOT!!! The load line for a circulator equipped
generator is *ALWAYS* 50 ohms (for a 50 ohm generator).
The generator *always* sees 50 ohms as a load. How could
the load-line possibly be anything else besides 50 ohms?
--
73, Cecil http://www.w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

On 19 Apr 2007 15:25:41 -0700, "Dr. Honeydew"
wrote:

If there's a summation to
zero

Hi Tom,

And how are you going to sum it without a load?

and there's nobody there to verify that the summation really
occured, did it occur?

Nobody, I presume to mean no body of a load. No load hence no
combination, hence no interference.

Fairly simple stuff, but mystics here still demand that energy
disappears in these situations to be "shuffled" around like balance
ledgers done by Arthur Andersen for billing electricity to California.
Some things never change.

If you (a body) happen to be there, then yes you "might" detect a
null, a peak, or any combination in between. You (the body) are the
load. Even that is a stretch of the imagination, but your
Doppelganger can no doubt spread it out. I suppose if the fields were
viciously strong you might feel a prickle of heat (or cool, some RF
waves lend that perception). Otherwise the waves simply go on their
way without any notice of the other, and certainly to no literal
notice at all. Why would it be otherwise?

Wheeee! Where will this take us next?
Beaker
is soooo excited by the possibilities.

Really? Don't hold back now on our account. :-)

73's
Richard Clark, KB7QHC

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 12:02 am, Cecil Moore wrote:
Keith Dysart wrote:
I have stated that there is no re-reflection of the reflected wave at
the
source. Since the source is matched to the line, the reflection
coefficient is 0 and the wave just .... Well it must go into the
source
since tau is one. But at least it is not reflected when rho is zero.

But you are missing the point. You say the source is matched
to the line but the source is obviously re-reflecting 100% of the
reflected energy.

But the same can be said for experiment A, can't it? Measured
conditions on the line are identical.

Your special magic source is doing exactly
the opposite of what you claim it is doing. The calculated
physical reflection coefficient may be 0 but the virtual
reflection coefficient, SQRT(Pref/Pfor), is 1.0.

Please apply this calculation to Experiment A and check
your result. No difference. Oooopppps.

This is
the point I have been making ever since you started posting.

As you observe for Experiment B, the current is zero so as you
say "The source is not only not sourcing any forward power, it is
also not sinking any reflected power."

Of course the current is also zero at the same point for
Experiment A, so there as well, the source is not only not sourcing
any forward power, it is also not sinking any reflected power.

That's again where you are wrong. In Experiment A, the circulator
load resistor is sinking 100W, i.e. 100% of the reflected power.
A bit of modulation will show that the power being sunk by the
circulator load resistor has made a round trip to the end of
the transmission line short and back.

And if you did the same test with Experiment B you would get the
same result.

A bit more analysis for Experiment A yields some more questions.
Terminate the line with a 50 Ohm resistor. The source is now
providing power to the line, there is no reflection on the line and
the circulator dissipates nothing.
Remove the resistor. The reflection returns. The circulator once
again dissipates 100 W. But as you said, in this condition,
"The source is not only not sourcing any forward power, it is also
not sinking any reflected power." So where did that 100 W being
dissipated in the circulator come from?

In Experiment A, the source is sourcing 100 watts and the
circulator load resistor is sinking 100 watts after the
round trip delay to the end of the line and back. If the
source signal is modulated, the delay between the source
signal and the dissipated signal is obvious and can be
measured.

No different for B.

I suggest a further extension to both Experiment A and
Experiment B. Replace the 1/4 WL stub with a 1 and 1/4 WL
stub. Now, at each 1/4 WL along the line coming back from
the load, no energy is flowing because either the current is
0 or the voltage is 0. So this absence of energy flow happens
not just at the source but repeatedly along the line. This
makes it difficult to accomodate the thought that the
forward or reflected travelling waves are transporting energy
along the line (at least at the quarter wave points).

The "absence of energy flow" is an illusion. There is 100
joules/sec in the forward wave and 100 joules/sec in the
reflected wave. Since the waves are flowing in opposite
directions, you can argue that there is no *net* energy
flow, but the component wave energy flow is alive and well.

Well this is the point you lock up on and it is one of the root
causes of all subsequent errors. I suspect your refusal to
accept the common knowledge that the output impedance
of the generator can be well known, that this controls the
amount of reflection at the generator and that superposition
works is the realization that this will conflict with "energy in
the waves". I encountered the same dilemma when first
dealing with these questions, but came to the answer that
works.

Now back to the quibble. You said: "The source sources 100 watts
and the circulator resistor dissipates 100 watts which is all of the
reflected power."

Yes, in Experiment A but obviously not in Experiment B.
Your source has failed to perform the way you said it would.
As I said in the beginning, there will be re-reflections from
your source. In this case, there is 100% re-reflection.
Real world conditions are not as simple-minded as you say.

But, of course, your proof of re-reflections was your apriori
knowledge of the interior of the generator. I present you with
two 50 Ohm generators; one constructed with a circulator and
one constructed with a 50 Ohm resistor. How do you tell which
is which? The line conditions will be the same, so you can't.
Do you really want a theory of reflections that is dependent on
knowing the internals of the generator?

It would be more precise to say "The source sources 100 watts
and the circulator resistor dissipates 100 watts which is numerically
equal to the reflected power." I contend that it is this "numerical
equality" that has led many astray into believing that the
circulator is dissipating the "reflected power".

No, modulation on the reflected wave proves that it has made
a round trip to the end of the line and back. There is no
getting around that fact. There is also no getting around
the fact that the energy content of the stub is identical
in both experiments. The number of joules in the stub, in
both cases, is exactly the magnitude needed to support the
100W forward wave and the 100W reflected wave. The energy
in the stub in Experiment A is obviously real. The energy
in the stub in Experiment B is identical to Experiment A.

Yes indeed. All line conditions are exactly the same. The same
energy is stored. The output impedance is the same. Modulation
has exactly the same effects. The reflected modulated signal is not
re-reflected at the source for either case. They are
indistinguishable unless you dissassemble the generator.

But as we have seen,
no energy crosses the 0 current node into the generator so the
"reflected power" can not make it to the circulator (or the source
resistance, if the generator happens to have one).

Your "no energy crosses the 0 current node" is just an ignorant
illusion.

You can not possible be arguing that P is not equal to V times I,
can you?

And are you disputing that if V or I is at all times 0, there must be
no energy flowing.
If so, back to grade 11 science please.

The forward current and reflected current are alive
and well and simply superpose to a net current of zero at that
point. We are discussing EM wave energy and a boundary condition
for EM waves to exist is that they must travel at c(VF). If they
don't, they are no longer EM waves.

At a current node, forward current equals 1.414 amps at 0 deg.
Reflected current equals 1.414 amps at 180 deg. Of course, the
*net* current is zero but there is no physical impedance discontinuity
to cause any change in the forward and reflected waves at that
point.

Well it is pretty clear to me that if the net current is always 0,
then
no current is ever flowing and the power must be zero.

It seems to be a bit of a common fallacy to assign meaning to the
intermediate currents computed for the superposition solution to
a problem. Connect two equivalent batteries in parallel. The only
sensible answer is that no current is flowing since the voltages
are the same. (In another post you seem to accept this), though
if you use superposition to solve the problem, you get a very large
current flowing in one direction and an equally large current flowing
in the other. Only the resultant current is in any sense real. Same
for those waves on a transmission line. Just superposition. Just a
convenience to help reach the final solution. Don't over extend
and assign them meaning (or energy). In the end it will cause
deep conceptual difficulties.

....Keith

Analyzing Stub Matching with Reflection Coefficients
 

Keith Dysart wrote:
Cecil Moore wrote:
But you are missing the point. You say the source is matched
to the line but the source is obviously re-reflecting 100% of the
reflected energy.

But the same can be said for experiment A, can't it? Measured
conditions on the line are identical.

But conditions in the sources are exactly opposite. One
is sourcing and sinking power. The other is completely
powerless.

Please apply this calculation to Experiment A and check
your result. No difference. Oooopppps.

Oooopppps means you obviously made a mistake. The conditions
are opposite not alike.

And if you did the same test with Experiment B you would get the
same result.

Obviously not since source B is at room temperature.

No different for B.

Source A is dissipating 200 watts. Source B is dissipating
zero watts. How is that not different?

Well this is the point you lock up on and it is one of the root
causes of all subsequent errors. I suspect your refusal to
accept the common knowledge that the output impedance
of the generator can be well known, that this controls the
amount of reflection at the generator ...

The example proves this to be a wrong-headed concept.

I present you with
two 50 Ohm generators; one constructed with a circulator and
one constructed with a 50 Ohm resistor. How do you tell which
is which?

The one with the rapidly rising temperature is the one with
the circulator. The one that remains at room temperature
is your ten cent resistor version.

Yes indeed. All line conditions are exactly the same.

But the source conditions are radically different. One
source is sourcing 100 watts and sinking 100 watts. The
other source is sourcing 0 watts and sinking 0 watts.

You can not possible be arguing that P is not equal to V times I,
can you?

Pfor - Pref = 0 where those Ps are Poynting vectors.
Pfor is not zero. Pref is not zero. Pnet is zero
only because of a directional convention.

And are you disputing that if V or I is at all times 0, there must be
no energy flowing.

Make that at all times AND AT ALL PLACES and I will agree.
If V is zero it only means that all the energy has migrated
into the magnetic field and indeed, when V is zero, I is
at a maximum.

Well it is pretty clear to me that if the net current is always 0,
then no current is ever flowing and the power must be zero.

True if the net current everywhere is zero. Not true if the
current is only zero at a point. Current on each side of
a zero current point is prima facie evidence of energy flow
in both directions.
--
73, Cecil http://www.w5dxp.com

Analyzing Stub Matching with Reflection Coefficients
 

Richard Clark wrote:

As waves are completely independant, then they never interact.

Perhaps we can agree that they could at least share a common media
through which to propagate.

A load
is required to reveal the cancellation.

A load - like a transducer of some sort. That would indeed be
required in order to convert the effect to a form that we can more
readily observe.

No load, and any issue of
cancelling fields is strictly limited to what goes on between the
ears.

I hope you're not suggesting that if we cannot observe the
interference effect, it does not occur. There is good reason to
believe that just the opposite is true, Richard. It's a real paradox.
;-)

73, Jim AC6XG

Analyzing Stub Matching with Reflection Coefficients
 

On Thu, 19 Apr 2007 16:27:14 -0700, Jim Kelley
wrote:

Richard Clark wrote:

As waves are completely independant, then they never interact.

Perhaps we can agree that they could at least share a common media
through which to propagate.

Hi Jim,

Certainly, at a minimum.

A load
is required to reveal the cancellation.

A load - like a transducer of some sort. That would indeed be
required in order to convert the effect to a form that we can more
readily observe.

Every mapping of an antenna's radiation lobe characteristics presumes
this. We call them receivers.

No load, and any issue of
cancelling fields is strictly limited to what goes on between the
ears.

I hope you're not suggesting that if we cannot observe the
interference effect, it does not occur.

Contrary to the implication of Tom's tree falling unheard in the
forest, no I am not suggesting that. If one plants a load at a
distance and ignores it; then, yes, interference occurs. Remove the
load, and you remove interference.

1. Interference follows the load.

2. A load will also perturb the fields by the degree it couples to
the fields, and create a new interference solution.

There is good reason to
believe that just the opposite is true, Richard. It's a real paradox.

Not sure what the paradox is, but I trust you will elaborate if
necessary.

73's
Richard Clark, KB7QHC

Analyzing Stub Matching with Reflection Coefficients
 

Richard Clark wrote:

Contrary to the implication of Tom's tree falling unheard in the
forest, no I am not suggesting that. If one plants a load at a
distance and ignores it; then, yes, interference occurs. Remove the
load, and you remove interference.

So I gotta ask: what do waves do instead of superposing when there
isn't a load somewhere? Whistle and look the other way? :-)

73, Jim ac6xg

Analyzing Stub Matching with Reflection Coefficients
 

On Apr 19, 7:20 pm, Cecil Moore wrote:
Keith Dysart wrote:
Cecil Moore wrote:
But you are missing the point. You say the source is matched
to the line but the source is obviously re-reflecting 100% of the
reflected energy.

But the same can be said for experiment A, can't it? Measured
conditions on the line are identical.

But conditions in the sources are exactly opposite. One
is sourcing and sinking power. The other is completely
powerless.

Of course we can turn that around by building the generator for
Experiment B in the Norton style instead of the Thevenin style.
Then it will dissipate 4 times the power it would when terminated
with 50 Ohms.

Or how about the variant that will dissipate exactly the same
as the circulator without having one. Its dissipation always
numerically rises by the same amount as the "reflected power".
You should work on this generator since it would really help
convince people that the reflected power is dissipated in the
generator.
(Hint: There are two ways to build it and you need a current
source, a voltage source and two resistors.)

Please apply this calculation to Experiment A and check
your result. No difference. Oooopppps.

Oooopppps means you obviously made a mistake. The conditions
are opposite not alike.

In your characteristic style, you have removed the description of
what is being compared so the reader can not refer back and notice
that you are just contradicting. Oh well.

And if you did the same test with Experiment B you would get the
same result.

Obviously not since source B is at room temperature.

Minor changes to the generator for B can give you a very hot one
or one that is exactly the same temperature as the one with
the circulator. Your simple contradiction is a an exceedingly weak
argument.

No different for B.

Source A is dissipating 200 watts. Source B is dissipating
zero watts. How is that not different?

The conditions on the lines are indistinguishable and yet you
claim one is reflecting and one is not. How did the line know
whether it should reflect or not? Or is the wave that knows?

Well this is the point you lock up on and it is one of the root
causes of all subsequent errors. I suspect your refusal to
accept the common knowledge that the output impedance
of the generator can be well known, that this controls the
amount of reflection at the generator ...

The example proves this to be a wrong-headed concept.

You really should crack a basic text book, although you are
in kind of deep now to back track so that path does carry
high risk. You could also google or try the simulation. All
will support the statement I made above.

I present you with
two 50 Ohm generators; one constructed with a circulator and
one constructed with a 50 Ohm resistor. How do you tell which
is which?

The one with the rapidly rising temperature is the one with
the circulator. The one that remains at room temperature
is your ten cent resistor version.

But if we use a Norton style, which one gets hotter?
Or the third style (have you worked out how to build it yet?),
which will dissipate exactly the same as the circulator.

Yes indeed. All line conditions are exactly the same.

But the source conditions are radically different. One
source is sourcing 100 watts and sinking 100 watts. The
other source is sourcing 0 watts and sinking 0 watts.

I won't repeat myself.

You can not possible be arguing that P is not equal to V times I,
can you?

Pfor - Pref = 0 where those Ps are Poynting vectors.
Pfor is not zero. Pref is not zero. Pnet is zero
only because of a directional convention.

Actually Pnet is zero because of basic circuit theory and the
universally accepted understanding that P = VI.

And are you disputing that if V or I is at all times 0, there must be
no energy flowing.

Make that at all times AND AT ALL PLACES and I will agree.
If V is zero it only means that all the energy has migrated
into the magnetic field and indeed, when V is zero, I is
at a maximum.

In circuits, we measure the power at a particular place.
I certainly want my power company to do this. If the voltage
or current is 0 at a particular place in the circuit then no
energy is flowing at that place in the circuit. If you are disputing
this, I contend that you do not accept that P = VI.

Well it is pretty clear to me that if the net current is always 0,
then no current is ever flowing and the power must be zero.

True if the net current everywhere is zero. Not true if the
current is only zero at a point. Current on each side of
a zero current point is prima facie evidence of energy flow
in both directions.

Inventive. But it doesn't fly. P = VI or it doesn't.

In fact what happens is the energy flows towards the voltage
and current nulls from both sides at the same time, then it flows
away. But it never crosses. Of course, the above statement
applies to sinusoidal excitation. The story is a bit different for
pulse and step. If the line is excited by a step function, for
example, after the reflection makes it back the generator, the
current is zero everywhere, though the 'Bird Watts' are still
'flowing' (but it does take a DC coupled directional wattmeter
to observe this).

....Keith

Analyzing Stub Matching with Reflection Coefficients
 

On 13 Apr, 09:37, Walter Maxwell wrote:
In the thread 'Constructive Interference and Radiowave Propagation', Owen, on 4-8-07 asserted that my writings
in Reflections concerning the analysis of stub matching procedures using reflection coefficients are
applicable only in cases where the transmission line is either lossless, or distortionless. I disagree, and in
what follows I hope to persuade those who agree with Owen's position to reconsider.

Are we there yet?
Does confusion still rein?
Are they still on topic?
Who has convinced who?
Who got the purple heart ?
Have you enough yet to write a new book?
Will it be a comedy that will make people laugh?
Will you give credits for information given or taken?

Analyzing Stub Matching with Reflection Coefficients
 

art wrote:
On 13 Apr, 09:37, Walter Maxwell wrote:

In the thread 'Constructive Interference and Radiowave Propagation', Owen, on 4-8-07 asserted that my writings
in Reflections concerning the analysis of stub matching procedures using reflection coefficients are
applicable only in cases where the transmission line is either lossless, or distortionless. I disagree, and in
what follows I hope to persuade those who agree with Owen's position to reconsider.


Are we there yet?
Does confusion still rein?
Are they still on topic?
Who has convinced who?
Who got the purple heart ?
Have you enough yet to write a new book?
Will it be a comedy that will make people laugh?
Will you give credits for information given or taken?

Jesus, I'm outta here

Analyzing Stub Matching with Reflection Coefficients
 

On Thu, 19 Apr 2007 17:51:10 -0700, Jim Kelley
wrote:

So I gotta ask: what do waves do instead of superposing when there
isn't a load somewhere? Whistle and look the other way? :-)

Hi Jim,

What do they DO?

What an odd question.

73's
Richard Clark, KB7QHC

Analyzing Stub Matching with Reflection Coefficients
 

Cecil Moore wrote:
Gene Fuller wrote:
All we need now is that you also understand that waves flowing in the
SAME direction do NOT interact unless there is an interface or other
discontinuity.

Please stop implying things that I have never said. When I
asserted that reflections only happen at a physical impedance
discontinuity, that implies that interaction can only happen
at a physical impedance discontinuity. It is impossible to
get two coherent waves flowing in the same direction except
at a physical impedance discontinuity.

Assume b1 = s11(a1) + a12(s2) = 0

What I have said is that s11(a1) and s12(a2) are wave components
that cancel without ever being incident upon an impedance discontinuity.
Those two wave components originate at the impedance discontinuity
flowing *AWAY FROM* the impedance discontinuity. They are canceled
in a delta-t, i.e. a very short time. Those two waves are the result
of interaction at the impedance discontinuity but neither of them
ever interacted with the impedance discontinuity because they
originated at the impedance discontinuity.
--
73, Cecil, w5dxp.com


Cecil,

I am familiar with all sorts of weird and wonderful things that happen
on surfaces and really close to interfaces and discontinuities. However,
classical transmission line theory does not deal with any of those
things. I don't believe any of the recent discussions on RRAA have dealt
with these close-in effects either.

Where are the equations that describe this "delta-t" stuff that you keep
bringing up? How long is delta-t? What justification do you have for
saying that the waves start out from some point and then shortly
thereafter decide to cancel? Do they annihilate each other suddenly or
is the interaction gradual from time zero up to delta-t? Do you have any
references for this behavior? I scanned the Melles Griot tutorial info
and the FSU website, but I couldn't find anything about delta-t.

Inquiring minds want to know.

73,
Gene
W4SZ

Analyzing Stub Matching with Reflection Coefficients
 

Keith Dysart wrote:
. . .
Well it is pretty clear to me that if the net current is always 0,
then
no current is ever flowing and the power must be zero.

It seems to be a bit of a common fallacy to assign meaning to the
intermediate currents computed for the superposition solution to
a problem. Connect two equivalent batteries in parallel. The only
sensible answer is that no current is flowing since the voltages
are the same. (In another post you seem to accept this), though
if you use superposition to solve the problem, you get a very large
current flowing in one direction and an equally large current flowing
in the other. Only the resultant current is in any sense real. Same
for those waves on a transmission line. Just superposition. Just a
convenience to help reach the final solution. Don't over extend
and assign them meaning (or energy). In the end it will cause
deep conceptual difficulties.

I think you've put your finger right on Cecil's conceptual problem. When
we solve the battery example by superposition, we get the right answer,
zero current. But now let's put a resistor between the two batteries and
repeat the solution. When we "turn off" the left hand battery, we have a
lot of power being dissipated in that resistor. Using Cecil's view, we
would assign this to be the power associated with the current flowing to
the left. Then we "turn on" the left hand battery and "turn off" the
right hand battery. Again we have a lot of power being dissipated. This
would be the power associated with the current flowing to the right. The
problem comes in having to somehow manipulate these powers to get zero,
which is what we actually see. The mistake, as you continually point
out, is attributing a power to each current -- or each wave -- in the
first place.

Roy Lewallen, W7EL

Analyzing Stub Matching with Reflection Coefficients
 

On Fri, 20 Apr 2007 02:55:59 GMT, Gene Fuller
wrote:

I am familiar with all sorts of weird and wonderful things that happen
on surfaces and really close to interfaces and discontinuities. However,
classical transmission line theory does not deal with any of those
things. I don't believe any of the recent discussions on RRAA have dealt
with these close-in effects either.

Hi Gene,

Nutz, I thought I had mentioned Plasmons some time or other....

Where are the equations that describe this "delta-t" stuff that you keep
bringing up? How long is delta-t? What justification do you have for
saying that the waves start out from some point and then shortly
thereafter decide to cancel? Do they annihilate each other suddenly or
is the interaction gradual from time zero up to delta-t? Do you have any
references for this behavior? I scanned the Melles Griot tutorial info
and the FSU website, but I couldn't find anything about delta-t.

Except for the conceit of "delta-t," I bet you already can answer the
other questions with positive examples (and that you are well aware
that the Melles Griot material is -um- light years behind in these
topics).

73's
Richard Clark, KB7QHC

Analyzing Stub Matching with Reflection Coefficients
 

Keith Dysart wrote:
In your characteristic style, you have removed the description of
what is being compared so the reader can not refer back and notice
that you are just contradicting.

Such diversions - almost everyone is running a threaded newsreader.
All one has to do is click on the previous posting. Not trimming
postings is a violation of usenet guidelines. My pet peeve is
when someone repeats ten pages of postings and adds one line,
like "Right on".

Minor changes to the generator for B can give you a very hot one
or one that is exactly the same temperature as the one with
the circulator.

You've been hammering people with the source of your choice
for days but choose to abandon it as soon as someone points out
a logical problem with it.

The conditions on the lines are indistinguishable and yet you
claim one is reflecting and one is not. How did the line know
whether it should reflect or not? Or is the wave that knows?

One wave encounters a 50 ohm resistor and is dissipated.
The other wave encounters an infinite impedance and is
100% re-reflected - all in accordance with the wave
reflection model.

Actually Pnet is zero because of basic circuit theory and the
universally accepted understanding that P = VI.

Circuit theory completely falls apart with distributed
network problems. The currents at two points in the
closed loop are often flowing in opposite directions.

In circuits, we measure the power at a particular place.
I certainly want my power company to do this. If the voltage
or current is 0 at a particular place in the circuit then no
energy is flowing at that place in the circuit. If you are disputing
this, I contend that you do not accept that P = VI.

Plenty of energy is flowing - two equal magnitudes
in opposite directions equals zero net energy.

Correction to your P = VI based on DC, not AC/RF:

Net P = V*I*cos(theta) = Pfor - Pref

Forget V and I being 0. cos(theta) is always 0 for a
standing wave. There is ZERO net power anywhere in a
standing wave. (It's a lot like my bank account.)

Inventive. But it doesn't fly. P = VI or it doesn't.

Forward waves and reflected waves are completely independent
of each other and do NOT interact. Their powers do NOT
superpose. There is nothing but joules moving at the
speed of light in a transmission line. There's no net
energy but your zero energy assertions are just illusions.
EM waves are incompatible with zero energy.
--
73, Cecil http://www.w5dxp.com