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