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  #141   Report Post  
Old August 29th 03, 01:23 AM
David Robbins
 
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"Peter O. Brackett" wrote in message
link.net...
Dave:


The impedance matching dynamics at the reference plane/junction point are
the same for
distributed and lumped systems, they obey all the same equations, their
electrodyanamics
is the same, one simply cannot tell the difference at the driving point.

If you don't like lumped models, then make the internal resistance of the
Thevenin
generator out of a distributed line. It will work just the same way.


i'm sorry, but that just isn't true. make me an equivalent, with a
distributed line, of a 1v step voltage source in series with a 1ohm
resistor.



  #142   Report Post  
Old August 29th 03, 01:08 PM
David Robbins
 
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"W5DXP" wrote in message
...
David Robbins wrote:
these discussions always seem to end up in this same quagmire, one group
trying to solve everything with wave equations, sinusoidal steady

states,
transmission line transformations, and the other holding on to the

lumped
models and trying to make them fit the wrong problem domain.


Plus a third group of particle physicists saying waves don't exist. :-)


what is really fun is watching those guys try to explain reflections with
photons getting absorbed and reemitted.


  #143   Report Post  
Old August 29th 03, 04:50 PM
W5DXP
 
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David Robbins wrote:

"W5DXP" wrote:
Plus a third group of particle physicists saying waves don't exist. :-)

what is really fun is watching those guys try to explain reflections with
photons getting absorbed and reemitted.


Yep, I notice I got no answer (so far) to my question about reflected
photons. And, apparently, when one electron gets too close to another,
they each emit virtual photons as a warning not to come any closer.
--
73, Cecil, W5DXP

  #144   Report Post  
Old August 29th 03, 07:10 PM
Peter O. Brackett
 
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David:

[snip]
sorry, not always... another clear generalization from oversimplifying and
applying the wrong model. there are cases where there is zero reflected
voltage for a conjugate match.

[snip]

David, my friend as I stated several times, there is only one such case NOT
"cases"
and occurs only when Zo is purely resistive.

In that case the conjugate is non-existent! What's your point?

Wanna proof:

The reflection coefficient is identically zero,

rho = (Z - Zo)/(Z + Zo) = 0

If and only if the numerator of rho is identically zero.

(Z - Zo) = 0

Solving for the unknown Z, this occurs whenever.

Z = Zo

For complex Zo = ro + jxo, conjugate match occurs whenever
Z = ro - jxo and so rho can only be zero when:

ro - jxo = ro + jxo

which only occurs when

-xo = xo

This can only happen if xo = 0, i.e. the reactive part of both Z and Zo
are identically zero.

i.e. -xo = xo if and only if xo = 0

And this only occurs when Zo is real, not when it is complex!

What exactly is your point?

--
Peter K1PO
Indialantic By-the-Sea, FL.


  #145   Report Post  
Old August 29th 03, 07:27 PM
Peter O. Brackett
 
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Roy:

[snip]
"Roy Lewallen" wrote in message
...
Not QED at all. You claimed to have proved that maximum power is
delivered to a load when a transmission line is terminated such that the
reflected voltage on the line is zero.

[snip]

No I did not! Never said that, never have. Where did you get that idea?

I said that for a general complex Zo the reflected voltage is generally
NOT zero at maximum power transfer.

To make myself perfectly clear, let me repeat that...

I said that for a general complex Zo the reflected voltage is generally
NOT zero at maximum power transfer.

I said that for a general complex Zo the reflected voltage is generally
NOT zero at maximum power transfer.

I said that for a general complex Zo the reflected voltage is generally
NOT zero at maximum power transfer.

[snip]
Here, you're agreeing that the
reflected voltage is zero when the line is terminated in its
characteristic impedance. So where's the proof that this condition leads
to maximum power to the load?

Roy Lewallen, W7EL

[snip]

What I was trying to prove was that the reflected voltage is NOT zero
at conjugate match for the case of complex Zo!

I proved that by setting up a transmission line with perfect image [not
conjugate]
matching on both ends [Zo is seen looking in both directions from any point
in
the system] and driven by a generator set up to create the incident wave.

That system has no impedance discontinuities anywhere. The impedance
is Zo all along the line and into the generator looking in either direction.
No impedance discontinuities no reflections, period!

I then calculated the classical reflection coefficient and showed it to be
zero
confirming that rho = 0 when there are no impedance discontinuities and the
classical formula for rho is used, rho = (Z - Zo)/(Z + Zo).

As the last step I changed the termination from Z0 to conj(Zo) i.e. a
conjugate
match, NOT an image match and showed that rho is NOT zero in this case.

QED!

Summarizing...

Image Match: A line of surge impedance Zo terminated in Zo has no impedance
discontinuities and no reflections.

Conjugate Match: A line of surge impedance terminated in conj(Zo) has an
impedance
discontinuity and hence has reflections. [Unless in the one unique case
that Zo is purely real]

BTW...

Aside: From the postings of Dave and yourself along this thread, I get the
impression that
ya'll beleive that lumped systems obey different laws and should should be
modeled
differently than distributed systems. I am surprised by that claim. Surely
you don't mean that!

Surely all electrical systems, lumped or distributed, must obey the laws of
electrodynamics as set
out by Maxwell-Heaviside. Do you know of any cases where they don't?

Regards,

--
Peter K1PO
Indialantic By-the-Sea, FL.





  #146   Report Post  
Old August 29th 03, 07:41 PM
Peter O. Brackett
 
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David:

[snip]
i'm sorry, but that just isn't true. make me an equivalent, with a
distributed line, of a 1v step voltage source in series with a 1ohm
resistor.

[snip]

A 1volt step voltage in series with a zero length transmission line
terminated in a 1 Ohm resistor!

Dave, all electrical systems, lumped and distributed alike, obey
the Maxwell-Heaviside equations. They are all the same, not
different as you claim!

Prior to Maxwell [mid 1800's] folks believed that lumped and
distributed systems might obey different laws, but ever since
Maxwell wrote down his celebrated 22
equations, using quaternions, and Oliver Heaviside reduced
them to 4 neat little vector differential equations back in
the mid 1800's, most everyone, with the apparent exception
of yourself, has accepted that lumped and distributed systems
obey the same laws!

What exactly is your point?

Do you believe that lumped systems are described by different
laws than distributed systems? Are you trying to convince me
of that 150 year old discredited idea?

All macro - electrical systems confirm to the same laws of
electrodynamics, namely the Maxwell-Heaviside equations.

The only systems where Maxwell-Heaviside fails to predict
physical reality is when dealing with the "very" small, i.e.
quantum mechanics when one has to do Engineering and
make predictions and design one-photon-at-time. In this
case you have to use quantum electrodynamics or QED
but still all systems, lumped or distributed must obey QED
and Maxwell-Heaviside is just a special case or approximation
to QED laws in the aggregate when there are lots of photons.

Dave you will have a lot of arguing to do to convince modern
electro-technologists that lumped systems obey different laws
from distributed systems. Or that the equations of lumped
impedance matching are any different from transmission
line impedance matching. They are the same! The models
are the same, the mathematics are the same, the experiments
confirm that they are the same.

Exactly what is your point?

--
Peter K1PO
Indialantic By-the-Sea, FL.



  #147   Report Post  
Old August 29th 03, 08:25 PM
Roy Lewallen
 
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Peter O. Brackett wrote:
Roy:

[snip]
"Roy Lewallen" wrote in message
...

Not QED at all. You claimed to have proved that maximum power is
delivered to a load when a transmission line is terminated such that the
reflected voltage on the line is zero.


[snip]

No I did not! Never said that, never have. Where did you get that idea?


This is from your posting of August 25:

-----------

Roy:

[snip]

No one from "Camp B" has given any justification for the assumption that
the condition for minimum reflection is the condition for maximum power
transfer. We're lacking either a proof, a derivation from known
principles, or even a numerical example. I maintain that this assumption
is false.


[snip]

I did just that in a separate posting on this thread a couple of days ago.

-----------

Then on August 26, I posted:

-----------

. . .


I'll restate something I mentioned before (first incorrectly, then
corrected). Connecting a load to a transmission line which is the
complex conjugate of the transmission line Z0 does *not* guarantee
maximum power delivery from the source, or to the load. The load
impedance which provides maximum load power is the complex conjugate of
the impedance looking back from the load toward the source. That
impedance is the source impedance transformed through the transmission
line between source and load, and it's not generally the same as the
line's Z0, or its complex conjugate. When this condition of maximum load
power is met, there will almost certainly be voltage and current wave
reflections on the line -- there would be none only if the optimum load
impedance coincidentally happened to be equal to the line Z0. So the
argument that there can be no reflection of the voltage wave under the
condition of maximum power transfer is wrong.

You didn't show differently in your analysis, and no one has stepped
forward with a contrary proof, derivation from known principles, or
numerical example that shows otherwise.

-----------

To which you replied, also on August 26:

-----------

Yes I did. I guess that you missed that post.

-----------

I haven't been able to find this proof in your postings.


I said that for a general complex Zo the reflected voltage is generally
NOT zero at maximum power transfer.


Well, shoot, I agree with that, as I always have.

. . .


BTW...

Aside: From the postings of Dave and yourself along this thread, I get the
impression that
ya'll beleive that lumped systems obey different laws and should should be
modeled
differently than distributed systems. I am surprised by that claim. Surely
you don't mean that!


I believe you can build a bad or inappropriate model with lumped or
distributed components, and draw invalid conclusions from them. Perhaps
you missed my posting a day or two ago where I pointed out that your
model using lumped components was clearly not the same as one using a
transmission line, by means of the very simple test of observing the
current in a load resistor.

And yes, lumped systems should generally be modeled differently than
distributed ones.


Surely all electrical systems, lumped or distributed, must obey the laws of
electrodynamics as set
out by Maxwell-Heaviside. Do you know of any cases where they don't?


This argument of "you don't agree with my view of how things work, or my
inappropriate models, therefore you don't believe in the Laws of
Physics" is as tiresome as it is pompous.

Roy Lewallen, W7EL

  #148   Report Post  
Old August 29th 03, 08:28 PM
David Robbins
 
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"Peter O. Brackett" wrote in message
k.net...
David:

[snip]
i'm sorry, but that just isn't true. make me an equivalent, with a
distributed line, of a 1v step voltage source in series with a 1ohm
resistor.

[snip]

A 1volt step voltage in series with a zero length transmission line
terminated in a 1 Ohm resistor!


sri, you cut off one important thing... your last sentence before my
request...


If you don't like lumped models, then make the internal resistance of the
Thevenin
generator out of a distributed line. It will work just the same way.


i am asking you to show me a distributed model for the internal resistance
of a thevenin generator that as a lumped model is a 1v step voltage source
in series with a 1 ohm resistor. a zero length transmission line doesn't
exist so the model is still lumped.


  #149   Report Post  
Old August 30th 03, 12:57 AM
Peter O. Brackett
 
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Roy:

[snip]
This argument of "you don't agree with my view of how things work, or my
inappropriate models, therefore you don't believe in the Laws of
Physics" is as tiresome as it is pompous.

Roy Lewallen, W7EL

[snip]

Sorry if I offended. I didn't mean to.

And all along here I thought you were the one being tiersome and pompus!

Such is the medium of news group postings.

In summary, I believe that we agree completely, and that we were typing at
"cross purposes".

Your general accusation that no one from Camp B, what ever camp that was,
seemed to show
your "pique" and so I responded in kind.

A waste of time, or... a lesson learned.

Maxwell rules, lumped or distributive, there is no discrimination.

--
Peter K1PO
Indialantic By-the-Sea, FL.




  #150   Report Post  
Old August 30th 03, 01:12 AM
Peter O. Brackett
 
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David:

[snip]
i am asking you to show me a distributed model for the internal resistance
of a thevenin generator that as a lumped model is a 1v step voltage source
in series with a 1 ohm resistor. a zero length transmission line doesn't
exist so the model is still lumped.

[snip]

Dave you are being picayune. No one wins a ****ing contest like this,
everyone just gets **** on their hands.

I could respond with... OK then... how about a transmission line of length
somewhat less than exp(-exp(-exp-1000))) meters in series with a 1 Ohm
resistor. Will that do? Or do I could use a "recursive" definition.

It simply doesn't address or affect the point at hand, which is that a
complex Zo line terminated in its' conjugate will exhibit a non-zero
reflected voltage. Do you agree? If not, what 's your point?

"When I use a word", Humpty Dumpty said, in a rather scornful tone,
"it means just what I choose it to mean, neither more nor less."

"The question is", said Alice, "whether you can make words mean so many
different things."

"The question is", said Humpty Dumpty, "Who is to be master: - that's all."

-- Lewis Carol, "Alice in Wonderland - The Turtle soup"

Dave, I am willing to help you understand my unimportant proof, I didn't
realize it was such a big
deal, but hey... I recall you asked or commented about my posting, but if
all you wanted is to fuss
with me over side issues such as if lumped systems obey different laws than
distributed systems, then
I presume that we will have to agree that we cannot have a productive
discussion..

If I have offended you in some way, I did not mean to, please accept my
appologies.

Best Regards,

--
Peter K1PO
Indialantic By-the-Sea, FL.





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