On Dec 31, 12:36*am, Cecil Moore wrote:
Keith Dysart wrote:
Cecil Moore wrote:
They engaged in typical author-speak.

I think not.

You are welcome to your opinion. Authors always
couch their assertions in probabilities by
never uttering an absolute lest they be proved
wrong by one esoteric example.

Of course. That is writing with precision, as I said.

Well, there is no energy flowing through the '+' points.

I proved that energy is flowing through the '+' points
before the line is cut.

Unfortunately, this has not being proved as yet, but
merely assumed.

Superposition proves that there
is energy flowing through those points.

I thought that you had previously agreed that it was
not appropriate to superpose power. This can be
revisited if you have changed your mind.

And I have no issue if you wish to claim that there
are reflections at these points, though I might use
'bouncing' to differentiate from reflections occuring
at points with non-zero reflection coefficients.

So bouncing is what happens at points with zero reflection
coefficients. You seem to have invented a new religion.

No. I was merely offering an alternate term tht you might
use when claiming that they reflect, since reflect causes
you such grief.

No energy is flowing (q.v. IEEE definition of
instantaneous power), and yet you want energy
to be flowing.

Lots of energy is flowing in both directions.
Only the *NET* energy flow is zero.

Back to superposing power.

Although many have tried to prove that the output (source)
impedance is the impedance encountered by the reflected waves,
all of those numerous experiments have failed.

You, Cecil, are the only one who believes this. Any good
book on transmission lines will tell you otherwise.

I am not surprised that you are ignorant of the raging
arguments that have been going on primarily between
Bruene and Maxwell and their respective supporters.
I believe it continued to rage in the 2007 letters to
the QEX editors.

That argument was more about whether the output impedance
of an amateur transmitter was well defined. In my encounters
with the arguments I don't recall any claim that if it
was well defined and equal to the line impedance, then
there would be a reflection. If this claim was made,
then someone needed to revisit the books.

Web references and Spice models which agree that "the
output (source) impedance is the impedance encountered
by the reflected waves" have been previously provided,
but you refused to explore them.

No, I asked you to measure the reflection coefficients
and report the results. You refused to do so.

Exactly. You refused to check your textbooks. You refused to
review the web references. You refused to examine the
spice models. Instead you ask me to measure something and
expect me to believe that some measurement I make will
convince you. Just another way to delay.

If the issue
had ever been resolved, it would be common knowledge and
we wouldn't be arguing about it.

There is only one place that this is being argued. If you
would review your textbooks, if you would look at the web
references, or if you would examine the spice models, you
would learn that the argument was settled long ago.
(Actually, there probably never was an argument, except
on r.r.a.a.)

...Keith

On Dec 31, 1:27*am, Cecil Moore wrote:
Keith Dysart wrote:
And a Thevenin source can be transformed into an
equivalent Norton source. Example...

A 100 V ideal voltage source in series with 50 ohms
has exactly the same output characteristics as a
2 amp ideal current source in parallel with a 50 ohm
resistor. Test using any load impedance: open, short,
any resistance value.

Indeed, take a look at the internal power dissipation
for an open and short and tell us again why those
sources are identical.

Are you saying that there output characteristics are
different because of differing internal power dissipations?

And are you not the lad who mentioned that one should
never examine the internal power dissipation of a Norton
or Thevenin equivalent circuit because, in general, it
bears no relation to the dissipation in the real
circuit? Or have you changed your view?

...Keith

Cecil Moore wrote:
Roger wrote:
I won't repeat that posting here, but please comment.

Will this source satisfy your needs? It is linear
and it prohibits reflected energy from reaching
the source making tracking energy rather simple.
I usually define it as a 50 ohm device but other
impedances could be chosen.

100w--1---2--
\ /
3
|
R

Thanks for alerting me to this device, which is real.

Thanks also for pointing out (in another posting) that the Norton source
is a constant current source.

But no, this will not do. The problem is that "We want to investigate a
1/2 wave length of transmission line, excited at one end. How soon is
stability reached?"

No doubt, past postings have not so clearly stated the scope of
investigation.

Unstated, and perhaps confusing, is the the power level must be limited
to some real value.

Also unstated, but reasonably assumed, is the understanding that the
exciting source would not be part of the circuit except as needed to
provide the excitation.

This last assumption was never achieved because the responders all
insisted that the source must be part of the investigation. It was
further insisted that the source invert the reflected waves with a -1
reflection factor. Had a +1 factor been acceptable, which is equivalent
to the reflection factor of an open circuit, the assumption would have
been realized.

Several responders discussed the Norton or Thévenin equivalent circuits.
These circuits assume steady state conditions, and are intended to be
replacements for groups of components. A very useful concept, but not
appropriate for startup excitation of a transmission line unless the
intent was to investigate the source AND transmission line as a system.

More later. I as still thinking about the "perfect power source".

73, Roger, W7WKB

Keith Dysart wrote:
Anyway, examples of what you are looking for exist
in most amplifiers. They are often called blocking
capacitors. They charge to the DC voltage but pass
the signal. They are not particularly good voltage
sources, but that is their role in the circuit, and
they do it admirably well.

Sorry, no modifications allowed. I simply want you
to prove that the voltage source impedance minus
the series resistor is zero ohms as you say.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
Do you ever answer a direct question?

No answer needed or expected for irrelevant rhetorical
questions.
--
73, Cecil http://www.w5dxp.com

Roger wrote:
The problem is that "We want to investigate a
1/2 wave length of transmission line, excited at one end. How soon is
stability reached?"

I guess the answer depends upon your definition of
"stability" above.

You might start with a loaded version:

http://www.w5dxp.com/1secsgat.gif
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
No. I was merely offering an alternate term tht you might
use when claiming that they reflect, since reflect causes
you such grief.

When your alternative involves something supernatural
happening when the reflection coefficient is zero,
I think I will pass.

Back to superposing power.

Power can certainly be added using the power density
equations but scalars cannot be superposed.

... the argument was settled long ago.

Absolutely false since the argument is still raging.
--
73, Cecil http://www.w5dxp.com

Keith Dysart wrote:
On Dec 31, 1:27 am, Cecil Moore wrote:
Indeed, take a look at the internal power dissipation
for an open and short and tell us again why those
sources are identical.

Are you saying that there output characteristics are
different because of differing internal power dissipations?

No, I'm saying what all the references say - that power
dissipation inside an equivalent source is irrelevant.
Yet you seem convinced that you know the internal power
reflection coefficient. You are contradicting the
references.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:


Lots of energy is flowing in both directions.
Only the *NET* energy flow is zero.


Cecil,

I guess you still have not gone back to the books to try to understand
what electromagnetic energy is all about. A good review of the Poynting
theorem would help to minimize the sort of nonsense you spouted above.

73,
Gene
W4SZ

Cecil Moore wrote:
Roger wrote:
Maybe we should be considering a perfect POWER source, which could
only emit power, never absorb it. The power out would be defined by
load impedance, just as it is for the perfect voltage source.

I have been using such a source as an example for years.
I call it the SGCL, signal generator equipped with a
circulator and load resistor. Here's the diagram.


100wSG---1---2----
\ /
3
|
R

No reflections incident upon the source because they
are all dissipated in the resistor R. It's a great
way to simplify examples.


Cecil,

It is interesting that you ridicule zero impedance ideal sources, and
then you provide an example with a circulator. Do you really think a
circulator is more ideal than a good voltage source?

73,
Gene
W4SZ