On Jan 2, 9:38*am, Cecil Moore wrote:
Keith Dysart wrote:
The impedance of the Thevenin/Norton equivalent source
is not V/I but rather the slope of the line representing
the relationship of the voltage to the current.

However, after the interference patterns have been
established, the reflected waves do not encounter that
source impedance. That is why the reflection coefficient
seen by the reflected waves is relatively unrelated to
the value of resistance in a Thevenin equivalent circuit.

I assume that you have not provided a reference to support
this assertion because you have not been able to find one.

You need to complete step 3 of the superposition process
to realize exactly what is happening. Reference the
irradiance equation from the field of EM wave optics
to ascertain the interference levels. What do you have
to lose by alleviating your ignorance?

Unfortunately optics do not do well at explaining
transmission lines since they do not extend down
to DC.

Keith, until you take time to understand destructive and
constructive interference, you will never understand what
is happening inside a source and will be forever confused
by your blinders-on-come-hell-or-high-water method of
thinking. Optical physicists figured out a couple of
centuries ago exactly what you are wrestling with now.
Your present problem was already solved before your
grandfather was born.

I have yet to find anything about transmission lines
that needs constructive and destructive interference
for explanation. Volts, amps and superposition seem
to be able to do it all, and have the added benefit
of explaining the behaviour for step functions and
pulses. With the volts, amps and superposition,
sinusoids are just a special case of the general
one.

I am unsure why some are content to constrain
themselves to solution techniques and explanations
that only work on the special case of sinusoids.

...Keith

Keith Dysart wrote:
I assume that you have not provided a reference to support
this assertion because you have not been able to find one.

I provided the reference a number of times and you
chose to ignore it. The reference is the chapter on
interference in "Optics", by Hecht.

Unfortunately optics do not do well at explaining
transmission lines since they do not extend down
to DC.

On the contrary, most physics books on "Light" do
indeed extend down to DC. I'm surprised you don't
know that. "Light" and "visible light" are two
entirely different subjects. "Light" covers all
EM waves all the way down to DC.

I have yet to find anything about transmission lines
that needs constructive and destructive interference
for explanation.

Well, there's your entire problem in a nutshell. If
you don't ever look for something because you don't
"feel the need", you will never find it. Please don't
blame anyone else for your feelings. And you are not
alone. My mother never "felt the need" to understand
anything except God.

I am unsure why some are content to constrain
themselves to solution techniques and explanations
that only work on the special case of sinusoids.

Sinusoids are a test of your comprehension level.
Because we know if you cannot even comprehend the
most simple case, you have no hope of comprehending
anything more complicated. Don't feel bad. My
girlfriend cannot comprehend sinusoids either.
--
73, Cecil http://www.w5dxp.com

On Jan 2, 2:48*pm, Cecil Moore wrote:
Keith Dysart wrote:
I assume that you have not provided a reference to support
this assertion because you have not been able to find one.

I provided the reference a number of times and you
chose to ignore it. The reference is the chapter on
interference in "Optics", by Hecht.

I am suprised that a book on optics would discuss the
output impedance of Thevenin equivalent circuits.

Be that as it may, could you kindly provide the brief
extract from "Optics", by Hecht, that clearly states
that the impedance in a Thevenin equivalent circuit
can not be used to compute the reflection coefficient.

...Keith

Keith Dysart wrote:
On Jan 2, 2:48 pm, Cecil Moore wrote:
Keith Dysart wrote:
I assume that you have not provided a reference to support
this assertion because you have not been able to find one.
I provided the reference a number of times and you
chose to ignore it. The reference is the chapter on
interference in "Optics", by Hecht.

I am suprised that a book on optics would discuss the
output impedance of Thevenin equivalent circuits.

The "Optics", by Hecht reference is for destructive
and constructive interference, not Thevenin equivalent
circuits, but your attempt to confuse everyone is noted.
"Thevenin" is not even in the index of "Optics" so your
attempted diversion is ridiculous on the face of it.

I will repeat an earlier posting that you conveniently
chose to ignore. If we measure the forward power and
reflected power with a Bird wattmeter at the output of
your source during steady-state, it will tell you that:

forward power = reflected power

From that we can calculate the reflection coefficient.

rho = SQRT(Pref/Pfor) = plus or minus 1.0
--
73, Cecil http://www.w5dxp.com

On Jan 3, 12:04*pm, Cecil Moore wrote:
Keith Dysart wrote:
On Jan 2, 2:48 pm, Cecil Moore wrote:
Keith Dysart wrote:
I assume that you have not provided a reference to support
this assertion because you have not been able to find one.
I provided the reference a number of times and you
chose to ignore it. The reference is the chapter on
interference in "Optics", by Hecht.

I am suprised that a book on optics would discuss the
output impedance of Thevenin equivalent circuits.

The "Optics", by Hecht reference is for destructive
and constructive interference, not Thevenin equivalent
circuits, but your attempt to confuse everyone is noted.

My attempt to confuse!? We were discussing the determination
of reflection coefficients for Thevenin equivalent circuits.

But in another post, you have agreed that there
is a complete lack of references supporting your
position, so the question is now settled and you
can use the standard methodology to compute
reflection coefficient at a generator where
the output impedance is well defined.

Enjoy the new ability to solve problems that
were previously outside your grasp.

...Keith

Keith Dysart wrote:
My attempt to confuse!? We were discussing the determination
of reflection coefficients for Thevenin equivalent circuits.

No, we were discussing destructive and constructive
interference. Sorry about your confusion.

But in another post, you have agreed that there
is a complete lack of references supporting your
position, ...

No, I said I am not going to look for them. Sorry
about your confusion.

Enjoy the new ability to solve problems that
were previously outside your grasp.

I'm sorry, Keith, delusions of grandeur are a problem
outside of my field of expertise. Perhaps a professional
shrink could help you better than I.
--
73, Cecil http://www.w5dxp.com

Keith wrote:
"I am surprised that a book on optics would discuss the output impedance
of Thevenin`s equivalent circuits."

Hecht is a physicist.

On page 74 of Terman`s 1955 0pus, he writes:
"According to Thevenin`s theorem, any linear network containing one or
more sources of voltage and having two terminals behaves, in so far as a
load impedance connected across these terminals is concerned, as though
the network and its generators were equivalent to a simple generator
having an internal impedance Z and a generated voltage E, where E is the
voltage that appears across the terminals when no load is connected and
Z is the impedance that is measured between the terminals when all
sources of voltage are short-circuited."

On page 87 of his 1955 opus, Terman writes:
"The vector ratio of E2/E1 of the voltage of the reflected wave to the
voltage of the incident wave at the load is termed the "reflection
coefficient" of the load."

On page 97, Terman writes:
"The standing-wave ratio S is one means of expressing the magnitude of
the reflection coefficient;"

On page 214 of "Schaum`s Outline of College Physics", Bueche & Hecht
write:
"Standing waves---These might better not be called waves at all since
they do not transport energy and momentum.---"

Cecil is vindicated.

Best regards, Richard Harrison, KB5WZI