On Dec 29, 7:10*pm, Cecil Moore wrote:
Keith Dysart wrote:
When the source impedance is the same as Z0 there
is no impedance discontinuity to produce a reflection.

Here's a quote from "Fields and Waves ..." by
Ramo and Whinnery: "... significance cannot be
automatically attached to a calculation of power
loss in the internal impedance of the equivalent
circuit."

True indeed.

And from "T-Lines and Networks" by Walter C. Johnson:
"Although the Thevenin equivalent produces the correct
exterior results, its internal power relations may be
quite different from those of the network it replaces.
The power dissipated in the equivalent impedance of the
Thevenin circuit is not the same as the power dissipated
in the resistance of the actual network."

Different words, but still true.

Translation: Do not use a Thevenin source impedance
to try to track power dissipation within the Thevenin
equivalent box - it won't work.

No need for translation, though this is not quite what
was said above. Note the words "automatically" in the
first quote and "may be quite different" in the second.
The original authors allow for the possibility that it
might be the same, while your "translation" removes
that possibility.

Your argument that
there is zero power dissipation in the source resistor
inside the Thevenin equivalent box is bogus.

Nowhere has that argument been made.

Is the reflected wave reflected even without a
discontinuity?

The incident reflected wave is either reflected by the
source or it isn't. You cannot have it both ways.

It is not I who wants it both ways. For me it is clear
that there is no reflection when the output (source)
impedance is the same as Z0. And when it is not equal
to Z0, there is a reflection.

Since
the internal conditions inside a Thevenin equivalent
circuit are a complete unknown, either choice is
a possibility.

Not when the output (source) impedance is known. It is
then easy to compute the magnitude of the reflection
using the standard rules for reflection coeficient.

What you will find is that, for a real-world source,
the destructive interference on one side of the source
equals the constructive interference on the other side
of the source. The conservation of energy principle
prohibits having it any other way.

Except when the output (source) impedance is equal to
Z0, in which case there is no reflection, and, if I
understand your claim, no interference, destructive
or constructive.

...Keith