Keith Dysart wrote:
I have stated that there is no re-reflection of the reflected wave at
the
source. Since the source is matched to the line, the reflection
coefficient is 0 and the wave just .... Well it must go into the
source
since tau is one. But at least it is not reflected when rho is zero.

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. Your special magic source is doing exactly
the opposite of what you claim it is doing. The calculated
physical reflection coefficient may be 0 but the virtual
reflection coefficient, SQRT(Pref/Pfor), is 1.0. This is
the point I have been making ever since you started posting.

As you observe for Experiment B, the current is zero so as you
say "The source is not only not sourcing any forward power, it is
also not sinking any reflected power."

Of course the current is also zero at the same point for
Experiment A, so there as well, the source is not only not sourcing
any forward power, it is also not sinking any reflected power.

That's again where you are wrong. In Experiment A, the circulator
load resistor is sinking 100W, i.e. 100% of the reflected power.
A bit of modulation will show that the power being sunk by the
circulator load resistor has made a round trip to the end of
the transmission line short and back.

A bit more analysis for Experiment A yields some more questions.
Terminate the line with a 50 Ohm resistor. The source is now
providing power to the line, there is no reflection on the line and
the circulator dissipates nothing.
Remove the resistor. The reflection returns. The circulator once
again dissipates 100 W. But as you said, in this condition,
"The source is not only not sourcing any forward power, it is also
not sinking any reflected power." So where did that 100 W being
dissipated in the circulator come from?

In Experiment A, the source is sourcing 100 watts and the
circulator load resistor is sinking 100 watts after the
round trip delay to the end of the line and back. If the
source signal is modulated, the delay between the source
signal and the dissipated signal is obvious and can be
measured.

I suggest a further extension to both Experiment A and
Experiment B. Replace the 1/4 WL stub with a 1 and 1/4 WL
stub. Now, at each 1/4 WL along the line coming back from
the load, no energy is flowing because either the current is
0 or the voltage is 0. So this absence of energy flow happens
not just at the source but repeatedly along the line. This
makes it difficult to accomodate the thought that the
forward or reflected travelling waves are transporting energy
along the line (at least at the quarter wave points).

The "absence of energy flow" is an illusion. There is 100
joules/sec in the forward wave and 100 joules/sec in the
reflected wave. Since the waves are flowing in opposite
directions, you can argue that there is no *net* energy
flow, but the component wave energy flow is alive and well.

Now back to the quibble. You said: "The source sources 100 watts
and the circulator resistor dissipates 100 watts which is all of the
reflected power."

Yes, in Experiment A but obviously not in Experiment B.
Your source has failed to perform the way you said it would.
As I said in the beginning, there will be re-reflections from
your source. In this case, there is 100% re-reflection.
Real world conditions are not as simple-minded as you say.

It would be more precise to say "The source sources 100 watts
and the circulator resistor dissipates 100 watts which is numerically
equal to the reflected power." I contend that it is this "numerical
equality" that has led many astray into believing that the
circulator is dissipating the "reflected power".

No, modulation on the reflected wave proves that it has made
a round trip to the end of the line and back. There is no
getting around that fact. There is also no getting around
the fact that the energy content of the stub is identical
in both experiments. The number of joules in the stub, in
both cases, is exactly the magnitude needed to support the
100W forward wave and the 100W reflected wave. The energy
in the stub in Experiment A is obviously real. The energy
in the stub in Experiment B is identical to Experiment A.

But as we have seen,
no energy crosses the 0 current node into the generator so the
"reflected power" can not make it to the circulator (or the source
resistance, if the generator happens to have one).

Your "no energy crosses the 0 current node" is just an ignorant
illusion. The forward current and reflected current are alive
and well and simply superpose to a net current of zero at that
point. We are discussing EM wave energy and a boundary condition
for EM waves to exist is that they must travel at c(VF). If they
don't, they are no longer EM waves.

At a current node, forward current equals 1.414 amps at 0 deg.
Reflected current equals 1.414 amps at 180 deg. Of course, the
*net* current is zero but there is no physical impedance discontinuity
to cause any change in the forward and reflected waves at that
point.
--
73, Cecil http://www.w5dxp.com