Keith Dysart wrote:
Cecil Moore wrote:
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.

But the same can be said for experiment A, can't it? Measured
conditions on the line are identical.

But conditions in the sources are exactly opposite. One
is sourcing and sinking power. The other is completely
powerless.

Please apply this calculation to Experiment A and check
your result. No difference. Oooopppps.

Oooopppps means you obviously made a mistake. The conditions
are opposite not alike.

And if you did the same test with Experiment B you would get the
same result.

Obviously not since source B is at room temperature.

No different for B.

Source A is dissipating 200 watts. Source B is dissipating
zero watts. How is that not different?

Well this is the point you lock up on and it is one of the root
causes of all subsequent errors. I suspect your refusal to
accept the common knowledge that the output impedance
of the generator can be well known, that this controls the
amount of reflection at the generator ...

The example proves this to be a wrong-headed concept.

I present you with
two 50 Ohm generators; one constructed with a circulator and
one constructed with a 50 Ohm resistor. How do you tell which
is which?

The one with the rapidly rising temperature is the one with
the circulator. The one that remains at room temperature
is your ten cent resistor version.

Yes indeed. All line conditions are exactly the same.

But the source conditions are radically different. One
source is sourcing 100 watts and sinking 100 watts. The
other source is sourcing 0 watts and sinking 0 watts.

You can not possible be arguing that P is not equal to V times I,
can you?

Pfor - Pref = 0 where those Ps are Poynting vectors.
Pfor is not zero. Pref is not zero. Pnet is zero
only because of a directional convention.

And are you disputing that if V or I is at all times 0, there must be
no energy flowing.

Make that at all times AND AT ALL PLACES and I will agree.
If V is zero it only means that all the energy has migrated
into the magnetic field and indeed, when V is zero, I is
at a maximum.

Well it is pretty clear to me that if the net current is always 0,
then no current is ever flowing and the power must be zero.

True if the net current everywhere is zero. Not true if the
current is only zero at a point. Current on each side of
a zero current point is prima facie evidence of energy flow
in both directions.
--
73, Cecil http://www.w5dxp.com