Keith Dysart wrote:
Any reader is invited to prove me wrong by providing an accounting for
the 'reverse power' when it reaches the generator whose output
impedance
matches the characteristic impedance of the line (i.e. no reflection).

Destructive interference at the generator output
terminal is all the accounting one needs.

Here's a mental aid to help see what happens to
the reflected energy. Assume the output impedance of
the generator and the characteristic impedance of the
line are Z1. Assume THE GENERATOR SEES Z2 AS A LOAD.
Z2 is a general case impedance and could have any
value depending upon the load ZLoad which is not
equal to Z1. The load is mismatched and therefore
Pref1 is not zero.

Gen---Z1 t-line----ZloadZ1
Pfor1--
--Pref1

You say reflected energy flows into the generator.
I'll show you why it does NOT and that total
destructive interference is responsible for
eliminating reflections at the generator.

Add any length of lossless transmission line
with a characteristic impedance of Z2 at the output
of the generator (nothing changes) so it looks like:

Gen---Z2 t-line---+---Z1 t-line----loadZ1
Pfor2-- Pfor1--
--Pref2=0 --Pref1

Pfor1 and Pref1 are the same values as above.

The Z2 t-line has NO reflected waves because it
is terminated in its characteristic impedance Z2.
The Generator continues to see Z2 as a load. One
has to admit that nothing at the Generator output
has changed. THE GENERATOR SEES EXACTLY THE SAME
LOAD IMPEDANCE IN BOTH CASES. NOTHING HAS CHANGED
IN THE SYSTEM EXCEPT OUR ABILITY TO ANALYZE IT.

Now a simple energy analysis will indicate what
happens to the reflected waves on the Z1 t-line. Since
Pref2=0, the system is Z0-matched to Z2 at point '+'.
Total destructive interference is what happens to the
reflected waves on the Z2 t-line. All of the reflected
energy is re-reflected back toward the load at the Z2-
match point '+'.

NONE OF THE REFLECTED ENERGY REACHES THE GENERATOR SO
NONE OF THE REFLECTED ENERGY CAN BE ABSORBED BY THE
GENERATOR IMPEDANCE.

So there you have it - a detailed mathematically based
reason why the reflected energy does not make it into
the generator in your example. To fully understand why
zero reflected energy flows in the generator, one needs
to understand superposition along with destructive and
constructive interference. This is covered in more detail
in my WorldRadio Energy Analysis article at:

http://www.w5dxp.com/energy.htm

I would recommend that everyone interested in this subject
read the "Optics", by Hecht chapters on superposition and
interference of EM waves. It is the best treatment that
I have seen in writing.
--
73, Cecil http://www.w5dxp.com