Roger Sparks wrote:

I think we have had a discussion about this previously. I can see
that within this thread we have at least three expectations of what
happens within the source when a reflection arrives; absorbed,
controled reflection, and acts like a short. Vigourus arguments are
presented for each expectation, but who can measure what happens
within an imaginary device? The seed for an endless argument!

We can calculate the voltage and current of an imaginary resistance,
imaginary capacitance, imaginary inductance, imaginary
current-controlled voltage source, imaginary ideal transformer, and
ideal lossless transmission line. And we can calculate them for a
perfect voltage source, too. From the voltage and current, we know the
power, and from its sign the direction of energy flow. Certainly we
can't know what happens to the energy which goes into the source. But
why should we care? I can tell you, using the fact that an ideal voltage
source reflects like a short circuit, the voltage and current in every
forward and reflected voltage and current wave from turn-on to steady
state of a transmission line/source/load system. At all times, the
voltage across the ideal source will be invariant, as it must be,
regardless of the current into and out of it. And I can show exactly
where every erg of energy is at every instant in any component and at
every point along the transmission line. I submit that any analysis
technique which can't do this without knowing what happens to energy
entering the source is inferior.

Roy Lewallen, W7EL