Keith wrote:
"Stick to the incident and reflected voltage (or current) waves for
analysis. They work."

Bird Technical Series #1 may be enlightning:
"By proper combination of the two samples (derived from volts and amps)
we obtain an RF voltage proportional to the square root of main line
power---."

"---the scale which has been marked in watts corresponding to the power
being sampled from the main line."

With a little review of wave behavior on transmission lines (I like
Terman) in almost any good text, it is seen that voltage and current
continuously vary along a line containing a reflection. This results
from interference between the forward and reflected waves.

However, The power, forward or reflected, is free of the oscillations
produced in the volts and amps by interference between forward and
reflected waves. This steady power flow makes power the electrical
property to measure and this was the impetus for the Bird wattmeter.
It`s been around for about 50 years, and I`d wager it will be around for
another 50 years.

Best regards, Richard Harrison, KB5WZI