Bart, I don't doubt that your description of how to calculate line loss is
correct.

But it's more simple than that.

The input and output currents (or voltages) of any line are very rigid and
well defined. Regardless of generator internal impedance. Just as a
transformer's input and output currents and voltages are defined.

Their ratio is even more simply defined, albeit in complex terms.

So when the line input RESISTANCE, regardless of input reactance, and the
terminating RESISTANCE, regardless of termiating reactance, are known then
the power input to power output ratio is easily directly calculated from I
squared R.

The hardest but still straightforward part of the calculation is for the
input impedance, Rin+jXin, for given line attenuation and phase shift, and
for given terminating impedance, Rt+jXt.

The power dissipated in the line, although distributed in a highly complex
manner along its length due to standing waves, is very simply Pin - Pout.

Throughout the calculations, things like reflection coefficients and SWR do
not appear, You cant use them as spin-off benefits. What practical use could
you make of them anyway? The calculations have already been done, finished,
ended, caput!
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Reg.