Richard Clark wrote in
:

I have restricted myself to the cyclic display of powers.
....
Well, at a quick glance and noting no tabular form of data, what is
presented wouldn't reveal cyclic variation anyway for two reasons:
1. It lacks resolution (not enough places);
2. It lacks sufficient mismatch.
This is not a complaint, merely an observation because the evidence
for your example is hidden deep in the decimal places.

The graph at http://www.vk1od.net/lost/RG58sol.gif has not been labelled
for presentation, so you will need to make some allowance in reading it.

The case that is plotted is an extreme mismatch, ou you might argue
impractical, but it is extreme enought to show the effects clearly on a
graph. The x axis is displacement from the load (-ve towards the
generator).

The red line is the so called "forward power" (Real(Vf^2/Zo)) that would
be indicated by a correctly calibrated sampler like a Bird 43, but
correctly calibrated means for the actual Zo, not the nominal 50+j0.

The dashed purple line is the so called "reflected power" (Real(Vr^2/Zo))
under the same conditions.

The power at a point is shown by the cyan line.

The dashed olive line is Real(Vf^2/Zo))-Real(Vf^2/Zo) (so called forward
power - reflected power). It is not the same as as the power because it
ignores two terms of the power expansion. A Bird 43 callibrated for the
actual Zo would lead you to this line.

This is a very detailed RLGC model, and it reveals from the P(x) line
that attenuation per unit length is not constant, a result of the loss
being higher in the region of a current maximum. Nevertheless, a sampler
that responds to Vf or Vr will not expose the true power curve (due to
the two missing terms).

I have thought at times of writing an article that explains the effects
on a true practical transmission line, and what practical instruments
calibrated for 50+j0 would indicate. I doubt that it would have appeal,
people like the "reflected power is dissipated in the transmitter and may
overheat it" explanation... it is easier to swallow.

Owen