Roger wrote:
Hi Roy,

Could I add this observation? Both traveling waves and standing waves
can be measured. A single volt meter or ammeter will measure the
standing wave which is the sum of the traveling waves..

This isn't quite correct. A standing wave is the result of isn't the sum
of traveling waves. It's a description of the envelope of the current
distribution that sum produces. The sum of the traveling wave voltages
is the total voltage. The sum of the traveling wave currents is the
total current. It's relatively to measure the total voltage or current
at any point and, if you measure them at enough points you can use the
measurements to draw a graph of the standing wave.

A DIRECTIONAL
volt meter or ammeter will measure only the traveling wave within the
design direction, but can not distinguish between components from
multiple reflections that might combine.

Yes.

A directional voltmeter or ammeter will measure the same voltage or
current no matter where it is placed in the transmission line under
steady state conditions, assuming no resistive losses in the
transmission line.

That's only partially true. Both the traveling waves and the total
voltage and current have not only magnitude but also phase. A
directional coupler can measure both the magnitude and phase of the
traveling waves (but some directional detectors like a Bird wattmeter
indirectly measure only the amplitude). Traveling wave measurements at
different points along a lossless line will have the same magnitude, but
different phases. So the voltages or currents at those points aren't the
same.

Roy Lewallen, W7EL