Roy Lewallen wrote:
-- we get
exactly the same result either way because superposition holds.

Thinking that the result is the same and that nothing gets
lost during superpositon is a misconception. Consider the
following.

PSK modem A--------------------------------------PSK modem B

When a single signal flows from A to B, perfect information
transfer occurs. When a single signal flows from B to A,
perfect information transfer occurs. Now superpose the
two information streams. ZERO information transfer occurs.
Superposition is not magic and the result is not the same.

The superposition of forward and reflected currents cause
100% loss of phase information in the standing wave current
phase measurement. It is analogous to the problem above.

A standing wave current cannot be used to determine the
delay through a coil.
--
73, Cecil http://www.qsl.net/w5dxp