J. B. Wood wrote:
In the steady-state there is one voltage/current (as seen by an RF
voltmeter or ammeter) placed at the measurement point. We need a
directional coupler (part of a Bird model 43) or impedance bridge
(referenced to Zo) inserted at the measurment point in order to partition
the sampled voltage/current into incident (forward) and reflected waves.

Hi John, one important fact that some people would like to
forget is that the reflected wave can indeed be partitioned
from the forward wave. Some people on this newsgroup argue
that the forward wave and reflected wave are inseparable and
that reflected waves contain no rearward traveling energy.

However a circulator plus load resistor located at the source
will prevent reflected wave energy from being incident upon
the source and will heat up that load resistor in the process
proving that reflected waves are real and do contain energy.

My favorite illustration of such is a one-second lossless
transmission line with reflections. The number of watts in
the forward wave plus the number of watts in the reflected
wave equals the number of joules stored in the line during
steady-state. For instance, if Pfor = 200w and Pref = 100w,
then 300 joules of RF energy exist in the one-second long
lossless line during steady-state.
--
73, Cecil, http://www.qsl.net/w5dxp