Keith Dysart wrote:
There are many ways to obtain the instaneous
voltage and current for the subtraction (or addition).

Here are the associated equations:

Vz = V*e^-jBz + V'*e^+jBz

Iz*Z0 = V*e^-jBz - V'*e^+jBz

Current is sampled in such a way as to perform
the multiplication by Z0. That's where the calibration
to Z0 comes in.

If one adds the two equations (samples) the reflected
terms drop out and the result is a voltage proportional
to the forward wave.

If one subtracts the two equations (samples) the
forward terms drop out and the result is a voltage
proportional to the reflected wave.
--
73, Cecil http://www.w5dxp.com