Keith Dysart wrote:
So the next question is: What is the phase change
at the terminals of the black box?

It just occurred to me that you and I may be talking
about two different phases.

---Z01---+---Z02---

Vfor1--|--Vfor2

Vref1--|--Vref2

I am talking about the phase shift in the forward waves
across the impedance discontinuity, i.e. the phase shift
between Vfor1 and Vfor2. The list of phase shifts is
the phase shift in the forward voltages at the impedance
discontinuity. It is different for all the black boxes.

If you are talking about the phase between Vfor1 and Vref1,
then, yes, that phase is the same for all the black boxes.
It is impossible for it to be otherwise.
--
73, Cecil http://www.w5dxp.com