Cecil Moore wrote:
(snip)
We may understand the results of Tom's latest
measurement by considering the following:

50 ohm source===1 WL 50 ohm lossless coax===8+j2500 load
(snip)

I am not sure I understand this. As I understand an S parameter
tester, both source and load are 50 ohms. Tom says he fed and
monitored the signal with a pair of current transformers. I assume
that one transformer was fed from the 50 ohm source, and the other fed
the 50 ohm load, and S21 is the forward transfer gain parameter that
the analyzer can use to calculate a net delay at any frequency. But
if I am right about these connections, it leaves open the question of
what was on the other side of the current transformers, if the coil
was between them. Were those points grounded, terminated, what?