Frank, this is consistent with what I am observing. The claim is for a given
frequency when a 0j load (in the range of 10 to 40 Ohms) and an unknown load
(assumed to be in the range of 10 to 40 Ohms) show the same phase shift then the
unknown is 0j also. It is not necessary that the loads be the same value, only
within the range. (I will have to experiment with loads over 60.)

So far nothing has surfaced to contradict this.

Thanks - Dan

Your method will exhibit a constant reflection coefficient circle (and
VSWR), with the angle varying from 180 degrees through zero degrees and then
back, through negative angles, to 180 degrees.

Frank