Hi,

A little obvious perhaps but have you tried a 50-ohm resistor
across the output of the 269 to check its calibration. I have a
259B and will wind a similar inductor to see what results that
network yields. I did a SPICE run on your values and it came up
with figures within the correct range although phase resonance and
maximum impedance were off by a MHz or so.

Will report back - Joe