And here is a hint a first order cable correction (assuming the cable impedance is not exactly Z0) can improve the results
The model corrects for the long cable impedance mismatch for the 3GHz VNA
Mismatch is identified to be frequency independent and around -0.015-0.769i ohm, impact is visible in the upper left chart yellow/orange logmag S11 of the long cable which becomes more of a straight line. Now I can use this approach to reduce the cable impact on the other VNA's and see what is left to correct in the bridge.
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Erik, PD0EK
