We are facing measurement issues with Ecal module N4691B.
After performing 2 port CAL on E5071C the network analyzer is showing S11 as 0.3 to 0.5 dB on Port A
S11
2.5GHz 0.0915dB
2.8Ghz 0.0701dB
3.1Ghz 0.01446dB
3.3GHz 0.2353dB
3.5GHz 0.3102dB
3.8GHz 0.4163dB
4.1GHz 0.4363dB
seems a bit large for normal error associated with an ecal. How long since the last calibration of the Ecal unit? But at these frequencies I would expect much smaller error. consult the ENA spec sheet to see what is the specified uncertainty for S11 and S21.