antenna impedance measurement method

When I measure antenna impedance with a striped coaxial cable (taken into account port extension) I get very different readings from measuring with a normal SMA connector. Why would they be different? They are both soldered to the same pad.

Port extension does not remove cable attenuation, so the matching with cable will be better (better by 2* cable loss).

Depending on how long/short you have connected the cable leads, you have inserted extra series inductance.