Whenever I have made measurements to antennas I have had very different results -even calibrating the antenna feed coaxial cable- than placing my VNA-F with a 10 cm. patch cord directly to the antenna feed. Obviously I have had to remove the antenna feed cable and calibrate the VNA with the cable stretched on the ground. If you want a precise and real measurement you should connect the NANO-VNA as close as possible to the antenna feed point.
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ALVARO, EA8ARX
?lvaro Felipe Hern¨¢ndez