Antenna's S11 parameter are out of spec in terms of impedance and frequency response.

Thread Starter


Joined Dec 26, 2020
I bought a GSM antenna from AliExpress. According to the specifications, it should work properly at 900 MHz But when I tested it on the nanoVNA. I got strange results:
Firstly, its impedance was never 50ohm, and
Secondly, its 900 MHz band was shifted to approximately 1 GHz. (Highlighted Yellow)

I have taken these reading at IPX end of the antenna (see below for Antenna Picture) . My nanoVNA was fully calibrated.

My question is why am I getting wrong results ?