I compared the measurements with Anritsu S362E and it's within 1 dBi, at least in the 2.4GHz band. The SWR curves are the same across the range and 1dBi, while not negligible, is enough for a pass/fail test on basic antenna tests, which is what I bought it for. This is accurate on Anritsu testing the Diamond 771, so lower frequencies may be more accurate. This seller didn't include calibration weights so I can't verify if it's calibrated or not. It comes with firmware version 0.83 and I can't find the firmware for it online.
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