I did some measurements today on a vertical whip antenna tuned for the top end of the 2M amateur band. I wanted to see the effect of calibrating the NanoVNA on SWR and Return Loss measurements? The conventional wisdom is that the closer you calibrate to the frequency range of interest the more accurate the results. How close is close enough? That depends on how important accuracy is to you in your measurements. The first measurement was done using the factory default 50 to 900 MHz. calibration. The second was done by changing the Stimulus range (zooming) of the NanoVNA to 140 to 155 MHz. while still using the factory calibration. I then re-calibrated from 140 to 155 MHz. and repeated the measurement. Subsequent tests did zooming and calibrating to an even narrower range. You can clearly see the effect of calibration on the results...
Roger
Roger Need