Most of the RF equipment I own have BNC connectors, so one of the first things I did was install SMA-BNC adapters on channels 0 and 1 of my nanoVNA. After recalibrating using a 50 ohm BNC OSL kit, the Smith chart display looked as expected when BNC OSL standards were sequentially connected to CH0. BNC mismatches of 33, 75, 100 and 150 ohms all looked good with expected return losses. I saved the BNC calibration data in "SAVE 1" and retained the original SMA calibration in "SAVE 0" in case I need to remove the SMA-BNC adapters.
qrp.ddc's discussion in group regarding the electrical delay menu option reminded me of how the port extension feature of the HP8753C was used to correct for an adapter attached to the native "N" connector. The HP8753C has a menu option allowing you to enter an electrical delay value, extending the measurement plane out to the end of the adapter and correcting for its additional length. I wondered if this would work with the nanoVNA and so tried the following:
1.Turn on nanoVNA. With nothing connected to the CH0 BNC adapter, the Smith chart displays an open with a tail corresponding to the reactance of the SMA-BNC adapter.
2. On the nanoVNA select DISPLAY_SCALE_ELECTRICAL DELAY.
3. I didn't have a clue as to the electrical delay value for the SMA-BNC adapter, so starting at 100 (ps?) I tried successive values until the nanoVNA displayed a single dot with no tail to the far right of the Smith Chart display. The value needed to achieve this for my SMA-BNC adapter was 180 x 1 as entered on the nanovna screen keypad.
4. With BNC OSL standards sequentially connected to CH0, the results looked almost as good as the original SMA calibration data.
5. BNC mismatches of 33, 75, 100 and 150 ohms looked as good or better than the values obtained during the earlier calibration using my BNC OSL kit.
6. I saved the port extension corrected data in "SAVE 2" .
Thanks qrp.ddc for pointing out the electrical delay menu option and how it could be used for correcting for port extensions. For those users that want to add different adapters to channels 0 and 1 but don't have a suitable OSL kit to correct for the adapters, give the electrical delay menu option a try.
