On Wed, Aug 23, 2023 at 10:07 AM, Geoff Peters - AB6BT wrote:
How does calibration affect the Thansform measurement?
You need to be calibrated over the frequency range that you select. However there is calibration interpolation used on some NanoVNA's, like the -H and -H4, so you can arrow the frequency range if you want to measure longer cables. However for best accuracy calibrate over the frequency range that accommodates your cable length. The lower frequency should be kept at 50 kHz and the upper frequency limit , number of sample points and velocity factor entered will determine the maximum length that can be measured.
If I set the stimulus start and stop to 50KHz and 1.5GHz the transform maximum
length is shown as 19.36m. If I set the sweep to 401 points what resolution
and accuracy can I expect, provided that I have the VF entered correctly.
1936mm/401 equals just over 4.8mm.
Your calculation is correct. However you won't be accurate to 4.8 mm becasue the velocity factor you enter (in percent) is only in steps of 1 so this is the limiting factor.
Roger
Roger Need