开云体育

(Hi, I didn't see this covered in the wiki or other topics. Apologies if it has been)

I'd like to save three calibrations (corresponding to 3 different frequency ranges) for repeated recall.

How often does the calibration need to be redone for a given set of parameters? Ie, does the NanoVNA drift over time or usage (or temperature)?

Thanks again,

Connie

I've been using the same calibrations over the HF range for over a year, and when I check the SOLT loads, they're still on the money.
I've done one 401 point calibration from 3.5 to 30 MHz and can use it anywhere between at any resolution due to the firmware's interpolation.

Except to tell a stupidity, I prefer, to make the calibration on all the range of frequency which I will use, with many points (therefore many segments). Like: 20 segments for 1-30 MHz with smoothing 25-6 (2020 points with my -F). It takes time but only once. Then I use this calibration file for the current sub-bands.

Why :
You will see that the calibration file contains errors which will show up as straight lines in the graphs (like "parasites"). As these errors are in the calibration file they are found, in fact, by the calculations in nanovna-saver, on all the measurements (at the same frequency) and it has a very bad effect.

So, I correct in this single configuration file the faults by interpolation (by hand).
--
Fran?ois

Just from a physics-based opinion, things that require calibration do tend to drift over time. Component aging, thermal/environmental cycling, physical impact (dropping on the ground), and overvoltage can all cause calibration errors. That's why my company has a calibration lab, and all test equipment is on a calibration/recalibration cycle. How often for the Nano is how confident you are in the saved cal vs the actual cal when it is done again.

I calibrate for each frequency segment I am checking. I use mine mostly as an antenna analyzer.

I calibrate at the beginning of each session to insure the best accuracy.

Calibration is so quick and easy with these things that it's just a short simple step in the operation process.

I have a few saved calibrations for frequency sweeps that I use often like VHF and UHF ham bands.

But even there I'll save fresh calibrations every few times I use it so I know everything is good.

If you do use it as an antenna analyzer, don't forget to calibrate it for the smallest portion of the band you will be using, and specifically for the part of the band you will be transmitting on.

For instance, you could calibrate for 430 to 450MHZ as that is the US UHF ham band, but ultimately, the majority of transmitting is done from 448 to 450 on that band so it would make sense to calibrate for that segment rather than the full 20MHZ.

It seems the narrower the frequency range you calibrate the more accurate the instrument will be.


Regards

Colin

To amplify on my previous post, one application I have is routinely tuning an HF screwdriver antenna which I use on 80-10m. For this purpose, I so one 401 point calibration over that entire range, and then have set up and saved higher resolution scans (using that single calibration) over each of the relevant segments of the ham bands. I can recall a scan setup, tune the screwdriver to achieve the lowest SWR at the desired frequency, and when I switch to transmit, I get essentially the same SWR indication on my transceiver and the external SWR meter. Prior to using the nanoVNAPlus4, I used my venerable MFJ259B, which is ~22 years old now and has never been re-calibrated since it was new. I can still use that and compare what I get with the nanoVNA. They agree pretty well, to maybe a couple of tenths. Of course I can also compare or check either using a few dummies (and SOLT loads) I've created for the purpose.

This is a simple HF application. Depending on what your doing, particularly in UHF and above, things can be more sensitive.