Hello Bob,
I seem to recall reading on one of the eBay vendor's auction pages for a NanoVNA, some wording that claimed the following: "The buyer should not worry that the picture shows a NanoVNA with a range of 50 kHz to 300 MHz. The unit that will be shipped will have a firmware upgrade to allow operation from 50 kHz. to 900 MHz. and it will be calibrated to factory standards using the same included calibration devices." Of course, when I went back and tried to find that listing - I couldn't.
In my opinion, I don't think that any seller would be using "better" standards to calibrate the unit than the standards they were shipping with the unit. None of these manufacturers or sellers are trying to compete with HP/Agilent/Keysight or any of the other VNA manufactures out there. They all just want to build and ship a unit that meets the advertised specifications and do that as inexpensively as possible to maximize their profit. I see nothing in it for the seller.
Certainly the end user can take the supplied C0 data and save it in one the other Memory locations (SAVE1 thru SAVE4) and then load C0 with some other data so that it is always readily available at power-up. This would allow the initial data to be reloaded into C0 at some other time. But I have not seen or read any reason to believe that the factory furnished C0 calibration data is any better than the data that can be recreated using the furnished calibration tools.
I offer all of this IMHO.
Larry, AE5CZ
