Dear Mr. Smith,
Please allow me to congratulate you for your impressive work and for the amability to share it to the public!
What's my story, on the short, and why I am writing to you ?
I purchased a nanoVNA_V2 Plus4 in the hope that it would help my old father to measure crystals and to learn to build& tune his own SSB filters.
I already have a VNWA3-E that I used for such tasks, but my father asked me to find a cheaper solution (if possible), as his own "toy" for personal experiments and learning.
So, I ordered a NanoVNA V2 Plus4 on 04/04.2021 and after 73 days, I managed to pick it up (on 17Jun2021).
Before buying the device, I read the disclaimer on the site, the one that OwO quoted there: "
the V2 is not suited to very narrowband measurements (coherent bandwidth <1kHz) because of the fast switching of the transmit and receive paths. In practice this only becomes a problem when measuring crystals (does not affect SAW or any other filters) " .
Hmmm... "any other filters"...
Well, now I am *very* dissapointed, because the V2_Plus4 fails to read a classic 10.7 MHz SSB DIY ladder filter (look at my first attached screenshot, where I compared the same filter sweeped with the VNWA3 and with the NanoVNA V2Plus4):
I've been also disappointed to find out that neither VNA-QT or NanoVNA-Saver cannot offer some very useful functions as zooming into the bandwidth of the filter or moving the markers directly with the mouse. So, the only way to "zoom" is to see first a larger characteristic, then establish the new needed limits, make a new sweep setting and finally, a new calibration.
That's horrible, eating a lot of time and nerves.
Finally, I borrowed a NanoVNA V1 (2.8" LCD) from a friend, to see if I may normally sweep an SSB filter with it.
Yesterday, I discovered your excellent software for NanoVNA while I was seeking for alternatives to NanoVNA-saver and VNA-QT.
Until then, I read about 80% of the manual, I installed your software (1.0 and then the latest released binaries) and I started to play with both versions of it, for NanoVNA V1 and also for NanoVNA V2Plus4.
Not long after, I found out that you were right when you mentioned that NanoVNA V1 crashes for longer operating times.
This is a big and frustrating problem. Yes, I know that this is it (firmware/hardware), but I mentioned just for "the record"

V2 Plus4 is performing well, but cannot sweep narrowband devices, that is clear.
However, I encountered a problem while using your very nice software: after SOLT calibration, the sweep is not working.
The problem occurs with both NanoVNA V1 and V2 Plus4, and I tend to think it's more of an operating error (by my fault). Maybe I'm doing something wrong...
Steps:1) Power on NanoVNA
2) Launching your software
3) Go to "Setup/Diagnostics" -> Select NanoPort (ComX) -> Click on "Link" button (and wait to became green);
4) Check the status form to see link confirmation

5) Check the device LCD and see "USB PC" message
6) Return to "Main" menu of your software and establish the Start & Stop freqs, then the number of sweep points;
7) Start the filter sweep for test, without calibration; check S21 using <Xmsn rectangular>, check S11 using <Reflection Coeff> and check the <Impd Smith> graphs. The sweep is working (except the bad waveform due to the V2 Plus4 narrowband problems):

8 ) Deactivate sweeping, check the <ChnRef> button to be inactive and then starting the SOLT calibration using <2PortCal> button, as you described in the manual, at page 49 /chapter 12.8: SOLT Calibration. Start = 10.69 MHz, Stop = 10.704 MHz, 201 points.
9) Saving the calibration in a distinct, separate file.
10) Starting to sweep -> and see that nothing is happening:

Well, sorry for such a large text, but I don't know what to do, how to debug from this point !
Please give me some help, if possible.
In the hope of your answer, please allow me to wish you all the best and to encourage you to keep the good work on !
Best regards,
Bob