Hello,
I have a NanoVNA V2 Plus 4 with serial number 35552083-00063333-35343234.
It worked fine for several years and I normally use NanoVNASaver.
I upgraded the firmware from 20220814 to 20250121.
After that I noticed strange behavior of the traces in NanoVNASaver while
the traces on the built-in screen are normal and show reliable measurement
results. The results in NanoVNASAver did not correspond anymore with the
results on the in-built screen.
I downgraded the firmware to 20220814 but the strange behavior remained.
To find out what was going on I checked the data from the USB serial port
and found that the s11 data are strange. Many data points showed something
like 0j or -2.-2.j
Is there anything I can do to restore the normal behavior of the USB data
stream. As far as I can conclude from what I see on the built-in screen the
RF circuits and the calculation of the results is OK. It seems to be just
the USB datastream that acts strangely.
Of course I already tried to use another USB cable and another PC, but that
did not make any difference. I also disconnected the battery in the device,
but also no difference.
Any ideas what to do?
Regards, Jos

Have you tried another software, Jos?

NanoVNA-QT is the recommended `default` .
Available here: <https://nanorfe.com/nanovna-v2-software.html>

HTH
Dave, G1OGY


On Sun, 2 Mar 2025 at 15:59, Jos F.M. VanderList via groups.io <jvdrlist=
gmail.com@groups.io> wrote:

> Hello,
> I have a NanoVNA V2 Plus 4 with serial number 35552083-00063333-35343234.
> It worked fine for several years and I normally use NanoVNASaver.
> I upgraded the firmware from 20220814 to 20250121.
> After that I noticed strange behavior of the traces in NanoVNASaver while
> the traces on the built-in screen are normal and show reliable measurement
> results. The results in NanoVNASAver did not correspond anymore with the
> results on the in-built screen.
> I downgraded the firmware to 20220814 but the strange behavior remained.
> To find out what was going on I checked the data from the USB serial port
> and found that the s11 data are strange. Many data points showed something
> like 0j or -2.-2.j
> Is there anything I can do to restore the normal behavior of the USB data
> stream. As far as I can conclude from what I see on the built-in screen the
> RF circuits and the calculation of the results is OK. It seems to be just
> the USB datastream that acts strangely.
> Of course I already tried to use another USB cable and another PC, but
> that did not make any difference. I also disconnected the battery in the
> device, but also no difference.
> Any ideas what to do?
> Regards, Jos
>
>
>

Good morning Dave,
Yes, forgot to mention, but also NanoVNA-QT shows strange traces.
There is definitely something wrong with the data from the USB-port.
The traces on the in-built screen are OK.
73, Jos, PA0JOZ

Have you tried another cable?

Hi, can you post a screenshot of the incorrect traces and smith chart, and the correct traces on the device?
Thanks

Good morning,
I am attaching three files. One is a picture of the screen of the NanoVNA Plus 4, the second is a screenshot of the VNAView and the third is a text file containing USB data.
The nanoVNA Plus4 (which was bought from Tindie, so no clone!) was calibrated for 100 MHz to 900 MHz.
The data in the text file was captured with pynanovna (from Github). I am worried about the 0j values for s11. I sometimes also see values like -2.2-j.
cocopuppy asked if I tried another cable and yes I did. It makes no difference.
Is there a method to restore all contents in the microprocessor to the original state?
Best Regards, Jos

@nanov2support,
I posted the requested info. Do you need anything more to diagnose the problem?
Is it possible to replace the microprocessor and how can it be programmed after the replacement?
Hope to hear from you!
best Regards, Jos

Hi, if the traces on the device are correct, then it can't be a hardware issue, as USB communication is error checked and any errors will cause USB to disconnect.
I have asked engineering and it is most likely that another program on your computer is using the serial port at the same time, can you check for any modem programs (such as ModemManager on Linux)?

Can you try an earlier version of NanoVNA-QT?
https://nanorfe.com/nanovna-v2-software.html
Thanks

Good evening,
I tried an older version of nanoVNA-QT and the result is identical.
I also tried another PC (without anything else connected), also with identical results.
As you can see from the results in the data file that I sent it is mainly the s11 data that are corrupt.
I also have an older nanoVNA V2.2 (SAA2-V2). If I connect that VNA to nanoVNA-QT the results are normal.
So, I agree that the RF hardware is OK, since the traces on the built-in screen are OK.
Also the calculation of the traces is OK, but something is wrong with how the results are sent via USB.
The USB connection itself seems OK, because it does not disconnect and I can also change firmware via nanoVNA-QT.
Hope you can find some kind of fix for this problem.
Thank you, best regards,
Jos

Hi, can you try firmware version 20220210 (this was the firmware version for most of the units shipped in 2022):
https://nanorfe.com/downloads/20220210/nanovna-v2-20220210-v2plus4.bin
Thanks

Hello again,
I tried firmware 20220210. The result is the same as with the other versions.
Note that the traces are around +10 dB while they should be around or below 0 dB.
The traces on the built-in screen are still OK.
I am awaiting new information.
Thank you!
Best regards, Jos

Hello again,
I tried firmware 20220210. The result is the same as with the other
versions.
Note that the traces are around +10 dB while they should be around or
below 0 dB.
The traces on the built-in screen are still OK.
I am awaiting new information.
Thank you!
Best regards, Jos

Is the VNAView program using internal calibration? I think on some
programs like NanoVNA-Saver, they default to calibration values saved in
the program. You have to perform a calibration with the program.

-ken-
Sent From My Desktop Via EMClient.

Hello Ken,
Thanks for thinking with me.
The problem is that data from the nanoVNA Plus4 to the PC is corrupted. Many datapoints for s11 seem to default to 0j instead of a float like -0.12345678 +0.987654321j .
The result is that even if I do a calibration in the nanoVNA-QT program the resulting measurement results after calibration are way off.
The problem is really in the data from the vna to the PC. Either they get corrupted by a firmware problem or by hardware faults in the microprocessor. That is my thinking anyway.
I still hope that nanovna support can find a fix. Otherwise the vna will land in the bin.
Best Regards, Jos

@nanovna2support,
Is there any new information or suggestion to remedy the problem?
I have provisionally made connections to the microprocessor to connect an ST-Link device.
Would it help you if I send a download of the contents of the flash memory? And if so, what range of flash memory do you need?
Hope to hear from you!
Best Regards,
Jos, PA0JOZ