NanoVNA Custom Software

[joeqsmith]

I dialed back the sample points to try and get a better look at the noise.


Noise1:  1200 sweeps 300K to 4.58GHz.
Noise3:  To zoom into the area of the low band, changed the start and stop to 99.847MHz to 99.852MHz
Note the spur is close to 99.85MHz. 

Noise4/5:  Even with 100 samples and such a narrow sweep, the spur isn't always captured.  It looks like one particular frequency.  It's amplitude varies a fair amount. 

[joeqsmith]

Narrowing the span much further, reducing the number of points to 4, turning off the color mesh, we can clearly see this is a single data point.  Oddly of the 3800 sweeps, there appears to only be three states. 

[joeqsmith]

Running similar tests with the V2+4.  First thing I noticed is that using the same 800 data points has yet to cause it to hang.    I also found that this particular unit would go unstable at a much lower frequency.   4.4GHz seems to be stable.

Noise7:  Sweep 300K to 4.4GHz, 800 points per sweep.   Notice the very low frequency noise is gone.  We can also see the unit drifting a bit as it warms up.  Something is happening around 900MHz.

Noise8: Looking below 1GHz.  Pretty decent.   
Noise9: Sweeping from 850 to 950, looking at raw data, we can see some short of shift happening at 910MHz.  Shouldn't cause any problems.


I like the speed of the V2+4 and having the ability to pull more samples without crashing.   I was sweeping in small segments with the original Nano to increase the resolution in order to look at narrow band parts.   Now I have all these samples and can't put them to use.   I want my cake and to be able to eat it too!! 

[joeqsmith]

I wanted to try running something a bit closer to the 4GHz limit of the V2plus4.    Shown are the S21 plots for the V2+4 compared with one of my old VNAs.   

Cal:  Showing both units after calibration.  The Nano is using the cables supplied with the unit.  The cal kit was changed as mentioned previously.   The Nano looks pretty good.  Consider in the previous plots the amount of noise above 3GHz.   

Notch: Showing a 3.8GHz notch filter (stub).   The two VNAs track fairly close except for the notch where we see a 4dB difference. 

MidWest: Let's have a look at Midwest Microwave DC-18GHz 40dB attenuator. 

See Posts below for corrections:
https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg3341186/#msg3341186

[joeqsmith]

Using the V2+4 to look at a small preamplifer.   

[joeqsmith]

No real point to this exorcise other than just playing with the Nano and testing my software.   I'm sure a few of you wonder if I have a CB radio.     I don't.
   
Looking at a small power amplifer.  The total attenuation between the amplifier and Nano is 60dB.   The step attenuator was then set to 0dB and a amplifier was bypassed to get a relative measurement from the Nano.   The step attenuator was then set to 30dB (90dB total) and the amplifier installed.   The total gain is about 80dB which is close to the limit of the Nano.  Note the 1dB steps.  Starts to compress above 7dB.   

[Kean]

Note the spur is close to 99.85MHz. 

Not a local broadcast station is it?

[joeqsmith]

Note the spur is close to 99.85MHz. 

Not a local broadcast station is it?

It's possible it's an external source. 0.3dBm is up there pretty high. Seeing the three states is also really odd.  I would expect it to be random.   A thru was installed to collect this data.  The v2+4 does have a metal case, vs the v2+'s plastic.  I could install the V2+ into a shielded case and see if anything changes.   If I had the battery pack, I could also try it stand alone.  Maybe something from the PC getting in through the USB cable.

[joeqsmith]

Case is made from PCB, soldered together.  Lined with Teflon.  Ferrite added internal and external on the USB cable.  Case grounded by large braid.   Section of semi-ridged used for through.  No calibration performed.  Showing the raw data.   

Swept the V2+ from 90 to 110MHz.   Started test with cover open to get a baseline.  At roughly half way through the test (750 sweeps), the enclosure was sealed off.  There appears to be no difference.   

[joeqsmith]

I used a small USB battery to power the v2+, then used the menus to program the start/stop.  Turned off all other traces.  Couldn't sort out how to get a good scale and reference. So cal'ed it with a thru only and set it to 0.1dB/div.  Sure enough, I can see the spike randomly show up.  Tossed it all into the shielded box and watched it through the screen.  Still does it.   Should be easy enough to reproduce. 

You may have seen they claim the v2+ is rated for 3GHz, where the v2+4 is rated for 4GHz.  I have been meaning to go back and repeat the 40dB attenuator test with the v2+ and see what difference there is.   It actually looks like my v2+ is slightly better with this test than the v2+4.   I doubt anyone is expecting them to perform as well as my vintage Agilent.   

Seeing a claimed 4GHz system off by 20dB below that, well...  Pretty much what I have been saying about keeping the original Nano below 300MHz, goes for the Plus.  Stay below 3GHz, don't expect to do anything narrow and if you use the V2+, stay with a smaller number of points (maybe these lockup problems can be corrected with firmware).   It's pretty good for only $120.       

[joeqsmith]

The 3GHz upper limit of the v2+ and v2+4 improves the TDR.  512 steps per unit length or 0.025.  After 200 samples, the standard deviation is 0.0018".   The histogram and unit length per sample are much more stable now.   It would be interesting to see how it would perform with a commercial airline rather than my homemade one.  Still, a big improvement over the original Nano.   

[joeqsmith]

Looking through some older data for the original Nano, it appears I had ran a test using increments of 0.010".    I replicated this test with the V2P and the results were nearly identical.    I repeated the test with the V2+ set to 900MHz and 101 data points like the original Nano.   

It's very possible that the mechanical hardware is the limiting factor. 

[joeqsmith]

Tried a few tests with the +4.  Added a digit to the standard deviation which is a bit lower.  We can see the p-p is also slightly better.   Could just be a matter of running the slide. 

[joeqsmith]

Continuing to play with the software and slide. 
Sweeping the V2+4 100K to 3GHz and incrementing the slide by  0.100".   Looking at the return loss, we can see how the travel effects the reflections.  As the number of sweeps increases, so does the distance from the V2+4 to the end of our airline.     

[joeqsmith]

They claim the lower limit of the V2+/+4 is 50KHz. 

Looking at a 5.6pf between port1&2.   The V2+ was swept from 50KHz to 5MHz.  No calibration was performed.  The USB has proven to be unreliable with this unit and I am using 101 data points (like the Nano).  Strange as the V2+4 has never hung.  Maybe a bad unit? 

Notice how bad the noise is as we go below 500KHz. 

The second plot is looking at the same capacitor but I have now calibrated the unit and am sweeping from 2MHz to 10MHz.  The jig adds a bit of error but no matter.  Notice it really doesn't settle until 6MHz or so.  Below 500KHz or so there's a lot of error.  Difficult to calibrate noise out. 

[OwO]

The attenuator measurement doesn't look right; here is what I'm getting with a 40dB attenuator 3-4GHz, calibrated with the cal kit supplied with the V2 plus4, and no averaging:



Please check your measurements with NanoVNA-QT, right now even nanovna-saver does not implement the isolation calibration correctly. If you are not sure how to implement it, check the code here: https://github.com/nanovna/NanoVNA-QT/blob/master/libxavna/calibration.C#L63

[joeqsmith]

I tried to run the software again and it basically seems to hang.  When I select various menus nothing happens.   After several seconds it will flash up the menu, then it goes away.   

The software doesn't show a version number anywhere on it.  There appears to be no text files included with it that provide any details about the software.   I am running Windows 10.  LabView talks just fine to the device (when it doesn't hang).  So it doesn't seem hardware related.    If you have better software or know of a way to get this version working, let me know and I will try it. 

*****
Playing around a bit more, I finally was able to get it to select the communications port.  It started sweeping but came up with this error.   

[Mechatrommer]

have you updated the driver to the one given/suggested by the SW documentation? CH340 iirc. that message appeared to me when i disconnected Nano while the SW is sweeping.

[joeqsmith]

have you updated the driver to the one given/suggested by the SW documentation? CH340 iirc. that message appeared to me when i disconnected Nano while the SW is sweeping.

As I have mentioned a few times, the V2P appears to hang when using the USB.  Again, maybe firmware or a defective unit.  It's possible this could have caused the error but it happened pretty fast and normally when it see it I am using large data sets.

I have attached a screenshot of the driver.   Is this what you are using?  It's what they had when I downloaded the software.  When I first plugged in the device, Windows recognized it but their software was hanging.  When I changed to this diver, I saw no difference. 

Again, their software hangs with both the V2+ and +4.   

I tried to follow the undocumented code and it does appear that the could be the problem.  I ignore the leakage terms with my software.   It may be faster to add this to my software than spend time trying to get their software working.   I didn't have any luck with the original Nano's software as well.  I have not tried this new software on a different PC. 

[Mechatrommer]

yes thats the same driver but i'm on Win7.. havent played much with large dataset but i just tried 5000 points, it took a while before the sweep starts, but i dont wait until completion. communication interruption (esp USB) is likely due to the driver or the USB IC or the how your PC is setup. too many USB devices and data transfer may affect that channel too? is there such thing as dropped USB packets?  . it could be out of the HW designer's hand as well or the NanoVNA-QT. you may ask the original programmer (xaxaxa) maybe? lets hope OwO frequently reply to Q&A.

[joeqsmith]

I still have a Windows 7 PC that I could try. 

I am seeing the V2+ crash with even 400 points.  But again, I am running it non-stop for hours on end.  It does appear to have something to do with the number of points.  The average time between crashes seems to increase with the number of points selected.   The V2+4 has yet to crash with my software.     I've been unsuccessful in finding a way to cause the V2+ to crash at will.     

That VNA's communications is very slow.  It's hard to believe it's a driver or hardware problem as LabView talks to it V2+4 just fine even with 800 points selected.  LabView isn't known for it's ultra fast speeds.   

Adding support to my software to include the crosstalk error terms isn't a big deal.  It would still be nice to be able to compare the data from my software with the included software.   

The one thing I noticed in their software was the ability to change the power level.   I didn't see anything in their documentation about how to change this setting.   Like the checksum, it may just be another undocumented feature.   I would like to add support for it.   

[joeqsmith]

I added support for the leakage and repeated the test with the 40dB attenuator sweeping 3 to 4GHz.     I then repeated the test sweeping up to 4.4GHz as before. 

Looks MUCH better!   Thank you very much for that little hint OWO! 

[joeqsmith]

I loaded the software onto my Windows 7 PC and it seems to work fine.  This PC has an old i7 2630QM processor where the Window 10 PC uses a Xeon E5-1650 v4.

Attempting to sweep down in the 50KHz range where the worse noise is but their software appears to limit it to 100KHz.   

Before digging into their source code, I tried adjusting the Ouput Power but it appears to have no effect.   My guess is that it's not supported and that's why there is nothing in the documentation about how to set it.   

****************
Talking with a friend today about the USB problems with this V2P hanging.   Apparently they ran into a similar problem with Windows 10 USB selective suspend causing them problems.  They suggesting disabling all of the USB power saving features.  I tried it and the V2P has been collecting 400 point datasets for a bit over an hour and a half now without a fault (using my software).   This is the longest I have seen it run with this amount of data but I'll let it continue to run just to make sure.   
****************
It made it to two hours and I aborted the test.   I restarted collecting with 800 data points.  It finally hung at 2200 cycles.  It collects at roughly 17 sweeps per minute with 800 points.   So roughly 129 minutes until it failed. 
*****************
The next attempt to run am 800 point test, the unit crashed after 210 sweeps.   I tried it one last time and it made it to 4500 sweeps or around 4 hours before it crashed.

When the Nano crashed, it still shows the USB menu but doesn't respond to any USB commands.  The PC still see's the port.   The only way I have found to recover from it is by power cycling the Nano V2+.   

After several attempts to get the VNA View (VNA QT) software to run on this PC, I did eventually get it to sweep.  There isn't any way to tell how many sweeps it has ran.  I'll check on it over the day and see if it has hung or not.

*****************
I ran their software for roughly seven hours and the V2P never crashed using the same PC, driver, cables, Nano.  I started my software and the Nano crashed within a half hour.  So it's not the USB power savings features in 10.   

My software is pretty simple.  When it causes the Nano to crash, it's just asking for a single data point and reading it.   

[Darko8]

Hi,

I checked few pages of this long forum thread, but I could not find any application attachment or link. Is this application going to be released or is it just for internal use? Or maybe I missed link/attachment?

I would gladly try it on my new SAA2 v4 which I got yesterday

Regards, Darko

[joeqsmith]

Hi,

I checked few pages of this long forum thread, but I could not find any application attachment or link. Is this application going to be released or is it just for internal use? Or maybe I missed link/attachment?

I would gladly try it on my new SAA2 v4 which I got yesterday

Regards, Darko

Reading has become a lost art. 

I have no plans of making my software available.  However, I understand there are a few open source packages that are well supported and excellent to use.  You should join one of the many groups for the Nano as I am sure many people would provide you with any help you need getting it setup.  There was one person that dropped me a couple of bread crumbs on the V2+ interface.  It sounded like they were working on their own program for it as well.   Check them out.