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Warning about NanoVNA clones and comparison with Siglent VNA
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The Bootloader:
Hi,


--- Quote from: joeqsmith on January 08, 2023, 03:29:45 pm ---1) Power on the Siglent and allow it to warm up for at least a half hour.
2) Set the VNA to sweep over the entire frequency range using an IFBW of somewhere around 100Hz (make a note of this).  Use something around 800 to 1600 points. 
2) Using your best cables and standards, perform a SOLT calibration
3) Attach a load to each port and measure S21.   
4) Save the data to a Touchstone file and upload it here.  You may need to rename it or ZIP it up.  Maybe name the file to include the model, IFBW, range.  Something meaningful.   

--- End quote ---

I tried, but I cannot set the IFBW to anything other than 10kHz. The setting is greyed out and locked at 10kHz. I do have the capability to change the sweep time, I tried increasing it significantly, but it does not change the IFBW.

In the specs of the SVA1032X from Tequipment, they do write that the IFBW for the VNA feature is 10kHz:
https://www.tequipment.net/Siglent/SVA1032X/Spectrum-Analyzers/

However, on the website of Siglent NA, they write "Minimum RBW 1Hz" but I suspect this applies to the Spectrum Analyzer feature and not the VNA feature.

The SVA1032X I have has all options enabled so I doubt it's an issue about software options.

I looked into the Siglent Programming Guide for this instrument. The corresponding SCPI command seems to be ":BWIDth?", I tried and it returns 10000.
I tried issuing ":BWIDth 100", it returns success, but when querying the bandwidth again it's still stuck at 10000, and it does not change on the GUI either.

So... it looks like the IFBW is locked at 10kHz.

The datasheet confirms:


So, I proceeded to still capture the data for you, with that 10kHz IFBW. See attached.

I believe the most valuable measurement is the one where I averaged 100 readings, it displays the true noise floor of the Siglent SVA1032X:



I attached all measurement raw data along with a file describing all measurement conditions.
Mechatrommer:

--- Quote from: 807 on January 08, 2023, 06:21:01 pm ---Considering the vast difference in price, the SAA2 held up very well against the Siglent.

--- End quote ---
not just the price, but BW difference. "real" 4GHz and above VNA's are simply unaffordable. but credit to OP bootloader for making a review comparing them with more expensive unit and revealed how cloned NanoVNA fair up - NanoVNA V2.2, LiteVNA and KC901V owner here.
The Bootloader:
Alright, alright, I like this, we are finding interesting things together!

I took the averaged data I posted above from the Siglent (100 readings 1600 points 100k-3.2G), and plotted it against averaged data from the SAA2 V2.2 (200 readings 801 points 10M-1.5G)
[EDIT] Adding measurements from the clone NanoVNA (50 readings 801 points 10M-1.5G)

Results:
joeqsmith:
Thanks for posting that data.  As promised the attached shows how your VNA compares with some others.  The large step in the LiteVNA's data is where it switches to use harmonics.

As you can see, my original NanoVNA performs very well at the lower frequencies (<1MHz).  I never used it above 300MHz.    I never found stable enough firmware for the H4 to use it.   The LiteVNA64 cost about $120 and if you don't care about narrow band measurements and want to experiment beyond 300MHz, it's my  choice.

***
Looks like I forgot to include the V2Plus4 and V2Plus.  It's limited to 4GHz and has similar noise as the LiteVNA.  The V2Plus was a little worse than the V2Plus4.  I understand they jacked up the prices for it and I doubt many people would consider it now.   
joeqsmith:
I mentioned that my friend had sent me their first LiteVNA which exhibited very poor noise.  This was due to the designer's not considering the specs of the USB standards.   I had added a series diode to the power lines which improved it.   I then set about attempting to further improve its noise floor by changing the bypass, increasing the IF gain and removing the TVS diodes.  I also changes some other values.  First attachment shows my original stock LiteVNA compared with my modified one.

The second attachment shows how the modified one compares with your Siglent.  Easier to see without all the clutter.   You can see the twp lay on top of one another all the way up to 3GHz. 

The Lite does allow setting the IFBW and I can also average and smooth if you like to make it look better but I do not typically use it this way. 

***
pictures are out of order....
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