Products > Test Equipment
Warning about NanoVNA clones and comparison with Siglent VNA
The Bootloader:
--- Quote from: Mechatrommer on January 09, 2023, 11:06:36 am ---btw what surprised me from your report, is how come cloned Nano becomes a joke past 400MHz albeit using same components/BOM? and probably same OSHW gerber file.
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Right! I have no idea. This is why I started doing a video adding shields, I was expecting an impressive improvement... surely it's just a lack of shielding? oh boy I was wrong. Although adding shielding did seem to fix a few artifacts particularly that weird dip around 1100MHz.
The next hypothesis I have is inferior components (capacitors, inductors, fake ICs, rejected ICs, or simply a BOM mistake causing them to use the wrong ICs), and/or materials (PCB substrate?). It would definitely be interesting to identify what is causing this.
The fact that my particular clone is missing shields is not encouraging. It's not something that they could have missed. They left the shields out on purpose. So who knows what other shortcut they may have taken to produce these
Mechatrommer:
shield only to shield EMI, if your room is clear of EMI, i think there should be no difference shield or no shield... the dip caused by shield i imagine is due to some resonance or impedance modifier when geometry/space changed by adding shield. btw... looking back at your video in OP, the cloned one is different pcb design (sma connectors at the side) compared to ori SAA2 sma at the bottom. that may explain the very different performance.
joeqsmith:
Your original NAnoVNA is similar to what I show. I'm not sure why you feel its a problem. You have the Siglent. Use it to look at the output signal. At 300MHz, the NanoVNA will change to using harmonic mode. As you go up frequency, the VNA will continue to change bands and which harmonic is used. I'm guessing it was designed for 300MHz. Of course, the S/N ratio is going to get much worse the higher up you go, shielding or not.
That was a benefit to the LiteVNA. Now that the firmware supports harmonics you can see where it changes. They have limited it to 9.3GHz which like the original NanoVNA at 1.5G, is poor. You can see that in the plots I provided.
Of course, you need to be aware that when you are using harmonics, that fundamental frequency with all it's power is still present. It can lead to problems with the measurement and damage of your device and VNA. Think of testing a wideband amplifier.
And of course, with these low cost VNAs you have a squarewave drive. Another can of worms....
I watched your 1st video. While easy enough to follow along, I was really hoping for you showing a lot more than just a couple of antennas and filters. Maybe consider a detailed review at some point once you have learned more about it.
Video demonstrating an amplifier being tested on my low cost VNAs with squarewave drive vs my vintage tech.
Mechatrommer:
--- Quote from: joeqsmith on January 09, 2023, 01:39:27 pm ---And of course, with these low cost VNAs you have a squarewave drive. Another can of worms....
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i think designer already figured it out and dealt with its shortcoming in IF...
--- Quote from: joeqsmith on January 09, 2023, 01:39:27 pm ---I watched your 1st video. While easy enough to follow along, I was really hoping for you showing a lot more than just a couple of antennas and filters. Maybe consider a detailed review at some point once you have learned more about it.
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imho its enough to show one example that its broke to prove that its broke...
thinkfat:
Just a remark: The "nanoVNA-H clone" is not a clone of the SAA2 V2.2. They have a very different hardware architecture. A fair comparison would be between a genuine nanoVNA-H and the Aliexpress clone. There's just no way adding a couple of shields would get them to the same level.
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