Since I started selling the Common Mode Current Choke Test Rig I’ve had several people ask me this question, and it’s a good one.
tl,dr: I recommend the “NanoVNA V2 Plus4” from NanoRFE
If you don’t care about my reasons and just want to throw money at something you’re not likely to regret, get the original from the people doing the actual design work. Currently (2022-07-25) that’s the NanoVNA V2 Plus4.
Disclaimer on my opinion
I’m not a metrologist, so I have basically no leg to stand on to recommend one device over another. Historically, I just recommended one with a large screen (because these eyes aren’t getting any better), with no knowledge of the quality of the VNA itself.
There are people with much more informed opinions than mine. I’d recommend Joe Smith’s YouTube channel (no relation) for WAY more information than I’ll list here. Anywhere his opinion differs from mine, trust him rather than me.
Why the NanoVNA V2 Plus4?
I’ve owned three “cheap” NanoVNAs I picked up from Amazon or eBay. All three have had problems and/or limitations.
All three of the VNAs I’ve used claim to work up to 1.5GHz. In reality, all three work fine at HF frequencies, but were incredibly noisy above 300MHz, and completely unusable above 600MHz.
The problem is, the internal oscillator in early units can only go up to 300MHz. Above that, it operates on harmonics of the oscillator and that doesn’t work nearly as well. Apparently, some NanoVNAs do a better job at operating at harmonics than others do, but all three that I had were rubbish when operating above 300MHz.
Look for a NanoVNA that has an oscillator that can actually operate natively at the frequencies you are interested in. The NanoVNA V2 Plus 4 can operate up to 1GHz with basically no noise, 3GHz with very little noise, and do not publish stats for the 3GHz to 4GHz range but it’s almost certainly better than the cheap ones.
I’m only 47, but my eyes aren’t getting any better with age. The small NanoVNAs that conveniently fit in a pocket are just too small to be usable as a portable device. My sausage fingers can’t use the touch screen without a stylist. And no matter how I calibrated it, I could never get the touchscreen calibration to work right.
Look for a NanoVNA that has a user interface that you can use. The NanoVNA V2 Plus 4 has a 4 inch 480×320 screen, compared to the 2.8 inch 320×240 screens of the small pocket sized units.
This thing is a brick. Metal chassis, SMAs mounted to the metal panel instead of just soldered to the board, USB-A connector that’s not likely to be ripped off the board by a bumped cable, etc. The pocket sized NanoVNAs look like they could be destroyed by pocket lint.
Ok, that’s a bit of an exaggeration, but I trust this unit in a backpack of other equipment a lot more than the cheaper units.
Who’s selling it?
To me, there’s also value to buying from the people who are doing the engineering, actually designing the hardware, and putting money directly into their hands rather than into the hands of the company that just copies the design and makes it cheaper by compromising on build quality, component quality, etc.
Granted, this is a ~3x premium when compared against the ~$60 super-cheap units. (But probably closer to 1.5x premium when compared to more similar units; there’s a huge variety). Its for you to decide whether it’s worth it.
It’s $200! Do I really need that?
That’s a valid point. Maybe you only need it for HF, possibly up to 6m or 2m. Maybe your eyes are way better than mine, or you intend to use it connected to a computer running NanoVNA Saver or NanoVNA-QT or some other PC software.
Then an inexpensive VNA will probably be ok. If you’re buying a VNA to use with the CMCC Test Rig, the Test Rig is only intended for HF use so you can use an inexpensive VNA with it I successfully used my inexpensive NanoVNAs on HF for several years. So, there’s a good argument to be made here. I only needed to upgrade when I started working on a GPS antenna/LNA design at 1.575GHz.
But, I can’t RECOMMEND any of those NanoVNAs. I’ve had problems with them, as others have had as well. The one that I’m comfortable putting my name behind is the NanoVNA V2 Plus4 by NanoRFE.
73 de N6MTS