Overall, although jadew has some points (i.e. the post isn't as bad say treez), it would've been nice to know about the tracking generator project in the first post...I can't honestly make myself believe this question was asked in good faith.
I think I made it pretty clear from the original post that I'm directly affected by this, as proven by the following quote (from the opening post):
I'm kind of annoyed by this, because I've been bit by it several times already and I have suspicions that some of these sellers are also behind a recent attack against my server.
Why is this happening and how can you work against it - is it even worth it?
The TG was just one of the examples I could have given, so it's not the only product I canceled because of unfair competition of this type.
Nowhere in the original post is your tracking generator project mentioned. The "I've been bit by it several times already" thing could refer to anything: a multimeter that you bought that's certified as IEC CAT VIII++ 10000V rated but clearly isn't, dodgy power cables you bought with too thin wiring, etc. None of these things are great, and if that was all that your original post was about, I don't think you'd have too many disagreements here.
The only thing that might allude to your tracking generator project is the part about other sellers supposedly trying to attack your servers, which I glanced over originally and I don't think many people have commented on so far, but let me be the first to say: step back for a minute and think about this a bit. The nanoVNA is in a completely different market than yours, and it's doubtful any reseller is even aware of your project or cares. The market overlap of someone looking for a clean $300-400 tracking generator to go with a much-more-expensive, lab-grade spectrum analyzer is simply non-existent for the $40 nanoVNA. The nanoVNA is in the same market as the extremely cheap "antenna analyzers" and SWR meters so popular with hams. I don't doubt some people may have told you that they wouldn't consider your project because of the nanoVNA, but these people probably never actually should've been looking at your project in the first place and likely should've been looking in a completely different market than yours. The likelihood that some nanoVNA reseller was aware of your project, saw it as a threat, and then tried to attack your server is pretty small. Opportunistic drive-by attacks on any potentially unsecured server are a lot more common than most people would expect.
And now more about the nanoVNA part of your post. (You may claim otherwise, but it's going to be hard to convince me that your original post wasn't a sob story about how the "unfair" nanoVNA ruined your tracking generator project. When I said you do have some points, I mean I don't like blatantly mis-advertised products like IEC CAT VIII++ 10000V or misrated batteries either. I don't think the nanoVNA falls under that category of products though, sorry.) Let's take a look at the history of the nanoVNA and various advertisements (by resellers).
The original nanoVNA was designed by Edy555, for "the category of hobbies" and with "no guarantee of performance" according to the google translation from japanese of
https://ttrf.tk/kit/nanovna/Even the current official github
https://github.com/ttrftech/NanoVNA says very little about the performance of the nanoVNA, although the software has been updated to also use harmonics to allow frequencies above 300MHz. (I do agree with many previous posts that it's not great that a lot of resellers don't advertise/follow the open source spirit of this projects and similar projects like the AVR transistor tester.) The hugen version of the nanoVNA (
https://github.com/hugen79/NanoVNA-H) was the first to use harmonics to measure above 300MHz, but fairly clearly states that it uses "the odd harmonic extension of si5351 to support the measurement frequency up to 900MHz", and also complains about "bad clones". I think this is also the original source of the (not-very-well-specified) 70dB "dynamic" (whatever that means) for 50K-300MHz claim, 50dB of "dynamics" for 300-600MHz, and 40dB of "dynamics" for 600-900MHz.
Now let's take a look at some of the text of various resellers:
https://www.aliexpress.com/item/4000378025298.html from tautech from aliexpress
From my 1st two google results:
https://www.amazon.com/50KHz-900MHz-Vector-Network-Analyzer-Antenna/dp/B07WJ3FJD9/ from amazon
https://www.ebay.com/itm/Nanovna-50KHz-900MHz-Vector-Network-Analyzer-VNA-VHF-UV-UHF-HF-Antenna-Analyzer-/362727846597 from eBay.
The aliexpress listing says that it uses "the odd-order harmonic expansion of si5351 to support the measurement frequency of 900MHz", almost a direct copy from the hugen github text. The amazon listing has the exact same text. The eBay listing (which also has pictures of scantily-clad pin-up girls -- very relevant to vector network analysis) says nothing about using harmonics for higher frequencies, although does refer to them as "extended" and needing "extended firmware".
All of the listings mention using an si5351 as the signal source. None of the listings mention that the output is a square wave, that the output is not as clean as shown here
https://www.eevblog.com/forum/chat/why-do-so-many-people-here-go-nuts-over-garbage-gear-from-china/?action=dlattach;attach=892652;image, or that jadew's tracking generator + lab grade spectrum analyzer would give much better performance if you could actually purchase it.
You could claim that not stating that the output is a square wave is a lie of omission (and you wouldn't be wrong), but compared to IEC CAT VIII++ 10000V multimeters or misrated batteries, this is really more of a yawn for me, and not the blatantly "unfair" competition that jadew claims. (RF instruments are notoriously underspecified anyways with specifications that don't tell the whole story, and this includes top lab-grade instruments also.)
The elephant in the room is this: for someone with complete knowledge of the nanoVNA's shortcomings, would the nanoVNA's existence still prevent someone from being interested in jadew's product or is it only with its "unfair" advertising that the nanoVNA appears as "competition"? I would argue that the two products were never competing with each other in the first place.
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