Thank you for demonstrating the difference between a measurement vs. a mess of noise and interference.
If we try to compare the two screenshots, we have all the information on the Siglent: FFT-sample rate, FFT-length and the Averaging mode. For convenience, we also get the frequency step - and in future versions of the FW we'll also get the RBW, which depends on the window function. About the only useful window for SA applications is Flattop, so we have to multiply the frequency step by ~3.8 and get a RBW of ~362 Hz in this case.
By contrast, the Rigol shows a much lower sample rate and claims a RBW of "20" - whatever that means. If we assume that the scope actually uses its maximum of 1 Mpts FFT, then the frequency step is about 30 Hz. How can we get a RBW of 20(Hz?) under these conditions? Only explanation could be the rather useless rectangle window, which can't be used for accurate measurements at all and doesn't have a constant RBW either - at the border between frequency bins it can be even much worse than a proper window function.
We can see the excessive noise and high internal spur levels. It does not look like it would measure the individual harmonics correctly. Considering the enormous difference in RBW (362/20), the dynamic appears to be inferior too. And don't forget, the Siglent is just an 8 bit DSO!
But then again, all this does not matter - it's incredibly fast after all!
FFT has always been an Achilles heel of cheap Rigol scopes if I'm not mistaken. Also, the screenshots are comparing a 500€ scope with a 1500€ one (assuming 4 channels in both cases). For many, that's peanuts. I don't work in an engineering environment, but, for my job, 1000€ is peanuts if it gets more work done, faster and more reliably.
For a hobbyist that can be the difference between 1 year of savings and 3. That's 3 years without a scope. If you extend that to the multimeters, power supply, AWG, logic analyzer, soldering iron, lab computer etc. it gets out of hand pretty fast. Ask me why I know.
There are a lot of problems, IMHO, with the DHO900, which roughly amounts to paying more for the same, as neither the bode plot nor LA work properly.
But the 800 is really good. It's cheaper than all the alternatives, Siglent, GWInstek or Micsig, its basic functionality is good, high resolution, reasonably low noise, fast interface, touchscreen, mouse support, HDMI out, fast data out to PC, good web interface, and a lot of other stuff.
I really don't get the hate. I mean, user 2N3055's criticism to the DHO900 is well deserved, I think. I would be really pissed with the FRA myself.
But why bash a bottom-of-the-barrel scope (in terms of it's price) comparing it with scopes 3 times (or even 7 with the 2000HD) the price?
The software is not finished, indeed, but everyone expected that, because that's how Rigol operates, at least with their entry-level scopes.
So, yeah, it's the best standalone scope you can buy for <500€. And yes, I don't think anybody would chose this over an SDS2000X+ or HD.
I agree with you that cheap scopes don't have unlimited development budget..
And I can see that it can seen as bashing when someone has large list of problems to complaint about.
In addition to that, I'm old enough that I remember well how it is if you simply cannot afford 50€ more..
Problem is:
DHO4000 that is NOT cheap scope has equally bad BODE plot and FFT implementation as cheap DHO900/800.
Actually Rigol here developed a common platform. If they make excellent FFT for DHO4000, users of DHO800 could get same excellent FFT.
This is happening with Siglent: many features from Siglent's 10000 € scopes are available on much cheaper touchscopes...
Also cheap GW-Instek has very good FFT implementation, and slightly more expensive model has full realtime spectrum mode, well implemented.
Trust me, low price is not reason for shoddy FFT implementation.
So if all the problems, and unknowns are put together, DHO800 is
not best scope you can buy
today for 500ish €.
12 bit makes not such a big advantage to trade off that for many other (maybe necessary stuff, people need to decide for themselves what they need) that is missing or does not work well yet.
It does
have capability to become good buy,
when Rigol actually makes it work properly.
I can see future in which that statement might be true. But right now, today, no.
Of course, people, fully aware of current unfinished status, might chose to consciously buy it in this state of development and simply wait for as long as needed for Rigol to debug and finish it. We all have our own will, priorities, etc. But make sure you understand you are buying unfinished product and sort of promise that Rigol will eventually finish it in due time. If that is OK with you, it's perfect.
I must admit I tend to project a different perspective: I cannot afford to have a measurement instrument that I cannot trust. Even with very expensive instruments I sometimes measure with two different ones to verify.. Keysight has bugs too... R&S and Tek too...
My experience have proven that it is best to avoid ANY product for at least 1 year after initial release, if you actually need to depend on it...
With that in mind, my opinions are obviously influenced by that.
Best,
Siniša