Even the cheap(er) Rigols are 2k-sample FFTs, which is also fairly anemic.
It is. What's even worse, though, is that for the DS4000 and DS6000 (both pretty expensive scopes) it's apparently only 700 points:
http://beyondmeasure.rigoltech.com/acton/attachment/1579/f-00f2/0/-/-/-/-/file.pdfThis is pretty embarrassing. The listed 600pts for the old DS1000 Series looks great in comparison.
I assume this is being done to maintain a decent refresh rate, but when the acquisition is stopped, it would provide an opportunity to do a lot more with the available sample set. Siglent should take advantage of that.
The reason is very likely the severe limitations in processing capabilities in these low-end scopes (which as a result will of course also affect the refresh rate). FFT is pretty heavy in CPU ressources, and I doubt the simple controllers in these scopes can deal with anything like say 10kpts at a somewhat reasonable speed.
And I suspect the reason it is that way is simply so they (all the lower-end guys, not picking on Siglent) can claim they have FFT, regardless of how poor it may be in practice. Just a box to check off on their Feature List.
I fully agree, FFT seems to be merely a check-box exercise so that they can list it on the data sheet, no matter that at this stage it's borderline useless.
There's a big difference between things done right, and things just done. Many vendors these days are opting for quantity of features over quality. And considering that the ones they do have on their Feature Lists often don't even work (or work poorly), it's probably too much to ask that they do it "right". That will only come as things evolve (and competition forces it), and they can leverage off a core foundation of existing code, in their next-gen product lines. Rather than starting from scratch and re-inventing the wheel each new hardware/firmware cycle.
Indeed. That's one reason why I rather buy a not too old second-hand scope than a new entry-level scope. The performance per buck in the low end class, while having increased dramatically in recent years, is for me still much better with a second hand scope.