Since this thread is about the SDS800X HD, you shall not get the impression that it cannot do something similar. It can do it, despite its FFT producing spurious responses at lower RBW (error report has already been filed) – it is just a little less accurate and I had to look for a sweet spot in the spectrum where there were no spurious signals getting into the way…
SDS824X HD_FFT_1.77MHz_-125dBm_AM100_10kHz
The signal was -125 dBm at 1.77 MHz, 100% amplitude modulated with 10 kHz.
The level measurement is 1.175 dB high, and the sidebands are -5.668 and -5.276 dBc.
Well, there should be a little gap between a low end SDS800 and the 2000/3000 series.
Regarding the speed, it takes about 1.28 seconds to produce a single 2 Mpts FFT result (including acquisition). Even tough I’ve used 64x averaging in this example, usable (but less nice looking) results can be expected with just 4 averages already.