I wonder if there a digital low pass filter implemented in the fpga.. seems like that would be an easy thing (edit: easy for Rigol) to turn on/off in the firmware.
Could be a possible way, something like an FIR in particular a polyphase filter or IIR filter is typical.
But right now I'm a little bit confused. It seems, that my 70MHz device delivers the full 200MHz bandwidth and the real limiting factor is the delivered probe (1x 8MHz, 10x 350MHz) itself.
I today connected a 50MHz XO91 quartz oszillator via BNC connector. The signal I can see on the screen is not what I would expect. Instead of the fundamental 50MHz with trend to a triangle waveform, I can see a nice square-wave (see 50MHz Oscillator 1.png).
Probing the same source with the probe the signal looks different (see 50MHz Oscillator 2.png).
From this point of view it makes completly no sense to pay USD 1789.- for the DS2202 instead of USD 925.- for the DS2072 and the search for a bandwidth limiting circuit was wasted time.
branadic