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Gw Instek GDS2204E (200MHz 4 channel DSO) review
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nctnico:
I did some testing with the GDS2204E and aliasing is minimal because it has anti-aliasing filters in place. With a 200MHz bandwidth the 500Ms/s is more than enough to show the signal. You have to keep in mind that in theory the minimum sampling frequency is twice the bandwidth. Everything more is overkill but in practical situations you need some margin for the anti-aliasing filters.
marmad:

--- Quote from: nctnico on September 16, 2016, 07:41:34 pm ---You have to keep in mind that in theory the minimum sampling frequency is twice the bandwidth. Everything more is overkill but in practical situations you need some margin for the anti-aliasing filters.

--- End quote ---

It has nothing to do with "overkill"; it has to do with design. Out-of-band signals may only be attenuated by 10 dB beyond the band-edge of the instrument, and it doesn't matter what kind of anti-aliasing filters the DSO has, they absolutely don't roll-off infinitely fast and some buffer room is needed.
nctnico:
That is why I wrote: some margin is required. Also the typical passive probing solution will load a high frequency signal way more so there is already filtering before the signal gets into the scope.
marmad:
Reliable sampling and reconstructing frequencies at exactly the Nyquist Rate is physically not attainable, and thus a higher sampling rate is not "overkill"; your precise descriptor which I was responding to.
nctnico:
Again: I wrote 'margin' so don't insist on reading something different!
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