Using fft on DSO

[Dan Moos]

I have a Rigol 1052e. I have some questions on setting up my scope properly for fft.

My biggest question is how to set the time base for the channel I'm running the fft on. It seems to me that I get better "looking" results with longer horizontal time per division on the scope channel. I also seem to get freq info lower than the fundamental with longer times.

I guess I just don't know why that happens, so I don't know what the trade offs are with different time per division settings.

[w2aew]

I have a Rigol 1052e. I have some questions on setting up my scope properly for fft.

My biggest question is how to set the time base for the channel I'm running the fft on. It seems to me that I get better "looking" results with longer horizontal time per division on the scope channel. I also seem to get freq info lower than the fundamental with longer times.

I guess I just don't know why that happens, so I don't know what the trade offs are with different time per division settings.

Two things to keep in mind:
1) the maximum frequency in the FFT is equal to 1/2 the waveform sample rate.
2) the frequency resolution is inversely proportional to the time duration of the waveform record

This video might help:

[Dan Moos]

Thanks! Btw, your videos have single handedly inspired me to tackle Rf duff for the first time. Thanks for the good work! I could fill a book with the questions I could ask in the matter. Perhaps you should write it!