Let's take the signal to be sampled to be made up of several sine waves close to one another in frequency, e.g. 1MHz, 1.001MHz, 1.002MHz,... 1.005MHz
I assume in the time domain we would see beats 1ms apart with little voltage in between. The minimum sampling frequency would follow the Nyquist theorem and be 2.01MHz. However, what would the minimum sampling duration (i.e. number of samples needed) be to make sure the signal is fully captured?
If we take just a few samples between the beats, there would be little signal to see. I assume it would be the beat period (1ms) because this is when the pattern in the time domain starts repeating itself.
Am I correct and is there a general rule?