Oversampling and Digital Filtration

We saw in Section 2-4g that the receiver gain must be set neither too high nor too low. A potential problem arises, especially in the H NMR spectroscopy of mixtures, when one wishes to observe the small signals of minor components in the presence of much larger signals from major components. In such a situation, the receiver gain is, of course, set to a low value to avoid overload the trouble is that the signals of the minor components then tend to be weak. 

A second potential problem concerns aliased noise due to the increased spectral width. Digital filters, when combined with analog ones (Section 2-4c), do an excellent job of keeping unwanted noise (and signals, too ) from aliasing into the selected spectral window. This very efficient filtration can become a liability, however, if spectral widths are not carefully chosen, because the presence of signals that have been accidentally left outside of the spectral window is not revealed by the appearance of aliased resonances. 

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