gain (RG) characterizes the amplification of the signal coming from
the sample; the higher the gain, the greater the amplification. This
parameter is usually adjusted automatically; the system varies the gain
values until the signal fills the range of the receiver without being
cut off, or truncated. An RG that is too low is inefficient,
as it does not fully utilize the voltage (y) range of the system's
In practice, when
the computer is allowed to optimize RG, neither inefficient digitization
nor signal clipping will likely be an issue. The problem may be encountered
if 1H spectra of very viscous, concentrated samples are being
recorded. The isotopic abundance
of 1H is naturally high, and viscous samples tend to have
rapidly decaying FID's in which much of the signal occurs at early times.
Both of these factors yield a strong signal, especially at the beginning
of the data acquisition, potentially leading to receiver overload.