The restrictions imposed by bandwidth- and time-smearing are summarised in Table 4.6.
The restricted maximum bandwidths of 1 MHz at 151 MHz and 4 MHz at 408 MHz mean it is possible to use channels as narrow as 15.6 kHz and 62.5 kHz respectively without loss of data. At frequencies above 1 GHz it is also possible to observe using channel widths less than 1 MHz, at the cost of a reduction in the total bandwidth or number of polarizations. Using a channel width so narrow that the integration time has to be increased should be avoided as time-smearing is a more serious problem at higher frequencies.
Table 4.4 and §4.4.2 give the maximum number of channels
available for a given total bandwidth in
relation to these constraints.
The volume of 
data is increased and many aspects of the off-line
processing become slower in proportion to the number of channels
and the number of integrations
present. Therefore by default 1 MHz channels are used and observers
should specifically request a suitable narrow channel width if this is
required, and make sure the other constraints (integration time,
number of polarizations) are still met.
The default integration time for continuum MERLIN observations is 16 s, although this can be reduced to 3 s providing the maximum data rate is not exceeded. Even shorter integration times may be obtained by gating the correlator, although one has to discard either some baselines or some time-segments of the data.