When the model contains multiple planes, it should be noted that the self-calibration tasks do not perform any interpolation of models along the spectral dimension. The self-calibration tasks assume that there is a one-to-one correspondence between a model plane and some average of the channels. The correspondence is determined in a rather imperfect fashion - the self-calibration tasks use the standard line parameter (see Section 5.4). This parameter determines the channels selected from the visibility dataset, and the averaging performed on them. Unfortunately, the self-calibration tasks only perform rudimentary checks on whether the line parameter makes sense (i.e. whether the selected channels have the same frequencies as the model planes). Despite this, in many instances, the self-calibration tasks will provide appropriate defaults for the line parameter. Below we outline those instances where you can or should allow the line parameter to default, and those instances where you should not.
mfsoption, you should also set the line parameter explicitly - see the next subsection.