To get sufficient signal to noise in each channel, specific observations of a bright source are normally carried out in each project. There are basically two modes for solving RF bandpass. One can either fit a Chebishev polynomial to the data (low signal to noise ratio) or use the data (or a smoothed version of the data) as the RF solution. In the latter case, the actual solution is linearly interpolated between data points. The mode used is controlled by the command SET RF FREQUENCY SPECTRUM.
RF bandpass calibration is done baseband per baseband (see section 2.1). It is hence necessary to select a proper baseband with SET BBAND command before solving for the RF. The solution is computed in an intermediate frequency space adapted to each generation of signal transport, selected with SET X I_F.