The correlator passband (Intermediate Frequency passband) has already been calibrated in the quasi real time processing, so the next step is to calibrate the receivers passband (RF passband), i.e. to compute the Sik. To improve the sensitivity, this should be done with data where the time dependence of the phase is small or has already been calibrated. The optimum way, actually used by the ``automatic'' calibration procedure, is to self-calibrate the phase on the calibrator before averaging in time to get the RF passband.
Typical RF calibration errors (given by the command SOLVE RF) are a few o of phase, and a few % of amplitude.