Bandpass Calibration of the Correlators

The bandpass (in phase) of the correlator units can be calibrated using the built-in noise source of each unit. Cross correlation on this noise source then gives the phases of each entry with a high signal-to-noise ratio since this input is 100% correlated. The OBS $\backslash$BANDPASS command is intended for this measurement. It automatically switches the correlator input to the noise source, disables Walsh switching on the first LO, and disables delay and phase tracking. After the measurement, the original state is restored.

This procedure can be done while the antenna are slewing to a new pointing direction, so it introduces practically no loss of observing time when inserted at appropriate position in observing procedures. Some misfunctions of the correlators can be detected by this procedure.