... There are four independent correlator boards available in the correlator spectrometer. Each board can be assigned any available bandwidth, center frequency, sampling level, polarization, and number of channels. ... Sampling level: Your data can be sampled with either 3-level, 3-level interleaved, or 9-level sampling. 9-level operation achieves 98% of the signal-to-noise of analog correlation whereas 3-level sampling achieves 81%. ... You cannot use 9-level sampling with a 50-MHz bandpass. ...

... 2.3 Data acquisition Spectra generated by the Multibeam correlator contain the usual structure seen in spectra from other H i instruments: a bandpass spectrum which is the sum of the sky , ground and receiver temperatures multiplied by the product of the filters in the receiver chain; superimposed on this is a noise ... Note also that sources extended much beyond ,40 arcmin can be imaged poorly in HIPASS images because of the bandpass sidelobe effect described in Section 3.3. ...