... The ALFALFA Extragalactic Legacy Survey: Description and Preliminary Results . The Arecibo Legacy Fast ALFA Survey has been designed to cover 7000 square degrees of sky at L band. The HI line will thus be surveyed between 1340 and 1430 MHz, with a resolution of 25 kHz. ... Observations started in early February 2005. ... The scientific motivation, goals and expectations of the survey will be presented, as well as examples of data products and the science results of the early observations. ...

... 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. ...