The Arecibo L-band Feed Array is a seven pixel spectroscopic radio camera. It has dual linear polarisation with cooled low noise amplifiers, for a total of fourteen outputs. The frontend of the system was designed and constructed by the instrumentation group of the Australia Telescope National Facility.

ALFA has the capability of simultaneous observations with multiple backends. The Wideband Arecibo Pulsar Processor (WAPP) was upgraded to accept the fourteen ALFA outputs at 50 MHz instantaneous bandwidth each. This backend was developed mainly by Bill Sisk and Jeff Hagen, with considerable input on the file format definition by Erik Muller, and the other members of the Arecibo astronomy staff of 2003-05.

A second backend was developed by Jeff Mock. This second backend is optimised for the galactic HI survey.

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