A procedure for the design of linearly polarized slotted waveguide line feeds for spherical reflector antennas is described. The necessary equations for determining the complex propagation constant

in a line source are given in terms of reflector parameters. Guide and slot dimensions that will yield the desired

and

are then found by making use of experimental data, presented herein. These data consist of measured values of

and

as functions of slot length for a number of slotted waveguide test sections of various widths. The technique is applicable over a wide range of frequencies and reflector sizes. An example is given in which a feed is designed at 1420 MHz to illuminate 700 ft of aperture in the Arecibo spherical reflector.