Beam forming system for the Molonglo radio telescope

The requirements of phase and delay for cross (or Tee) type telescopes are discussed, together with the permissible errors. Details are given of the beam forming and steering system of the Molonglo radio telescope. In this instrument 177 separate 11 MHz signals from the north-south arm are combined to form 11 steerable beams, each with a resolution of 2. 8 by 2. 8 min of arc at 408 MHz. Unusual features include the '%'beam'%' configuration of the switched delay lines and the use of resistors in the multiple-beam phasing circuits. General factors relevant to the design of electronic beam forming systems for large arrays are discussed.