The new L/K-band polarimeter system for the 32 m radiotelescope at Cambridge

A new 32 m Cassegrain radio telescope has been added to Jodrell Bank's MERLIN network. For wavelengths of 6 cm and less, conical corrugated feed horns have been employed with excellent results, both in terms of aperture efficiency and system noise temperature. Furthermore such feeds perform well in the reception of circularly polarized waves, an essential requirement for MERLIN. A low-cost alternative to the conical corrugated horn has been sought. The 'diagonal horn' was identified as a possible candidate and investigations have been carried out into its suitability as a low-cost 20 cm horn, using scale models at 6 cm and 1.3 cm wavelengths. The authors describe the diagonal horn design and polarization characteristics and compare the radiotelescope performance at 6 cm with diagonal and corrugated horns.