A 210-280 Ghz Sis Heterodyne Receiver for the Maxwell,James,Clerk Telescope .1. Design and Performance

We describe the design and performance of a 210 - 280 GHz SlS heterodyne receiver built for use on the Maxwell Telescope. The mixer utilises a lead alloy SIS tunnel junction mounted in 4:1 reduced height rectangular waveguide, and is tuned with a backshort in 2:1 reduced height guide. The receiver has a receiver noise temperature of < 200K (DSB) across the RF band from 210 - 270 GHz, with a best noise temperature measured in the laboratory of 113K (DSB) at 231 GHz. A prototype version of this receiver was successfully operated on the telescope in May 1989. By direct intercalibration with a Schottky diode receiver we deduced a best receiver noise temperature of 140K (DSB) at 245 GHz. Discrepancies between this figure and that derived from broad band thermal load calibration are discussed in the accompanying paper (Little et al., 1992, this issue).