An absolute cold reference for measurements at UHF and in the microwave band

Abstract

The authors describe a cold source operating at liquid helium temperature, used for absolute calibrations during radioastronomical observations at 600 MHz and 2500 MHz. Made with commercial dummy loads and coaxial cables in a standard Dewar bottle, it operates both at liquid helium and liquid nitrogen temperatures. A procedure for measuring the effective noise temperature of the source is described.