Measurement of a Cryogenically Cooled Ultra Wideband Feed Horn for the Effelsberg Telescope

We present the radiation patterns and S-parameters of a UWB feed designed for the Effelsberg 100m radio telescope, measured at a cryogenic temperature of 50K. Compensation is made for thermal changes which have an impact on dielectric properties as well as the dimensional stability of mechanical parts. There is excellent agreement between the measured and simulated results.