  In this paper we present the realization and a preliminary characterization
of a SIS based receiver. It has been developed for the MASTER experiment that
consists in a three-band SIS receiver (94, 225 and 345 GHz) for astrophysical
observations through the atmospheric windows available at high altitude dry
sites. The measurements performed establish an upper limit to the overall
receiver noise temperature. A comparison has been tried with the MASTER
requirements and with state of the art results. A noise figure of 110 K has
been obtained at 94 GHz, about 22 times the quantum limit.
