Masers for the Telstar Satellite Communications Experiment

In an active satellite communication system, the ultimate in ground station receiver performance is highly desirable, if not absolutely necessary. This follows directly from the limitations imposed by present rocketry on the payload, and thereby on the transmitter power, which can be placed in orbit. A major improvement in over-all system signalto-noise ratio can be achieved much more easily and economically on the ground than in the satellite. Recognition of this fact led to the adoption of a giant horn-reflector antenna, and the selection of a ruby travelingwave maser as a preamplifier in order to fully exploit this antenna's remarkable low-noise performance. The design considerations and performance of this maser are the subjects of this paper. I I . DESIGN O B J E C T I V E S AND TIIEIR S I G N I F I C A N C E At the outset of the maser development program the following objectives and constraints were established: (a) a minimum stable gain of 25 db 1863 1804 T H E BELL SYSTEM TECHNICAL J O U R N A L , JULY