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The Spacecraft Communications Repeater

01 July 1963

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This paper describes the communications repeater portion of the Telstar satellite. This repeater receives the weak, --60 dbm nominal, FM signal from the earth at a center frequency of 0389.58 me, shifts the frequency to 90 mc for amplification by transistors, shifts the frequency to 41 (>9.72 mc for further amplification by the traveling-wave amplifier, and irradiates the signal at a minimum power of 33 dbm. The signals are received and transmitted through separate circularly polarized antennas which are nearly isotropic. 1 The satellite also radiates, for tracking purposes, a very stable microwave beacon signal at a frequency of 4079.73 mc and at a power of greater than 13 dbm. The bandwidth of the repeater is 50 mc, although to date only 25 mc has been used in the experiments because of bandwidth limitations of the maser in the ground receiver.