The Communication Satellite Corporation Phase-I study program was conducted jointly by the Astro-Electronics Division of the Radio Corporation of America and Bell Telephone Laboratories to develop an 80 MHz solid-state i.f. repeater (for 270 duplex voice channels). The i.f. repeater developed utilizes a waveguide-cavity diode down converter, a transistorized i. f. amplifier, and a varactor up converter. This type of i.f. repeater lends itself to communication satellite system applications because of the high gains obtainable. The alternate, the rf repeater, requires either cascaded traveling-wave-tubes or a high-gain, tunnel-diode front end, followed by traveling-wave-tube amplification, to obtain comparable gains. The i.f. repeater facilitates design of an Automatic Gain Control (AGC) system that has the dynamic range necessary for systems in which different users' signals may vary widely in level. The feasibility of increasing the repeater bandwidth to 230 MHz (accommodating 600 duplex voice channels) was investigated. Laboratory confirmation of these goals was achieved. The operating parameters are input signal, 5925 to 6155 MHz: i.f. signal, 20 to 250 MHz; and output signal, 3970 to 4200 MHz. The results of the program indicate that there is no basic limitation to producing an all-solid-state i.f. repeater with 230 MHz bandwidth, exhibiting an over-all noise figure of 11 db, which would be applicable to space communications systems.