A Unique Exciter and RF Subsystem for ABC'S Mobile Satellite News Gathering Terminal the ABSCamp System

ABC's mobile Satellite News Gathering (SNG) terminal consists of an antenna subsystem, RF subsystem, video exciter, and voice/data communications package. This paper describes the RF subsystem and video exciter. The SNG terminal is designed to provide the highest quality video transmission available in a mobile configuration. The exciter subsystem includes a new direct coupled (DC) modulator to optimize spectrum utilization and transmission quality. The RF subsystem features 300 watt traveling wave tube (TWT) amplifiers integral to the antenna feed support assembly which maximizes the power output capability of the SNG terminal. The RF subsystem also includes RF combining facilities required to simultaneously transmit both video and voice/data carriers, and RF switching facilities required to select between alternate polarizations and test modes. The RF subsystem incorporates built in test equipment useful for testing the SNG uplink prior to live transmissions, and includes monitor and control facilities which allow an operator in the SNG truck to operate the RF equipment mounted on the antenna. The RF subsystem is designed to allow configuration as a fully redundant terminal. However, the RF subsystem may be configured for non-redundant operation where the reduced system availability is justified by the cost savings.