Satellite audio distribution on a video transponder using digital compression and band-edge SCPC technologies

Digital audio compression and SCPC (single channel per carrier) technologies permit efficient distribution of audio and data to a network of radio stations using small antennas. Transmitting the SCPC signals on the band-edge of a video transponder can be a cost-effective way of providing the space segment. This paper describes the design phase and the results of implementing band-edge SCPC carriers on an analog-video transponder. Before attempting an operational test, Comsat Laboratories investigated the proposed configuration using the Comsat C-band transponder simulator. The simulation tests showed that the SCPC signals are more efficient than video subcarriers in use of transponder power and validated that band-edge SCPC could be achieved without degrading the analog video signal. The transponder can be operated into saturation. The actual implementation of the video and SCPC system required careful tradeoffs in the operating power of the video and the SCPC signals because of the power demands of the video signal and the need to operate in the nonlinear portion of the transponder. The system has been operating for more than a year. Three digital SCPC carriers, each with a FM-quality, stereo audio program, are received with 2.4 meter antennas throughout South America. VOA is now investigating digital-audio SCPC´s operating with digital-video carriers on the same transponder. Preliminary results are also given here