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ABSTRACT WORKING PAPER There are powerful economic, operational, political and cultural reasons for pursuing the establishment of a high-quality, high-capacity, DBS-A, common-user worldwide system-service. Surface-based shortwave broadcasting is beset with serious and growing problems of limited coverage, capacity, reliability and quality; exceedingly complex globe] frequency assignment and monitoring, and ever-increasing signal interference. The world community of audio broadcasters should explore the possibility of using orbiting transmitters to provide worldwide audio broadcasting services to eliminate these problems. Two conceptual common-user, common-carrier, system designs are described in this paper that would allow Direct to the receiver Broadcast from Space-Audio (DBS-A) services to be provided throughout the world with excellent quality, reliability, and at low cost. One service uses a frequency band in the upper part of the high frequency (HF) portion of the radiowave spectrum, the other uses a frequency band in the high ultra high frequency (UHF) region. The paper compares the relative advantages and limitations of each. Although either could serve al] countries of the world on an equitable basis, the UHF band offers important cost and service advantages. A worldwide system of this character could be installed region-by-region and could provide a standard service of as many as 1,000 5-kHz audio channels for each of as many as 1,000 individual surface areas. Each area would be 10,000 square miles (25,000 square kilometers) at the Earth's surface. The acquisition cost of a technologically sophisticated space segment, installed and serviced in space using the Space Station, of a global system with a large capacity could approximate $500 million (U.S. 1985), and the ongoing cost of ownership and operation would approximate, roughly, $100 million (U.S. 1985) per year. This cost would be much lower than the tote] now being paid by the wor1d's shortwave broadcasters for a service with much less coverage, and lower quality and reliability. The surface segment would be made up of new fixed and portable spacewave receivers, each costing tens of dollars, would cost $10 billion on a worldwide basis. Although governments could finance the space segments of such a system, the private sector could reasonably be expected to finance and acquire the system and offer its services to government broadcasters throughout the world. Such a system-service could be in operation by the end of the century. Smaller channel capacity or coverage area services could be provided in less than a decade and at lower space segment cost. Regional system-services could be installed initially and expanded to provide worldwide coverage. The space technology used to provide such worldwide audio broadcasting could be employed for national, domestic, low-cost broadcasting as well; it could do so at a low marginal cost. Reliability, quality, and cost also suggest that the private sector, as well as governments, would be interested in using the system. . ~ WORKI NG PAP ER