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WORKING PAPER SECTION 7 THE ACQU I SIT ION COST OF AN HF DB S-A SY STEM- SE RV I C E ~ . There does not appear to be any significant cost difference between a fine HF and a fine UHF receiver, if there is a sufficiently large market. It is somewhat more difficult to estimate the acquisition cost, and therefore the related financial cost of ownership and operation of an HF DBS-A system-service than it is for a UHF service at this time.54 The individual space segment cost would be somewhat greater because of the larger antenna required and the increased demand that its size would put upon transporting it to orbit and assembling it there. Greater RF power would be required to overcome the external electrical noise at 26-MHz--particularly greater at the absolute DC power level to be associated with a high-capacity, high-quality system-service where the in-space cost of providing the service would be very great. And because of the influence of the ionosphere on limiting reliable coverage areas, more space segments would be required. The following cost-related changes appear to be indicated for the space segment of an HF DBS-A system-service, as compared with the costs outlined in Section 4 for UHF: 1. Perhaps six (or more) active satellites would be required instead of four in order to obtain adequate coverage. 2. The cost of the much larger HF space segment antenna would be greater. 3. Fewer subtransmitters would be employed, but their required power-handling capability would be greater. 4. Much greater DC power would be required--hundreds of kilowatts for a full capacity AM system-service and at least 10 kW for one employing FM. 5. The complexity of in-space assembly of the antennas would be greater. 6. Perhaps two additional Shuttle flights would be required to transport and deploy the larger antenna and the greater number of satellites required. 34. Our present statistical (time and location) knowledge of the influence of some ionospheric characteristics upon system engineering considerations is incomplete, and the cost of much greater in-space DC power levels that would be required at HF is not yet known with high confidence. - 54 - WORKI NO PAP ER
WORKING PAPER Setting aside, momentarily, the matter of greater space segment DC power, it appears that the cost of an individual AM HF space segment, including is insurance, would be about $10 million greater and, with the larger number of HF space segments and their Shuttle launches required, the total space segment initial acquisition cost would approximate $900 million, i.e., it would approximate l.5X to 2X the tote] cost of the space segments of a worldwide UHF system-service. But such an HF AM space segment would provide only one channel of Standard Service for each of all beams in all regions with a space segment DC power of 5,000 watts. Each such additional channel, requiring 5,000 DC watts/space segment to serve six beams/region simultaneously, would therefore cost ($5,000) (5,000) (6) = $150 million. Unless the technique of providing large amounts of power from the surface is perfected, a worldwide, high-quality, high-capacity AM system-service will be extremely expensive. A worldwide 26-MHz FM system-service could provide 60 channels with each of six space segments having 5,000 DC watts of power. The acquisition cost of this power would be ($5,000~5,000 watts)~6 space segments) = $150 million. Thus the cost of the space segment power required to provide a commensurate number of channels, about 150, at 26-MHz as at 2.5 GHz would be (150/60) = 2.5X as great, or an additional $200 million. Finally the tote] worldwide system-service space segment cost would be $900 million + $200 million = $~.] billion. While this cost would be much less than that of an equivalent 26-MHz AM system-service, it is much more, 2X as much, as that of a 2.5 GHz FM system-service of roughly the same maximum system capacity and surface coverage. There does not appear to be a significant difference in the cost of the surface feeder. While the acquisition and ongoing cost of the space segments of an HF DBS-A system-service would be great in absolute terms, and greater relative to the cost of a comparable UHF DBS-A system-service, its cost would sti ~ ~ be only iO percent of the total global system-service cost because the bulk of the total cost would be concentrated in the surface segment.35 35. In considering employment of a frequency band other than 26-MHz or 2.5 GHz, several important observations can be made. As the frequency increases above 26-MHz, the size of the space segment antenna, the receiver external noise, and the influence of the ionosphere on radiowave propagation decrease rapidly. At the same time the service area footprints become smaller so that system cost would decrease and service flexibility would increase. Eventually, however, excess radiowave attenuation caused by building structures, foliage, rough terrain, and surface flux density limitations begin to become important. (Continued on following page) - 55 - WORKING PAPER
WORKING PAPER It is important to appreciate that throughout this paper estimates of cost have considered only the financial cost, not the political cost, of either, and indeed any, DBS-A system-service. Of course the great economic, political, and cultural benefits that could be derived from all countries of the world having such a new, worldwide service, are most important to note. (footnote continued from preceding page) Careful analysis could lead to the conclusion that the most efficient use of the electromagnetic spectrum for DBS-A would result from use of a frequency band intermediate to the two studied here. Two other regions should be given particular attention. The VHF region presently used for FM broadcasting, among other services, offers many of the advantages of the UHF region: the influence of the ionosphere is no longer very important, diffraction field radiowave attenuation rates are much more modest than at UHF, building wall and foliage radiowave attenuation concerns are modest, and relatively sensitive receivers are in wide use throughout the world in various frequency bands. And the large UHF television band, which also is relatively attractive in many respects, also could be looked into: the amount of radiowave spectrum now used for one surface-based UHF television channel would be sufficient to accommodate thousands of audio channels throughout the world via a DBS-A system-servi ce. - 56 - WORK] NO PAP ER
