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If the whole earth is to be connected by LOS communication using space waves (no restriction of antenna size or tower height), what is the minimum number of antennas required? Calculate the tower height of these antennas in terms of earth's radius?                                        2mark

Explanation:

dm2=2R+hT2                                                                                       1/2mark

8RhT=2R+hT2      Qdm  =22RhT4RhT=R2+hT2+2RhTR-hT2=0

R=hT                                                                                                 1/2mark

Since space wave frequency is used, λ<<hT, hence only tower height is taken to consideration. In three diamensions, 6 antenna towers of hT=R would do.                        1mark          

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