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Communications satellites have a quiet, yet profound, effect on our daily lives. They link remote areas of the Earth with telephone and television. Modern financial business is conducted at high speed via satellite. The newspaper USA Today is typeset and transmitted to printing plants via satellite.
Radio signals near the microwave frequency range are best suited to carry large volumes of communications traffic. They are not deflected by the Earth's atmosphere as lower frequencies are. Basically, they travel in a straight line, known as line of sight communication. If someone in San Francisco tried to beam a microwave signal directly to Hawaii, it would never get there; it would disappear into space or dissipate into the ocean. Over short distances, we can erect microwave towers every 25 miles or so to act as "repeaters" to repeat and boost the signal. Think of a geostationary communications satellite as a repeater in the sky.
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SATELLITES & ORBITS