Communication satellite are microwave relay stations placed in outer space. They are launched by rockets or space shuttles, and are positioned 36,000 km’s above the equator with  an orbit speed spathe match earth’s rotation speed exactly. A satellite is positioned in go synchronous orbit, it is stationary relation to earth, and always stage over same point on the ground. A ground station to aim its antenna at a fixed point in the sky. Each satellite can receive signals to slightly less then half the earths surface.

In satellite communication, microwave signal at 6 GHz or 14 GHz in transmitted from a transmitted on earth to a satellite positioned in space. By the time that signal reaches the satellite, it become weak duo to 36,000 km’s travel. The transponder, mountain on the satellite amplifies the weak signal and transmits it back to earth of a frequency of 4 GHz or 11 GHz. that signal is received at a receiving station on earth. The transponder can support typically 1200 voice channel each of 4800 bps or 400 digital channels each of 64 k bps.