Microwave Communication

Microwaves are radio signals with a very short wavelength. Microwave signals can be focused by antennas just as a searchlight concentrates light into a narrow beam. Signals are transmitted directly from a source to a receiver site. Reliable microwave signal range does not extend very far beyond the visible horizon.

If microwave signals were visible to the eye, cities would be seen to be crisscrossed by microwave transmissions carrying important signals. Any type of information that can move over telephone wires or coaxial cables can be transmitted over a microwave circuit as efficiently as through the wires and cables they supplement.

The lower-powered microwave signals used by communication transmitters are usually produced by solid-state devices. The Gunn diode is an example. When supplied with voltage from a well-regulated power supply these devices reliably produce a few watts of microwave signal.

Earth satellites relaying microwave signals from the ground have increased the distance that can be covered in one hop. Microwave repeaters in a satellite in a stationary orbit 22,300 mi (35,881 km) above the earth is high enough to reach one third of the earth's surface. Microwave signals can be relayed by just one satellite repeater when that satellite is simultaneously above the horizon for both the earth-bound transmitter and the receiver.