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Microwave signals are normally limited to the line of sight, so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter , but such systems are expensive and generally used only in ...
A telecommunications tower with a variety of dish antennas for microwave relay links on Frazier Peak, Ventura County, California. The apertures of the dishes are covered by plastic sheets to keep out moisture. Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves.
The wireless communication is typically bi-directional and either time-division multiple access (TDMA) or channelized. This can be a microwave relay link consisting of a transmitter which transmits a narrow beam of microwaves with a parabolic dish antenna to a second parabolic dish at the receiver.
Normally, signals in the microwave frequency range travel in straight lines, and so are limited to line-of-sight applications, in which the receiver can be 'seen' by the transmitter. Communication distances are limited by the visual horizon to around 48–64 kilometres (30–40 mi). Troposcatter allows microwave communication beyond the horizon.
Networks of microwave relay stations transmit telephone calls, television programs, and computer data from one city to another over continent-wide areas. Passive repeater: This is a microwave relay that simply consists of a flat metal surface to reflect the microwave beam in another direction. It is used to get microwave relay signals over ...
A typical larger microwave antenna designed for mid to long range A parabolic satellite antenna for Erdfunkstelle Raisting, based in Raisting, Bavaria, Germany. C band horn-reflector antennas on the roof of a telephone switching center in Seattle, Washington, part of the U.S. AT&T Long Lines microwave relay network.
A radio relay receives weak signals and retransmits them, often in a different direction, as a stronger signal. Examples include airborne radio relay, microwave radio relay, and communications satellite. The American Radio Relay League was founded for this purpose but did not change its name when this became a less important part of its work.
Communication satellite – an artificial satellite used as a telecommunications relay to transmit data between widely separated points on Earth. These are used because the microwaves used for telecommunications travel by line of sight and so cannot propagate around the curve of the Earth.