Repeater

Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.

Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.

When an information-bearing signal passes through a communication channel, it is progressively degraded due to loss of power.

A repeater is an electronic device in a communication channel that increases the power of a signal and retransmits it, allowing it to travel further.

The term "repeater" originated with telegraphy in the 19th century, and referred to an electromechanical device (a relay) used to regenerate telegraph signals.

Since the telephone is a duplex (bidirectional) communication system, the wire pair carries two audio signals, one going in each direction.

So telephone repeaters have to be bilateral, amplifying the signal in both directions without causing feedback, which complicates their design considerably.

The history of radio relay repeaters began in 1898 from the publication by Johann Mattausch in Austrian Journal Zeitschrift für Electrotechnik (v. 16, 35 - 36).

Without a repeater, these systems are limited in range by the curvature of the Earth and the blocking effect of terrain or high buildings.

While the repeater station is designed for simultaneous reception and transmission, mobile units need not be equipped with the bulky and costly duplexers, as they only transmit or receive at any time.

[9] An engineered radio communication system designer will analyze the coverage area desired and select repeater locations, elevations, antennas, operating frequencies and power levels to permit a predictable level of reliable communication over the designed coverage area.

Analog repeaters are composed of a linear amplifier, and may include electronic filters to compensate for frequency and phase distortion in the line.