Repeater

In telecommunication, the term repeater has the following meanings:

1. An analog device that amplifies an input signal regardless of its nature (analog or digital).
2. A digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.

(Source: from Federal Standard 1037C in support of MIL-STD-188)

A repeater is an electronic device that receives a weaker signal and retransmits it at a higher level, so that the signal can cover longer distances without degradation. The term "repeater" originated with telegraphy and referred to an electromechanical device used to regenerate telegraph signals. Use of the term has continued in telephony and data communications.

Table of contents

1 Telecom cables 2 Duplex radio 3 Broadcasting

Telecom cables

Repeaters are often used in trans-continental and trans-oceanic cables, because the attenuation (signal loss) over such distances would be completely unacceptable without them. Repeaters are not only used in copper-wire cables carrying electrical signals, but in fibre optics carrying light as well.

Duplex radio

Broadcasting

A broadcast repeater is usually called a translator. Just as a verbal translator (person) listens in one language and speaks in another, a broadcast translator takes a signal from one channel and transmits it again, usually on another channel or other frequency assignment. This is common in North America, especially in the United States and in the mountains.

Translators which broadcast within or very near the parent station's coverage area on the same channel or frequency are called booster stations. However, this can be tricky because it is possible to have both stations interfering with each other unless they are carefully designed. Interference can also be avoided by using exact atomic time obtained from GPS satellites to perfectly synchronise co-channel stations, as in a single-frequency network (SFN).

Translator stations in the U.S. are given callsigns which begin with a W or K (respectively east or west of the Mississippi River, as with regular stations), followed by a channel number, and two serial letterss for each channel. Television channels are always two-digit, from 02 to 69, while FM radio channels are from 201 (88.1MHz) to 300 (107.9MHz), one every 0.2MHz. (Example: W42BD, K263AF.) FM booster stations are given the full callsign of the parent station, plus a serial number, such as WXYZ-FM1, WXYZ-FM2, etc. In Canada and Mexico, all translator and booster stations are given the callsign of the parent station plus a serial number, such as XHABC and XHABC1, XHABC2, or CFON and CFON1, CFON2, etc.

TV stations cannot have same-channel boosters due to video synchronization issues such as ghosting. AM stations do not have translators or boosters, though they are actually easier to create an SFN with.