An amateur radio repeater is a piece of equipment used by amateur radio operators to amplify radio frequency (RF) signals, which allows the operators to communicate further than radio to radio transmissions would allow. In addition to audio, some types of repeaters may relay images and television transmissions. Nations may regulate the use of amateur radio repeaters.
Repeaters consist of a number of components, including an antenna, feed line, and duplexer. Additionally, a receiver, controller and transmitter are all integral parts of this piece of equipment. The radio signal is picked up by the antenna. It is then transmitted to the feed line, which is cabling that connects the antenna to a duplexer. Often a “hard” line, this type of cable has less signal loss than standard coaxial cable.
Next, the signal is sent to the duplexer, which in turn sends this input to a receiver. The receiver recodes the signal to audio, and sends it to the controller, a small computer that manages the repeater. From the controller, the audio is transmitted to the repeater’s transmitter, which modulates the audio, and boosts its power. The output is sent back to the duplexer, through the feed line, and finally, through the antenna. Repeaters are usually situated on hills, or the top of buildings or towers, as these types of locations tend to improve the repeaters’ range.
Repeaters usually offset amateur radio repeater frequencies, so that received and transmitted signals are at different frequencies to keep the signals separated. Amateur radio repeater frequencies may be coordinated by national organizations to reduce interference. Listings for locations and frequencies of repeater stations may be found in amateur radio repeater directories.
There are several types of amateur radio repeaters. Simplex repeaters don’t offset the frequency of the transmission; these may also be called parrot repeaters. Same band repeaters use separate antennas for receiving and transmitting. Digipeaters may be used for communicating between computers, using the same frequency to receive and send data.
Amateur radio repeaters may take on more sophisticated tasks than just audio transmissions. SSTV repeaters can be used for relaying graphics and special amateur television (ATV) repeaters may be used for sending video. Amateur satellites may use transponder repeaters.
An amateur radio operator may also wish to understand repeater etiquette before attempting to transmit using one. Amateur radio can be used for emergency reporting, and operators may need to allow these transmissions to be relayed immediately. National regulations may also mandate repeater usage, for example, allowing only licensed amateur radio operators to relay through repeaters.