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An amateur radio repeater system consisting of a 70 cm repeater and a 2-meter digipeater and iGate. Coaxial cavity RF filter at 2 meter repeater An amateur radio repeater is an electronic device that receives a weak or low-level amateur radio signal and retransmits it at a higher level or higher power, so that the signal can cover longer ...
English: Rochester Institute of Technology Amateur Radio Club K2GXT repeater rack. Top to bottom: Monitor, ARPS digipeater and iGate, EchoIRLP node controller, APRS radio, power supply, repeater controller, 70cm repeater. The repeater is located on top of Ellingson Hall, the tallest building on the RIT campus.
Most amateurs operating on 70 cm use either equipment purpose-built for ham radio, or commercial equipment designed for nearby land mobile frequencies. Amateurs usually use the band for FM or digital voice communications through repeaters (useful for emergency communications), as well narrow band modes (analog and digital) for long-distance ...
A duplexer is an electronic device that allows bi-directional communication over a single path. In radar and radio communications systems, it isolates the receiver from the transmitter while permitting them to share a common antenna. Most radio repeater systems include a duplexer.
In same-band repeaters, isolation between transmitter and receiver can be created by using a single antenna and a device called a duplexer. The device is a tuned filter connected to the antenna. In this example, consider a type of device called a band-pass duplexer. It allows, or passes, a band, (or a narrow range,) of frequencies.
Diplexing is used to prevent intermodulation and keep reflected power to a minimum for each input transmitter and frequency.While diplexers can combine a relatively wide bandwidth, the major limitation comes with the antenna itself, which must be sufficiently wideband to accept all of the signals being passed through it, and transfer them to the air efficiently.
In 1985, the Federal Communications Commission allocated the frequency band between 902 and 928 MHz to Part 18 ISM (industrial, scientific, and medical) devices. In that proceeding, the band was also allocated to the Amateur Radio Service on a secondary basis meaning amateurs could use the band as long as they accepted interference from, and did not cause interference to, primary users.
ATV operation in the 70 cm band is particularly popular, because the signals can be received on any cable-ready television. Operation in the 33 cm and 23 cm bands is easily augmented by the availability of various varieties of consumer-grade wireless video devices that exist and operate in unlicensed frequencies coincident to these bands.