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An SSTV repeater is an amateur radio repeater station that relays slow-scan television signals. A typical SSTV repeater is equipped with a HF or VHF transceiver and a computer with a sound card, which serves as a demodulator/modulator of SSTV signals. SSTV repeaters are used by amateur radio operators for exchanging pictures.
For example, in US two-way radio, 30–50 MHz is one band and 150–174 MHz is another. A repeater with an input of 33.980 MHz and an output of 46.140 MHz is a same band repeater. In same band repeaters, a central design problem is keeping the repeater's own transmitter from interfering with the receiver.
A land mobile radio system (LMRS) is a person-to-person voice communication system consisting of two-way radio transceivers (an audio transmitter and receiver in one unit) which can be stationary (base station units), mobile (installed in vehicles), or portable (handheld transceivers e.g. "walkie-talkies").
In a traditional half-duplex land mobile radio system a group of users (a talkgroup) with mobile and portable two-way radios communicate over a single shared radio channel, with one user at a time talking. These systems typically have access to multiple channels, up to 40-60, so multiple groups in the same area can communicate simultaneously.
GMRS radios are typically handheld portable (walkie-talkies) much like Family Radio Service (FRS) radios, and they share a frequency band with FRS near 462 and 467 MHz. Mobile and base station -style radios are available as well, but these are normally commercial UHF radios as often used in the public service and commercial land mobile bands.
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Several hand-held Project 25 radios used around the world. Project 25 (P25 or APCO-25) is a suite of standards for interoperable digital two-way radio products. P25 was developed by public safety professionals in North America and has gained acceptance for public safety, security, public service, and commercial applications worldwide. [1]
The first repeater to use the band, the NU6X/R (Amateur TV Network) on 923.25 MHz, was activated and used at the minute the FCC allowed amateur use of the band and featured in QST Magazine. The repeater moved to 919.25 MHz and call changed to W6ATN because AVM part 90 service at 927 MHz began operation as a primary user of the band.