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RFinder's main service is the World Wide Repeater Directory (WWRD), which is a directory of amateur radio repeaters. RFinder is the official repeater directory of several amateur radio associations. RFinder has listings for several amateur radio modes , including FM , D-STAR , DMR , and ATV .
M17 uses Frequency-Division Multiple Access (FDMA) technology in which different communication streams are separated by frequency and run concurrently. It utilizes 4,800 symbols per second, 4-level frequency-shift keying (4FSK) with a root Nyquist filter applied to the bitstream. Radio channels are 9 kHz wide, with channel spacing of 12.5 kHz.
Repeater frequency sets are known as "repeater pairs", and in the ham radio community most follow ad hoc standards for the difference between the two frequencies, commonly called the offset. In the USA two-meter band, the standard offset is 600 kHz (0.6 MHz), but sometimes unusual offsets, referred to as oddball splits, are used. The actual ...
A radio repeater is a combination of a radio receiver and a radio transmitter that receives a signal and retransmits it, so that two-way radio signals can cover longer distances. A repeater sited at a high elevation can allow two mobile stations, otherwise out of line-of-sight propagation range of each other, to communicate. [1]
values 1, 2, and 3 are used to identify sectors of bisector or trisector antennas. In UMTS, there is a distinction between Cell ID (CID) and UTRAN Cell ID (also called LCID). The UTRAN Cell ID (LCID) is a concatenation of the RNC-ID (12 bits, ID of the Radio Network Controller) and Cell ID (16 bits, unique ID of the Cell). CID is just the Cell ID.
The military station operator will announce the specific amateur-band frequency being monitored. Usually, MARS stations are located in military and government installations such as The Pentagon , [ 5 ] Fort Huachuca , Andrews Air Force Base , Nellis Air Force Base , as well as Navy bases such as NAS Whidbey Island and several Coast Guard locations.
Theoretically, the range between two hand-held units on flat ground would be about one or two miles (about 1.5–3 km). Mobile units might have a slightly farther range when mounted on a car roof. A GMRS repeater with an antenna mounted high above the surrounding terrain can extend the usable range to 20 miles or more (30+ km) depending on height.
The required signal-to-noise ratio in a 2500 Hz bandwidth is −21 dB, so the corresponding E b /N 0 is 10 log 10 (2500/6.09) = 26.1 dB greater, or −21 dB + 26.1 = 5.1 dB. [ 1 ] Although FT8 transmissions occur within fixed time windows, the software can cope with discrepancies between sending and receiving systems of up to a second or two.