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The DMR standard operates within the existing 12.5 kHz channel spacing used in land mobile frequency bands globally, but achieves two voice channels through two-slot TDMA technology built around a 30 ms structure.
Digital DMR Tier I TDMA PMR446 channels are also available, eight channels from 446.10625 MHz to 446.19375 MHz with 12.5 kHz channel spacing steps. 4-level FSK modulation at 3.6 kbit/s is used. All three of the PMR446 channel plans occupy the same European-harmonized 446.0 MHz to 446.2 MHz frequency band.
Motorola TA288 PMR446 licence-free radio Motorola TLKR T40 radio tuned to PMR channel 1. PMR446 (Private Mobile Radio, 446 MHz) is a licence-exempt service or UHF CB in the UHF radio frequency band, as personal radio service or citizens band radio, and is available for business and personal use in most countries throughout the European Union, [1] Malaysia, [2] Singapore, [3] Norway, [4] and ...
In general narrow band frequency modulation is the chosen form of modulation, although airport services use amplitude modulation.Typically a deviation of 2.5 kHz is used for FM and this enables a channel spacing of 12.5 kHz to be implemented.
There is also nothing to prevent multiple groups in the same area from choosing the same channel, causing conflicts and 'cross-talk'. A trunked radio system is an advanced alternative in which the channel selection process is done automatically, so as to avoid channel conflicts and maintain frequency efficiency across multiple talkgroups.
Land mobile radio systems are widely used by the military. Separate bands in the radio spectrum are reserved for their use. This includes portions of the 30-50 MHz band, and the entire 100-100, 100-100.8, and 540-2400 MHz bands, plus shared use of the 170- 170 MHz band.
Channel spacing, also known as bandwidth [citation needed], is a term used in radio frequency planning. It describes the frequency difference between adjacent allocations in a frequency plan . Channels for mediumwave radio stations, for example are allocated in internationally agreed steps of 9 or 10 kHz : 10 kHz in ITU Region 2 (the Americas ...
Radio channels are 9 kHz wide, with channel spacing of 12.5 kHz. The gross data rate is 9,600 bits per second, with the actual data transfer at 3,200. The transmission, called stream , is divided into 40-millisecond long frames , each prepended with a 16-bit long synchronization word.