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Mobile Earth Station - The generic name used to describe an Inmarsat-approved terminal which is allowed to access the network, and applicable to both maritime and land mobile communications.
The world is divided into 16 (plus 5 polar - not operational yet) METeorogical AREAs. This are regions of the seas, with same outer boundaries as NAVAREA, for which specified nations have the responsibility for the co-ordination of the provision of meteorological information. METAREAs are usually divided into sea areas for weather forecast broadcast using EGC, NAVTEX or voice messages through VHF, MF or HF.
Medium frequency - same meaning as medium wave (MW). Frequency bands from 300 to 3000 kHz. For distress calls in sea area A2 Mfrequencies should be used.
MF/HF DSC radio
MF/HF RT radio
Maritime Mobile Service Identity - MMSI is a unique 9 digit number and acts in the same way as a telephone number. The MMSI allows the radio operator to make automatic calls through VHF DSC radio and is the identity that is automatically transmitted within DSC calls. These MMSI numbers are issued by the appropriate authorities in the country of registration of the vessel and can be referenced back to a database of information about the vessel and its owners and so forth.
Maritime Safety Information - Navigational and meteorological warnings, meteorological forecasts, and other urgent safety-related information broadcast to ships.
Maximum Usable Frequency is the frequency at which radio communications just starts to fail. It is caculated by formula: MUF=f0/cos alpha where is
h= layer height
f0= layer density
alpha = arc tg ((d/2)/h)