At these wavelengths, they can curve (diffract) over hills and expand beyond the visible horizon, although they can be blocked by mountain chains. Ground waves follow the shape of the Earth.
Radio waves at MF wavelengths travel through terrestrial waves and are reflected off the ionosphere (called sky waves). The FCC requires that all new types of marine VHF and MF/HF radiotelephones accepted after June 1999 have at least a basic DSC capability. That connection ensures that an accurate location information will be sent to a rescue coordination centre if a distress alert is transmitted.
#Hf papploc install location code#
The correct programming of the MMSI code is to be verified during the GMDSS survey.Īlso, IMO and ITU-R both require that the DSC-equipped MF/HF and VHF radios be externally connected to a satellite navigation receiver (GPS). Each DSC radio on a ship is programmed once and forever with a unique 9 digit ID number (Maritime Mobile Service Identity – MMSI code). DSC calls can also be made to individual stations, groups of stations, or “all stations” on the same radio band. Primarily, DSC is designed to set up ship-to-ship, ship-to-shore and shore-to-ship radiotelephone and MF/HF radiotelex calls. DSC is a mandatory equipment both for coast stations included in the GMDSS system, and for ships making voyages in any navigation areas. IMO has designated Digital Selective Calling (DSC) on MF, HF and VHF marine radios as a part of the GMDSS system. The system is subject to mandatory annual GMDSS survey. An MF/HF radio installation with DSC should be installed with a TELEX terminal. MF/HF on board the ship provides radiotelephony, narrow-band direct printing and DSC over long distances. MF/HF radio is an important part of GMDSS, that’s why most of the vessels are obliged to install it in accordance to international safety regulations. It usually consists of a transceiver, a control block, and an antenna.įor any vessel crossing oceans and seas as well as for those working offshore, an MF/HF radio is an indispensable section of equipment, it ensures long-distance radio communication. MF/HF radio station is a high tech equipment, designed for receiving and transmitting messages between vessels in the medium and high frequency range.
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