User talk:PalesoTecuzo

Coastal Navigation

Along the ages different signaling methods were developed. The most romantic of them, was no doubt a "message in a bottle". This way of communication is far from reliable, but certainly an interesting one (where is even an international club around it, people made a game out of sending bottle messages through the ocean).

Coastal Navigation - In the old days distress signals were not like today. Canon fire, smoke and various flag signals were used.

With the invention of radio communication most signaling problems were solved. But not all, it still required a human to operate the radio; it also took a lot of time for a distress signal to be sent and received. Reception of the signal was never guarantied and depended on the weather conditions.

The situation improved considerably with the implementation of satellite technologies. With the invention of an automatic radio beacon safety services made a giant leap forward - the distress signal was now being transmitted automatically without any human intervention. However, rescuers had to have consistent reception of the signal, which greatly reduced the systems effectiveness of the search and rescue. In addition the beacon had no means of identifying the source of the signal.

These problems were addressed during the making of the next generation of emergency radio beacons. A satellite system was developed for a worldwide coverage on the 406MHz band. A digital signal on the 406MHz could be received from anywhere on earth and the source of the transmission could be identified, where it was a ship or an aircraft.

Development of the system took several years to complete. Simultaneous work was being done in the USSR on the COSPAS network and in the USA, Canada and France on the SARSAT network. Sometime during this work it became apparent that the projects were quite expensive and basically duplicating one another. So in 1979 it was decided to combine the two projects in to one system - COSPAS-SARSAT. The system was brought in to service in 1984. Since that time the system is continuously upgraded. 121.5 MHz band was added in addition to the 406 MHz band, so older beacons could be used in the system.

Initially the COSPAS-SARSAT system was intended for aircraft, but in 1986 the International Maritime Organization (IMO) decided to change the 121.5 MHz beacons over to the 406 MHz band. COSPAS-SARSAT became an integral part of the Global Maritime Distress and Safety System (GMDSS). All seagoing vessels were equipped with 406 MHz Emergency Position Indicating Radio Beacons.

Presently GMDSS incorporates several devices: Search and Rescue Radar Transponder (SART), VHF radio with DSC, portable 406 / 121.5 MHz EPIRB.

SART is a Search and Rescue Radar Transponder that is activated by ships radar and sends homing signals on 9 GHz band. It allows locating survivors at close range - about 8 nautical miles. Then a SAR vessel is within 8 nautical miles the SART receives radiation from the radar and sends an answerback signal, which can be seen on the radar as a serious of dots leading from the SARTS position.

VHF radio with DSC (Digital Selective Calling) is today the primary means of distress alert on coastal vessels and yachts. It is a requirement for GMDSS A1 area (in sight of at least one shore VHF station, about 30 - 35 nautical miles). The radio can be automatically linked to the ships GPS, so it always "knows" the ships position. In addition it is programmed with the ships name and its Maritime Mobile Service Identity (MMSI) number. In case of emergency the crew needs to press only one button (Distress Call), and the radio will transmit the distress signal with the ships information.

Coastal Navigation

Emergency Position Indicating Radio Beacon (EPIRB) is a float-free transmitter for sending distress and homing signals to SAR services. It is used by ships, airplanes and people at sea and on land. Unlike a VHF DSC signal a signal from 406 EPIRB is received not only in coastal areas, but worldwide in the COSPAS-SARSAT network.