If a NAVTEX receiver becomes inoperative, the MSI broadcasts can be copied by using HF NBDP, INMARSAT-C SafetyNET or copy NAVTEX broadcasts on NBDP on 518 Khz on your MF/HF receiver. However you will not get the reject/select feature as you would have on the NAVTEX receiver . The frequency of 4209.5 KHz using NBDP and FEC is used in some European areas . The IMO as established some performance standards for NAVTEX receivers. The receiver has three main parts. The receiver section is designed for one frequency only (518 Khz); a small computer to process the message and a printing device to allow display of the message on paper.
Some units are designed to store at least 30 message header ID .
These messages are saved in the memory for about 70 hours and will be erased from the memory. If there is a lot of traffic when the memory section is filled then the oldest message will be deleted to make way for the newest. The station ID and items in the memory should remain in the unit for at least 6 hours when the power is off.
One nice thing about the receiver is that if a character is garbled then the receiver will print a star (*). The message will still be readable under some severe radio conditions. A message will be considered received if the character error rate is below 5% .
If a message is received from a Search and Rescue operation there will be an alarm sound at the position from which the ship is normally navigated. It may then be reset at the receiver.
There is a second system of receiving the MSI (Maritime Safety Information) and that is the SafetyNET. This network is a product of the IMARSAT Corporation and is a free service to the Maritime Industry. This service is an automated service using the INMARSAT-C system. This service is authorized by the IMO, within the auspices of the GMDSS, providing safety service for mariners. The coverage is as for INMARSA T coverage that is, from about 70 degrees North to 70 degrees South. Out side of
NAVTEX and beyond 70 degrees we must use HF Radio.
Some of the services of SafetyNET include:
Shore to ship distress alerts and urgent information from RCC
Meteorological warning and forecasts compiled by the National Weather Center
Navigational warning and electronic chart corrections from Hydrographic Office
International Ice Patrol information for the North Atlantic Ocean
