Page 14 - Our advices

The fixed VHF has a maximum power of 25 watts imposed by regulations which limits its range from 15 to 20 miles boat/boat and from 30 to 40 miles toward coastal stations. The new generation of VHF on the market, come equipped with the DSC (Digital Selective Calling) system, ASN (Appel Sélectif Numérique) in French.

 

 

-A portable VHF can be taken with you in all situations, especially

The AIS system, transmits to other vessels, equipped with compatible receivers, information concerning the vessel on which it is installed. Thus is transmitted, the vessel’s identification (MMSI number and name,) its position, course, speed, characteristics (length, width, water displacement,) and possibly information concerning its cargo and destination…All this information is emitted continuously, whether in coastal waters or on the high seas. A vessel which receives an AIS signal can thus visualise the course and speed of the sender and assess the chances of a collision long before it occurs. It is therefore, an invaluable tool for avoiding collisions at sea. This system operates on VHF frequencies (161.95MHz and 162.025MHz.) It is mandatory on all vessels over 300 tons and passenger ships. But many fishing vessels and
even recreational boaters also utilise it. For leisure craft, one may choose to be limited to a single receiver. Thus, "we see, but without being seen."

The Navtex (Navigational Telex) is an official international system developed in the area of GMDSS, for sailing professionals. The receivers have been developed for leisure craft. They are simple to use and once programmed, will receive bulletins and keep them stored in the memory.
Two types of receptors are proposed: autonomous with LCD screen for reading messages and without screen with a PC output, which connects via a USB port to a computer.

All transmitters operate on a single frequency, 518 kHz (with a second frequency of 490 kHz to issue national language.) In order to avoid interference between stations in the same area, the diffusion of messages is on specific time slots (every 4 hours) except for BMS. In practice, each service area, called NAVAREA, is divided into geographic area and assigned a letter. For example,

In coastal Europe, the weather is broadcast, according to the areas and times, on the long wave (LW 150 to 250 KHz), short wave (MW from 530 to 1620 kHz) and frequency modulation (FM 88 to 105 MHz). To capture these frequency bands, a general public receiver is useful. For long range sailing, it is not enough. An MHF-SSB, receiver is a necessity, sensitive enough for fine tuning. Note that some receivers have an output for receiving the Navtex and weather charts on a computer.