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INTRODUCTION
NAVTEX is a method of transmitting navigational warnings and weather forecasts
from designated coast radio stations. All English language transmissions are made on
the 518 kHz NAVTEX channel. Each NAVTEX station is allocated several time slots
during the day when it is permitted to transmit, normally at four hourly intervals. The
exceptions to this are gale warnings and search and rescue messages which may be
transmitted at any time.
Reception of 518 kHz NAVTEX transmissions is normally limited to an area of 200 -
300 miles radius around each transmitting station, although considerably greater
ranges are possible at night. Subject to IMO approval, additional local language
transmissions are sent on 490 kHz and on 4209.5 kHz, NAV-7 supports simultaneous
reception of all three NAVTEX channels.
Designed to the latest International specifications, NAV-7 meets IMO requirements
under GMDSS and is designed for simplicity of operation. It will provide up to date
MSI (Marine Safety Information) and weather forecasts and is suitable for use by all
classes of commercial vessels and large pleasure craft. It will display and store
NAVTEX messages without manual intervention within designated areas of NAVTEX
service coverage.
If the vessel is located within the coverage area of several NAVTEX stations
(particularly at night), the NAV-7 may overwhelm you with information. It can therefore
be set up to display only those stations and message categories you want to receive
and which are applicable to the area in which the vessel is currently sailing.
Normally, routine NAVTEX messages are repeated at four hourly intervals. Provided
that the NAV-7 is left running, repeated messages are not displayed more than once.
Each message is retained for three days (72 hours) after its last reception before
being automatically deleted, unless the message has been marked as locked.
Full detail of the GMDSS NAVTEX service is published in the Admiralty List of Radio
Signals Volume 5, Global Maritime Distress and Safety System (GMDSS). Published
by the United Kingdom Hydrographic Office.
The IMO and various national coastguards also have informative websites; see the
links page at
www.mcmurdo.co.uk
