A dedicated NAVTEX receiver is used to receive incoming message and then prints the information. The receiver has the capability to select a number of special messages by using a predetermined code. These codes are set into the receiver by the radio operator and will determine what type of messages will be printed.
Each station in the NAVTEX system has a unique transmitter identification, these determine the area they will provide MSI. The Identification is a unique letter from A to Z. There is also a special letter to determine the type or category of message. There are additional letters to have a specific functions in the message. The first line of the message is:
ZCZC FV01
These are designated as: Start signal [ZCZC] then; B1 B2 xy Second group of four
B1 = The station code as "F" above
B2 = The subject matter code.
xy = the serial number of the message, starting with 01
The B1 designator is the station obtained form IMO Master Plan of Shore-Based Facilities; Publication 117, Radio Navigational Aids, list many of the active NA VTEX stations worldwide.
The B2 designator is the Subject matter of the message and is shown in the table below.
The xy characters are the serial number of the category of message and if this is a "OO" then it is for distress and will be sent immediately.
There are several Categories of MSI. Navigational Warnings, Distress Alerts, and Meteorological Warnings.
The first to discuss is Navigational Warnings. Under this title we will consider some of the following: buoys out of position, new wrecks, floating debris, oil rig moves, naval gunfire exercises, unlit buoys .
The second is Meteorological Warnings and these consist of messages concerning: gale force winds, severe weather conditions requiring immediate transmission.
And third are Distress Alerts these messages are the first details of any distress situation will often be broadcast as MSI upon receipt. Additional information will be transmitted as distress traffic and on those designated frequencies.
Subject Matter of NA VTEX Messages
A Navigational Warnings
B Meteoroloaical Warnings
C Ice Reports
D SAR Information
E Meteorological Forecast
F Pilot Service Messages
G Decca Messages
H Loran Messages
I Omeaa Messages
J SATNAV messages
K Other Electronic Navigation Messages
L Navigational Warnings in addition to A (Overflow from A)
M-U Reserved
V Fishing Vessels
Y Reserved
Z No messaaes to transmit
These station and subject matter designators are programable into the NAVTEX receiver and allows the operator to choose only the safety messages pertinent to the sailing area and other item of interest. The other designators not programmed in the receiver will be rejected.
A typical SafetyNET MSI broadcast is shown below. Please note the following on the message:
Date and time of the message in UTC .
The identifier of the CES send the message
A unique number identifying the message
The priority of the message
The nature of the message
