7.8 NAVTEX Operation
NAVTEX is an international system which stands for NAVIGATIONAL TELEX.
It is a direct printing service designed to distribute navigational
and meteorological warnings and other urgent information to ships.
To enter the NAVTEX mode, simply type "NAVTEX" at the command prompt.
The ARRL has also adopted this format for transmitting bulletins. In
amateur radio this same format is starting to be referred to as AMTEX.
AMTEX transmissions can be found on ARRL bulletin frequencies.
NAVTEX is broadcast in Mode-B AMTOR (SITOR) on a frequency of 518 KHz.
NAVTEX may be selectively monitored, so you will see only information
of interest and never see the same message twice. It is this unique
feature of NAVTEX that the PK-232 uses with the NAVSTN and NAVMSG
commands to allow the user to monitor only messages of importance.
NAVTEX/AMTEX messages are prefaced by the characters "ZCZC" and
then a four character Preamble as diagrammed below.
ZCZC AA99
3333
333@DSerial Number 2nd DigitDD?
33@DDSerial Number 1st DigitDDY
3@DDDMessage Classification (A to Z)
@DDDDNAVTEX Station Identification (A to Z)
The first character of the Preamble is a letter that identifies the
NAVTEX transmitter. Transmitter Identification letters can be any of
the characters A through Z. This limits the number of NAVTEX stations
in an area to 26. The NAVSTN Command can be used to selectively
monitor or reject certain NAVTEX transmitters.
The second character of the Preamble is the Message Classification.
The NAVMSG command is used to selectively monitor or reject any of the
NAVTEX message classes shown below:
A. Navigational Warnings
B. Meteorological Warnings (Storm Warnings)
C. Ice Reports
D. Search and Rescue Information
E. Weather Forecasts
F. Pilot Service Messages
G. DECCA System Information
H. LORAN-C System Information
I. Omega Systems Messages
J. SATNAV System Messages
K-Z. Reserved for future use
The exception to this is that message classes A, B and D CANNOT be
excluded and will always be copied if the transmitting station is
enabled by NAVSTN.
The last two numbers form a serial number from 00 through 99 that is
different for each message. The PK-232 remembers the Preamble of the
200 most recent messages and will not re-print a message that has the
same preamble if it has already been received without many errors.
8/91 7-14
