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