<Ctrl+C>R Changeover from ISS to IRS immediately.
Return to receive immediately
(FED mode—AMTOR FEC)
<Ctrl+C>T Seize the link if IRS (ARQ mode)
Enter AMTOR FEC transmit mode
<Ctrl+C>X Disconnect the link (if linked) and
return to Packet
<Ctrl+C>0 Set automatic baud rate selection
<Ctrl+C>1 Force 100 baud operation (IRS only)
<Ctrl+C>2 Force 200 baud operation (IRS only)
<Ctrl+C>3 Force 300 baud operation (IRS only)
<Ctrl+C><Ctrl+T> Toggle TRACE mode ON/OFF
MODEM BREAK Exit data transparency mode
NAVTEX Operation
NAVTEX/AMTEX Theory
Navtex transmissions are, in reality, Mode B AMTOR (FEC). What makes
Navtex unique, however, is the actual message format. Navtex stations always
transmit on 518 kHz LSB, and are generally located on the coastlines. The same
format is now being used by the American Radio Relay League (ARRL) to trans-
mit bulletins on a daily basis. These bulletins are transmitted during scheduled
teleprinter bulletins.
At the beginning of a NAVTEX (or AMTEX) transmission, the sending station
will send a preamble, identifying the station that is transmitting, the type of mes
-
sage, and the message sequence number. The preamble looks like this:
ZCZC AG25
The ZCZC is always present, and the receiving unit sees this as the indication
that the identifier is coming next. The components of the identifier, as defined in
the NAVTEX documentation, are:
B1 B2 B3 B4
B1 is used to identify the station that is transmitting, and consists of the letters A
through Z. B2 indicates the messages class (A through Z). Note that class A, B
NAVTEX Operation Non-Packet Modes of Communication
KAM’98 v 8.3 133 User’s Guide
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