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5 PTC-Firmware
5.8.5
AMTEX
The American Radio Relay League (ARRL) has used one system (among others) for its
radio bulletins via HF radio for a number of years, which closely resembles the maritime
NAVTEX system, and follows the same protocol rules. It is called AMTEX. This amateur
radio NAVTEX differs only in its special definition of possible message types, which
have been adjusted for amateur radio usage. The existing NAVTEX processor in the
PTC-IIIusb is thus very suitable for fully automatic reception of AMTEX transmissions,
provided suitable adjustments are made. The messages are transmitted (as with
NAVTEX) in AMTOR FEC ("mode B") normally from 1800 and 2100 American local
time (i.e. 2300 and 0200 UTC - or one hour earlier during summer time). The AMTEX
transmissions take place on the frequencies of 3625, 7095, 14095, 18102.5, 21095 and
28095 kHz (Mark). The following message types have been defined to date:
E: DX
News
Bulletin
G:
General News Bulletin
K:
Keplerian Data Bulletin
P: Propagation
News
Bulletin
S: Space
Bulletin
X: Special
Bulletin
Table 5.6: AMTEX message types
Generally, "A" is used as the area code (Station ident). Exceptionally, "S" has been used.
5.9
GPS
The "Global Positioning System" (GPS) has very quickly become a standard for all areas
that require exact positional information e.g. shipping, in-car navigation systems etc.
Today, GPS receivers are cheaply available and widely used. The PTC-IIIusb offers the
possibility to link the GPS technology with PACTOR, and also to PR. It now becomes
possible for example to call up the present position of small ships or deep sea yachts via
shortwave, without requiring a PC to be running on the mobile station and without a ships
radio operator.
5.9.1
Connecting the GPS receiver
The PTC-IIIusb uses a 3-pole screw terminator to connect to a GPS reciever. This input is
compatible with 5V-TTL and RS232/V24 signal levels. This pins are assignes as follows:
Figure 5.1: GPS connector
The PTC-IIIusb expects GPS data with 4800 baud and in NMEA format.
Some GPS receivers offer various protocolls for control via the serial port. The PTC-
IIIusb expects a NMEA compatible GPS receiver. The GPS equipment must therefore
be set to "NMEA compatible"!
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