Kantronics MT1200, Руководство пользователя, Страница: 74 / 157

GTEXT $GGA$$CHKSUM$ <CR>
Each variable name must be enclosed in $ characters and entered in CAPITAL letters.
The NMEA strings usually begin with a $ also, and that is entered with the variable
string. The entry above designates the $GPGGA sentence with a checksum. A
maximum of 126 characters can be entered in the GTEXT command. Note that the
transmitted data can be more than 126 characters, depending on the variables
specified.
Next, set the interval of the beacon, with the command GBEACON. The interval can be
from 1 per second, or up to 1 in 24 hours. Other options can be added, such as when to
start the beacon (number of seconds from the top of the minute or hour), or sending a
beacon after some change in GPS position (distance traveled) or direction.
For example, if you want to beacon to GPS via a digipeater (called WIDE1-1), and you
want the beacon to occur every 30 minutes, use the following commands:
GPATH GPS via WIDE1-1
GBEACON EVERY 00:30:00
Several amateur groups, such as APRS (see the bibliography at the end of the GPS
section), have developed special programs for enhancing amateur GPS activities.
Check with them for current practice in setting GPS beacon paths, beacon rates, and
frequencies used in your area.
Other GPS Beacon Features
Slotted Beacons
The GBEACON command provides for the ability to specify not only the interval
between beacons, but a starting time for the beacons. This permits a “slotted” system of
beacons by numerous stations. For instance, lets say your local area has 30 stations
that each should beacon their location every 30 minutes, each with its own unique time
slot to avoid packet collisions so all stations can be heard. A beacon would be
transmitted every n minutes from the time the user sets the time that the beacon should
be transmitted. As an example, if you set the beacon interval with the command:
GBEACON EVERY 00:30:00 START 00:00:01
the TNC would transmit a beacon at 00:00:01 (time after midnight) and every 30
minutes after that, in its own particular time slot. The second user could set the beacon
interval with the command:
GBEACON EVERY 00:30:00 START 00:01:01
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