ashtech DG14, Reference Manual

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70 DG14 and DG16 Board & Sensor Reference Manual
The DG16 has several modes of beacon operation Use the
$PASHS,BCN,MOD command to set the beacon operation mode:
• Automatic Mode—the receiver determines which beacon station(s) to use
• Single Automatic Mode
• Dual Automatic Mode
• Manual Mode—you manually set which beacon station(s) to use
• Single Manual Mode
• Dual Manual Mode
The default Beacon mode is Single Automatic. On power up, the DG16
remembers the last beacon stations used, and begins searching with those
frequencies.
Automatic Modes
In Automatic mode, the beacon receiver automatically determines the MSK
bit rate(s), and it utilizes its own position information in conjunction with a
Beacon Station Location Table (stored in memory) to identify the nearest
beacon stations and begin searching for these stations. On power up, the
beacon receiver remembers the last used beacon ID’s and begin searching
for these frequencies.
You can view the default beacon directory using the
$PASHQ,BCN,DIR
command. The beacon directory in the receiver is similar to, but usually larger
than, the beacon almanac received in RTCM Type 7. The receiver beacon
directory is updated by both RTCM Type 7 and what you add manually with
the
$PASHS,BCN,DIR,ADD command. The last received record (RTCM
Type 7 or user entry) overrides any preceding entries. Therefore, to avoid
overwriting your entries with RTCM type 7 update information, disable RTCM
Type 7 processing using the
$PASHS,BCN,RT7,N command.
A beacon station is identified by latitude, longitude, range, frequency, health,
Station ID, bit rate, Modulation code, Sync type, and Broadcast Coding.
In Automatic Mode, you can mark a frequency to “never be used” using the
$PASHS,BCN,NVR command.
Single Automatic Mode
In Single Automatic Mode, the beacon receiver automatically detects all
available radio beacon signals and select the best one station, switching
automatically as the user moves from one coverage area to another. Channel
1 tracks the best available beacon signal and sends the demodulated DGPS
corrections to the DG16 receiver. Channel 2 scans for other available DGPS
beacon signals, maintaining a DGPS beacon directory in a battery-backed
memory. The beacon almanac/directory is automatically saved.