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961 Operations and Reference Manual Rev. D
2. Press the CURSOR PAD left or right to select either ON or
OFF.
3. When done, press the ACCEPT key (or CANCEL to leave
the option unchanged).
Setting beacon frequency and baud rate
You can set the receiver to operate automatically or be con-
trolled manually.
Automatic tuning
Northstar's two-channel differential receiver enters automatic
differential mode as soon as corrections are received, and
doesn't require any further supervision for differential opera-
tion, automatically tuning to the appropriate differential fre-
quency as you move from one differential coverage area to
another or as weather conditions change. First, it finds the dif-
ferential frequency and data transfer (baud) rate, then it
receives data fully automatically. The receiver constantly eval-
uates available radio beacon signals for signal quality, and
selects only the best station. The receiver is prepared to switch
to another frequency automatically, as you travel, as condi-
tions require.
The unit maintains automatic operation by using its two inde-
pendent receiver channels: Channel 1 tracks the best available
differential signal (the one with the lowest data error rate) and
sends the demodulated DGPS corrections to the 961's GPS
receiver. Channel 2 continuously scans the entire differential
frequency band (283.5 to 325 kHz), locating and measuring
received DGPS differential signals, which is then stored as a
DGPS differential directory in its battery-powered memory.
If the signal that's received and monitored by Channel 1
degrades for any reason, such as bad weather between you
and the transmitter, the unit tries to select a better frequency
from the differential directory it has compiled. This feature
enables it to switch to the best differential signal—before affect-
ing your GPS accuracy.
For normal operation, Northstar recommends that you leave
both beacon frequency and baud rate at the AUTO setting.
Chapter 14 - Service and Maintenance Functions
Page 14-7
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