NorthStar 961 Install Manual page 71

961/962 INSTALLATION MANUAL Revision A
Setting beacon frequency and baud rate
You can set the receiver to operate automatically or manually.
Automatic tuning
Northstar's two-channel differential receiver enters automatic differential
mode as soon as corrections are received. Automatic mode doesn't
require any further supervision for differential operation; rather,
automatically tunes to the appropriate differential frequency as you move
from one differential coverage area to another or as weather conditions
change. First the receiver finds the differential frequency and data
transfer (baud) rate, then it receives data fully automatically. The receiver
constantly evaluates available radiobeacon signals for signal quality, and
selects only the best station. The receiver is prepared to switch to another
frequency automatically, as you travel, and as conditions require.
The system maintains automatic operation by using its two independent
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 961/962'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 are 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 system
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 affecting your GPS accuracy.
For normal operation, Northstar recommends that you leave beacon
frequency and baud rate at the
automatic mode for everything except specialized applications.
To choose automatic mode:
1. At the
highlight the
2. Press the
the key (or press
Manual tuning
You can override the receiver's selection of automatic differential stations
at any time. Under manual control, you manually set the differential
frequency and baud rate to tune in a particular differential transmitter. In
manual, the differential receiver outputs DGPS corrections only from the
selected station. Although the need for manual control is rare, it's easily
accessed at the
differential frequency to any value between 283.5kHz and 325kHz, and
SECTION FOUR - Service/Maintenance
settings. Generally, you'll use
screen, press the
field, then press the
pad left to highlight the
to leave the option unchanged).
screen. Here, you can set the
to
key.
field, then press
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