Page 166 951/952 Operator’s Manual Rev. B
Chapter 11 - Customizing the Unit
Using automatic mode
The 951XD/952XD, with its two-channel Northstar differential
receiver, enters automatic differential mode as soon as correc-
tions are received, and requires no further supervision of dif-
ferential operation. It maintains automatic operation by using
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
unit’s GPS receiver. Channel 2
continuously
scans the entire
differential frequency band (283.5 to 325kHz), locating and
measuring received DGPS differential signals. The unit then
stores this information as a DGPS differential “directory” in its
battery-powered memory.
If the signal being received and monitored by Channel 1
degrades for any reason (such as bad weather between your
vessel and the transmitter), the unit tries to select a better fre-
quency from the directory it has compiled. This function
allows it to switch to the best differential signal before your
GPS accuracy is affected.
Automatic mode can normally be used for all applications
except specialized ones.
Using manual mode
At any time, you can override automatic differential station
selection of the differential receiver (if installed) by issuing
tuning commands using the . In manual mode, the
differential receiver outputs DGPS corrections only from the
selected station. Although the need for manual operation is
rare, you can easily access it from your unit’s .
To manually choose a differential station, you must select the
frequency of the desired station.
1. To select the frequency, press the key until you dis-
play the USER CUSTOMIZATION screen.
2. Press the menu key. Highlight BEA-
CON FREQUENCY and press the menu key.
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