Operating Modes - NorthStar 8700 Technical Reference Manual

5.1.4 Operating
modes
05/01/97 REV H
Signal detection: acquisition via frequency-locked loop (FLL); track-
•
ing via phase-locked loop (PLL)
Data processing
Minimum shift keying (MSK) demodulation
•
Data decoding: parallel-matched digital filters
•
MSK bit rates: 25, 50, 100, 200 (automatically selected)
•
Data ports
Control input port: RS-232-C and RS-422 or NMEA 0183; 9600 or
•
4800 baud (jumper-selectable)
DGPS correction output port: RTCM SC-104 Version 2.1; 6 of 8
•
RS-232-C and RS-422; 9600 or 4800 baud (jumper-selectable)
Monitor/control port: Bi-directional RS-232-C or RS-422 at 9600
•
baud
Environment
Operating temperature: Zero to 55 C
•
Relative humidity: 95 percent (non-condensing)
•
Electrical requirements
The 8800's power supply is protected against reverse-polarity power
inputs, and features a remote turn-on ability. The 8800 turns on when-
ever power is applied to pin 25, ground to pin 13, and remote turn-on pin
12 is connected to a source of 5 to 40 VDC.
The 8800 runs in two operating modes:
Automatic
•
Manual
•
Automatic mode
At power-up, the 8800 enters automatic mode, requiring no further
supervision from the host GPS receiver. The 8800 operates automatically
by using two independent channels: Channel 1 tracks the best beacon
signal available (the signal with the lowest data error rate), and sends the
demodulated DGPS corrections to the GPS receiver; Channel 2 continu-
ously scans the entire beacon frequency band (283.5 kHz to 325 kHz),
locating and measuring received DGPS beacon signals.
The 8800 then stores this information as a DGPS beacon "directory" in
battery-powered memory. If the signal that's received and monitored by
Channel 1 degrades for any reason, the 8800 selects a better frequency
from its beacon "memory." This function lets the 8800 automatically
switch to the best beacon signal before affecting your GPS accuracy.
Automatic mode can be used for all applications except specialized ones,
and is the only mode supported by most commercially-available GPS
receivers.
Section 5 - Beacon receivers
PAGE 17