Gps Receiver And Antenna [70170101] (Separate Receiver And Antenna, Sk-Ii); Theory Of Operation - SeaSpace TeraScan 1.5M Operation And Maintenance Manual

8.6 GPS R
ECEIVER AND
A , S
NTENNA

8.6.1 Theory of Operation

1. Overview
The GPS unit mounted on the radome provides clock time and position information. The GPS unit is
attached to the radome as two assemblies:
a. The GPS antenna [70347001].
b. The GPS receiver [70320001] (Sk-II).
Both parts are mounted to the inside of the radome bottom. See drawing 70909055, page 69, and
Figure 8-23 below.
The GPS receiver attaches to a mounting plate (for purposes of repair). The receiver mounting plate and
the GPS antenna are held to the radome bottom with double-sided VHB adhesive tape.
2. Communications
To communicate with the GPS receiver, the programs whereami and sunclock talk directly to the receiver
using a dedicated port without switching the serial port. RS422 electrical protocol is used.
3. Configuration in $PASSDIR/config/system.config or $PASSDIR/system.config :
a. The GPS lock type must be set to gps.index: external-acutime
b. The GPS device must be set to the GPS's command serial port.
gps.device: /dev/xxxx
c. The GPS lock file will be inferred using the gps.device serial port. The lock file will be named
$PASSDIR/gps_lock_DEVICE.
A [70170101] (S
NTENNA
-II)
K
xxxx=GPS's serial port, such as /dev/ttys4
TeraScan 1.5m Polar Satellite Tracking Antenna O & M Manual 159
R
EPARATE ECEIVER AND