Settings
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Chapter 4: Setup of the antenna
4-18
Tracking for satellite elevation between 5 and 75 degrees
When the system has found the satellite and is in pointing mode, the performance of a
system with heading input and a system without heading input will be very similar.
Note that this is only the case for a satellite elevation range from 5 to 75 degrees.
If the satellite is an inclined orbit satellite, the missing heading information introduces
a polarization error depending on the satellite elevation and the inclination. Normally
it is required that the polarization is controlled within 1 degree towards the satellite.
This gives the following limit for use of inclined orbit satellites (a purely physical limit),
and all systems without heading input have this limit.
Tracking for satellite elevation above 75 degrees
It is not possible to use a system without heading input from the vessel's gyro compass
with satellites at an elevation of higher than 75 degrees because the system will not
have the required polarization accuracy of the transmitted signal.
4.2.6 Acquisition process and search pattern
With heading input or fixed heading
1. The antenna starts the acquisition, searches for 10 seconds at the expected
position. If RX lock is detected the antenna goes to Tracking.
2. If no RX lock is detected, a box search pattern is started and the positions where RF
power can be received are stored.
3. The antenna checks each stored position for up to 10 seconds. If RX lock is detected
for more than 20% of the time, the antenna goes to Tracking.
Satellite elevation
Maximum allowed
inclination
<20
2.5
<50
0.7
<70
0.3
75
0
Table 4-16: Satellite elevation and maximum allowed
inclination
Figure 4-12: Acquisition, search pattern
+0.7°
0.0°
-0.7°
4.0°
3-4 seconds
