Furuno FELCOM 70 Operator's Manual page 207

9. SYSTEM DESCRIPTION
Antenna search pattern
Azimuth sweep
A 360° rotation of the antenna in azimuth at a fixed elevation angle.
Hemispheric search
A hemispheric search is constituted by azimuth sweeps at elevation angles 5°,
25°, 45°, 65° and 85°.
The antenna searches on the NCS Common TDM channel frequency (NCSC),
initiated by the FELCOM 70 Communication Unit (CU).
When finding the satellite signal, it completes the hemispheric search and moves
to the position where the strongest signal was detected.
The Antenna reports back to the CU for verification of valid NCSC.
If no valid signal is detected, no further automatic action occurs until the CU
initiates a new search.
A search request from the CU may contain channel frequency and an order to
make a full 360° search at a specific elevation, calculated from map and GPS
information. If the request contains channel frequency, a hemispheric search will
be performed.
Tracking
At the end of a search, FELCOM 70 performs a fine-tuning of the antenna
position around the strongest detected signal. The fine-tuning is obtained by
conical scan function based on an antenna rate sensor and a tilt sensor.
85˚
65˚
45˚
25˚
5˚
T
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