The antenna will be used onboard a ship and it will have to be able to provide uninterrupted satellite usage while under a variety of motion.
What are the key points :
- Pointing/Targeting - Accurately driving the antenna to a precise Azimuth and Elevation angles in three dimensional free space to be consistent with where the satellite signal is emanating from.
- Stabilization - Maintaining the Azimuth and Elevation pointing angles while the ship is rolling, pitching and turning.
- Tracking - Use of the received satellite signal level to continuously evaluate and optimize the pointing angles of the antenna for maximum signal level reception.
Definitions of other relevant terms :
Relative (REL)
Mechanical azimuth rotational position of the antenna relative to the Bow of the ship. When the antenna is pointed inline with the Bow of the ship the REL display should be 360.0/000.0. Range of display is 000.0-359.9.
Azimuth (AZ)
True Azimuth (requires Ships’ Gyro Compass input). the Azimuth pointing angle of the antenna relative to True North (North Pole of the Earth). When the antenna is pointed True North display will be 000.0, East at 090.0, South at 180.0 and West at 270.0. Range of display is 000.0-359.9, Up direction is CW rotation of the antenna.
Elevation (EL)
Elevation pointing angle of the antenna between Horizon (000.0) and Zenith (090.0).
Level (LV)
Pedestal Fore/Aft upright position relative to the Horizon. Level Sensor is a gravity reference to bring the Level Cage (fore/aft) aspect to “level”. This input is used to stabilize Elevation.
Cross-Level CL)
Pedestal Left/Right tilt position relative to the Horizon. Level Sensor is a gravity reference to bring the Level Cage (Left/Right) aspect to “level”. This input is used to stabilize The Left/Right Tilt of the antenna.
Roll
Tilting motion of the ship from side (Port) to side (Starboard).
Pitch
Tilting motion of the ship from Bow to Aft.
Yaw
Serpentine oscillation of the ship along a desired heading (steering badly)
Center of Gravity (C/G)
Center of gravity of the mass of the antenna. Azimuth, Elevation and Cross Level are aligned at the factory to be coincident within 0.003 inch.
Static Balance
Proper 3 dimensional balance of the antenna is critical to stabilization. When properly balanced the un-energized antenna can be pointed to any AZ/EL pointing position and it will remain pointed there when released.
Tangential Acceleration
G-Force exerted on the mass of the antenna as it swings through free space during ship motions.
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