Field Replacement Procedure
Following legal entities are trading as / doing business as Cobham SATCOM
Thrane and Thrane A/S, Kgs. Lyngby, Denmark
Sea Tel Inc., Concord USA
TracStar Systems Inc., Orlando, USA
Omnipless Manufacturing (Pty) Limited, Cape Town, RSA
www.cobham.com/satcom
SAILOR 800, 900A & 900B VSAT– Polarization Motor Procedure
Brief Summary:
Troubleshooting document for inspecting and replacing the polarization motor (S-62-134493) on the
SAILOR 800 (7008A), 900A (7009A) and 900B (7009B) VSAT antennas.
Checklist:
Status LEDs
Events List / Error Log. Identify Defective Part
Replace Part
Verify Initialization and Run POST Test
Theory of Operation:
A stepper motor is installed on the rear of the dish of the SAILOR 900 VSAT antenna to rotate the
polarization unit through its 270 degree range of motion.
A zero reference point (magnet) is installed in the drive pulley of the polarization as a reference
position. When the system is energised the stepper motor will drive the polarization unit from one end
stop to the other with the hall effect sensor on the Zero Reference Module (ZRM) reading the
magnetic forces in each direction and taking a mean value as a reference position.
Upon initialization the encoder on the polarization unit will be calibrated based on the axis’s zero
reference position and will increment/decrement the drive steps made by the polarization motor.
When targeting a linear satellite the polarization motor will drive the polarization unit until it reaches
the calculated position, based on the vessels GPS position and the look angle to the satellite. At this
point the encoder will be outputting the desired target value, meaning that the Ortho-Mode
Transducer (OMT) is correctly aligned to the linear receive and transmit signals of the satellite for
maximum signal strength and quality.
As the vessels sails and the GPS position changes small adjustments will need to be made to the angle
of the polarization unit to maintain alignment with the linear satellite signal. This will cause the value
the Pedestal Control Module (PCM) is expecting from the encoder to change, meaning the PCM will
issue the command to drive the polarization motor until the correct feedback from the encoder is
received.
Cobham SATCOM
Global Customer Service dept.
Document no.: 97-139037-C
Revision: C
Date: April 2013
