Mechanical Checks; Check Balance; Observe Antenna Initialization; Troubleshooting - Sea Tel 4006-23 IN A 60” RADOME Installation And Operation Manual

Maintenance and Troubleshooting

7.2.7. Mechanical Checks

Turn the pedestal power supply OFF
1. Inspect inside of radome for signs that the dish or feed have been rubbing against the
2. Rotate the pedestal through its full range of azimuth motion. The antenna should rotate
3. Rotate the pedestal through full range of elevation rotation. The antenna should rotate
4. Rotate the pedestal through full range of cross-level rotation. The antenna should rotate
5. Rotate the level cage through the full 90 degrees of rotation from CCW stop to CW stop.
6. Inspect all drive belts for wear (black dust on/under the area of the belt).

7.2.8. Check Balance

Check the balance of the antenna, re-balance as needed (refer to the Balancing the Antenna
procedure below).

7.2.9. Observe Antenna Initialization

Observe the Antenna Initialization as described in the Troubleshooting section below.
7.3.

Troubleshooting

7.3.1. Theory Of Stabilization Operation

The antenna system is mounted on a three axis stabilization assembly that provides free motion
with 3 degrees of freedom. This assembly allows the inertia of the antenna system to hold the
antenna pointed motionless in inertial space while the ship rolls, pitches and yaws beneath the
assembly. Three low friction torque motors attached to each of the three free axes of the
assembly provide the required force to overcome the disturbing torque imposed on the antenna
system by cable restraints, bearing friction and small air currents within the radome. These
motors are also used to re-position the antenna in azimuth and elevation.
The Pedestal Control Unit (PCU) uses inputs from the level cage sensors to calculate the amount
of torque required in each axis to keep the antenna pointed within +/-0.2 degrees. The basic
control loops for Cross Level, Level and Azimuth are shown in the Control Loop Diagram,
drawing 116287. The primary sensor input for each loop is the rate sensor mounted in the Level
Cage Assembly. This sensor reports all motion of the antenna to the PCU. The PCU
immediately responds by applying a torque in the opposite direction to the disturbance to bring
the antenna back to its desired position. Both the instantaneous output of the rate sensor
(Velocity Error) and the integrated output of the rate sensor (Position Error) are used to achieve
the high pointing accuracy specification.
The calculated torque commands are converted to a 5 volt differential analog signal by a Digital
to Analog converter (D/A) and sent to each of three Brush-Less Servo Amplifiers. These
amplifiers provide the proper drive polarities and commutation required to operate the Brush-
inside of the fiberglass radome.
freely and easily with light finger pressure.
through the full range but offer resistance to rotation in this axis because of the
elevation motor brake.
through the full range but offer resistance to rotation in this axis because of the cross-
level motor brake.
The level cage antenna should rotate freely and easily with light finger pressure.
Attached cables should not cause the cage to spring back more that a few degrees from
either stop when released.
4006-23 Broadband At Sea
7-3