Andrew 3.7-Meter Earth Station Antenna manual Subreflector Adjustment

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Subreflector Adjustment

After the satellite has been acquired and testing has taken place with the spectrum analyzer, the subreflector may need to be adjusted to maximize optimum performance of your anten- na. The following procedures should be followed if a subreflector adjustment is required to maximize optimum performance.

NOTE: All INTELSAT Type Approved antennas do not require subreflector adjustment. Using the provided setting bar and procedures will correctly place the subreflector.

Before proceeding, azimuth and elevation patterns should be conducted to determine the adjustments that need to be made. The goal is to achieve a high peak on the main lobe and even distances between the main lobe and sidelobes as shown in Figure 4-6.

NOTE: No adjustments should be made in the receive band.

If your pattern dictates a need to adjust the azimuth angle(the left sidelobe requires adjust- ment), the west side of the subreflector should be adjusted outward by loosening the screws on the subreflector and adjusting the left side outward. An easy way to remember this adjustment feature is through the acronym WOLD (West Out Left Down).

If your pattern dictates a need to adjust the elevation angle(the right sidelobe requires adjust- ment), the bottom side of the subreflector should be adjusted downward by loosening the screws between the subreflector and the struts and adjusting the bottom side of the subre- flector downward. An easy way to remember this adjustment is through the acronym BOLD (Bold Out Left Down).

Each of these adjustments should be repeated until each sidelobe is of equal distance from the peak of the mainlobe.

After the BOLD and WOLD adjustments have been made, it may be necessary to adjust the main lobe. The goal is to achieve a high null depth (distance between lower intersection of sidelobes and top of main lobe) as shown in Figure 4-6.

In order to adjust the main lobe pattern characteristics ALL subreflector adjustment screws should be adjusted at the same degree (Note: Because the azimuth and elevation adjust- ments have been set, it is very important that the null depth adjustment be carefully conduct- ed. Be careful not to alter any previous adjustments that have been made to the subreflector. Follow the procedure listed below when adjusting the null depth of the main lobe.

C-band feeds - Adjustment screws are 3/4 X 10. Move 1 turn per 1dB of imbalance.

Ku-band feeds - Adjustment screws are 1/4 X 20. Move 1 turn per 1 dB of imbalance.

All adjustments should be continued until the desired pattern is achieved. Upon completion the antenna should be properly aligned with the satellite for maximum performance.

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Operation

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Contents Meter ESA Table of Contents Introduction Meter Earth Station AntennaProprietary Data Information and Assistance Technical Customer Service CenterHow to Use This Manual Overview ContentGetting Started OverviewRecommended Tools Getting Started Returning Equipment Step Getting Started For Mpjk Types Only Main Reflector Assembly Enclosure Assembly Reflector-To- Mount Assembly Subreflector Feed System Overview Foundation Preparation Installation Procedures1b A-325 Tensioning For bolts over four diameters Tensioning StepMount Unpacking Assembly Using a Crane Step 4b Ground Mount Assembly Base Hardware Ground Mount Assembly Alignment with Anchor Bolts Assembly Without a Crane Step6a Manual Lift 8a Ground Mount Assembly Base Hardware 8b Ground Mount Assembly Tiller Arm Hardware Motorizable Pedestal Ground Mount Assembly Step8d Ground Mount Assembly Tiller Arm Hardware 10 Waxing Bolts Manual Pedestal Ground Mount Assembly StepStep 13 Elevation and Azimuth Struts Step 17a Azimuth Strut Assembly Front 17b Azimuth Strut Assembly Rear 20 Bracket-Support Plates Top View 21a Elevation Strut Bracket 22a Manual Actuator Assembly Manual Actuator Assembly Step23 Azimuth Pivot Bracket Assembly 25a Jack Unscrew Procedure 26 Protective Boot Attachment 28a Elevation Jack Step 29b Left Side Frame Attachment Embedded Pipe Ground Mount Assembly Step29d Elevation/Azimuth Strut Assembly Step Elevation/Azimuth Strut Assembly29f Elevation Axis Weldment Attachment 29g Azimuth Strut/Pointer Attachment 29i Fine Azimuth Adjustment Attachment 30a Domestic Pack Reflector Unpacking Step30b Export Pack 31 Reflector Seam Alignment Step Assembly32 Seam Bolt Insertions Very Important 33c Alignment Bolt Insertions 34a Mounting Ring Placement 35a Mounting and Center Rings -35b Mounting and Center Rings Alignment Test Step Enclosure Pedestal Mount Only Step 38a Enclosure Final Assembly39a Enclosure Hardware Step 43 Safety Rope Tag Lines Reflector-to-Mount Assembly Using a Crane Step44b Crane Lift Without a Crane Step 46 Reflector to Mount 48 Enclosure Bracket Alignment Step 50a Reflector to Mount Reflector-to-Mount Assembly Embedded Pipe Ground Mount Step Subreflector Step 52a Subreflector Strut Assembly53a Subreflector Assembly 53c Subreflector Assembly 54a Subreflector Attachment Subreflector Struts Embedded Pipe Ground Mount Assembly Step Subreflector Adjustment Step Step Step Feed System Operation Overview Acquiring a Satellite StepPure Noise Signal on Spectrum Analyzer Step Polarization at 45 degrees from Optimum Setting Maximizing Odd Transponders Operation Subreflector Adjustment Overview General Cleaning Electrical Parts Preventive MaintenancePreventive Maintenance Antenna Preventive Maintenance Drive System Voltage Current Checks Step Step Pedestal Mount Bearing Pad Adjustment Preventive Maintenance Jackscrews/Motors Gear Motor/Housing Fill Drain Requirements Service Lube Quantity Andrew