Antenna Troubleshooting Guide For SpaceCom SPAC2A and SPAC3A SkyTerra Network Antennas Version 2.9

Transcription

1 Antenna Troubleshooting Guide For SpaceCom SPAC2A and SPAC3A SkyTerra Network Antennas

2 Table Of Contents Table Of Contents... 2 About this Troubleshooting Guide... 4 SpaceCom Antenna Basics... 4 The Antenna Platform... 4 The Junction Box... 4 Antenna Normal Powerup Behaviour... 5 How to Troubleshoot... 5 Level One Diagnostic... 6 Level Two Diagnostic... 7 Voltages and current draw tests (w/ antenna connected to Junction Box)... 7 Comprehensive Current Draw Test (w/ Antenna Connected To Junction Box)... 7 Antenna Current Draw Table... 7 Cable Continuity Check simplified... 7 Resistance (Co-ax cable integrity cable to antenna and cable to AEU)... 8 Level Three Diagnostic... 9 Tools / Equipment Required... 9 The list of replaceable parts is as follows:... 9 Start by removing first the antenna mount then the dome:... 9 Antenna Platform And Element Array Check Verify Correct Satellite Being Tracked Satellite Acquisition Disconnecting Antenna Element Array Cables Antenna Element Array Cable Test Cross elevation axis (3-axis antenna) explained Cross-elevation axis diagnostic (3-axis antenna only) Changing the cross elevation axis drive belt Elevation Axis Control System Elevation Controller diagnostic (2-axis antenna) Elevation Controller diagnostic (3-axis antenna only) Tilt Rate Sensor Operation (3axis Antenna Only) Tilt Rate Sensor Problem Behavior: Test Of The Tilt Rate Sensor (3 axis only) Replacing The Elevation Axis Drive Belt And The Rate Sensor PCB (3-axis antenna only) Changing the Elevation Axis Drive Belt Aligning the Rate Sensor AGC Voltage Measurement (2 and 3 axis antenna) Changing the PIC16F873 CPU (2 and 3 axis) Changing the Azimuth Axis Drive Belt And Rotary Joint (2 and 3 Axis) The LNA/HPA module assembly Switched Mode Power Supply (SMPS) Changing Out The SMPS And Removing The LNA/HPA Module Re-taping the Dome (2-axis) Re-installing the Dome (3-axis) SpaceCom SkyTerra Antenna Troubleshooting Guide 2

3 Reattach the locking screws and tighten Acronyms SpaceCom SkyTerra Antenna Troubleshooting Guide 3

4 About this Troubleshooting Guide This guide has 2 purposes: It is designed to assist in identifying any problems with the SpaceCom 2 and 3 axis antennas. It is also intended to provide a more detailed technical explanation of how the various components work the idea being that the more familiar one is with how the individual subsystems work and interact, the easier it should be to troubleshoot problems. The guide is divided into a series of diagnostic test suites with each subsequent one going into more detail. SpaceCom Antenna Basics A complete SpaceCom antenna system is composed of two separate hardware components: The antenna platform itself (2 or 3 axis) enclosed in a dome - and the Junction Box (JB). These components are universal in that they will function with both Mitsubishi and Westinghouse Mobile Terminals. The Antenna Platform Inside the dome can be found the antenna element array, the antenna steering/tracking system, the receive (RX) and transmit (TX) electronics including the necessary amplification and power control systems. The onboard TX High Power Amplifier (HPA) system is designed to keep the antenna RF output (EIRP) at 16.0 dbwi. Compensation for attenuation introduced by long cable lengths between the antenna and the JB will be automatically done by the HPA. The antenna is connected to the JB by a co-axial cable using type N connectors on both ends. The Junction Box The JB is the interface hardware between the antenna and the Mobile Terminal (MT). As the antenna requires power separately from the MT (and it cannot be powered from the MT), the JB contains a step-up power converter that converts the 12 VDC into 25 VDC. The 12 VDC may or may not be the same voltage used for powering the MT The JB is connected to the MT Antenna Electronics Unit (AEU) by a co-axial cable using TNC connectors. The JB is not sealed against the environment and must be installed in a weatherproof location. To meet the SkyTerra network requirements, the JB monitors the antenna RF output (EIRP) and will shut down the DC power to the antenna if it detects a problem. The JB shut-down conditions are as follows: The JB detects a positive signal input to the antenna from the MT and that the antenna EIRP is higher than 19.5 dbw. This can be caused by the MT malfunctioning and transmitting too high a signal level to the antenna or it can be caused by a malfunction in the onboard HPA system. In the case of a malfunctioning MT, the appropriate error message should be displayed on the handset. If no such message is displayed on the handset, than it is more likely that the onboard HPA system is malfunctioning. The JB detects that the antenna is transmitting even though there is no TX signal input to the antenna from the MT. The antenna should not be transmitting anything if the MT is not doing so. This faulty condition indicates that there is a malfunction in the antenna s onboard HPA system and will immediately trigger the shut-down preventing the HPA from transmitting further. SpaceCom SkyTerra Antenna Troubleshooting Guide 4

5 The Power Trip LED will be lit up if the JB has shut down the antenna. The JB can only be reset by cycling the 12 VDC input power. The LED will briefly flash when the JB is powered up. The JB contains the necessary filters to ensure that: The RX and TX signals are directed to the MT AEU. The DC power is directed to the antenna. DO NOT CONNECT THE MT AEU TO THE TYPE N ANTENNA PORT ON THE JB. YOU WILL BE FEEDING 25 VDC INTO THE AEU WHICH MAY CAUSE IT TO FAIL. Antenna Normal Powerup Behaviour When powered up, the antenna will first enter the Calibration state where the necessary calibration of the elevation and rate sensors is performed. Following the completion of the calibration process, the antenna will then enter the 360 Azimuth Scan state where it will search for the satellite by locating the strongest GC-S frequency in its on-board list (depending on which satellite is to be tracked). The 360 Azimuth Scan is initially done with the antenna element array at the last known elevation (also using the last known GC-S frequency). If this initial scan is unsuccessful, the antenna will perform a slower azimuth scan at 30 degrees elevation while sampling all of the GC-S frequencies. If the 30 degree scan is unsuccessful, the antenna will repeat the slower scan while at 60 degrees elevation. These 2 scans are repeated until the satellite is acquired. Once the satellite has been acquired, the antenna will enter the Tracking State. In this state, it will finetune the elevation and in the case of the 3-axis version, the cross-elevation axis so that the platform is lined up with the cross elevation axis centered if so equipped. Should the antenna s line-of-sight be blocked for 15 seconds or more, it will enter 360 Azimuth Scan mode to re-acquire the satellite. How to Troubleshoot The antenna does not appear to work properly So where do you start? Start by gathering as much information on the nature and causes of the problem(s). Ask the person who is reporting the problem(s) to provide you with the details. When was the antenna last operating correctly? When was the problem first encountered? What happened to the antenna during that time? Run through a Level One Diagnostic with them. While going through the diagnostic, start relating the problem symptoms to the three signal types: Receive (RX), Transmit (TX) and DC power. Does the problem relate to any one specific signal type? The results of the Level One Diagnostic will provide you with a general picture of the antenna system s health. Use all of the information that you have gathered up to this point to narrow down your troubleshooting list. Run through the Level Two Diagnostic for each item on this list unless the problems are not covered by this diagnostic. Suspected mechanical problems will require you to run a Level Three Diagnostic at this point. The results of the Level Two Diagnostic will give you an overall picture of the electrical current flow throughout the antenna system as well as its performance from an electricity consumption point of view. At this point, you will have narrowed down your troubleshooting list further. You can now run a Level Three Diagnostic on this list or, if the problems appear to be beyond your capacity to fix, contact your SpaceCom repair center and arrange for servicing. SpaceCom SkyTerra Antenna Troubleshooting Guide 5

6 Level One Diagnostic The Level One Diagnostic is the most basic of troubleshooting for a SpaceCom antenna. You do not require any special hardware or tools in order to do this. Check all antenna cable connections. Do this check first as a loose cable will become a problem later on. Can you make a voice call using the MT? Perform this once you have checked out the cable connections. When you place a voice call, are you able to hear the called party clearly? Can they hear you? If you cannot hear the called party clearly and the MT volume level is correct, then the RX portion of the antenna system needs to be debugged. If the called party cannot hear you clearly and the MT volume level is correct, then the TX portion of the antenna system needs to be debugged. Line of sight to the satellite: Are you in a questionable coverage area? Are there any objects (trees, mountains, buildings etc.) that could be between the antenna and the satellite? If possible, re-locate the antenna so that you have a clean line-of-sight. If line-of-sight is suspected as the cause, run the Satellite Acquisition test in the Level Three Diagnostic section. Check the Junction Box (antenna must be connected to it via the coaxial cable) Check to see that the Junction Box Power-trip LED is not lit. If the LED is lit, cycle the input DC voltage to the JB by turning it off and back on again). If the Junction Box LED is continuously lit, check the MT handset. If no error code is displayed on the handset, then the antenna or junction box is likely at fault. The LED will briefly flash when first powered up. Note: Disconnecting and reconnecting the cable from the Junction Box to the antenna with the Junction Box powered up may trigger the Power-trip circuit causing the LED to light up. This is part of the Junction Box s normal activities and does not indicate a problem. Listen to the antenna what sounds does it make (or not make) when powered up. There should be some detectable vibrations when the antenna is acquiring the satellite if you place your hands on the antenna dome. Does the antenna make any unusual grinding or slipping noises? Observe the RSSI level on the handset. Does it reach a relatively stable level ~2 minutes after power-up? The indicated RSSI will vary from MT to MT and unfortunately cannot be treated as a reliable and accurate indication of the actual signal strength. It does however provide clues as to the antenna s tracking ability. While the antenna is in seek mode, the indicated signal strength should vary as the antenna is searching for the satellite. Once the satellite has been acquired and the antenna enters tracking mode, a relatively stable signal strength should be displayed. Check that the plastic retaining block is installed at the base of the antenna mount. This is shown in the antenna user guide document. Verify the integrity of the installation by checking that all screws, nuts and bolts are in place and sufficiently tightened. SpaceCom SkyTerra Antenna Troubleshooting Guide 6

7 Level Two Diagnostic Note: this requires a multimeter able to read DC V and A, continuity and resistance Voltages and current draw tests (w/ antenna connected to Junction Box) DC voltage is supplied to the Junction Box by means of a pair of wires one red and one black with the red (+) wire carrying the current into the JB and the black (-) wire carrying the return current from the JB. The black wire has the same electrical potential (voltage) as the entire metal structure and cable screens of the terminal so therefore the metal structures of the antenna and JB have this same potential as well. Check that: Input voltage going into the JB is V DC Output voltage from the JB to Antenna ~25 V DC Input current going into the JB ~1.2 A DC on the Red (+) lead. If the MT is connected to the JB via the coaxial cable, the MT and JB will be electrically grounded together. If you measure the return DC current in the Black (-) lead to the JB the reading may be different (i.e. have a lower value) from the forward current (Red +) lead. Comprehensive Current Draw Test (w/ Antenna Connected To Junction Box) Cycle the power to the Junction Box. Observe the current draw of the JB as the antenna goes through each state. NOTE:GIVEN THE RELATIONSHIP BETWEEN VOLTAGE AND CURRENT DRAW, IF YOUR POWER SUPPLY TO THE JUNCTION BOX IS LESS THAN 13.7 V DC, YOU CAN EXPECT TO SEE HIGHER CURRENT DRAW VALUES THAN WHAT IS LISTED ON THE CURRENT DRAW TABLE. ON THE OTHER HAND, IF YOUR POWER SUPPLY IS GREATE THAN 13.7 V DC, THEN YOU CAN EXPECT TO SEE LOWER CURRENT DRAW VALUES. Antenna Current Draw Table Antenna State (3-axis) Typical Current 13.7 V DC Input (Amps) Maximum Normal Current Draw Including Active Tracking (Amps) Powerup 1.0 A (+/- 0.2 A) 1.5 A Initialization 0.7 A (+/- 0.2 A) 1.5 A Azimuth Scan 1.2 A (+/- 0.2 A) 1.5 A Track 0.7 A (+/- 0.2 A) 1.5 A TX and Track 1.3 A (+/- 0.2 A) 2.1 A Antenna State (2 axis) Typical Current 13.7 V DC Input (Amps) Maximum Normal Current Draw Including Active Tracking (Amps) Powerup 0.75 A (+/- 0.2 A) 1.0 A Azimuth Scan 0.75 A (+/- 0.2 A) 1.0 A Track 0.65 A (+/- 0.2 A) 1.0 A TX and Tracking 1.1 A (+/- 0.2 A) 1.6 A Cable Continuity Check simplified With the Junction Box connected and DC power enabled, check the JB output voltage at the end of the cable that plugs into the antenna it should be ~25 VDC. This also represents a basic continuity of the JB to antenna cable. SpaceCom SkyTerra Antenna Troubleshooting Guide 7

8 Note: a separate check of the continuity should be done on the Junction Box to AEU cable. Normally this cable is shorter enough to do an actual continuity check using the multimeter. Resistance (Co-ax cable integrity cable to antenna and cable to AEU) Ensure that the cable is not grounding out. Check the resistance between the center conductor of the cable and the exterior portion (rotating part) of the cable connector. There should be a high resistance indicated. If low or nonexistent resistance, the cable should be checked for the damage that is compromising its integrity and either repaired or (preferably) replaced. SpaceCom SkyTerra Antenna Troubleshooting Guide 8

9 Level Three Diagnostic Notes: Only perform these tests if you have replacement tape for the antenna dome (2-axis antenna only) Only perform these tests if you are comfortable with removing the antenna dome (all antennas) Keep the exposure of the antenna components to the elements (i.e. rain, dust, salt spray) at a minimum. NOTE: THE ANTENNA IS COMPOSED OF SEVERAL MODULAR COMPONENTS. THE FOLLOWING DIAGNOSTIC PROCEDURES ARE TO DETERMINE THOSE MODULES THAT ARE SUSPECTED OF FAILURE. MODULE AND SUB-MODULE REPAIRS SHOULD ONLY BE CARRIED OUT BY QUALIFIED SPACECOM SERVICING PERSONNEL. ATTEMPTING MODULE AND SUB-MODULE REPAIRS CAN AFFECT THE SPACECOM WARRANTY. USE COMMON SENSE: IF THE PROBLEM CAN BE TRACKED TO A GIVEN MODULE, CONFIRM YOUR FINDINGS WITH A QUALIFIED SPACECOM SERVICE PERSON AND THEN SEND THE AFFECTED MODULE IN FOR REPAIR. IF MORE THAN ONE MODULE IS DEFECTIVE, OR IF YOU ARE UNSURE OF THE AFFECTED MODULE(S), SEND THE ENTIRE ANTENNA TO A QUALIFIED SPACECOM SERVICE FACILITY FOR REPAIR. Tools / Equipment Required TORX T10 screwdriver Needlenose Pliers PZ1 screwdriver 5 and 5.5 mm Metric wrenches. #1 Phillips Screwdriver PZ2 screwdriver A good quality, calibrated MultiMeter 1.5 mm Allen Key A good quality, clean DC power source 3.0 mm Allen Key When re-assembling, turn all bolts Counter ClockWise (CCW) holding the nut at the threaded end until the nut clicks. Then turn the bolt ClockWise (CW) to tighten. The list of replaceable parts is as follows: Antenna Element Array Cross Elevation Unit (3-axis marine antenna only) Elevation controller PCB (P00005) Tilt and rate sensor PCB (P00024) (3-axis marine antenna only) PIC16F873 CPU chip SMPS PCB (P00015) Rotary Joint Contactor HPA (P00402), LNA & Receive/Tracking module (AS00008) Junction Box (P00401) covered in the Level 2 Diagnostic section Start by removing first the antenna mount then the dome: Remove the tape holding the two portions of the antenna dome together (2-axis antenna only) Remove the locking screws and separate the antenna dome (3-axis antenna only) by unscrewing the antenna dome off CCW (as seen from the TOP of the antenna dome) Trace the propagation path of the signals based on your analysis either RX, TX or DC power. Perform a basic visual inspection of the antenna components. Is anything loose/bent/damaged/scorched? Are any components radiating excess heat? SpaceCom SkyTerra Antenna Troubleshooting Guide 9

10 Remove Locking Screws (3) Locate the alignment markers on the top and bottom of the dome Figure 1 3-Axis Dome In Locked Position Unscrew this direction Unscrew (CCW) the Antenna top until the top alignment marker is at the center of the bottome one Figure 2 3-Axis Dome In Unlocked Position SpaceCom SkyTerra Antenna Troubleshooting Guide 10

11 Antenna Platform And Element Array Check Is the antenna element array intact? Check the integrity of the solder joints for the RX and TX wires. Cycle power to the antenna. On re-energizing, the antenna should go through its seek, acquire and track states. Does the antenna platform rotate completely on powerup? does it follow the correct powerup behavior as described below? 2-axis Powerup Behaviour: On power up, the antenna element array will be angled at minimum elevation ( the antenna element array appears to go to minimum elevation and vibrate ). The vibrating is produced by the stepper motor and is not harmful to the antenna. After ~30-45 seconds, the antenna element array should be set to its last known elevation angle. The antenna should then perform an azimuthal (horizontal) CW sweep. If the satellite is not detected, then the antenna will perform the azimuthal sweep at 60 and 30 degrees elevation. Once the satellite has been acquired, the antenna will lock on to the azimuth position then perform a fine tuning operation along the elevation (vertical) axis. 3-axis powerup behaviour: On power up, the antenna element array will be angled at maximum elevation ( the antenna element array appears to flip up ). After ~30-45 seconds, once the elevation sensor has been calibrated, the antenna element array should be lowered to its last known elevation angle. The antenna should then perform an azimuthal (horizontal) sweep CCW with the cross elevation axis set at maximum lefthandside deflection. If the satellite is not detected, then the antenna will perform the azimuthal sweep at 60 and 30 degrees elevation. Once the satellite has been acquired, the antenna will lock on to the azimuth position then perform a fine tuning operation along the elevation (vertical) axis as well as a cross-elevation axis fine tuning. Observe the physical condition of the antenna platform. Is anything damaged/bent/broken? Does the platform move smoothly throughout its axes? are the drive belts intact? are they too lose (slipping)? Are all wires connected? Has anything worked itself loose? Verify Correct Satellite Being Tracked Ensure that antenna CPU is correct (M1 or M2 GC-S frequencies).if necessary, replace the CPU and perform the powerup check as listed above. Check that the CPU is inserted NOTCH SIDE UP. Satellite Acquisition Verify that the antenna can acquire the target satellite. With the cover off, power up and observe. Confirm line of sight. Given your location area, check that the satellite antenna elements are tracking in the approximate line-of-sight elevation and direction for your current position. Confirm re-acquisition of the target satellite: using your hands or another RF-blocking object, place the object or your hands in front of the antenna element array long enough for the antenna to enter search mode (azimuth turn) Disconnecting Antenna Element Array Cables Use needlenose pliers to disconnect the two identical flexible co-ax cables from the LNA/HPA module. Be careful as these are not replaceable and the cable is not soldered to the connector. Apart from the cables, the antenna element array has no user-serviceable parts and can only be replaced as a unit. 2 bolts are used to attach the Antenna Element Array to the antenna frame. The bolts are located in the center of the face (the front of the antenna element array) Antenna Element Array Cable Test Test the continuity from the cable connector to the solder point on the antenna element array. SpaceCom SkyTerra Antenna Troubleshooting Guide 11

12 Cross elevation axis (3-axis antenna) explained The cross elevation axis moves +/- 30 degrees left or right from the center point. At the maximum travel (+/-30 degrees) setting, the appropriate left or right pin is grounded out. The grounding of either on of the two end-stop pins causes the antenna to travel about the azimuth (horizontal) axis until the electronic (beam squint) steering causes the cross elevation axis platform to enter a non-maximum travel setting. The azimuth axis stepper motor then moves a known number of steps so that the antenna platform is positioned in such a way that the cross elevation axis is centered. The electronic (beam squint) steering continuously works to determine the antenna element array position that minimizes the AGC voltage. Once the antenna has entered a AGC minimized state, it will hibernate after a while and will not adjust the azimuth axis platform until a +/- 30 degree change in the cross-elevation axis has occurred. Cross-elevation axis diagnostic (3-axis antenna only) Once the antenna has locked onto the satellite, physically rotate the antenna about the azimuth (horizontal) axis. Hold the antenna at the base of the dome and rotate it left or right (check by testing both left and right cases). After a ~30 degree departure from the current position, the antenna should respond to the change by maintaining satellite track using the cross-elevation axis system. Check that the cross elevation axis system reaches the maximum travel position and that when the end-stop switches are contacted, that the azimuth axis system takes over to maintain the satellite track. Cross Elevation Axis Stop Pins Ground Pin Cross Elevation Axis Motor Figure 3 Cross Elevation Axis System SpaceCom SkyTerra Antenna Troubleshooting Guide 12

13 Changing the cross elevation axis drive belt Loosen the 4 cross elevation drive motor bolts. Slide the motor forwards (towards the Antenna Element Array) to loosen the belt. If the belt cannot be removed at this point, loosen the locking hub with the 1.5 mm Allen Key and disengage the gear from the motor shaft. Re-install the gear after removing the belt. Thread the new belt through the antenna element array gear first. Then assemble the cross elevation axis motor, gear and locking hub. Make sure that the locking hub is secured tightly Re-install (but do not tighten) the cross elevation axis motor mounting bolts. Tighten up the belt by pulling the drive away from the antenna element array. You do not have to excessively tighten the belt just take up the slack so that the belt does not slip. When the belt is tensioned up, tighten the cross elevation axis motor mounting bolts. Cross Elevation Axis Drive Belt Antenna Element Array Gear Locking Hub Cross Elevation Axis Motor Mounting Bolts (4) Cross Elevation Axis Motor Figure 4 Cross Elevation Axis Components SpaceCom SkyTerra Antenna Troubleshooting Guide 13

14 Elevation Axis Control System The elevation axis control system is different between the 2 and 3-axis antennas. In the 2-axis model, the elevation control is done directly by the CPU on the LNA/HPA Module there is no separate elevation controller. In the 3-axis model, the task is done by the Elevation Controller PCB with inputs from the Tilt Rate Sensor and the CPU. The CPU in this case provides the minimum ACG voltage value that the Elevation Controller uses as a reference whenever it has to re-align the Antenna Element Array. Elevation Controller diagnostic (2-axis antenna) Once the antenna has locked onto the satellite, physically raise either the front or rear of the antenna by 45 degrees or more. Using your hands or another RF-blocking object, place the object or your hands in front of the antenna element array long enough for the antenna to enter search mode (azimuth turn). Observe that the elevation angle of the antenna element array has been adjusted to compensate for the raising of the antenna. Elevation Controller diagnostic (3-axis antenna only) Once the antenna has locked onto the satellite, physically rotate the antenna about the elevation (horizontal) axis. The antenna should immediately respond to the change by re-acquiring the satellite using the elevation (horizontal) axis system. Elevation Controller Mounting Bolts Figure 5 Elevation Controller Elevation Installed Controller On A installed 3-axis Antenna on a 3-axis antenna SpaceCom SkyTerra Antenna Troubleshooting Guide 14

15 Tilt Rate Sensor Operation (3axis Antenna Only) The Tilt Rate Sensor measures absolute elevation relative to a horizontal plane. The inside cavity of the sensor assembly is filled with a viscous non-conducting fluid. As the sensor is tilted, the fluid level will change and will result in a different sensor output. The combination of the Tilt Rate Sensor and the cross elevation axis system endows the antenna with extremely accurate tracking of the satellite while the ship is in heavy seas. Elevation Axis Gear Hub Connection to Elevation Controller PCB Tilt Sensor Figure 6 Tilt Rate Sensor Tilt Rate Sensor Problem Behavior: Tilt Rate Sensor failures will manifest themselves in 3 possible ways: If the rate sensor has completely failed, there will be no response to changes in the antenna platform s orientation along the elevation axis. If the Tilt Rate Sensor is providing too high a voltage, this will result in the tracking system thinking that is moving too fast. The system will attempt to compensate by slowing down the movement of the antenna platform. If the Tilt Rate Sensor is providing too low a voltage, this will result in the tracking system thinking that it is moving too slowly. The system will attempt to compensate by speeding up the movement of the antenna. This will make the antenna tracking system unstable and will result in poor tracking resolution as the antenna will be continuously over-compensating. SpaceCom SkyTerra Antenna Troubleshooting Guide 15

16 Test Of The Tilt Rate Sensor (3 axis only) This straightforward test consists of observing the reaction of the antenna element array to simulated pitching of a vessel motion that the antenna tilt rate sensor is designed to counteract. With the dome removed, power up the antenna in a location where it is able to acquire and track the satellite. Once the antenna is actively tracking the satellite, slowly pitch the antenna base up and down as illustrated below Antenna Element Array is always Tracking Satellite when the Tilt Rate Sensor is functioning normally Antenna base at rest (as seen sideways) Figure 7 Tilt Rate Sensor Testing Antenna base ptiched downwards Antenna base ptiched upwards Observe the antenna platform movement along the elevation axis. The antenna should smoothly keep on tracking the satellite. A malfunctioning Tilt Rate Sensor will exhibit the problem behaviors described in the preceding section. SpaceCom SkyTerra Antenna Troubleshooting Guide 16

17 Replacing The Elevation Axis Drive Belt And The Rate Sensor PCB (3-axis antenna only) Using needlenose pliers, disconnect the Antenna Element Array RX and TX leads from the LNA/HPA Module. The lead connections are friction fit and must be handled carefully. HPA/LNA Module RX and TX Leads from Antenna Element Array Grab here with pliers Figure 8 Antenna Element Array RX and TX Leads SpaceCom SkyTerra Antenna Troubleshooting Guide 17

18 Disconnect the Module from the antenna frame as described in the Changing Out The SMPS And Removing The LNA/HPA Module section on page 34. Remove the 4 nuts/bolts securing the Elevation Axis Motor Elevation Motor Mounting Bolts (4) Figure 9 - Elevation Motor Installation SpaceCom SkyTerra Antenna Troubleshooting Guide 18

19 Loosen the Rate Sensor PCB screw so that the Elevation Axis Motor and shaft can be separated from the gear hub and Tilt Rate Sensor PCB Remove Elevation Axis Motor from Gear Hub and Rate Sensor PCB Elevation Axis Gear Hub Rate Sensor PCB Screw (center) Figure 10 Removing The Tilt Rate Sensor SpaceCom SkyTerra Antenna Troubleshooting Guide 19

20 Remove the elevation Controller Cover located on the RHS of the antenna frame when viewed from the front of the antenna. Cable Binders Elevation Controller Cover Figure 11 Tilt Rate Sensor Cabling Cut the cable binders so that the Rate Sensor PCB cables are free and the Rate Sensor PCB can be disconnected from the Elevation Controller. SpaceCom SkyTerra Antenna Troubleshooting Guide 20

21 Re-install new Rate Sensor PCB with the Elevation Axis gear hub and drive belt. Ensure that the Elevation Axis drive belt is loose enough so that the Rate Sensor PCB can be aligned. Figure 12 Installed New Rate Sensor PCB Elevation Axis Drive Belt Elevation Axis Gear Hub Install New Rate Sensor PCB SpaceCom SkyTerra Antenna Troubleshooting Guide 21

22 Connect the Rate Sensor PCB cables to the Elevation Controller. Replace cut cable holders. Ensure that the cables do not rub against the Antenna Frame Arm Correctly threaded Rate Sensor PCB cables with new cable holders Figure 13 Correct Threading Of Rate Sensor PCB Cables SpaceCom SkyTerra Antenna Troubleshooting Guide 22

23 Changing the Elevation Axis Drive Belt Loosen the Cross Elevation Axis Bolt Assembly (Bolt head and nut). Cross Elevation Axis Bolt Head Cross Elevation Axis Gear Hub Self Tightening Nut Washer Washer Bearing (inside) male and female (2 parts) Nut for Cross- Elevation Bolt Antenna Frame Arms Remove the Elevation Axis drive belt from the Cross Elevation Axis Bolt Assembly. Remove the Elevation Axis drive belt from the Elevation Axis gear hub. Slip the new drive belt over the Cross Elevation Axis Bolt Assembly gear and re-install the Cross Elevation Axis Bolt Assembly. Do not tighten it yet. Slip the new drive belt over the Elevation Axis gear Hub and re-assemble it with the Rate Sensor PCB and Elevation Axis motor. Install and tighten the Elevation Axis motor bolts. Aligning the Rate Sensor Once you have replaced the Elevation Axis Drive Belt and/or Rate Sensor, you must correctly align the Rate Sensor. At lowest Elevation angle, the Rate Sensor is vertical (with the Green PCB facing the Module) To set the Lowest elevation angle, ensure that the bottom of the antenna element array is touching both antenna frame arms. SpaceCom SkyTerra Antenna Troubleshooting Guide 23

24 At Minimum Elevation, the bottom of the Antenna Element Array touch the Antenna Frame Arms Rate Sensor at 90 (Vertical) Figure 14 Rate Sensor At 90 elevation Tighten the Rate Sensor PCB Screw Rate Sensor at 90 with Antenna Element Array at minimum elevation Figure 15 Rate Sensor At 90 (Rear View) SpaceCom SkyTerra Antenna Troubleshooting Guide 24

25 Tension up the elevation Axis Drive belt. Insert the needlenose pliers between the cross elevation axis motor frame and the metal part of the rate sensor. Insert Pliers here Figure 16 Pliers Location For Tensioning Elevation Axis Drive Belt SpaceCom SkyTerra Antenna Troubleshooting Guide 25

26 Take up the drive belt slack by pushing down on the cross elevation axis motor hub (in the direction of the arrow in fig.) The drive belt does not need extreme tension so once you have taken up the slack in the drive belt, tighten the cross elevation axis bolt assembly Tighten up Cross Elevation Axis Bolt Head (CW) Press downwards in this direction to tension up drive belt Pliers correctly inserted Figure 17 Tightening Cross Elevation Axis Bolt SpaceCom SkyTerra Antenna Troubleshooting Guide 26

27 Confirm the Rate Sensor alignment. Set the Antenna Element Array at 90 deg. The Rate sensor should be at a 45 deg elevation. If not, loosen the cross elevation axis bolt assembly, the rate sensor PCB screw, re-align the rate sensor with the antenna element array at min elevation. Elevation Axis Drive Belt Elevation Axis Motor Tilt Rate Sensor at 45 elevation Figure 18 Correctly Aligned Tilt Rate Sensor SpaceCom SkyTerra Antenna Troubleshooting Guide 27

28 Antenna Element Array at 90 elevation Elevation Axis Drive Belt Tilt rate sensor at 45 elevation Elevation Axis Drive Motor Figure 19 Rearward View Of Correctly Aligned Tilt Rate Sensor SpaceCom SkyTerra Antenna Troubleshooting Guide 28

29 AGC Voltage Measurement (2 and 3 axis antenna) Measuring the AGC voltage with the antenna tracking the satellite will confirm that the antenna is actually receiving the satellite signals There are 2 testcases that can be done. The first one is to measure the AGC voltage with the antenna tracking the satellite. The second one should be run if the antenna is not able to acquire and track the satellite. The Test Steps for the first testcase are: Using a multimeter set on V DC, measure the AGC voltage from Pin 2 (second pin on the LHS using the + red multimeter lead) of the antenna CPU. Ground the ve (black) lead of the multimeter to the antenna frame. As a general rule of thumb, the reading should be less than ~ 2.8 V DC. Given the inverse relationship between RSSI and AGC voltage, the lower the ACG voltage, the better the RSSI level. The second testcase requires the following extra steps: Locate the antenna so that it has line-of-sight to the satellite. Take the azimuth axis motor off-line by removing the Azimuth Axis Drive Belt. See the Changing The Azimuth Axis Drive Belt section for instructions on how to do this. Carefully rotate the antenna through 360 observing the AGC voltage while doing so. You should see the AGC voltage drop when the antenna is approaching line of sight. An AGC level higher than 2.8 V DC and an antenna that is unable to acquire and track the satellite once the azimuth axis motor is back on-line indicates a reception problem most likely in the LNA portion of the Module. Ground negative (Black) Multimeter Probe on this metallic surface Location of Pin #2 CPU Installed Notch Side UP Figure 20 Checking The AGC Voltage SpaceCom SkyTerra Antenna Troubleshooting Guide 29

30 Changing the PIC16F873 CPU (2 and 3 axis) Carefully lift the CPU up out of its socket as shown. Avoid bending the pins. Chip Changing Tool Inserted Under CPU Slide Tool under CPU and CAREFULLY lift it up CPU Chip Installed NOTCH SIDE UP Figure 21 CPU Chip Removal Disconnect this lead before removing CPU SpaceCom SkyTerra Antenna Troubleshooting Guide 30

31 CPU and Chip Changing Tool. CPU CHIP NOTCH Figure 22 CPU and CPU Removal Tool SpaceCom SkyTerra Antenna Troubleshooting Guide 31

32 Changing the Azimuth Axis Drive Belt And Rotary Joint (2 and 3 Axis) Remove the hex bolts attaching the antenna mount to the antenna base Remove the rubber weatherseal Remove the 2 phillips bolts attaching the base of the antenna dome to the antenna frame BE CAREFUL NOT TO DROP THE ANTENNA FRAME AND ELECTRONICS. DO NOT STAND THE ANTENNA FRAME UPSIDE DOWN ON THE HPA PINS N Connector Phillips Bolts holding antenna dome base to antenna frame SpaceCom SkyTerra Antenna Troubleshooting Guide 32

33 The Azimuth motor and drive belt are now accessible Azimuth Motor Mounting Bolts Azimuth Axis Drive Belt Type N Connector Rotary Joint Bolts N-Connector Screws Figure 23 Aximuth Axis Drive System Loosen the Azimuth motor mounting bolts (4 bolts - M2.5) Remove the N-connector screws (4 screws Torx M3) Remove the N-connector. Note the condition of the silver/graphite contactor at the end of the spring. If worn or damaged, replace SpaceCom SkyTerra Antenna Troubleshooting Guide 33

34 Graphite/silver contactor Spring N-Connector Figure 24 N Connector w/ Silver/Graphite Contactor Remove the 4 screws (Torx M4) holding the flange to the rotary joint (the large gear). Run the new drive belt around the Azimuth motor shaft gear (small plastic gear) then around the rotor gear (the large gear). Re-attach the flange using the 4 M4 screws. Make sure that you line up the screw holes Carefully insert the N-connector. If the silver/graphite contactor is installed correctly, you should feel a slight spring action when you attach the 4 M3 screws. Tension up the drive belt at the Azimuth motor shaft. Tighten the Azimuth motor mounting bolts Check that the antenna will rotate freely and that the belt is tight enough not to slip. Do not overtighten as it will cause excess fricion along with shaft and belt wear SpaceCom SkyTerra Antenna Troubleshooting Guide 34

35 The LNA/HPA module assembly Removing the LNA/HPA module assembly Remove the Antenna Element Array and the SMPS cover and (3-axis only) the elevation controller cover Locate the 3 (2 axis) or 5 (3-axis) screws holding the Module to the antenna frame CPU Socket PIC16F873 Stepper Motor Driver PIC J3 (9 Pins) J4 (4 Pins) J5 (6 Pins) J2 (5 Pins) J1 (4 Pins) Front of HPA SMPS Cable Port 5 (3-axis) or 3 (2-axis) Bolts securing the HPA/LNA Module to the antenna frame Figure 25 LNA/HPA Module Looking at the back of the LNA/HPA module assembly, the connections present along the top from left to right are: J1 - J2 - J5 - J4 - J3 Connection Purpose Pins J1 To Elevation Control (3-axis only) 4 J2 To LNA PCB 5 J3 To SMPS 9 J4 To Cross Elevation (3-axis only) 4 J5 Not Used 6 SpaceCom SkyTerra Antenna Troubleshooting Guide 35

36 LNA PCB (P00013) Ceramic Filter Assembly CPU Socket PIC16F873 RX Input Connector HPA PCB (P00402) TX Output Connector Stepper Motor Driver PIC (Hidden) J3 (9 Pins) J4 (4 Pins) J5 (6 Pins) J2 (5 Pins) J1 (4 Pins) Figure 26 LNA/HPA Module As Seen From THe Back (LNA PCB Up) Disconnect the J1 through J5 connections on the top of the LNA/HPA module assembly. Disconnect the input cable from the rotary joint Disconnect the cable to the SMPS on the front of the module. *****IMPORTANT: DO NOT REST THE LNA/HPA MODULE ASSEMBLY ON THE CERAMIC FILTERS (RAISED WHITE RECTANGLE ON THE BACK OF THE LNA PCB. SpaceCom SkyTerra Antenna Troubleshooting Guide 36

37 Switched Mode Power Supply (SMPS) From the front of the antenna (looking at the Antenna Element Array), the SMPS is located on the Lefthand side. SMPS PCB Mounting Bolts Connection To Elevation Stepper Motor Elevation Axis Stepper Motor and Drive SMPS Grounding Figure 27 SMPS w/ Cover Removed Changing Out The SMPS And Removing The LNA/HPA Module Remove the bolts holding the SMPS cover to the antenna frame NOTE: The countersunk bolts are used to attach the cover to the bottom of the antenna frame. Disconnect the cables going from the Module to the SMPS. Remove the bolts (3) securing the Module to the antenna frame SpaceCom SkyTerra Antenna Troubleshooting Guide 37

38 Cable to Roray Joint HPA) Plug J3 Wire Guide Module Mounting Bolts Figure 28 Disconnecting The SMPS Disconnect the cable going from the HPA to the Rotary Joint through the Antenna Frame SpaceCom SkyTerra Antenna Troubleshooting Guide 38

39 Disconnect This Cable Figure 29 Rotary Joint Cable To Disconnect Unscrew the white plastic wire guide attached to the antenna frame and holding the wiring from port J3 (9 pins) Disconnect the cable going from the SMPS to the HPA (4 wires) SpaceCom SkyTerra Antenna Troubleshooting Guide 39

40 Cable from Module to SMPS Disconnect Here Figure 30 Module - SMPS Cable To Disconnect Disconnect the SMPS grounding to the antenna frame Remove the bolts attaching the SMPS to the antenna frame Disconnect the wires going to the Elevation Motor Re-install the new SMPS following the reverse of the removal instructions SpaceCom SkyTerra Antenna Troubleshooting Guide 40

41 Re-taping the Dome (2-axis) Line the middle of the tape up with the antenna dome joint. Half of the tape should be above the joint with the other half below. Start winding the tape before (to the left hand side of) the warning label on the bottom center rear of the antenna dome. Wind 2.5 times around the dome joint. Stop winding after (to the right hand side of) of the warning label on the bottom of the antenna dome. Start Taping Here Half of Tape above antenna dome joint Stop Taping Here Top Half Of Antenna Dome Wind 2.5 X Around Antenna Dome The other half below Warning label Location Bottom Half Of Antenna Dome SpaceCom SkyTerra Antenna Troubleshooting Guide 41

42 Re-installing the Dome (3-axis) Ensure that the antenna weatherseal (red-orange rubber O-ring around the base of the antenna) is intact and in place Re-align the antenna dome notch with the antenna base notch Turn in this direction Place the Antenna dome so that the top alignment marker is at the center of the bottome one. Then turn (CW) SpaceCom SkyTerra Antenna Troubleshooting Guide 42

43 Screw on the antenna dome CW as seen from the top until it clicks If the alignment is correct, the locking screw holes should be lined up. Top and Base of Antenna Dome are correctly attached when the locking screw holes line up Reattach the locking screws and tighten SpaceCom SkyTerra Antenna Troubleshooting Guide 43

44 Acronyms RSSI Received Signal Strength Indication RX Receive TX Transmit CCW Counter Clockwise (turn from right to left) CW Clockwise (turn from left to right) LED Light Emitting Diode AGC Automatic Gain Control AEU Antenna Electronics Unit MT Mobile Terminal EIRP Effective Isotropic Radiated Power TNC Threaded Navy Connector HPA High Power Amplifier LNA Low Noise Amplifier SpaceCom SkyTerra Antenna Troubleshooting Guide 44