VSAT for Marine

RSS Feed Homepage

What Is a Satellite Stabilizer?
2007-08-27 04:03:00
A satellite stabilizer allows a moving vessel (such as a boat or a semi-submersible drilling structure, to receive and send a signal to a geo-stationary satellite. The parabola sits on top of a system of motors and counter-balances that allow the parabola to swing 360° horizontally (azimuth) and 180° vertically (elevation). All of the electronics for the outdoor unit (ODU) also sit on the robotic stabilizer. Because of this, power leads and other cables cannot be run direct to the electronics; power is supplied through a series of slip-rings.Because of its large mass, the stabilizer relies on being balanced in perfect equilibrium to prevent excessive wear and tear on the positioning motors.The stabilizer, once locked onto the signal of its assigned satellite, will ensure that the antenna parabola stays positioned on that one point in the sky despite the movements of the vessel to which it is attached.The stabilizer is connected to an indoor unit (usually situated in the radio roo...
More About: Satellite

Finding Satellite
2007-08-27 04:02:00
Finding a satellite's position in the sky from a fixed position is easy when you know these things:The satellite's longitude. (Because it has to be on the equator, the latitude must always be 0°).The elevation of the satellite relative to the horizon.The azimuth of the satellite relative to true north.This is fine for fixed applications, where this is a one-time job that takes a few minutes with a compass and a wrench. However, I am concerned here with providing continuous access to a satellite from a moving vessel. Here, I need to find the satellite continuously, every time the vessel moves. To do this, there are a few more things I need to know:The heading of the vessel (where is it pointing relative to true north)The latitude and longitude of the vessel (where is it on the surface of the earth)The pitch of the vessel (elevation angle relative to the bow-aft line of the vessel)The roll of the vessel (elevation angle relative to a line running port to starboard on the vessel...
More About: Satellite

DAC-97 Displays “Remote not responding”
2007-07-12 05:41:00
Either the RS422 communications link with the antenna has failed or the pedestal control unit has failed. For Conscan equipped systems observe if the disk sensor light on the Conscan PC Board is flashing. A flashing light indicates the communication from the PCU to the ACU is functioning.Verify the operation of the PCU if possible by using a handheld ASCII terminal connected to the interface cable at the pedestal multiplexer. Verify the RS422 signal levels and connections.Using a spectrum analyzer observe the 1.1 and 1.5 MHz Pedestal M&C carrier signals on the RX IF cable. Hold the DAC-97 RESET, key down and observe the 1.5 MHz signal is a steady high frequency of 1.525 MHz. Release the RESET key and the signal should occasionally be seen switching to 1.475 MHz. this indicates the base Multiplexer is transmitting to the PCU.
More About: Displays , Mote

Open Loop Motor Test
2007-07-12 05:39:00
The DAC-97 provides a means for driving each individual torque motor to test that motors functionality.By driving each axis and observing the resulting motion of the antenna, a coarse operational status of the motor and motor driver can be established.To manually drive the motors, select the REMOTE COMMAND window on the DAC-97. key in “.94 ENTER” (note the decimal point). “^0000” should appear in the command window.To drive the Cross Level motor, key in 1064, 1128 or 1192 to drive the Cross level axis left, off and right respectively.To drive the Level motor, key in 2064, 2128 or 2192 to drive level axis forward, off or back.To drive the Azimuth motor, key in 3064, 3128 or 3192 to drive the Azimuth axis CW, off or CCW.
More About: Motor , Open , Test , Loop

Reference Sensor Monitoring
2007-07-05 05:05:00
To monitor the reference sensors, select the REMOTE COMMAND window on the DAC-97. key in “.118 ENTER” (note the decimal point). “v0000” should appear in the command window. Press the MODE key once more to display the REMOTE MONITPR window. The lower display will show “v” and three 4 digit decimal number.The numbers represent the Cross-Level and level Tilt Sensor output and the Azimuth home flag respectively. The nominal display is 2048 for the Tilt sensors and either 0020 0r 4050 for the home flag.The Cross-Level Tilt display should decrease when the antenna is tilted to the left and increase when tilted to the right. The level tilt display should decrease when the antenna is tilted forward and increase when tilted back.The Home Flag display will show 4050 when the home flag magnet is away from the sensor and 0000 when the home flag magnet is under the sensor. The display changes are static and remain displaced asa long as the level platform is disturbed or the home flag...
More About: Reference , Monitoring , Refer

Monitoring activity current consumption of motors
2007-07-05 05:02:00
The DAC-97 provides a means for monitoring the position error of the antenna for diagnostic purpose. If this error excessive, it indicates external forces are acting on the antenna. These forces may be the result of static imbalance, excessive bearing friction, cable binding, or wind loading.To view the position error, select the REMOTE COMMAND window on the DAC-97 by pressing the MODE key seversl times. Key in “.120 ENTER” (NOTE THE DECIMAL POINT). “X0000” should appear in the command window. Press the MODE key once more to display the REMOTE MONITOR window. The lower display will show “iv” and three 4 digit hexadecimal numbers.The numbers indicate Cross Level, Level and Azimuth errors at a resolution of 1 part in 65536 or 0.0055 degrees. For example a display like “iv FFFF 0001 FFFD” indicates the Cross Level error is -.005 degrees, the level error is +.005 degrees and the Azimuth error is -.016 degrees. The normal range of these numbers is FFF0 to 000F and they t...
More About: Motors , Current , Monitoring , Consumption

Dac Input Specifications
2007-07-02 09:59:00
These are RF tracking input, RS 232 monitor and control interface, NMEA interface, and external AGC input specifications :
More About: Input

Ready to Install
2007-07-02 08:56:00
These are the two autotrack VSAT antenna dome that will be installed on the barges. Unlike rig, barge has to use Autotrack VSAT antenna because his body is floating on the sea.The Autotrack Vsat antenna will be used onboard barges and it will have to be able to provide uninterrupted satellite usage while under a variety of motion.Here are 3 points of principle operation of our autotrack VSAT system :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 barge/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.
More About: Ready

Troubleshooting and Repair
2007-06-26 02:21:00
4 aspect to do troubleshooting and repair the "SeaTel" autotrack VSAT :Test equipment System block diagramTest pointsIsolate the problemTest equipmentTest equipment that needed :VoltmeterSpectrum analyzerOscilloscopeSystem block diagramHere are the component function in the system block diagram :ADE componentBDE componentsPower and signal flowADE componentADE component consists of :Pedestal componentsStabilization componentsRF (Radio) equipmentBDE componentsBDE Component consists of :Antenna Control UnitTX/RX Splitter, modem, Multiplexer, Computer and other ancillary equipmentTVRO splitter/matrix switch, satellite receiver/IRD, modulator, standards converter, combiner amp and other ancillary equipment.Power and signal flowPower and signal flow consists of :AC power distribution in the antennaPedestal power supplyRF signals IF signal ADE-BDEPedestal and Radio M&C signals (ADE-BDE)Distribution of IF in the BDETest pointsTest points consists of two primary section :Block Diagram - Poin...
More About: Troubleshooting , Repair , Shoot

Functional Testing & Commissioning
2007-06-25 04:42:00
Above deck equipmentCheck freedom of motionCheck feed alignmentCheck antenna balanceEnergize antenna and note mechanical position of reflector pointing when at home switch to calculate Home Flag OffsetBelow deck equipmentSet parameters on ACUSystem typeTracking parameters Gyro Type Home flag offsetGyro compass HeadingVessel position (automatic if GPS input is used)Internal tuner selection and tuning frequencyDesired satellite longitudeFunctional testingCheck each function to assure proper operation :ACU Power "ON”Verify ACU/PCU communications.Ships Heading - Initial setting and subsequent updating of the heading correctly follows the ships gyro compass.LAT/LON - Verify manual entry and automatic GPS update. Internal tuner selection and frequency. Choose best tracking frequency. Never use TXIF frequency.AZ Drive - Step, slew and target AZ to verify proper drive.EL Drive - Step, slew and target EL to verify proper drive.Feed polarization - Verify that polarization of the feed is o...
More About: Testing , Missi

Remote Commands
2007-06-25 04:24:00
To Monitor Position Of The Motors, Home Flag:While at the Remote Command window key in: . , 1 , 1 , 8 , ENTERVOOOO will appear, press ENTER again.Press MODE to go to Remote Monitor Window. Typical readout will be A/D counts of CL LV AZ (eg 2048 2050 0012). In this example 2048 = Cross Level when antenna cross level beam is level, 2050 = Level (elevation) when elevation is at 45 degress and 0012 = azimuth position readout (4079 will appear when the home flag relay is energized). The range of values that can be displayed in each of these axis is from 0000 to 4096.To Reset/Reinitialize the Antenna:While at the Remote Command window key in: . , 9 , 4 , ENTERThen key in 9 , 0 , ENTER.This resets the PCU on the antenna. The antenna will reinitialize with this command (Performs a similar function as a power reset of the antenna).Setting the PCU system model :- While at the Remote Command window key in: . , 7 , 8 , ENTER- NOOOO will appear, press O, # , # , # , ENTER the system model....
More About: Commands , Mote

Antenna Control Unit
2007-06-18 01:40:00
Antenna Control Unit 's front panel consists of :Vacuum fluorescent (VF) displayKeypadLED enunciatorsFront Panel Layout & DisplaysPower-Up Display = On power-up the 4 line blue plasma display initially displays the Sea Tel controller model and software version, then “Remote Initializing” if the antenna is in the process of power-up cycle also, and finally the remote PCU model and software version will be displayed.AUX1 & AUX2 = Sequential pressing of the AUX1 key toggles tracking ON/OFF. As a shortcut to “Save New Parameters” (bypassing the password) press & hold the AUX2 key and press the “C” key on the numeric keypad.Ship Displays = Initial display of all present settings of the information listed below. Sequentially pressing the Ship key will access entry mode for each of these displays to enter, or correct, the desired setting :LAT (Ships Latitude) = Manual entry of the present position of the ship or position as automatically updated by GPS input.LON ( Shi...
More About: Antenna

Operation
2007-06-16 05:33:00
Normal System Operation Normal operation of the system from a cold start involves the following steps :Turn on the AC Power switches for the ACU and the Radio packages. Press the RESET button on the ACU front panel to initialize the system and show the current DAC-97 software version. Wait 1-2 minutes for the antenna to initialize. After initialization the display will show the model and software version of the (remote) PCU.Press SHIP to select the ship's position displays. Press SHIP again to select the LAT entry mode. Key in the ships Latitude to the nearest degree. Pressing the decimal key can enter tenths of a degree. Use the NS/EW key to set the correct hemisphere. Press ENTER to save the entry. Press ENTER again to select the LON entry mode. Key in the ships Longitude. Press ENTER to save the entry.Press ENTER again to select the HDG entry mode. Key in the ships heading if using an SBS or 36:1, 90:1 or 360:1 synchro gyro interface. Do not enter a ships heading fo...

Installation Photos
2007-06-12 02:45:00
Dome Antenna lifting 1Dome Antenna lifting 2Dome Antenna lifting 3Dome Antenna lifting 4Dome Antenna lifting 5Steady on place
More About: Photos , Alla

Installation
2007-06-11 04:36:00
The Installation Steps :Location Site Survey.Above Deck installation.Wiring.Below Deck Installation.Above deck equipment.Normal System Operation. Special operation functions.Location Site Survey :Check for blockage.Check for sources of other RF interference.Above Deck installation :Assemble base frame. Locktite and torque all hardware.Assemble lower half of the radome. Start all hardware. Silicon one flange, Locktite and tighten all hardware. Repeat for remaining flanges.Assemble upper half of the radome.Start all hardware. Silicon one flange, Locktite and tighten all hardware. Repeat for remaining flanges.Assemble reflector assembly (dish, feed and struts).Attach lower radome half to base frame.Start all hardware. Silicon one flange, Locktite and tighten all hardware. Lift antenna pedestal into lower radome half.Locktite and tighten all hardware.Lift and attach reflector and RF equipment.Lift upper radome half on lower half.Start all hardware. Silicon one flange, Locktite an...
More About: Alla

Antenna Tracking
2007-06-11 04:25:00
Antenna Tracking (Tracking of the satellite) - Fine adjustments to the pointing of the antenna to optimize the received signal level (AGC is monitored by the ACU). Tracking is controlled by the ACU.AGCThe internal tuner provides a DC voltage output that is directly proportional to the level of the satellite signal input. The receiver output will be positive going (voltage increases as satellite signal level increases) between 0.00-5.00 VDC. This output is converted from the analog voltage to a digital value be a 4096 bit A/D converter on the DAC-97 Main PCB. 30-40 digital counts of AGC is approximately 1dB of satellite signal. Satellite IF signal is provided into the internal tuner of the DAC-97 using the BNC or “F” connectors mounted in the rear panel.Receiver selection and tuning is set by pressing SAT key 4 times to the RCVR menu. The input is selected by pressing the NSEW key until the appropriate input is selected. Selections are Ext AGC (external connection to the...
More About: Antenna

Stabilization Loops
2007-06-11 04:02:00
Stabilization Loop s :Azimuth Servo LoopLevel Servo LoopCross-Level Servo LoopAzimuth Servo LoopLevel Servo LoopCross-Level Servo LoopAntenna balance :Reduces the load on the motorsResponsible for 75% of the stability of the antennaTop/bottom balancingFront/rear balancingLeft/Right balancing

Components of Stabilization
2007-06-08 04:19:00
These are 5 of Stabilizator components :Level Cage Stepper MotorServo Amp/Motor ControllersBLDC Motors (Torque Motors)Azimuth EncoderHome SwitchLevel Cage Stepper Motor consists of :Transistors in PCU step windings (current flow) in sequence of discrete steps. These are S1, S3, S2 & S4 for full step mode or S1, S1+S3, S3, S2+S3, S2, S2+S4, S4, S4+S1 in half step mode. In each case the sequence is repeated to continue rotation.When observing voltage, a winding will be high 5 steps and low 3 steps.Continuity of each “S” winding is about 36 ohms (S1-S2 or S3-S4 would be 72 ohms).Servo Amp/Motor Controllers consists of :Commutates the Brush-Less DC motor.Controls the torque output of the BLDC motorInput from PCU 2.50VDC (NOM) for no motor drive. As voltage increases the motor shaft will be driven one direction. Decreasing voltage below 2.5VDC will drive the motor shaft the opposite direction.Outputs A,B & C to the BLDC motorHall sensor feedback from the BLDC motorBLDC Motors (To...
More About: Components

Level Platform Installation and bias correction
2007-06-08 03:49:00
Level Platform Replacement Procedure :Loosen the 4 Level Platform Motor mounting screws and move the motor toward the level cage to slacken the drive belt.loosen the 2 screws that retain the 15 pin harness connector to the top level platform assembly and remove the connectorremove the hex nut on the end of the level platform spindle and remove the level cage (the gold colored box).Place the drive belt over the pulley on the new level cage and assemble onto the spindle. Attach the belt to drive motor, pull the motor back to remove the slack in the belt and tighten then retaining nut.Replace the hex nut and tighten the nut until the endplay is just reduce to zero. Do not over-tighten the retaining nut.Replace the 15 pin harness connector and tighten the 2 retaining screws.Turn the antenna on and let it initialize. Place a bubble level on the top of the level platform. If the platform is level within 1 to 2 degrees, no level trim adjustment is required. If the platform is off level by...
More About: Bias , Alla , Rect

Antenna Stabilization
2007-06-07 03:45:00
Pointing and Targeting the antenna is accurately pointing the antenna to an angular position in 3-dimensional free space. Controlled by the ACU :Antenna DriveSatellite targetingPositional Display Antenna Drive consists of :AZ stepping, slewing and targetingEL stepping, slewing and targetingPositionnal Display consists of :Azimuth DisplayRelative DisplayElevation DisplayACU & PCU Functions associated with Pointing and targeting the antenna :Antenna Control Unit - Master, controls the antenna through the PCUPedestal Control Unit (PCU)Antenna Control Unit - Master, controls the antenna through the PCU consists of :Interface with Ships Gyro CompassInterface for GPS inputControls Pointing and Targeting of the antennaPedestal Control Unit (PCU) takes pointing and tracking direction from the ACU.3-Axis Stabilization :Antenna Initialization - Every time the antenna is energized (or commanded to re-initialize) the PCU initializes the antenna in the following phases. Each phase must complet...

Pedestal Control Unit
2007-06-06 09:35:00
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 +/- 0.1 degrees of the desired position target. The basic control loops for Cross-Level, Level and Azimuth are shown in the control Loop Diagram. The primary sensor for each loop is a gyroscopic rate sensor mounted in the level Cage Assembly. This sensor reports all motion of the antenna to the PCU. The PCU immedietly responds by applying a torque in the opposite direction to a disturbance or command input to bring the antenna 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 archieve 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 Brushless Servo Amplifiers. These ampli...

Antenna Pointing / Stabilization / Tracking
2007-06-06 09:24:00
There are 4 primary componenet in antenna section where they make it stable in tracking the satellite signal :1. Antenna Control Unit - Master, controls the antenna through the PCUInterface with Ships Gyro CompassInterface for GPS inputInterface with computer to Monitor and Control the ACUControls Pointing and Targeting of the antennaControls Tracking 2. Pedestal Control Unit (PCU)Reads sensorsControls MotorsControls Stabilization of the antennaTakes pointing and tracking direction from the ACU3. ACU-PCU Control Signals - Pedestal M&CACU RS422 input/output via the Base MUXPCU RS422 input/output via the Pedestal MUXBase and Pedestal MUXes are mirror tuned4. Software versionsAre matched to hardware and functional capabilitiesACU and PCU software versions are reported by the ACU

Serial port connections
2007-06-06 09:07:00
Monitor and Control Connections The monitor and Control port allows external control from a modem, ASCII terminal or PC. SeaTel supplies a windows based antenna control program called PCDAC with allows choosing satellites and tracking functions and dialog box control of tracking and searching functions.The DAC-97 is wired as a DTE device for direct connection to a modem. For connection to another DTE device such as a terminal or PC, a null modem cable is required . connect the null modem cable between J11 on the back of DAC-97 and the ASCII terminal or PC serial interface port. Set the terminal or PC to 4800 baud, 8 bits, no parity (9600 baud operation is available on the Aux serial Board only by installing a jumper at D1). Enable the interface by selecting the system TYPE parameter under the MODE/SETUP display and verify that 8 or a combination that includes 8 is selected.The DAC-97 is available with one or two NMEA/M&C ports installed at J13 and J11. if two ports are installed , u...
More About: Port , Serial

System Block Diagram
2007-06-05 07:54:00
System Block Diagram consists of three section as describe below :TVRO System Block Diagram.TXRX System Block Diagram.Other inputs to the system.TVRO System Block Diagram consists of :Antenna Control Unit (ACU)Base MUX - Ped MUX (M&C and IF *DC*)Signal path to/from feedTVRO Equipment (TVRO Systems)TVRO Equipment (TVRO Systems) consists of :Multiplex switch or splittersSatellite receiversModulatorsStandards ConvertersCombiner/AmplifierOther distribution equipmentTXRX System Block Diagram consists of :Antenna Control Unit (ACU)Base MUX - Ped MUX (M&C and IF *DC*)Signal path to/from feedTX/RX Equipment (TX/RX Systems ONLY)TX/RX Equipment (TX/RX Systems ONLY) consists of :Satellite ModemIF SplitterRadio M&C Terminal (or PCDAC)MultiplexerOther Distribution equipmentOther inputs to the system consists of :Ships Gyro CompassGPSPCDACRadio M&CUnlimited Azimuth System Interconnect ADE - BDEPedestal Power Supply
More About: System , Stem

Other Inputs to the System
2007-06-05 07:39:00
There are two other inputs to the system :Global Positioning System (GPS) : NMEA signal - ASCII text DATA in RS-422 differential data signaling standard. Input is connected to an Aux Serial Port Adapter on the rear of the DAC-97. Updates the Latitude & Longitude of the ACU about once per second.PC Computer (PCDAC) :Remote Monitor & ControlTestsDiagnostic strip-chartBelow is ficture of NMEA signal :
More About: Stem