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Statistics |
| Unique Visitors: 0 |
| Total Unique Visitors: 80 |
| Visitors Out: 2610 |
| Total Visitors Out: 3759 |
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| What Is a Satellite Stabilizer? |
| 2007-08-26 21:03:00 |
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 s...
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| Finding Satellite |
| 2007-08-26 21:02:00 |
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 th...
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| DAC-97 Displays “Remote not responding” |
| 2007-07-11 22:41:00 |
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...
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| Open Loop Motor Test |
| 2007-07-11 22:39:00 |
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.......
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| Reference Sensor Monitoring |
| 2007-07-04 22:05:00 |
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 ma...
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| Monitoring activity current consumption of motors |
| 2007-07-04 22:02:00 |
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...
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| Dac Input Specifications |
| 2007-07-02 02:59:00 |
These are RF tracking input, RS 232 monitor and control interface, NMEA interface, and external AGC input specifications :......
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| Ready to Install |
| 2007-07-02 01:56:00 |
These is the 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 o...
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| Troubleshooting and Repair |
| 2007-06-25 19:21:00 |
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 si...
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| Functional Testing & Commissioning |
| 2007-06-24 21:42:00 |
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 u...
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| Remote Commands |
| 2007-06-24 21:24:00 |
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 fun...
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| Antenna Control Unit |
| 2007-06-17 18:40:00 |
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 belo...
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| Operation |
| 2007-06-15 22:33:00 |
Normal System OperationNormal 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 mo...
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| Installation Photos |
| 2007-06-11 19:45:00 |
Dome Antenna lifting 1Dome Antenna lifting 2Dome Antenna lifting 3Dome Antenna lifting 4Dome Antenna lifting 5Steady on place......
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| Installation |
| 2007-06-10 21:36:00 |
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 a...
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| Antenna Tracking |
| 2007-06-10 21:25:00 |
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 ...
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| Stabilization Loops |
| 2007-06-10 21:02:00 |
Stabilization Loops :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......
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| Components of Stabilization |
| 2007-06-07 21:19:00 |
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 ...
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| Level Platform Installation and bias correction |
| 2007-06-07 20:49:00 |
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 ...
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| Antenna Stabilization |
| 2007-06-06 20:45:00 |
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 ...
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| Pedestal Control Unit |
| 2007-06-06 02:35:00 |
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 ...
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| Antenna Pointing / Stabilization / Tracking |
| 2007-06-06 02:24:00 |
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 Tracking2. 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 matc...
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| Serial port connections |
| 2007-06-06 02:07:00 |
Monitor and Control ConnectionsThe 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 ...
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| System Block Diagram |
| 2007-06-05 00:54:00 |
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 Modem...
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| Other Inputs to the System |
| 2007-06-05 00:39:00 |
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 :......
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| Nmeah Gyro Information |
| 2007-06-05 00:31:00 |
When the ACU is configured for gyro type 2, there are two heading displays. The display on the left shows the remote PCU heading register and the display on the right shows the local heading register. In software version prior to 3.24, the right hand display always shows 0000 since this register reading the SBS heading input and there is no data being supplied on this input. The left hand display will show any changes in the NMEA heading updates immediately as they are passed on from the NMEA interface board to the ACU processor and subsequently up to the remote PCU processor. It is recommended that the ACU be set to GYRO TYPE 2 for confirming that the NMEA interface is functioning properly by observing the left hand display and verifying that it changes in sync with the gyrocompass data.D...
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| NMEA Connections |
| 2007-06-04 07:24:00 |
The NMEA port allows automatic Latitude, Longitude and Heading updates from a GPS receiver or gyrocompass. For GPS input, connect the 4 wires from a GPS recever to connector J13 or J11 on the back of the DAC-97. For heading input, connect pins 1 & 2 only (RX+, RX-) to the gyrocompass. To enable the interface, select the system type 8 or a combination that include 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, use J13 for the NMEA input. If two NMEA inputs are used (heading and GPS) use J13 for the heading input. If only one M&C or NMEA GPS functions are available and only one at a time.NMEA GPS Checkout :When a NMEA GPS receiver is connected to J13 or J11, the NMEA LED on the AUX SERIAL PORT ADAPTOR (ASPA) ...
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| Ships' Gyro Compass |
| 2007-06-04 07:14:00 |
Synchro Signals is an AC voltage sinewave based signal :Step-By-Step (SBS) signals (DC voltage based signal)DC voltage output changes (ON/OFF) in a specific pattern of six discrete states per degree of ships heading change. All phases high, or low, at any instant in time are illegal states (violation of gyro truth table).NMEAH heading 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 and the software on that ASPA board will only accept one updates every 0.75 seconds (gyro output may be more frequent).......
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| Eliminating Gyro Errors |
| 2007-06-04 04:29:00 |
In Many cases, a corrupt or non existent ship's gyro compass input can couse tracking errors that are large enough to couse satellite signal losses. A gyro diagnostic mode is now available in xx96 and xx97. Pedestal Control Unit version 1.32 and higher that will uncouple the gyro reference from the azimuth rate sensor control loop. In this mode any change in ships gyro reading will not directly affect the azimuth control loop. The Pedestal Control Unit will stabilize the antenna based entirely on the azimuth rate sensor loop and the tracking information from Step Track or Conscan. To keep the azimuth rate sensor position from eventually drifting away at a rate faster than the tracking loop can correct, the tracking errors are used to regulate the rate sens...
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| Below Decks Equipment |
| 2007-05-29 03:36:00 |
Antenna Control Unit (ACU) & Terminal Mounting Strip (TMS) consists of :Antenna controller names.Displays ACU and PCU software version number on power up. Provides operator interface to control the antenna through the Pedestal Control Unit (PCU).Interfaces to Ship’s Gyro Compass for heading information (heading relative to True North). Interfaces to GPS for ships location information (Latitude & Longitude).Anttena Controller Names consists of :Antenna Control Unit (ACU)Tracking Antenna Controller (TAC-92)Digital Antenna Controller (DAC-97)Pedestal Control Unit (PCU) consists of :Optional connection to a personal computer allows remote control of ACU & antenna when using PCDAC software.Controls tracking (Step Track or Conscan) of the antenna through the PCU.Controls pointing and targ...
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| Antenna ConScan |
| 2007-05-28 04:12:00 |
Antenna ConScan section consists of :ConScan (Conical Scanning) - Uses a bore-sight shift of the signal entry into the throat of the OMT. Provides 75-150 RPM sampling of signal level on the four quadrants of the dish to provide intelligent tracking. Provides Timing marks of boresight location relative to the four quadrants of the dish (up, down, left & right).Conscan controller.Feed Modifications on ConScan :Ku-Band Feed - Eccentric scalar plate, motor drive and timing mark sensor. C-Band Feed - Eccentric throat, motor drive and timing mark sensor.Dual Band Feed. - Eccentric C-Band throat, Ku-Band teflon wedge, motor drive and timing mark sensor.The ConScan controller function is for :Timing Marks from feed (dish quadrant location of the feed eccent...
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| Feed Strut Assembly |
| 2007-05-28 03:42:00 |
Feed Assembly consists of :Scalar Plate - Improves the gain of the feed, recovering stray receive energy and focusing of transmit energy to improve illumination of the dish surface.OMT (Orthogonal Mode Transition) - Transition from an Orthogonal Mode chamber to standard Waveguide flanges appropriate for the frequency of usage. Must be designed specifically for the frequency of operation, must be the same f/D ratio as the dish, and polarization mode (Linear and/or Circular). Polarization Angle (PolAng) motor(s).Waveguide Filters.LNAs, LNBs, and LNCs - LNAs, LNBs and LNCs - Low Noise Amplifiers, Low Noise Block (down) Converters and Low Noise Converters.Polarization Angle (PolAng) motor(S) consists of :5VDC Pulse - Very li...
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| Antenna Reflector |
| 2007-05-25 08:45:00 |
The Gain & Efficiency of the dish is directly related to:Size of reflector (in square centimeters).Type of reflecting surface.Parabolic curve accuracy.Focal type of the reflector.Struts.Type of reflecting surface consists of Mesh and Solid. Mesh is Framed sections of screen material form a light weight reflector, but is not as efficient as solid surface dishes and has higher level side-lobes.The solid type of reflecting surface consists of :Spun - Least efficient of the solid dishes because the surface is not smooth and the ridges cause some energy to be lost as stray reflections.Hydro-formed - Good surface accuracy, efficiency and low side-lobes.Precision - Very high surface accuracy, efficiency and low side-lobes .Parabolic curve accuracy is how accurately formed the reflector surface c...
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| Above Decks Equipment |
| 2007-05-24 04:34:00 |
TVRO Above Decks Equipment (ADE)Component Identification :The Radome Assembly : Provides for the mechanical mounting and environmental protection of the antenna assembly.Base frame, legs and braces - This assembly provides a rigid attachment to the ship by being bolted, or welded, to the deck of the ship. Radome panels and Radome Cap - When properly bolted together and sealed with silicon sealant, this assembly provides an environmental enclosure for the antenna. This protects the antenna from rain and salt water and also prevents wind from disturbing the pointing of the antenna. A GPS Engine may be fitted to the radome cap, or any other suitable location nearby.The Support Assembly : Mechanical support for the antenna....
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| Basic Satellite Information |
| 2007-05-23 08:49:00 |
Satellite OrbitsClarke orbit 22,753.2 miles up, directly over the equator (0.0 Latitude).Satellites in Clarke orbit revolve around the earth at the same speed, appearing to be stationary when viewed from earth(Satellites’ orbital velocity matches the Earth's rotational velocity).Commonly referred to as Geostationary or Geosynchronous.Commonly referred to by their longitudinal position (000-180 East & West or 000-360 East) because they stay in position at their assigned longitude.About 170 currently in Geostationary Orbit relaying Telephone, Data and Television signals.Geosynchronous Orbital Spacing is controlled by agreements with multi-national regulatory organizations, to prevent interference by multiple satellites providing the same services.Polar ...
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| Autotrack VSAT Antenna Introduction |
| 2007-05-22 07:55:00 |
The antenna will be used onboard a ship and it will have to be able to provide uninterrupted satellite usage while under a variety of motion - we are a leading manufacturer of Marine Stabilized Antenna Pedestals.What are the key points :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 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.Definitions of other relevant terms :Relative (REL)Mec...
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| Pointing the VSAT Antenna |
| 2007-05-22 07:31:00 |
Pointing the VSAT Antenna – Beam vs Mechanical Axis as used for Physical, or Course Elevation Adjustment :Pointing the VSAT Antenna – Setting the Antenna Course Elevation Adjustment :......
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| Basic VSAT |
| 2007-05-22 06:00:00 |
Finding the required "look angle" has become very easy with the advent of the Internet and the World Wide Web.The following WWW Locations are just examples of the many sites possible:Our primary resource for satellite look angle calculations is Loral SkyNet’s SST calculator. It can be found and downloaded from their website: http://www.skynet.com/tech_resources/tools/tool_us.aspZip CodeLatitude/LongitudeAccounts for Antenna offset values in calculationsPolarization always calculated as ‘horizontal’ downlink (+/- 90 degrees if “vertical” downlink)"Online Satellite Calculations" at http://www.home.online.no/~jensts/satellite.html (Nokia) Domestic and International Perspective using:Lat/Long onlyAdditional Satellite/Engineering Calculations......
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| Link Budget |
| 2007-05-22 05:47:00 |
- The process of correctly sizing uplink and downlink paths- Takes into account:Established Satellite performancePath Loss (22,300 miles traversing space)Atmospheric effects (weather, ion storms, sunspots, etc.)Frequency bands used (Ku, C, Ka)Hub uplink antenna and amplifier performanceDownlink antenna size and receiver noise figureLink Budget Rain :Design for the specified availability99.5% availability will give you about two days of outage per year99.9% will give just 8 hours of outage per yearNote that only the Uplink at the Hub can compensate for rain, by using the UPC......
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| Modulation |
| 2007-05-22 05:29:00 |
Inbound Vs Outbound Transmission Characteristics :Outbound- Continuous output, bandwidth shared among remote sites receiving TDM frames- Emphasis on inexpensive receiver/LNB- High bit rate (up to 32Mbps)Inbound- Random access, transmitter bursts as required to communicate with the hub- Emphasis on inexpensive modulator- Medium bit rate (up to 2Mbps, with large scale VSAT)......
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