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Basic System Information 9497B-1 C/Ku-Band TVRO satellite signal level required for your size of antenna (refer to the Specifications section of this manual) to provide suitable reception. This limits the number of satellites that can be used and the geographic areas where the ship can travel where the signal level is expected to be strong enough to continue providing uninterrupted reception. When traveling outside this minimum signal coverage area, it is normal for the system to experience an interruption in its ability to provide the desired satellite services until entering (or reentering) an area of adequate signal level.
3.1.6.
Satellite Footprints
The focused beam(s) from the satellites are normally aimed at the major land masses where there are large population centers. Footprint charts graphically display the signal level expected to be received in different geographic locations within the area of coverage. The signal will always be strongest in the center of the coverage area and weaker out toward the outer edges of the pattern. The coverage areas are intended to be a guide to reception, however, the actual coverage area and signal level and vary. Also the signal strength is affected by weather.
3.1.7.
Linear Satellite polarization
Satellites may transmit their signals in one of two different polarization modes. The feed installed on your antenna must be designed to operate with linear polarized satellite transmissions.
Circular polarized satellite transmissions do not require polarization adjustment to optimize the reception.
Linear polarized satellite transmissions require periodic adjustment of Figure 3-1 Satellite Signal Polarization
“polarization” to optimize the alignment of the LNB to the angle of the signal from the satellite.
When you are at the same longitude as the satellite, its’ horizontal and vertical signals will be aligned to your local horizon. When you are east or west of the satellite, the signals will appear to be rotated clockwise or counter-clockwise from your local horizontal and vertical. Both horizontal and vertical signals from a satellite will appear to be rotated the same amount and are always perpendicular to each other. The amount of rotation is dependent on how far east or west you are form the satellite and how close you are to the
Equator.
3.2.
Antenna Basics
The following information is provided to explain some of the basic functions of the antenna:
3.2.1.
Unlimited Azimuth
Azimuth rotation of the antenna is unlimited (no mechanical stops). Azimuth drive, provided by the azimuth motor, is required during stabilization, searching and tracking operations of the antenna. When the ship turns, azimuth is driven in the opposite direction to remain pointed at the satellite. The actual azimuth pointing angle to the satellite is determined by your latitude & longitude and the longitude of the satellite. It is important to know that the antenna should be pointed (generally) toward the equator.
The azimuth angle to the satellite would be 180 degrees true (relative to true north) if the satellite is on the same longitude that you are on. If the satellite is east, or west, of your longitude the azimuth will be less than, or greater than 180 degrees respectively.
When checking for blockage you can visually look over the antenna radome toward the equator to see if any objects are in that sighted area. If you are not able to find any satellites it may also be useful to remove the radome hatch to visually see if the dish is aimed the correct direction (towards the equator).
3.2.2.
Elevation
In normal operation the elevation of the antenna will be between 00.0 (horizon) and 90.0 (zenith). The antenna can physically be rotated in elevation below horizon and beyond zenith to allow for ship motion.
Elevation drive, provided by the elevation motor, is required during stabilization, searching and tracking
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9497B-1 C/Ku-Band TVRO Basic System Information operations of the antenna. The actual elevation pointing angle to the satellite is determined by your latitude
& longitude and the longitude of the satellite. In general terms the elevation angle will be low when you are at a high latitudes and will increase as you get closer to the equator.
Additionally, from any given latitude, the elevation will be highest when the satellite is at the same longitude that you are on. If the satellite is east, or west, of your longitude the elevation angle will be lower.
3.2.3.
Feed Assembly
The scalar section of the feed is fitted with a polarization motor and a potentiometer for position feedback required for linear signal operation. The feed may be fitted for Linear or Circular reception. The appropriate
LNA, LNB or LNC must be installed on the Linear or Circular section of the feed to receive the frequencies of the desired satellite.
When a Linear feed is installed, the ACU automatically adjusts the feed by remotely controlling the 24 volt
DC motor, using the potentiometer feedback for Linear polarization position (Auto-Polarization mode).
When a Circular feed is installed, no polarization adjustment is required because the circular feed receives the signal properly regardless of its polarization position.
The feed may be dual band (C-Band and Ku-Band) allowing you to use either band. The Tracking - Band
Selection remotely controls coax switches mounted on the antenna pedestal to select which LNB outputs are routed through the antenna pedestal to the Below Decks Equipment.
3.2.4.
Antenna polarization
You have a linear polarization feed installed, the system should have been adjusted properly and set-up to operate in Auto-Polarization mode. The ACU will then automatically adjust the polarization of the feed, as necessary, while the ship travels in Latitude and Longitude.
3.2.5.
Stabilization
Your antenna is stabilized in all three axes of motion. Stabilization is the process of de-coupling the ships’ motion from the antenna. Simply put, this allows the antenna to remain pointed at a point in space while the boat turns, rolls or pitches under it. To accomplish this, the Pedestal Control Unit (PCU) on the antenna pedestal assembly senses the motion and applies drive to the appropriate motor(s) in opposition to the sensed motion. Azimuth (AZ), Elevation (EL) and Cross-Level (left-right tilt) are actively stabilized automatically by the PCU as part of its normal operation.
3.2.6.
Search Pattern
Whenever the desired satellite signal is lost (such as when the antenna is blocked) the Antenna Control Unit will automatically initiated a Search to re-acquire the desired signal.
Search is conducted in a two-axis pattern consisting of alternate movements in azimuth and elevation. The size and direction of the movements are increased and reversed every other time resulting in an expanding square pattern.
When the antenna is able to re-acquire the desired signal the ACU will automatically stop searching and begin
Tracking the signal to optimize the pointing of the antenna to get the highest signal level from the satellite.
3.2.7.
Tracking Receiver - Satellite Identification Receiver
The Satellite Identification Receiver located in the Antenna Control Unit (ACU) is used to acquire, identify and track a specific satellite by its unique hexadecimal ID code. When properly setup, the settings for the satellite are saved to expedite future acquisition of the desired satellite.
When searching for the selected satellite this receiver compares the present satellite ID to the targeted satellite ID code. If the ID code does not match the antenna will continue searching until the correct satellite is found. The system must have adequate satellite signal level, AND the matching NID, to stop searching (and begin tracking the desired satellite).
3.2.8.
Tracking
Your Antenna Control Unit actively optimizes the pointing of the dish for maximum signal reception. This process is called tracking and is accomplished by continuously making small movements of the dish while monitoring the level of the received signal. Evaluation of this information is used to continuously move the stabilization point toward peak satellite signal reception. These minor pointing corrections keep the signal level “peaked” as part of normal operation.
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