Sea Tel DAC-03, Инструкция по установке и эксплуатации

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Basic System Information DAC-03 Tracking Antenna Controller
3-2
Figure 3-1 Satellite Signal Polarization
four inches per hour will cause complete loss of signal. In weaker signal areas the effects would be
more pronounced.
3.1.5. Signal level
The level of the receive signal is dependant upon how powerful the transmission is and how wide
the signal beam coverage area is. Focusing the signal into a narrower beam concentrates its energy
over a smaller geographic area, thereby increasing the signal level throughout that area of coverage.
This makes it possible for you to use a smaller antenna size to receive that satellite signal. The
antenna system must be geographically located in an area where the signal level from the satellite
meets (or exceeds) the minimum satellite signal level required for your size of antenna (refer to the
Specifications section of your antenna 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 re-entering) an
area of adequate signal level.
3.1.6. Satellite Footprint Charts
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.
You can refer to satellite footprint charts (coverage maps) in World Satellite Almanacs or on the
Internet (
www.SatCoDX.com or www.Lyngsat.com ). Many satellites have their own web sites to
provide programming and footprint information. The coverage areas are intended to be a guide to
reception, however, the actual coverage area and signal level may vary. Also the signal strength is
affected by weather.
To use these footprint charts you will need to know the minimum EIRP signal level required for your
antenna (refer to the Specifications section of your antenna manual).
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 “polarization” while the ship is in transit 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.