Sea Tel DTV04, Инструкция по установке и эксплуатации

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DTV04 HD TVRO Antenna Basic System Information
3-3
Figure 3-5 Satellite Signal Polarization
3.1.3.
The level of the receive signal at any given geographic location globe is dependent 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 satellites meets (or exceeds) the minimum satellite signal
level required for the antenna (refer to the Specifications section of this manual) to provide suitable
reception. This signal level requirement may limit the number of satellites that can be used and the
geographic areas where the ship can travel. 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. Tracking decisions
are based on single satellite and therefore is possible to have your system report proper tracking
status and still not be within coverage of one of the other 4 satellites.
Signal level
3.1.4.
Satellites may transmit their signals in one of two
different polarization modes, linear (like a flat ribbon
down from the satellite) or circular (like a twisted
ribbon spiraling down from the satellite). The
DTV04 HD antennas are designed to receive
circular satellite signals only.
Satellite polarization
3.2. Antenna Basics
The satellite dish is mounted on a three jointed pedestal. As
your boat rolls, pitches and turns in the water, these three
joints move to keep the dish pointed at the satellite. The
following information is provided to explain some of the basic functions of the antenna:
3.2.1.
The clockwise, or counter-clockwise, rotation of the antenna is called Azimuth rotation. The
antenna can rotate a total of 680 degrees between two mechanical stops. Azimuth drive, provided
by the azimuth motor, is required during stabilization, searching, tracking and unwrap operations of
the antenna. As the boat turns, azimuth is driven in the opposite direction so the dish remains
pointed at the desired satellite. The actual azimuth pointing angle to the satellite is determined by
the ships latitude & longitude and the longitude of the satellite. It is important to know that the
antenna should be pointed (generally) toward the equator.
If the ship is in the Northern Hemisphere, the azimuth angle to the satellite would be 180 degrees
true (relative to true north) if the satellite is on the same longitude as the ship. 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 top to see if the dish is aimed the correct direction (towards the
equator).
Azimuth
3.2.2.
The antenna can physically be rotated in elevation from –15 degrees (lower stop) to +110 degrees
(upper stop). However, you will only be pointing elevation between 00.0 (horizon) and 90.0
(zenith). Elevation drive, provided by the elevation motor, is required during stabilization, searching
and tracking 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 the ship is at a high latitude and will increase as the ship gets
closer to the equator.
Elevation