Sea Tel 9797B-70 C-Band TX/RX, Инструкция по установке и эксплуатации

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9797B-70 C-Band TXRX Basic System Information
3-1
3. Basic System Information
This section provides you with some additional information about the satellites you will be using, basics of your Series 97B
antenna system and some of the other equipment within your system configuration.
3.1. Satellite Basics
The satellites are in orbit at an altitude of 22,754 miles and are positioned directly above the equator. Their orbital
velocity matches the Earth’s rotational speed, therefore, each appears to remain at a fixed position in the sky (as
viewed from your location).
Your antenna can be used with any of the satellites in this orbit that have a strong enough receive signal level. Your
antenna is capable of being fitted with a Linear or Circular feed assembly. The feed may be designed to operate at C-
Band frequencies, Ku-Band frequencies or be capable of operation in both bands. With the correct feed assembly you
will be able to receive the linear or circular signal at the specific frequency range of the desired satellite.
3.1.1. C-Band Receive Frequency (3.625-4.2GHz)
At these frequencies the signal from the satellite travels only in a straight line and is affected by weather
changes in the atmosphere. There are several conditions that can cause a temporary loss of satellite signal,
even within an area where the signal level is known to be adequate. The most common of these
normal
temporary losses are blockage and rain fade . They will interrupt services only as long as the cause of the
loss persists.
3.1.2. Blockage
Blockage is loss due to an object in the path of the signal from the satellite to the dish. If an object that is
large and dense is positioned in the path of the signal from the satellite, it will prevent sufficient signal from
arriving at the dish. The signal can not bend around, or penetrate through, these objects and the reception
will be degraded or completely interrupted. The dish is actively driven to remain pointed at the satellite
(toward the equator) so, as the ship turns a mast or raised structure of your ship may become positioned
between the satellite and the dish. Blockage may also be caused a anything standing near the radome, tall
mountains, buildings, bridges, cranes or other larger ships near your ship. Moving or rotating the ship to
position the antenna where it has an unobstructed view to the desired satellite will restore the antennas’
ability to receive the satellite signal.
3.1.3. Rain Fade
Atmospheric conditions that may cause sufficient loss of signal level include rain, snow, heavy fog and some
solar activities (sun spot and flare activity). The most common of these is referred to as “rain fade”. Rain
drops in the atmosphere reduce the signal from the satellite. The heavier the rain the higher the amount of
signal loss. When the amount of loss is high enough, the antenna will not be able to stay locked onto the
satellite signal. When the amount of rain has decreased sufficiently, the antenna will re-acquire the satellite
signal. In a strong signal area, rain fall of about four inches per hour will cause complete loss of signal. In
weaker signal areas the effects would be more pronounced.
3.1.4. Signal level
The level of the receive signal is dependant upon how powerful the transmission is, how wide the signal beam
is, and what the 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 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 re-
entering) an area of adequate signal level.