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| The focus systems generally
used are:
Offset System |
Prime
Focus System
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|
| Net Antennae are generally used to
receive C Band, being unsuitable to receive KU Band
The holes of the net have to be smaller than
1/4 of the signal wavelength (/4)
|
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|
| Solid-plate antenna can be used
for both C and KU Bands
Because of its high efficiency, the plates
diameter is smaller than that of the net-antennas |
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|
| Antennae need to be directed to
satellites with high accuracy
so
The function of
antenna-mounting is very important
|
| There are 2 types of
antenna-mounting: |
| Fix System
directed to 1 satellite only
|
| Polar System
can be moved & directed to more than 1
satellites
|
|
|
| To move antenna on a polar system,
one needs:
Controller (Positioner).
 
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Actuator motor
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| An
actuator motor is usually a DC electrical motor (35Volt).
|
The motor is equipped with a
limit switch (Over Run Limit Switch) and a position sensor using magnet &
reed switch.
|
|
| A Motor
with Acme Screw can move linearly like a cylinder (Actuator).
Currently, a Linear actuator is the cheapest
& popular one, but it can only move the antenna with a range of 100 degrees
(max).
|
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|
Motor with gearbox gives rotational movement.
Gearbox system is more expensive, but movement range is 160 degrees. |
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|
A Positioner consists of:
35 Volt DC Power Source for antenna-motor.
Position Controller, to move antenna while detecting position signal from sensor which is attached in the actuator-motor. |
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LNBF (Low Noise Block w/ Feed) is the component placed at the reflector’s focus,
LNBF is the “REAL ANTENNA” |
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