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Through the use of special slope equalizers and amplifiers, the distance between the modem and
the BUC can be extended.
It is important to note that a +24/+48 VDC offset and a 10MHz reference signal may be present at
the modulator output. The DC voltage may supply up to 4 Amperes and will damage any DC
coupled device (such as an attenuator) connected to the modulator output. Also, a typical
attenuator on the modulator output would reduce the level of 10 MHz reference signal available to
the BUC.
Special inline10/20 dB attenuators are available from AdvantechAMT that pass DC (up to 6A) and
10-50MHz reference in either direction and only attenuate the L-Band signals by the amount
specified.
Also available are amplitude/slope equalizers that compensate for losses and "tilt" caused by the cable
and other devices between the modem and the BUC, such as power combiners. Some are rack-
mounted units, which include self-contained power supplies, and others are in-line modules that utilize
the DC power from the modem.
A.2 LNB, BUC & Antenna Installation
A.2.1 Choosing the LNB & BUC
The AMT-70 product line is compatible with all OEM compliant BUC / LNB products. However the
AMT-70 product line is fully tested with the AdvantechAMT high power solid state power amplifiers
(SSPAs), booster amplifiers, block up converters for up-link applications and low noise amplifiers
(LNAs) for down-link applications.
The AdvantechAMT SSPAs are available in L-, C-, X- and Ku-Band models and are available in both
indoor rack-mount or in outdoor hub-mount weatherproof enclosures. AdvantechAMT also features the
tri-band SSPA which is designed to operate in any of the C-, X- and Ku- satellite communication bands.
A.2.2 LNB Physical Installation
Fit the LNB with a suitable feed horn and attach to the antenna ensuring correct *LNB polarization.
Connect a suitable 75R low loss co-axial cable between the receiver RF input and the LNB. The
connection to the LNB should be protected with self-amalgamating tape.
If the antenna has previously been accurately pointed at the required satellite the modem may be
switched on and the receiver parameters set.
A.2.3 Antenna Alignment
The following sub sections provide information on pointing the receive antenna accurately at the
required satellite.
The antenna must have a clear "line of sight" view of the satellite. This means that the pointing angle
must be clear of tall buildings, trees and other high objects. If the view to the south is generally clear
the antenna site will be suitable. However if there are obstructions to the south the actual pointing
angles will have be checked to see if the site is suitable.
A.2.4 Satellite Position
Most communications satellites appear stationary in the sky from any location on the earth. This is
because their speed is matched to the rotational speed of the earth taking into account the fact that
their orbit is much greater than the earth's circumference. These satellites are said to be in
geostationary or geosynchronous orbits.
Geostationary satellites can only have one orbit, which is 22,238 miles (35,786 kilometers) directly
above the equator.
AMT-70/AMT-73/AMT-75 Installation and Operation
134
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