COBHAM Sailor 900 VSAT, Technical Manual

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Removal and replacement of ADU modules
98-133966-G1 Chapter 8: Service & maintenance 8-21
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Service & maintenance
14.Low Noise Block down converter (x2) (LNB).
The LNB receives the Ku-band (10.70-12.75 GHz) radio signal,
amplifies it and converts it down to a L-band (950 or 2150 MHz)
Intermediate Frequency (IF). The conversion is controlled by 2 Local
Oscillator (LO) frequencies and the LO frequency is locked to an
external reference signal.
The Ku-band interface is WR75 waveguide and the IF interface is for
– variant A: 75 Ohm F-connector
– variant B: 50 Ohm SMA connector.
DC power and 10 MHz external reference signal are also supplied
over the IF cable. The L-band IF output is routed to the VSAT
Interface Module (VIM) located on the ADU’s azimuth pedestal.
15.Ortho Mode Transducer (OMT). (behind cable screen, not visible on
photo)
The OMT provides a low-loss waveguide interface between the dual
polarised ADU feed-horn and the BUC/LNB.The main purpose of the
OMT is to separate transmitter and receiver signals and to provide
sufficient isolation between BUC and LNB. The OMT uses the
orthogonality of the signals to split and provide isolation. The OMT
also detects the BUC output power and temperature.
16.Inertial Sensor Module (ISM).
Figure 8-19: OMT – Block diagram
SAILOR900TM.book Page 21 Monday, September 16, 2013 11:01 AM