AMX TDS, Operation/Reference Manual

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Appendix C: LNB Recommendations for DTV-TX02-DVB-S Installations
91 AMX TDS (Television Delivery System)
Appendix C: LNB Recommendations for
DTV-TX02-DVB-S Installations
Products Applicability

DTV-TX02-DVB-S
Introduction
This tech note briefly describes Satellite Low Noise Block down-converters (LNBs) and recommended
methods for interfacing AMX DTV-TX02-DVB-S units.
Introduction To Satellite LNBs
An LNB is used to down convert high satellite frequencies down to an appropriate Intermediate Frequency (IF)
for distributing over cable and being received by a suitable receiver.
Most modern installations will have satellite dishes fitted with either a Quad or a Quattro LNB, the Quad being
suitable for small domestic installations whilst the Quattro is aimed at larger domestic/industrial installations
using a ‘head end’ IF distribution system.
Both of these LNBs provide four outputs:
1.
Horizontal polarization low band - (LNB 15.5 to 18V – no tone)
2.
Horizontal polarization high band - (LNB 15.5 to 18V - with 22kHz tone)
3.
Vertical polarization low band - (LNB 12.5 to 14.5v – no tone)
4.
Vertical polarization high band – (LNB 12.5 to 14.5v – with 22kHz tone)
Each output on the Quad LNB are switchable, requiring a DC LNB voltage and 22kHz tone to switch to select
the desired output and desired program selections. The DC voltage and tone are typically supplied by the
satellite receivers, and are inserted onto the RF cable, therefore providing the required voltage/tone to the
LNB. The Quad LNB is limited to distributing to 4 points, hence Quattro LNBs are recommended for most
large installations.
The Quattro LNB has a four fixed outputs, which are then fed into a suitable head end distribution system. This
will typically be a multiswitch, where the required LNB output is switched and routed to the receiver by the
receiver injecting a similar DC voltage and tone onto the RF cable.
The requirement for horizontal or vertical orientation can be identified by looking at the many Satellite Listing
sites available on the web.
The requirement for the 22kHz can also be determined from the same Satellite Listing sites, but this time the
required LNB down conversion frequency must be calculated by selecting either 9750Mhz (no LNB tone) or
10600MHz (22kHz tone) to be subtracted from the broadcast frequency to ensure the frequency fed into the
receiver falls within the range of 950MHz to 2150MHz. Please note that the frequency to be subtracted, called
to Local Oscillator frequency will depend on the LNB used, please refer to your LNB User Guide for actual
Local Oscillator frequencies.