Installation - Alcad 912-TQ Serie Manual De Instalación Y Programación

26 - ENG
For any given QPSK signal, the QAM signal bandwidth can be reduced
by changing the type of QAM modulation. The table below shows the
most common symbol rate related to different QAM modulations.
5.

INSTALLATION

The drawings in the ANNEX show how to perform the assembly and the
standard connections.
5.1 Unit supply
To supply the unit, it is necessary to connect every module to the MS-011
support framework, which performs the mass connection.
Placing of 75 Ω Ω load
5.2
Except the TEST output of the PA amplifier, verify that the remaining
unused inputs and outputs are loaded with an RS-275 (code 9120011)
load of 75 Ω.
5.3 Installation of external LNB units
It is very important to make a note of the dish, the quality of the digital
signals, which fade out very much when it is not properly recorded down
(in spite of being good for analogic signals).
Correctly adjust the skew of the external LNB unit to get the best possible
cross polarisation.
reception of the digital signal. The cross polarisation must be 20 dB
lower than the level of the digital signals.
Installation and programming manual
BW
QAM
BW
QAM
S/R
QAM
This adjustment is fundamental for high quality
LNB
Fig. 7 - Adjusting the LNB
= 1,15 . S/R
QAM
bandwidth QAM
symbol rate QAM
≥20dB