HR
X
-C-HB-1
C-B
AND
L
INK
H
ANDBOOK
17
2.4.3
Changing module RF gain
The link performance specifications apply when modules are operated in the factory preset
configuration. However, the gain of the modules can be changed to suit customer requirements.
The performance of the transmitter is highly dependent on the laser diode. Changing transmitter and
receiver gain will affect the sensitivity and linearity of the module. Detail of these effects are provided
in section 3.
2.4.4
Software control - via SNMP controller
ViaLiteHD
RF links can be controlled via a
ViaLiteHD
SNMP control module when fitted in the same
chassis, see the SNMP controller module handbook for further details. The SNMP module offers control
via both a web interface and SNMP.
Remember if you wish to use software control the manual attenuation has to be set to zero, i.e. all poles
of the switch should return to the OFF position. Failure to do so may prevent the module from controlling
the gain correctly.
2.5
LNA/LNB and BUC DC feeds
The C-band modules have an option to present a DC voltage at the RF connector to power any
connected equipment capable of receiving its power this way.
Warning!
Precautions must be taken to ensure that any connected equipment is tolerant
of the DC voltages supplied.
2.5.1
LNA/LNB feed - transmitter modules
Transmitter modules may be used to provide a power feed via the RF connection to a preceding low
noise amplifier (LNA) or low noise block down converter (LNB).
The voltage source for this function can be supplied externally via a chassis connection or from the
module’s on-board voltage generator
The external DC paths (option 3) of a module may be accessed via the chassis connector for plug-in
modules (see your chassis handbook) or the 15 way D-Type connector for the purple modules.
The LNA/LNB option can be determined from the part number.
Modules in this range offer a variety of feed options, shown below.
0
No LNA feed
1
Internally gen5 ± 0.5V at 80mA
2
Internally gen12 ± 1V at 300mA
3
External Feed from chassis connector 0 to +28V at 350mA
5
Internally gen13.4 ± 1 or +18.5 ± 1 selectable 350mA (up to 7.1GHz)
L
Internally gen13.4 ± 1 or +18.5 ± 1 selectable 700mA (up to 6.0GHz)
2.5.2
LNA/LNB feed efficiency - plug-in modules
The power consumption of a transmitter is specified without allowance for LNA/LNB power. When
calculating power consumption the module efficiency of the LNA/LNB power supply at full load is 89%
typically and 80% minimum
2.5.3
LNA/LNB voltage boost - plug-in modules
The output voltage of any module equipped with an internal 13/18/22 volt power supply (
option “5” and
“L”) can have its output voltage increased to allow for cable losses, the output voltage is increased by
