3810-rwt.ib.rev1.doc
Page 8 of 11
17/10/2007
RWR-3810 photo-diode receiver module
The RWR-3810 is factory preset for use with the accompanying RWT-3810 transmitter and a optical path
attenuation of 2 dB, to give unity gain in the RF signal path.
Installation requires the unit to be plugged into the front of the selected IRT frame and the rear assembly to be
secured to the rear panel of the IRT frame. To install the module in a FRU-3000 or FRU-1030 frame please see the
separate instruction manual “
Eurocard Frames & Power Supplies
”.
RF signal connection is made to the SMC connector on the
rear
of the RWT-3810, adapters are supplied to allow
connection to circuits using BNC or F series connectors
Optical signal connection is made to the optical connector on the
rear panel
of the RWR-3810.
Extreme care
must be taken to ensure the cleanliness and consequently the best return loss of the optical connections.
To overcome any optical path loss the RF signal level can be set using the front panel gain control (RV3), while at
the same time monitoring the output level using the front panel RF monitor connector which outputs the same RF
level as the rear output connector.
Note: the RF Monitor connector will need to be terminated with the 75 ohms
termination provided when not in use.
The optical input signal level is monitored by a current sense and comparator circuit, which is adjusted to change
state if the optical path loss exceeds the maximum optical budget by 3 dB.
The alarm circuit accepts signals from the optical level on LK1 closure and pilot fail circuits on LK2 closure to
operate relay RL1. The external connections for the alarm circuit are available on pins 2 and 3 of SK4 on the rear
panel. The alarm circuit is wired to give a relay contact closure when a fault condition such as power failure or low
optical input occurs. A second alarm contact closure is available at J3.
RWT-3810 adjustments.
RV1
sets the RF modulation level of the laser by applying a bias voltage to the RF attenuator circuit.
RWT-3810 Preset adjustments.
RV2
sets the output
LOW
indicator circuit as shown by LD3 on the front panel.
RV3
sets the output
HIGH
indicator circuit as shown by LD3 on the front panel.
RV4
sets the bias current to the laser diode and thus the optical output from the RWT-3810.
RWR-3810 adjustment.
RV3
sets the output RF level of the module by applying a bias voltage to the RF attenuator circuit.
RWR-3810 Preset adjustment.
RV1
sets the pilot
SIGNAL LOW
alarm circuit threshold as shown by LD2 on the front panel.
RV2
sets the input
SIGNAL LOW
alarm circuit threshold as shown by LD3 on the front panel.
Diagrams are provided for the RWT-3810 and the RWR-3810. The optical and RF signal sections are housed in
sealed shielded sections containing no user serviceable parts. Should service be required on these circuits, please
return the unit to the supplier for repair and alignment.
NOTE: If it is necessary to remove a component from the circuit board during
maintenance
IT IS ESSENTIAL TO ADD SOME SOLDER TO THE
COMPONENT SOLDER JOINTS BEFORE REMOVAL IS ATTEMPTED
. This
will add some solder flux to the joint and allow the heat from the iron to flow quickly
into the joint and prevent localised overheating and damage to the circuit board.
Rear assemblies may be removed for maintenance. Make sure that extraction force is
applied equally and steadily at the top and bottom of the rear assembly. SHOULD THIS
NOT BE DONE THERE IS A GOOD CHANCE THAT YOU WILL BEND THE
MODULE CONNECTOR PINS making it very difficult to re-install the rear assembly.
IRT
Communications
www.irtcommunications.com
