Motorola VSWR, Service Manual Supplement

Page: 36 / 44

Installing the VM
5th Feb 99
2–2
Service Manual Supplement: VSWR Monitor for M-Cell 6
68P02900W86-O
Installing the VM
Safety
precautions
Read through the information contained in Warnings and cautions at the beginning of
this document before starting the installation procedure. This equipment must only be
installed by suitably qualified personnel.
Disable the transmitter RF power in the BTS sector to be fitted with the VM by using lock
device commands from the OMC or via a PC connected to the MCU. Check that the
orange Tx STATUS LEDs on the relevant TCUs are not lit before starting to disconnect
the RF cables.
Cable loss
compensation
jumper settings
Figure 2-1 shows the arrangement of the three cable loss compensation jumper blocks
on the side of the VM.
TX
Off
RX2 RX1
2 3.5 5 Off 2 3.5 5 Off 2 3.5 5
JUMPER
JUMPER
BLOCK
ALARM
LEDs
Figure 2-1 Arrangement of cable loss compensation jumper blocks on the VM
Set the position of the jumpers for each of the Rx and Tx connections according to the
information supplied in Table 2-1 below:
Table 2-1 Cable loss compensation jumper positions
Cable Loss (dB) Jumper Position VSWR Range
Monitoring OFF Off –
0.0 – 2.0 2 > 1.5:1
2.1 – 3.5 3.5 > 2.0:1
3.6 – 5.0 5 > 3.0:1
Set the jumpers to position 3.5 if the cable loss figure is not known.
Set the appropriate Rx jumper to “Off” if either of the Rx cables is to be left
disconnected, otherwise a false alarm will be generated for that signal line.