User Manual

PBL UHF 1 & 2 Air Interface
Maintenance Handbook
H/book Number:-60-055900HBKM
Issue No:-1
Date:-13/02/2003
Page:-76 of 76
7. MAINTENANCE
7.1 General Procedures
7.1.1 Fault Finding
In the event that the performance of the system is suspect, a methodical and logical approach
to the problem will reveal the cause of the difficulty. The System consists of modules within a
wall mounted, environmentally protected enclosure.
Transmissions from the main base stations are passed though the system to the mobile radio
equipment; this could be a handheld walkie-talkie, mobile telephone or a transceiver in a
vehicle. This path is referred to as the downlink. The return signal path from the mobile radio
equipment to the base station is referred to as the uplink.
The first operation is to check the (optional) alarms of each of the active units and determine
that the power supplies to the equipment are connected and active.
This can be achieved remotely (via CEMS, the digital RS232 Cell Enhancer Management
System, if fitted), or locally with the front door LED’s. The green LED on the front door
should be illuminated, while the red alarm indicator should be off.
If an Alarm is on, then that individual module must be removed and tested against the original
test specification.
The individual amplifier units have a green LED showing through a hole in their piggy-back
alarm board (or directly through a hole in the the amplifier lid), which is illuminated if the unit
is working correctly.
If an amplifier is suspect, check the DC power supply to the unit. If no other fault is apparent
use a spectrum analyser to measure the incoming signal level at the input and then after
reconnecting the amplifier input, measure the output level. Consult with the system diagram
and amplifier specification to determine the expected gain and compare result.
In the event that there are no alarms on and all units appear to be functioning it will be
necessary to test the system in a logical manner to confirm correct operation.