User Manual

UHF Bandselective BDA
90dB 40/5W
Document Number 55-199102HBKM Issue No. 1 Page 20 of 28
6. FAULT FINDING / MAINTENANCE
6.1. Tools & Test Equipment
The minimum tools and test equipment needed to successfully service this AFL product are as
follows:-
Spectrum analyser: 100kHz to 2GHz (Dynamic range = 90dB).
Signal Generator: 30MHz to 2GHz (-120dBm to 0dBm o/p level).
Attenuator: 20dB, 10W, DC-2GHz, (N male – N female).
Test Antenna: Yagi or dipole for operating frequency.
Digital multi-meter: Universal Volt-Ohm-Amp meter.
Test cable x 2: N male – N male, 2M long RG214.
Test cable x 2: SMA male – N male, 1m long RG223.
Hand tools: Philips #1&2 tip screwdriver.
3mm flat bladed screwdriver.
SMA spanner and torque setter.
6.2. Basic 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 in a wall-mounted
enclosure.
Transmissions from the main base stations are passed though the system to the mobile radio
equipment; this could be a handheld radio or a transceiver in a vehicle. This path is referred to as the
downlink. The return signal path from mobile radio equipment to the base station is referred to as the
uplink.
The first fault finding operation is to check the 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 RS232
Coverage Enhancement Management System, if fitted), or locally with the front
panel LEDs. The green LED on the front panel should be illuminated, while the red alarm indicator
should be off. Note that passive only shelves will have no DC power or alarm indicators. If an Alarm is
on, then that individual shelf must be isolated and individually tested against the original test
specification. The individual amplifier units within any shelf have a green LED showing through a hole
in their cover, which is illuminated if the unit is working correctly. (Without active power supplies there
can be no alarm LED indicators, however without DC power, the fail-safe summary alarm system
[normally closed relay contacts] will be an open circuit, thereby activating any externally connected
system.)
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 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 systematic manner to confirm correct operation.