User's Manual

VHF Headstation & In-Line Amplifiers
User Handbook
Handbook Nō.-50-127201FCC Issue No:-A
Date:-14/06/2005
Page:-
40 of 45
6. MAINTENANCE
6.1 General Procedures
6.1.1 Quick Fault Checklist
All AFL equipment is individually tested to specification prior to despatch. Failure of this
type of equipment is not common. Experience has shown that a large number of fault
conditions relating to new equipment have simple causes often occurring as a result of
transportation, unpacking and installation. Below are listed some common problems which
have resulted in poor performance or an indicated non-functioning of the equipment.
• Mains power not connected or not switched on.
• External connectors not fitted or incorrectly fitted.
• Internal connectors/ports becoming loose due to transport vibration.
• Wiring becoming detached as a result of heavy handling.
• Input signals not present due to faults in the aerial and feeder system.
• Base transmissions not present due to faults at the base station.
• Modems fitted with incorrect software configuration/and or PIN Nō’s.
• Changes to channel frequencies and inhibiting channels.
• Hand held radio equipment not correctly set to repeater channels.
• Hand held radio equipment not correctly set to base station.
6.1.2 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 radio 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 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 C
overage Enhancement Management System, if fitted), or locally
with the front door LED’s. The green LED should be illuminated, while the red alarm
indicator should be off. If the alarm LED is on, then the amplifier (or any other alarmed
device connected to the summary output) that is causing the fault will have to be isolated and
individually tested against the original test specification. The individual amplifier modules
have a green LED showing through a hole in their lid/cover, which is illuminated if the unit
is working correctly, and extinguished if not.
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.