User's Manual

Output gain regulation is performed as soon as poor antenna isolation is
detected during operation.
If instability due to poor antenna isolation is detected at the lowest
output gain, the channel is blocked and BLOCK mode is indicated in the
status window. Error alarm is activated when instability is detected and
Ceasing when the instability has ceased.
A constant CW signal in the GSM frequency band is a ’jammer’ which
may be harmful to the cellular system. A BTS might, in worst case, be
disabled. The Allgon repeaters detect, however, strong CW signals. If a
constant CW signal is detected (channel board test point Power 1 or
Power 2 >27dBm), the channel is blocked and BLOCK mode is indicated
in the status window. Error alarm is activated when the channel is
blocked and Ceasing when the blocking has ceased.
Antenna isolation test and CW signal strength test are performed in the
uplink path. Gain regulation is then performed for uplink as well as
downlink using the uplink levels.
Antenna isolation test is a valuable feature to reveal isolation
problems when installing repeaters. Also, it is very useful when
making site specific repeater adjustments such as antenna
configuration (i.e. donor and service antenna vertical and horizontal
positions, beam alignment, and gain). The antenna isolation test is
also useful to reveal other environmental problems that must be
considered, e.g. reflections from buildings, masts, traffic, etc.
After performing the antenna isolation test, set the repeater gain
(Gain set to) to the value obtained (13dB under the instability level).
The repeater will then work with a safe gain margin to avoid
instability.
It is not recommended to use the repeater isolation test in an
instable environment to automatically and continuously adjust the
gain from the gain set by the operator.
ALLGON System AB AR Repeaters & OMT32 Software – Repeater Operations
User’s Manual VD202 90/EN Rev. 1A 1999-07 10 - 17