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Reply To: RX Diversity Alarm


Fault name RX diversity lost
Description The imbalance in signal strength between the receiver A- and B-side is
supervised on a TRU basis. The fault arises when one or several TRUs have
reported a signal strength imbalance of at least 12 dB during 50 minutes.
This indicates that an RX path to one or several TRUs is faulty. The
receiver sensitivity for these TRUs is reduced by about 3.5 dB. Note: This
fault is not raised if one of the faults SO CF I2A:7 (RXDA), SO CF I2A:11
(TMA current), SO CF I2A:34 (TMA voltage) or SO CF I2A:39 (RX cable)
is active.
Action Enable the diversity supervision monitor in OMT for each TRU, to find out
which TRUs are affected and which side (A or B) is faulty. The diversity
supervision measurements are only taken every 5 minutes so it takes some
time to notice changes. The measurements give signal strength imbalance
(SSI, expressed in dB) on each TS. The SSI is equal to RX signal A-side
minus B-side so positive values indicate that A-side is better and vice-versa.
Check that all cables on RX-path are properly connected (including HLin/
HLout). Also check the antennas. If several cells are affected then maybe
two RX feeders have been switched. If only one TRU is affected, then
check RX cable between TRU and CDU. Try moving TRUs, CDUs and
cables in the cabinet to see if the fault follows the unit(s).