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RTN 980 with improper installed feeder in antenna caused BER

Publication Date:  2015-02-16 Views:  88 Downloads:  0
Issue Description
Backhaul RTN 980 series for a long distance with 3.0 meter antenna installed at site. The U2000 detects bit errors. Since its at the back haul , its very much a dense convergence site. almost 12 coarse convergence site merging at back haul site. U2000 v1r9 is used to check the performance for a week . all the reported UAS, SES and BBE only indicates there is an error. A lot of site test was done including using spectrum analyser, SDH analyser and checking all the AM and also xpic features.But, it seems all working in a proper condition but Bit error kept reported.
Alarm Information
The alarm indicates R_LOS and TU_AIS for continous moment. The perfomance indicates there are huge errors occuring since the hop is hop.
Handling Process

Step by step procedure were done.

1. Hardware installation including RTN, ODu, IF cable, antenna was rechecked

2. Service configuration (operation manual fault) was carefully checked and handled

3.Performance event was enabled over a period of 2 weeks

4. all UAS,SES,BBE , CA , LA, RSLD,FMD were continously monitored

5. ATPC, XPIC were rechecked

6. Cable fault (IF) checked

7. Interefernce checked and K factor effects checked

8.Rainfall and LOS rechecked.

9. Antenna installation checked

Root Cause

After all checking was done, the silver line at dark sky seems to appear. All equipment and ODu were checked except the antenna(Feeder on the antenna installation).

The main working antenna site was switched to protection so that the inner feeder installation could be checked.

Solution
In the antenna, the feeder was not properly installed. The angle of feeder did not follow the specification. After the feeder is restated and when the services swtiched to the working antenna now. The system stop reporting any bit errors. The antenna was huge and the inner part of feeder is always difficult to see. sometimes a small angle in the horn installation could give such a terrible man per hour to solve it
Suggestions
The installation of feeder in the antenna must be properly done according the specified SOP by manufacturers.In the event if the bit errorerd reported in a weird way after we check and recheck the entire link and sites, it will be great if we could recheck the inner sites of antenna as antenna is the most important part in RTN transmission.

END