Forum Discussion

pete_at_home's avatar
pete_at_home
Superfast
4 days ago

Signal Levels now 6dB down following Fibre Node replacement

Last week (Thursday 14th Aug), there was an outage in my area while VM upgraded the local Fibre Node.

Since then my DS levels have dropped by 6dB, and US now sending 6dB higher.   In itself this would not sormally be an issue, BUT the SNR on my Hub-5 has definitely degraded on a percentage of the QAM channels.   US channels regularly drop back to 32QAM or sometimes 16QAM.

Yes, I know the levels are "within the standard VM range", but the Post RS Errors are excessive.

Somewhat frustrating for someone who has worked on HFC & Docsis for well over 20 years !! 

Someone has not aligned the new fibre Node correctly.  Guess I have to call customer service & chase through the maze of getting them to understand !! 

The outage:  

 

5 Replies

  • legacy1's avatar
    legacy1
    Alessandro Volta
    4 days ago

    Problem is it works but not 100% or 99.9% fine

    BQM clearly shows small drops then it should

  • Client62's avatar
    Client62
    Alessandro Volta
    4 days ago

    Post RS Errors occur on Downstream channels with a line noise fault,
    it is often caused by a cable defect the locality.

    Check your own cables are secure at the wall sockets and at the
    Hub + at any VM TV kit or splitters.

    I am not be too concerned by the signal & SNR levels so long as they
    remain in the preferred DOCSIS range.

    • pete_at_home's avatar
      pete_at_home
      Superfast
      3 days ago

      SNR used to be 40-41dB on all channels.  Now many are 38dB which is minimum for reliable 256QAM.    US is screaming at 50dB, which agin is theoretically ok, but the HFC plant works best with 40-45dB from the modem.   My V6 TV box signal is also well low due to the location of the splitter feeding the modem & then a long cable for the V6. 

      One of the problems is the VM procedure for aligning the HFC has flaws in it (yes I have a copy).

      The VM contractors did spot another cabinet with signals on the tap bank all a bit low, so he moved them all up one step.  Then got called away before doing my drop cable as well.

      All in all a badly setup area since the new fibre node !!   All they need t odo is align that properly, because the RF Amps were correct & not touched.

       

      • Kath_P's avatar
        Kath_P
        Icon for Forum Team rankForum Team
        6 hours ago

        Hi pete_at_home, 

        Thanks for taking the time to contact us via the Community. It's lovely having you on board with us in the Forums. ⭐

        We're sorry to hear your signals levels have changed following work. As mentioned on the thread, the signal levels are within the optimal range. In terms of the post RS errors, can you reboot the hub so these go back to 0? They may have occurred whilst the engineer was playing around with things. If you see an increase in these following the reboot, let us know. 

        Many thanks, 

  • Roger_Gooner's avatar
    Roger_Gooner
    Alessandro Volta
    6 hours ago

    The issue is whether your broadband is working well, and you only start to look at stats if it isn't.