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    Noise Margin

    This is a discussion on Noise Margin within the Sky Broadband help forums, part of the Sky Broadband help and support category; I am trying to understand Noise Margin. This info is from the Kitz site: "The Signal to Noise Ratio on ...

    1. #1
      castro's Avatar
      castro is offline Sky User Member
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      Noise Margin

      I am trying to understand Noise Margin.

      This info is from the Kitz site:

      "The Signal to Noise Ratio on the max product is more flexible than on traditional adsl. On the older fixed line speed products an SNR Margin of less than 6dB suggested that there was a problem with the line.

      With Max a target SNR margin is set on the DSLAM and its your router and the DSLAM that agree the best way of meeting this target margin. The target margin range is between 3dB and 15dB and rises in 3dB increments - although it is normal for it to fluctuate either side during the training period. The default is 6dB without interleaving."

      My question is if the Noise Margin is set to 6.0db by default then how do I find out the maximum speed my line will support?
      I live about 750m from the exchange (straight line distance)

      ADSL Link Downstream Upstream
      Connection Speed 7968 kbps 448 kbps
      Line Attenuation 21.0 db 12.0 db
      Noise Margin 6.0 db 22.0 db
      IP Profile 6500kbps


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    3. #2
      penrhyn's Avatar
      penrhyn is offline Sky User Member
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      Re: Noise Margin

      The SNR in your router is not set to 6db, 6db is highest noise level that your router will reliably synchronise at.
      With your line attenuation figures I would have expected a faster speed and a higher noise margin.
      I suggest you do the usual checks, i.e Connect your router to the test socket of your master socket, and see what improvement you get.
      Then read this:PLEASE READ FIRST: How to obtain and post router stats

      ...and post your router stats.


    4. #3
      castro's Avatar
      castro is offline Sky User Member
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      Re: Noise Margin

      Following a power cut, my router re-synched at a higher rate than previously.

      ADSL Link Downstream Upstream
      Connection Speed 8128 kbps 448 kbps
      Line Attenuation 21.0 db 12.0 db
      Noise Margin 4.6 db 25.0 db

      As before, the connection is perfectly stable with no dropouts.
      All that I read says that a noise margin below 6db will cause problems.
      The BT line into the house is new and I have fitted a faceplate.
      The only other connection to the line is a phone and both the phone and the router connect via the faceplate. ie no extension wiring.
      As the line attenuation is lowish, why is the noise margin so low?

     

     

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