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    Target Noise Margin

    This is a discussion on Target Noise Margin within the Sky Broadband help forums, part of the Sky Broadband help and support category; Last night CST changed my line from ADSL2 to G.DMT in an attempt to fix a problem with my router ...

    1. #1
      GRM's Avatar
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      Target Noise Margin

      Last night CST changed my line from ADSL2 to G.DMT in an attempt to fix a problem with my router rebooting several times an hour.

      My new stats are:

      Code:
      Mode:			G.DMT
      Channel:		Interleave
      Trellis:		ON
      Line Status:		No Defect
      Training Status:	Showtime
      		Down		Up
      SNR (dB):	9.7		14.0
      Attn(dB):	63.5		31.5
      Pwr(dBm):	17.9		12.5
      Max(Kbps):	2880		928
      Rate (Kbps):	2112		608
      Is there a way to lower the SNR to around 6 or 7dB to take advantage of the apparent headroom between my sync rate and max rate? I've tried resyncing, rebooting and Mel's target SNR tool but none of them result in anything less than 9.7dB. Is it likely to have been 'hard coded' by CST to 9.xdB?

      Router is connected to the test socket, there are no extensions.


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    3. #2
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      Re: Target Noise Margin

      You have been put on G.DMT because it is the best option for you on such a long line. Sky default SNR is 6.9db. You currently are on 9.7db which may drop lower in the evenings. The difference between the two figures would not give you more than say 300kbps on your sync.
      So I would be happy as you are. Do monitor the SNR in the evening and see if it does drop. Most do.

    4. #3
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      Re: Target Noise Margin

      CST have 3 SNR settings - 7, 9 and 12dB...it's possible they've set it to 9dB as you've been dropping out on 7dB...

      It's your choice to have speed or stability, on a line as long as yours would appear to be you might not get both...
      -------------------------------------------



      Useful Sticky: - How To Obtain Your Router Stats, BT Speed Test, Check For Test Socket

    5. #4
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      Re: Target Noise Margin

      Thanks for the replies - very informative.

      The 'true' attenuation of my line is 68dB as seen when I was on ADSL2. As I'm sure you know it's restricted to displaying 63.5dB on G.DMT.

      It was interesting if not a little disconcerting when I was on ADSL2 to see my line behaving quite happily with the SNR varying between 1 and 3dB. Only when it dropped below 1dB did errors become so high that data flow stopped and a resync was neccesary.

      It may only be 300kb/s but that's 15% for us out-in-the-sticks dwellers ;-)

      Anyway, a 5 BT 2Wire has just arrived in the post via eBay - time for a play....

    6. #5
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      Re: Target Noise Margin

      Know what you're saying about being 'out in the sticks' - I was in the same boat until recently and although my speeds were better than yours being on Connect didn't help!! Loving being on LLU now!!

      Post stats once you're 'had a play' and we can comment further...
      -------------------------------------------



      Useful Sticky: - How To Obtain Your Router Stats, BT Speed Test, Check For Test Socket

    7. #6
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      Re: Target Noise Margin

      Posting via the 2wire....

      Would have been about 90 minutes ago if I hadn't wasted all that time trying to diagnose why it wouldn't authenticate with Sky. Searched everywhere for a resolution.

      Putting the RJ11 cable in the right socket on the back helped :-/ Damn VOIP-enabled routers :-)

      Code:
        	        Down  	        Up
      Rate:        	2112 kbs 	608 kbs
      Max Rate: 	2668 kbs 	764 kbs
      Noise Margin: 	11.0 dB 	14.0 dB
      Attenuation: 	63.0 dB 	31.5 dB
      Output Power: 	17.6 dBm 	12.4 dBm
      Not that different although the SNR is even higher now, might be useful If I want to squeeze a little more speed out of the line. Think I'll leave the 2wire plugged in for a couple of days and see if any of the stats change.

      But at least I have a spare now in case the Netgear ever goes pop.

    8. #7
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      Re: Target Noise Margin

      Quote Originally Posted by IWasNotTheEnemy View Post
      Know what you're saying about being 'out in the sticks' - I was in the same boat until recently and although my speeds were better than yours being on Connect didn't help!! Loving being on LLU now!.
      Just realised you're on Be now. Did you move house to get the 6.8/1 Mb/s connection or are you still in the sticks? It's just that Be LLU are in my exchange but I dismissed the idea of moving thinking they wouldn't be able to offer much of an improvement over what I've had/have from Pipex/Connect/Sky LLU on my 5km line.

    9. #8
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      Re: Target Noise Margin

      Now in a city - can get 16Mbps but 8Mbps is more than enough for me...on a 2km line...and that speedtest was over wireless...

      looking at that now it looks like you're not on a 9dB profile - prob just the line syncing in a quiet period...reboot it first this in the morning and if it's still high then the line is capped speedwise - hence the higher SNR...which was probably due to the intermittent connection you had before...
      -------------------------------------------



      Useful Sticky: - How To Obtain Your Router Stats, BT Speed Test, Check For Test Socket

    10. #9
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      Re: Target Noise Margin

      O2/Be will not support very long lines and 5km may be over what they are willing to take on.

      Although I had real problems with Sky LLU with line instability yet with O2 all those problems went away.
      I'm a PC, and Windows 7 Backup saved my sanity when BitDefender imploded !!!

     

     

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