Very low noise margin?
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Very low noise margin?
11-02-2013 2:04 PM
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I switched to Plusnet towards the end of January, and watched with bated breath to see what speeds I would end up with. However, whilst not dissatisfied with 5-6 Mb download speeds, I noticed that the downstream Noise Margin was very low, 3dB dropping to 1 and even 0 dB. I have tried swapping from the master to the test socket, which increased the download speed marginally, but made no difference to the noise margin. I have also swapped from my 3Com router to the Technicolour one provided by Plusnet; again, no difference (except it seems to be reporting download speed as 9.935 - I suspect the period/decimal should actually be a comma?), the downstream SN Margin is 3,0
One interesting thing I did notice after changing to the plusnet router, was that my upstream attenuation had dropped from 25dB to 13dB, but my downstream attenuation didn't change
I have tried running the BT Speed test and its further diagnostics, which doesn't find any problems, although it does seem to suggest I'm 3 Mb below the IP profile (down speed 5.67 Mbps, range 4Mbps - 21Mbps, IP 8.77Mbps). Likewise the Member Centre estimate is 10Mb, with the actual 6Mb. The upload is also slower than I would have expected.
Anyway, if anyone has any suggestions as to why my noise margin is so low, and how/if I can increase it (if I need to), I would be very grateful. Full router stats and the speedtest further diagnostics results attached.
Re: Very low noise margin?
11-02-2013 3:49 PM
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I'm not sure what exactly has caused this to happen, however I can see that the line has been dropping more since so a reset to bring it back to 6db might be a good idea.
Do you want me to give that a try?
Adam
Re: Very low noise margin?
11-02-2013 3:56 PM
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Quote from: _Adam_Walker_
I'm not sure what exactly has caused this to happen, however I can see that the line has been dropping more since so a reset to bring it back to 6db might be a good idea.
Dropping more since when? I use the internet a lot and haven't noticed any interruptions, but there would have been several this morning and last night when I was fiddling around with hardware/cables etc. However, if you think a reset to bring it up is a good idea, please do give it a try
Re: Very low noise margin?
11-02-2013 4:13 PM
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If you go here http://www.kitz.co.uk/adsl/max_speed_calc.php and put in your attenutaion of 26dB then your sync rate should be around 17600kbps. So you seem to have some excess noise on your line. I would try the Test Socket again.
Re: Very low noise margin?
11-02-2013 4:24 PM
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Is 'sync rate' effectively the upload/download rate? I don't know if I'm correct in thinking that it is (in which case there was next to no change between master and test socket), or where to find this 'sync rate' if not, as no statistics that I've been able to find are actually labelled 'sync rate'.
Re: Very low noise margin?
11-02-2013 5:12 PM
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For some reason your actual measured download speeds (in the range 5-6 Mbps) fall way short of your IP Profile. But in the short term ignore measuring the download speed, just be guided by the router (downstream) bandwidth.
Re: Very low noise margin?
11-02-2013 7:53 PM
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Quote from: ReedRichards I would try the Test Socket again.
Oops, missed that earlier; router is still connected to the test socket (i.e. the stats in my first post are whilst plugged into the test socket).
Re: Very low noise margin?
11-02-2013 8:06 PM
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The other thing to do whilst connected to the Test Socket is to ring your number and check that the only phone that rings is the one connected to the Test Socket (if you have one).
Re: Very low noise margin?
11-02-2013 8:42 PM
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Also the phone is the only one that rings when calling it.
Re: Very low noise margin?
11-02-2013 9:00 PM
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Re: Very low noise margin?
11-02-2013 9:12 PM
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Re: Very low noise margin?
12-02-2013 9:12 AM
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I've changed your line profile to match your sync speed so you should see an improvement.
I've also posted a graph of you connection which Adam was referring to, it's certainly more stable although you did mention that the disconnections may have been caused by you?
<img src="http://ccgi.psmith12.plus.com/visradius/generated/image13606600061642.png"/>
Re: Very low noise margin?
12-02-2013 9:53 AM
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Still going to try out swapping the filter etc. as ReedRichards suggested, just to see whether the noise margin will come up a bit higher. Also need to move back into the master socket, so fingers crossed
Re: Very low noise margin?
12-02-2013 10:15 AM
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That is supposed to be updated within a few hours when the BT Original changes but the update can fail. So find that, and check it if this happens again.
That may be what Chris corrected, but as I understand from some other posts by PN staff there is a third point, (within the BT Wholesale system), that can also get out of step. That's a bit trickier for them to spot.
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