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Target SNR Margin

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Target SNR Margin

Hi all,

Can anyone tell me how I find out what the target SNR that BT has set my line at.

Regards

Jeremy
13 REPLIES
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Target SNR Margin

Hi,

The only real way to find it to resunc your line then check the line stats to see what the SNR is as soon as the line resyncs as that will be the target SNR.

This page:

http://www.kitz.co.uk/adsl/frogstats.htm

shows you how to check the line stats on most modems.
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Target SNR Margin

I see, many thanks. I shall continue to play.

BT it seems are still playing silly buggers with my. My line has been happily running at 6800 for over a week and now has come down to 2 again. I have tweaked it up to 4 but whenever I reconnect my SNR margin is usually 10+ so I am guessing that the target has been reset again.

Regards

Jeremy
James
Grafter
Posts: 21,036
Registered: 04-04-2007

Target SNR Margin

Jeremy,

I've tried running some checks on your line to find your noise margin, but it's not working I'm afraid.

BT have also changed your bRAS to 2272Kbps. Do you know what speed you are synching at?
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Target SNR Margin

Hi James,

I have changed my router to a Belkin F5D7633 so I can at least tweak the SNR margin at my end.

I have been synched quite happily since yesterday evening at 5280 and my noise margin is currently 15.3 although that will drop later. Last week i held up at 6400 all week without issues.

The basic problem seems to be that something regularly causes my line to drop 2 or 3 times a day and it doesn't matter what the SNR is so I imagine that it is some form of very loud interference. This doesnt bother me at all since it almost always happens in the early hours of the morning but BT must have adjusted my target margin as I am synching at a speed with 15db margin.

I had been connected at 4Meg ever since I was Maxed up until a few weeks back when it suddenly dropped to 2Meg. I reported a line fault as my phone was noisy as well but BT said there was no problem. I then reported it as a broadband fault but was again told there was no problem so I resigned myself to having to live with a lower speed. I replaced my master socket with a filtered one but it didnt make any difference. Then, out of the blue (after about 2 weeks) the router suddenly synched at 6800 and then settled at 6400 for over a week. I then noticed that it had resynched at 4Meg and then ultimately 2Meg. Now I have replaced the router I have pushed it back up to 5Meg and I am hoping it will stay there although I expect to continue to get the overnight disconnects.

In addition to the line dropouts, I live in the country and we often get transient power cuts so my router may drop 2 or 3 times in a short space of time which is another reason that the profile drops I think. At one point, my next door neighbour had a load of topsoil delivered by one of the locals with a tractor and trailer which caused my line to resynch several times in a couple of minutes and ended up getting interleaving turned on which completely ruined my online gaming and took me some time to get removed.

Is it possible to get the target SNR fixed so that it doesn't change? My router carries on working quite happily with a margin as low as 2 or 3 and even when it loses synch it usually resynchs with virtually no delay.

Phew! That was a screed but you did ask Cheesy

Cheers

Jeremy
pacem
Grafter
Posts: 175
Registered: 07-09-2007

Target SNR Margin

You mention the Belkin F5D7633:
Does anyone have a list of routers for which the target-SNR can be manually adjusted? I'm sure this would be a simpler solution than pestering PN & BT to lower my SNR-target from 15dB only to have it set back up at 15 again when it rains becuse my upstream connection is dodgy. (But never goes wrong for long enought to get a fault raised and inspected..)

Paul.<><
Community Veteran
Posts: 4,729
Registered: 04-04-2007

Target SNR Margin

This facility is on some version of the Netgear NG834 range. But I would recommend going some web research to check compatibility's with different versions/variants.

Chilly
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Target SNR Margin

The Netgear DG834G definitely doesn't. That is what i was using before. I believe that the Netgear DG834GT does and the one I mentioned, the Belkin F5D7633 does as well. I don't know about any others.

Regards

Jeremy
Community Veteran
Posts: 38,206
Thanks: 898
Fixes: 54
Registered: 15-06-2007

Target SNR Margin

The Speedtouch routers also do but you can only drop it by 5dB maximum using the DMT tool
Have a look at this site to see which routers are listed as being supported http://dmt.mhilfe.de/
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Target SNR Margin

DMT doesn't seem to work with the F5D7633 now even though it is mentioned in the compatibility list for version 8.04

I think it is because the latest firmware (1.00.17) has removed telnet so now you have to use ssh to access the CLI.

I am hoping that they will change that as it looks like a useful piece of software.

Regards

Jeremy
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Target SNR Margin

The Netgear DG834GT and Netgear DG834PN both allow you to adjust the noise margin. But you have to re-adjust each time you reboot. You cannot adjust the base noise margin which is set by BT but you can adjust the actual figure up or down.
I do this all the time. At the moment my base noise margin is 6dB but I increase this to 12dB which gives me a stable connection syncing at ca. 6300kbps.
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Target SNR Margin

Actually, someone out there may be able to answer this for me. The asdl configure --snr command used on the F5D7633 uses a number to adjust that I have seen referred to on one website as being a fixed table of SNR margins, e.g. 10 = SNR of 4.7,20 = SNR of 5.6, and on another website as the number being a percentage of the target SNR set by BT, e.g. 80 = SNR of 4.8 (4.8 being 80% of 6)

I haven't been able to determine which is correct. Can anyone confirm which is the case?

Regards

Jeremy
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Target SNR Margin

On the Netgear DG834GT and DG834PN router the number used to set the SNR is the percentage of the SNR set by BT.
eg adslctl configure --snr 200 will set the SNR to 12dB if the basic setting is 6dB. If the base setting is 15dB, 200 will set it to 30dB.
Unfortunately on the 'kitz' site for this router it says that N is (16 * the reqd. SNR). This is only true if the base SNR is set to 6dB.
i.e reqd. SNR(12) = 12 * 16 = 192 (ca.200)
If the base SNR was say 9dB, using 200 would give you an SNR of 18dB and not the reqd. 12dB.
If you want to reduce a base setting of 12dB to say 6dB, you would use 50 as the value for N.
Hope this is clear.

Perhaps I should add the 'kitz' site is an excellent source of information on ADSL which I have used on a number of occasions.
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Target SNR Margin

Thats what I thought.

Thanks for the info.