No problem at all. Like this photo here:

http://www.thinkbroadband.com/images/news/3257-maste...

I've popped off the faceplate like that and my filter's plugged into the master socket behind. The grey cable at the bottom of the shot leads to my extension upstairs.

Yes, like that, only yours.

Does your extension have 3 and 4 connected?

SNR will vary during the day on every line due to a number of factors which you have absolutely no control over - on some lines by 2 or 3 dB, others by 7 or 8 dB and some even more. There will be a minute by minute variation of 0.1 or 0.2 but ignore that.

Assuming no resyncs occur during the 24 hour periods, you will see a trend appearig with a low SNR from around 22:00 trough to 04:00 is when it will start to increase and it will continue to do so until maybe 07:00. It will vary slightly until 20:00 or so, when it starts to drop again.

http://i2.photobucket.com/albums/y31/Polchraine/TBB/... shows a typical 18 hours for my last modem.

Based on that, where the minimum is around 0.5 dB at 01:00, I would resync at about 17:30 or 04:30 which would, in my case be a 3dB SNR but yours would normally be 6dB.

It may take a couple of attempts but you want your line to be stable - if it looses sync it will do so at night and the resync will drop the sync speed and possibly profile which can take days to recover. Resyncing at a time when the line is 3dB better than the low point will allow the margin to drop below the 6dB threshold without loosing sync but you will see a margin of 8 dB or so during the day.

Does that make sense?

I think so. So my best bet is to resync at the time of day when it looks likely that the SNR will equal my 6dB target?

What's generating so much noise at 0100?

Edited by deleted (Sat 28-May-11 22:21:33)

No quite - whatever time you resync you will get an SNR of 6dB at that time.

In the extreme ... sync at 01:00 and it will be 6dB and 2400 sync speed, at 06:00 6 dB and 3500 and 15:00 6dB and 3900 but the last will drop out at maybe 00:30 and resync at 6dB 2450 ...

So, what you are doing is finding a time when the SNR is about 3 dB above minimum. The router will still sync at 6 dB but will hold down to 4 dB or 3 dB. So you are not getting the absolute best sync speed but a stable one which will avoid overnight resyncs with a significant speed drop.

Atmospheric noise from distant radio transmissions (and other causes) is the main problem overnight with additional noise from street lights &c.


You also have commented below about the phone - even with filters in place you are modifying the characteristic line impedance which will have an effect on the performance of the modem (both ends) and line attenuation. Changes of a few percent are to be expected.

Think about your hi-fi amplifier which may be designed or specified for speakers with an 8 ohm impedance. It will still work with 4, 6 or 16 ohm speakers but the performance in terms of volume and frequency repsonse will vary.

Ok; so what's my minimum, just the lowest it ever drops to if I record it? So if it falls to 0.5, I want to resync at a time where I'm normally at 3.5?

It will be the lowest you see when you record it. RouterStatsLite is freely available and useful for this. You are unlikely to get down to 0.5 dB ! it need a very good modem to achieve that, but don't worry about the number, just remember 3dB above the low point, so if your low point is 5 dB resync when it shows 8dB and your speed increase whilst the SNR should be 6 dB +/- a small variation.

So, identify the lowest value, then go 3dB above that and look at the time and plan to do it around that time the following day. Then just keep an eye on the figure in te run up - just to make sure. then resync - all quite easy.

Another quick question for the expert; should my SNRs be the same or similar upstream and downstream? That ADSL2 stats checker tells me there's an error because they're too different, which could have been caused by downstream noise that's now lessened, forcing the DSLAM to sync me at the higher SNR rate on the upstream.

Anyone available to translate that?

In reply to a post by Elmlea:

Another quick question for the expert; should my SNRs be the same or similar upstream and downstream? That ADSL2 stats checker tells me there's an error because they're too different, which could have been caused by downstream noise that's now lessened, forcing the DSLAM to sync me at the higher SNR rate on the upstream.

Anyone available to translate that?

I see you're using http://adsl.tin2tin.net/

Certainly am!