cancel
Showing results for 
Search instead for 
Did you mean: 

SNR is 3.0dB !? Frequent disconnections in the evenings too.

phile
Grafter
Posts: 32
Registered: 10-10-2009

SNR is 3.0dB !? Frequent disconnections in the evenings too.

Just moved house. Broadband followed me faithfully (nice job, PlusNet) but the new line seems to be acting up a bit with frequent connection drop-outs in the evening.
I notice from my router stats that the SNR drops to 2.5-3.0dB in the evenings, from about 5dB during the day.
I'm no expert, but 3dB seems very low... can anyone (esp. from PlusNet) tell me if this might be the cause of my flaky evening broadband? If it is, what can I do about it? (I've already tried all the usual stuff - plugging directly into the master socket, swapping microfilters, removing all other equipment from the line and so on).
If it's any help, here are my router stats about ten minutes after retraining the connection and then starting to download Mad Men on the BBC iPlayer - those upstream line error counts look suspiciously high...
Protocol  ADSL State      Showtime  
          Data Path      Interleave 
          Operation Mode  G.DMT 

                              Downstream  Upstream 
Line Status  ADSL Link Speed  4512kbps    448kbps 
            SNR              3.0 dB      - 
            ATEN            42dB        25dB 
Line Error  ADSL layer  FEC  2            42630 
                        CRC  0            25755 
            ATM layer  HEC  3            22660 

Thanks! Phil
31 REPLIES
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Resync in the evening and then leave the router on permanently
This will drop your speed to about 4200kbps and your profile to 3500 kbps
Having said that you should be getting much better speeds with that attenuation
Can you plug the router into the test socket and report the stats immediately after (I suggest waiting until tomorrow morning to do it for a proper comparison)
phile
Grafter
Posts: 32
Registered: 10-10-2009

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Thanks for the quick response Oldjim.
I've been doing pretty much what you recommend already, if only to try & keep the broadband alive & useable in the evenings, but things don't seem to be improving. The router (D-Link DSL-504) stays on all the time & I've been retraining the connection to re-establish it each time it drops out (in preference to either waiting for it to come back on its own, or physically switching the router off & on again).
Unfortunately I have an old-style BT master socket without the test socket inside.
I'd gladly trade a bit of line speed for a more robust connection though. Any ideas?
Cheers, Phil
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

When you reconnect in the evening what noise margin do you get at that point
phile
Grafter
Posts: 32
Registered: 10-10-2009

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Ah, now - is there a difference between noise margin and SNR? My router only reports SNR, which seems to be a steady 3dB whenever I reconnect in the evenings. I have seen it as high as 5dB during the day though.
Incidentally, I left it on all night and this morning it was not connected so I unplugged the router for a while. When I switched it back on, the sync speed was a rather impressive 4960kbps (highest I've seen it) and the SNR was still 3dB. Despite the low SNR, the connection has been rock solid so far this morning and I've downloaded about 1.5GB of iPlayer programmes. I also notice the line error stats are different - Upstream ADSL layer FEC is high (30,000 or so) but all the others are less than 20, whereas in the evenings they climb into the tens of thousands.
I'll monitor it all day but I expect it to go bad again when it gets dark...
Phil
Edit: SNR just went up to 4dB (11am)
[Moderator's note by Dick (Strat):  Full quote of preceding post removed, as per Forum Rules ]
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

You have two separate problems
The first is that the default noise margin at the exchange seems to be set at 3DB which is most unusual
The second (and this is why you are seeing the problem) is that when the router loses sync it doesn't automatically reconnect.
Can you borrow another router to test - you could get one from Plusnet for £4.99 p&p but with a 12 month tie in (you need to pay the full cost if you leave before 12 months) - or you could bite the bullet and buy one
Have you looked for an updated firmware for the D-Link
grahamt
Rising Star
Posts: 561
Thanks: 12
Registered: 05-04-2008

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

If you're getting lower speeds than you should be with your attenuation, it may be because the bell wire (aka ringwire) in your internal wiring is still active. I had the same kind of problems as you - lower speeds and a drop in SNR after dark. I still get the SNR drop (from 6db in daytime to around 0db in the middle of the night - my router, a ZyXEL, normally manages to hold onto the sync, but not always). I suspect it might be due to street lighting. But after I found someone competent and willing to cut my bell wire my downstream sync speed went up (for an attenuation of 3Cool from about 4500 to about 8000 (currently 830Cool. This is admittedly on ADSL2+, but I'm sure something similar would have happened with ADSL1.
Depending on what state your wiring and sockets are in, you may be able to achieve the same result with one of the faceplates on sale. Otherwise, there are diagrams on how to cut the bell wire on the Kitz site. There's a roundup of possible solutions to low SNR problems here.
http://www.kitz.co.uk/adsl/lowSNR.htm

Graham
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

The poster has an old style socket so non of the above is relevant
phile
Grafter
Posts: 32
Registered: 10-10-2009

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Thanks for staying on my case guys!
I'm currently monitoring my router's stats to see how things progress. The SNR, which has been at 4.5 all day, has now dropped to 4.0 simultaneous with a startling change in the pattern of upstream FEC errors. I'll post the graphs a bit later. Suffice to say for now that the changes coincided with the street lights around here starting to come on.
Oldjim, the router is pretty old and may be having trouble resynching. I'll look into a replacement - I've heard good things about the Netgear DG834 being a good one at keeping sync. So far as I know there has not been a firmware update for my current one since it was launched.
As for the low noise margin setting at the exchange, presumably there is a way to request an increase - any idea how I do that?
18:50 - OK my connection just dropped out for the first time today. Router reconnected itself about four minutes later but the SNR is now down to 3.5. From here on I would expect increasingly frequent disconnects until the broadband becomes effectively useless.
Graphs to follow...
Phil
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

The Netgear DG834G v5 is not good on long lines (I know because I tried one and sent it back as it was much worse than my DG834G v4 with a Broadcom chipset) but the DG834 v4 (non wireless)  does use a Broadcom chipset and is recommended. It must be the v4 as the earlier versions used an AR7 chipset which isn't as good
You can also tweak the noise margin yourself using DMT
phile
Grafter
Posts: 32
Registered: 10-10-2009

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Connection is flaking badly now. Here are the graphs from earlier. Tx FEC may or may not in itself be informative, but the graph does rather demonstrate that something goes wacky as the sun sets.
Thanks for the Netgear info. DMT is the tool available from Kitz.co.uk?
Phil
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

198kHz
Aspiring Champion
Posts: 3,442
Thanks: 404
Fixes: 11
Registered: 30-07-2008

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Quote from: Oldjim
The poster has an old style socket so non of the above is relevant

There's no reason why the OP cannot remove the ring wire(s) from pin 3.
Remember you are unique - just like everyone else
Community Veteran
Posts: 38,460
Thanks: 1,028
Fixes: 62
Registered: 15-06-2007

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Except that the wiring in the old style socket presumably belongs to BT and of course you are assuming that there are extension sockets in the house
198kHz
Aspiring Champion
Posts: 3,442
Thanks: 404
Fixes: 11
Registered: 30-07-2008

Re: SNR is 3.0dB !? Frequent disconnections in the evenings too.

Yes, of course, the wiring feeding the line into the master socket, and the socket itself, belong to BT. If there is any extension wiring, the OP is free to do as he wishes. His original post suggests that there is at least one extension socket.
Quote from: phile
I've already tried all the usual stuff - plugging directly into the master socket, swapping microfilters, removing all other equipment from the line and so on
Remember you are unique - just like everyone else