Issue with SNR + sync speed.

Hi guys,

After about a month or so with of being active, our line has a weird issue that I can't work out.

The line has been stable up until now, SNR has been locked to 6db and sync speeds have been great..until last weekend.

I have contacted the ISP about this issue but I'd like to get some feedback from you guys who may have seen this issue before and know where to look/what to do.

What happens is the SNR will start off at 6db then suddenly either raise or drop. When it raises or drops, the sync speed will also drop to around 2500kbps rather than the 8500kbps+. Yesterday, the connection was fine from around 9am until 4.30am. Here are some graphs showing what's happening.

http://i.imgur.com/pvDjveO.jpg

http://i.imgur.com/HnQ1JAv.jpg


Things I've tried:

Changing filters
Changing RJ11 cable
Changing Routers
Plugging directly into test socket
Changing plug sockets for the router
ISP increased target SNR to 9db (didn't help)

The master socket is the only socket we have wired up. Like I said, it's been stable until now and we haven't changed anything.

Any help with this would be great as it's driving me crazy!


Edit: Current stats:

ADSL Link Downstream Upstream
Connection Speed 2784 kbps 824 kbps
Line Attenuation 52.0 db 20.7 db
Noise Margin 7.7 db 7.0 db

Have a gander at my thread here:

http://forums.thinkbroadband.com/general/t/4212010-s...

Getting to the point, I finally managed to get BT to run diagnostics on my line, and they found 'nothing wrong' - but since they did that, all is back to noraml again. I even had a engineer booked to come around, but cancelled at the 11th hour due to my line mysteriously working properly again.

Nick

I'll take a read in a second but my ISP already did diagnostics and found nothing wrong also

Your ISP can only run certain line tests - BT do some sort of load test on the line (I dunno the specifics), so it is a different test. I got disconnected twice when this was going on (although I didn't know they was testing at the time) and each time sync'ed back at a higher rate. They it is stable again.

Nick

Run Router Stats for a whole 48 hour period with 30 secs samples and post those images.

That looks like an external noise source kicking in and running. My first guess has to be your (or your neighbour's) central heating. Check to see what time it is set to come on at - and compare the two clocks.

Everyone runs their central heating 24/7 around here due to it being included in the rent (apartments).

I don't understand how it can be stable for over 3 weeks then start to become unstable (which also leads me to believe it won't be CH).

Edited by deleted (Sat 23-Feb-13 09:42:29)

can you select G.dmt or G992.1 as the ADSL mode on the router, rather than auto / multimode etc ? See what that syncs at.

I shall do that in a second.


I've just done a quiet line test without the router turned on, line was deadly silent. I turned the router on and lots of noise, crackles and whistling occurred. I moved the router into another room and tried again, same thing. I disconnected the router and the noise went away. My question is, why does this happen, why has it only just started to happen and why does it happen at certain times?

Is there a central stair case which is heated during the day?

With apartments all lines are often bundled together and run in service ducts? Is this the case?

Just as a line can develop a fault, any electrical system can and you cannot rule out CH, fridges, freezers, jacuzzi baths &c just because it was stable for a long time and suddenly it is not.

You certainly need to get several days of stats together and see if there is any commonality.

No, it's an odd apartment setup. It's basically purpose built houses but split into apartments. Houses are attached, 3 storeys then split into apartments. We have a two floor apartment with an apartment below us. On the left of us we're attached but on the right of us there is an outside stairwell which separates us from the next house. I can only assume that there's a line per house bundled into two/three?

I'm going to do the following:

Put router into modem only mode to rule out RF interference
Check the MCB to see how the sockets are split, try a different socket completely
Cry if everything fails