adsl - my noise margin seems to be all over the place...

snow patrol · 2 Jan 2008 at 11:45

The past couple of days i've been experiencing dodgy internet speeds and low sync rates on my router, plus lots of drop outs. I'm on ukonline LLU which has been excellent for the past 2 years.

I've been checking my stats, and MOST of the time my noise margin is in the 8 - 12db range. However, every few minutes at the moment it starts dropping down, to 6db then 4db and sometimes even below 1db. Any ideas whether this may be temporary or not? I'm even consideing VM Cable.

neil_g · 2 Jan 2008 at 13:19

id get your ISP on the case. thats not right.

generally snr should be around a min of 12dB, any less than 6dB and id be suprised if you can connect at all.

make sure theres nothing near your modem/router that can generate noise too (PC fans, transformers, fridge, motors, bad electrical connections)

snow patrol · 2 Jan 2008 at 13:25

hmmn, well i actually have my modem on top of my pc, and there's also a couple of external hard disks right next to it. So is that a bad idea then.

I'll move it and see how it goes...

neil_g · 2 Jan 2008 at 13:26

does your router have an attenuation reading too?

snow patrol · 2 Jan 2008 at 13:34

yeah, downstream is 46.0 db

Thing is though, at my current address my stats have always been like this, although the noise margin never used to dip so low (under 6) and i'd be able to sync at 5 or 6 meg. Today i'm syncing at really low speeds.

i moved the router to the side of the pc but it hasn't really made any difference.

neil_g · 2 Jan 2008 at 13:37

46dB attenuation is approx that of a 1mb line..

tbh id give your ISP a shout.

snow patrol · 2 Jan 2008 at 13:45

but surely if it's a problem with my line they'll just tell me to contact bt

i'm really close to ordering virgin media XL. The only thing holding me back is some of the bad feedback i've heard about them

neil_g · 2 Jan 2008 at 13:46

not necessarily.. even though they should deal with BT on your behalf.

snow patrol · 2 Jan 2008 at 13:51

ok thanks neil, i'll give it a go.

neil_g · 2 Jan 2008 at 13:54

let us know what they say..

most of the time a "line test" may cure the problem (im sure they reset stuff as part of the test), although it could be a faulty DSLAM at the exchange or cabling somewhere between you and the exchange.

tolien · 2 Jan 2008 at 21:42

They shouldn't tell you to contact BT if it's not a fault with your voice service.

Fluctuation in your SNR margin isn't abnormal, but if you're seeing a big reduction in sync rate at the same time it could be a fault. Have you tried connecting the modem to the master socket with no extensions or filters?

snow patrol · 2 Jan 2008 at 22:04

Tolien said:
They shouldn't tell you to contact BT if it's not a fault with your voice service.

Fluctuation in your SNR margin isn't abnormal, but if you're seeing a big reduction in sync rate at the same time it could be a fault. Have you tried connecting the modem to the master socket with no extensions or filters?

well i ran a phone line extension to the master test socket but it didn't make any difference. I suppose i could put the modem there and run a long cat5 cable to the pc but tbh that would be very inconvenient

tolien · 2 Jan 2008 at 22:11

You really need to try to eliminate your own side of things - if UKOnline arrange for BT come out and discover it's your wiring at fault, you'll probably be charged.
Ideally that includes connecting at the master socket with no extensions or filters, or at the test socket, and a different modem.

Senture · 2 Jan 2008 at 22:47

Tolien said:
if UKOnline arrange for BT come out and discover it's your wiring at fault, you'll probably be charged.

£116 to be exact

$anch3z · 3 Jan 2008 at 04:23

Just to echo whats already been mentioned - connect back to the master socket (NTE5 if possible) - lose any extensions, xmas tree lights - especially if they flick on and off. If your SNR is fluctuating your line is being effected by noise spikes from an external source and the dslam at the exchange is attempting to compensate. Usually the snr is set as you sync at your exchange but if the margin is not great enough then the line becomes unstable.

If that fails get your isp to investigate, ask for a high snr profile to be set on your line which most can do remotely with LLU.

snow patrol · 3 Jan 2008 at 10:15

thanks guys. Interestingly enough, today i'm syncing close to 5meg but by snr is too low, around 4 - 7 and sometimes lower when the internet just doesn't work at all.

What's the best place to locate the router then? Should it be away from the pc / monitor etc? So if i were to plug it into the master socket, would i not need a micro filter even?

Senture · 3 Jan 2008 at 10:26

Right next to the master socket, microfilter goes into the master socket and router plugs into that. Try to keep speakers/microwave/phone away from the router, I had BT inspect my line due to noise I was getting. Turns out that the WiFi was causing the drop outs and noise, moving the phones away fixed it.

snow patrol · 3 Jan 2008 at 10:29

interesting stuff. i'm going to have a go at this later on.

tolien · 3 Jan 2008 at 11:12

If you only connect the router (as you really should if you're going to see if connecting to the master socket helps), you don't need a filter - you'll need an adapter to convert the RJ11 on the end of the cable to go into the master socket though.

snow patrol · 3 Jan 2008 at 15:38

hmnn, well i don't have any sort of adaptor unfortunately. I was thinking about running a 30ft network cable from my pc to the modem, and then running a very short phone line from the modem to the master socket, or even the test socket behind it. Would that make any difference? I'd previously tried running a long and old telephone extension cord to the master socket, but i'm guessing that isn't really a good idea.

If i run the network cable directly into the test socket, what kind of adaptor would i need (and where can i get it?)

Thank you again, lots of helpful responses here.