Noise Margin Fluctuation

[MarlyM]

Hi guys,

Question for you:  What's the normal amount of Noise Margin fluctuation on a line?

Mine seems to hover between 14.5dB and 15dB most of the time.  Sometimes it will drop to 12dB.  Then it may spike to 17dB, then is make drop to 0dB then pp back up to 15dB!

When I first had ADSL on this line, it was always about 6dB.

Any thoughts?

Thanks.

[Glenn]

I have a 9db target nm on my line, but the connection is generally around 6 - 7db, 24/7. Others have nm that fall during the evening losing around 3db or so, before recovering as the noise subsides.

[Steve]

I think you need to post some more details i.e router stats and a BT speedtest , then we can see what's going on.Certainly the margin is high which will be affecting your speed.

[Gary]

What Steve said  (damn your fast fingers) 

[Rik]

Fwiw, my target margin is fixed at 6db, and I see a range from 6.9 - 5.2db. On my other line, the range is greater 9.8db - 2db.

[klipp]

Mine is 5db in the day and 2db at night.

[MarlyM]

Hi guys, thanks for the replies.

Here's some info:

Today (between my first post and now) my NM has been between 14dB and 15dB apart from 6 occasions where it dropped to 0dB.

Here's a speedtest result from 2 mins ago:
Download Speed: 2319Kbps
DSL (D) - 2880Kbps
DSL (U) - 448Kbps
IP Profile - 2500Kbps

As a note, here's my specs from the beginning of August (around 8am one morning on old ISP):
Download Speed: 4225Kbps
DSL (D) - 5376Kbps
DSL (U) - 768Kbps
IP Profile - 4500Kbps

Hope these help.

MarlyM.

PS: I've just got more help from you guys than I ever got from my previous ISP on their forum!

[Glenn]

Have you made or received any calls today? If you have did the nm drop at the same time?

[Rik]

Thanks, we try hard.

A 15db target noise margin, which is what you appear to have, would cost you 2-2.5Mb, so that would explain things if you were on a target 6db before. The low upstream rate intrigues me and suggests errors. Let me make some enquiries, be right back.

[MarlyM]

Thanks guys.

I thought the upstream rate was what it was!

No calls made and no missed calls coming in.

[Rik]

Marley, were you a a premium or business package before you moved? All the stats IDNet have show your line as behaving correctly. You have a 54db attenuation, so would not normally see a much higher sync speed.

Do you have an NTE5 master socket, the type where the bottom half of the faceplate can be removed? If so, could you move the router to that for at least 24 hours? Do you have any BT speed tests or other details of your previous connection? If so, could you contact support so they can look further into the issue for you.

[MarlyM]

Hi,

Standard home package (with the 800Kbps upload).

Have got more speedtests than I can shake a stick at from the old ISP (one of the reasons I left was the evening speeds were awful and towards the end, I never got more than 1.2Mbps at any time of day).

Have tried the test socket previously, but the NM stayed about the same.

Just odd that a couple of months ago, it was twice as fast.

I've checked into dB loss, and I thought I'd get nearer to 4Mbps (I know there are lots of other things that can affect the speed).

If the line is behaving correctly, is there any way to foce the NM on the line, or do I have to wait for it to happen automatically?

Thanks.

[MarlyM]

Morning all.

Am now connected into the test socket.

Will continue to monitor.

Had a few more 0dB drops last night over night before moving to test socket.  Will see how it goes and keep you updated.

Thanks.

[Rik]

Hi Marly

It sounds like you haven't come across on a like for like migration, the 800k upstream means you were on a premium package. Support are going to try resetting your target noise margin, but keep the router in the test socket for at least 72 hours.

[MarlyM]

OK Guys, an update! (thanks to RouterStats Lite!)

Firstly, thanks Rik for liaising with Support and getting my target NM reset.  Here's the day so far:

From 6:20am this morning (after connected o test socket) until 8am, dB starting at 12.5 rising in spikes to 14dB.  A couple of full 0dB drops.

After 8:30am, a couple of spikes from 13.5dB until about 10:30 when my NM was reset (thanks!) (Sync up to almost 5Mbps!!!)

From about 13:00 a totally steady connection without a hint of fluctuation until 18:20 when My connection was totally dropped and the router resync'd.

Now steady again.

As another note though, I must add that from early this morning, BT had been working on a cable further down the road (not the one directly to my house, but from the pole with with the fat cable coming in to the area) as a neighbour had a very noisy line.

So, I don't know when that's a contributing factor to the line being less noisy, of it it's all the work of IDNet (and the guys here).

Either way, if the disconnections stop, and the speed and NM stay reliable, I'll be one extremely happy IDNetter!

Thanks again, and I'll keep you informed as to how it all goes.

PS: Rik, will my package be changed to a like for like from the migration or is this how it stays?  Thanks.

[Rik]

Only if you request it, Marly, apparently you ordered the 'ordinary' package when you migrated.  your problems are solved.

[MarlyM]

Ah, didn't realise I had the option of the like for like (then again, if it's any more pennies, I'm happy where I am as I've already gone up in monthly payments).

As another update, lost sync completely again 5 minutes ago (went to minus 9dB!) - resync now half a Mb down from 30 mins ago.

[Rik]

Sounds like DLM is kicking back in. Has your NM gone up? What's the downstream attenuation on your line?

[MarlyM]

NM is still 6dB (with none of the .5 fluctuations as before).
Downstream attenuation is still 54dB.

[Rik]

It might be worth your while getting a 2-Wire 2700 router, <£20 from eBay. Many of us afflicted with longer lines have found that they hold on to the line like glue. Your speed drop is probably just noise levels increasing, RFI and crosstalk, and what I'd expect to see is that, if the sync holds, you will have a larger NM tomorrow morning, as the noise goes away again.

[MarlyM]

OK.  May be able to borrow a 2700 to test.

Currently using a Netgear DG834 which I believe are very good at holding on to lines too.

Will see what the morning brings!

Stable will be great, anything above 4Mb, will be even greater!!

Thanks again Rik.

[Rik]

Many of us moved from Netgears to 2700s.

[MarlyM]

Oh well!

No end of drop outs last night.

NM graph now looks looks like a heart monitor again!

dB is back up to 11.5, but at least sync hasn't dropped too far below 4Mbps.

Edit: I've also unplugged a couple of things which are sitting near to the router, just to see if they're interfering in any way.

[MarlyM]

As another update (!!!)

Since I unplugged the other device which sits beside the router my NM has sat at a nice steady 11.5dB (where as previously it was up and down like a silhouette of the Andes!).

So, my questions:

As the NM has increased, has it now found a steady point anyway (and it's probably not related to the other devices nearby)?
If it stays steady and issue free for a period of time, will it automatically try to drop the NM or do IDNet have to do some trickery at their end?
The higher the NM, is it less susceptible to noise (i.e. as the margin increases, is it less likely to peak and trough)?

FYI - IP profile has dropped to 3000 this morning from 4500 yesterday evening.

Thanks.

[Rik]

If you maintain sync for 14 days, the target NM will drop by 3db, repeating until you reach 6db or the line becomes unstable again. It's an automatic process.

Any 'headroom' you have over 6db makes the line less susceptible to resyncs, ie it will give you stability at the cost of speed. BT's aim is to provide stable lines. The profile follows the sync speed, so that reduction is normal, if undesirable.