Latest SNR DSLAM algorithm?

Last night there was some very strange interference that affected my TV, my Radio and my broadband. I didn't see many reconnects at all, but for whatever reason my SNR has now moved to 9dB from 6dB.

The interference is gone now and of course I want my speed back!

I see conflicting information on the net about whether the latest changes by BTW mean that the SNR will ever go back on its own, or if its now stuck at 9dB permanently without intervention. I also see talk of a 14 day monitoring period, and that being refuted elsewhere.

Does anyone know the latest information on this?


Below are my hub stats. It has only been running for a bit over an hour because I manually reset it to make sure it really was stuck at 9dB. These stats are typical for any time of day though and show the line is clearly capable of more.

Line state Connected
Connection time 0 days, 01:19:56
Downstream 7,136 Kbps
Upstream 448 Kbps


ADSL Settings
VPI/VCI 0/38
Type PPPoA
Modulation G.992.1 Annex A
Latency type Fast
Noise margin (Down/Up) 8.9 dB / 22.0 dB
Line attenuation (Down/Up) 31.4 dB / 19.0 dB
Output power (Down/Up) 10.8 dBm / 1.5 dBm
Loss of Framing (Local/Remote) 0 / 0
Loss of Signal (Local/Remote) 0 / 0
Loss of Power (Local/Remote) 0 / 0
FEC Errors (Down/Up) 0 / 0
CRC Errors (Down/Up) 13 / 1
HEC Errors (Down/Up) 7 / 0
Error Seconds (Local/Remote) 13 / 1

Edited by jonstatt (Thu 03-Mar-11 11:42:54)

Unfortunately that's how BT's system works.

A storm, noise interference or just looking at your router in the wrong way can soon push up your Target SNRM in an attempt to stabilise your connection by decreasing your sync

If your line remains stable then your TSNRM will automatically reduce to the default 6db and return your normal sync. As you say, 14 days is often mentioned but it's often longer depending on your error levels and which way the wind is blowing!

All you can do is monitor your line and make sure none of your equipment etc. is causing problems...

The minimum is 10 days. I reckon above 14 and it isn't going to happen.

Re the question about whether there has been a change, it seems that the DLM on WBC FTTC is quite a different thing, and the one on ADSL2+ randomly breaks.

it seems that the DLM on WBC FTTC is quite a different thing

to be pedantic it's Openreach DLM not WBC and it does work differently, using PPP negotiation to hand on the line rate.

In reply to a post by yarwell:

it seems that the DLM on WBC FTTC is quite a different thing

to be pedantic it's Openreach DLM not WBC and it does work differently, using PPP negotiation to hand on the line rate.

That's not pedantic .

It's important.

Isn't the ADSLx one BT Wholesale though? Or have I had the wrong impression for years?

Isn't the ADSLx one BT Wholesale though?

I believe so, they run the exchange DSLAMs and Openreach run the cabinet ones (for which they have a dispensation from OFCOM).

Ah - thanks .

In reply to a post by RobertoS:

The minimum is 10 days. I reckon above 14 and it isn't going to happen.

That's not my experience.

My line has shifted a few times over the years due to line damage and storms.
Often it has been many weeks sometimes a month or two before my TSNRM is reduced.

This will probably be my next problem!

In reply to a post by b4dger:

In reply to a post by RobertoS:

The minimum is 10 days. I reckon above 14 and it isn't going to happen.

That's not my experience.

My line has shifted a few times over the years due to line damage and storms.
Often it has been many weeks sometimes a month or two before my TSNRM is reduced.

This will probably be my next problem!

If that was me i would go jump on that tree until it took the line down
Then call it into to BT

In reply to a post by b4dger:

In reply to a post by RobertoS:

The minimum is 10 days. I reckon above 14 and it isn't going to happen.

That's not my experience.

My line has shifted a few times over the years due to line damage and storms.
Often it has been many weeks sometimes a month or two before my TSNRM is reduced.

This will probably be my next problem!

Ring openreach and get it sorted.