Advice required - should I raise this as a fault

Hi Guys,

I've had ADSL Max on my line for 6 years - historically I've always sync'd at 8128 and had a good noise margin of 11/12db.

Last year I experienced some random audible noise on the line and the target margin was raised by DLM to 9db. It's never dropped back to 6db but that wasn't a problem as I could still sync at 8128 with a bit of spare margin (9.8db).

Over the last couple of weeks however my SNR has dropped quite a bit and now I can't sync at 8128. I've also noticed that my error rate has suddenly started going up - nothing massive but a big change as previously I had a few error seconds per day.

ADSL line status

Connection Information

Line state Connected
Connection time 0 days, 11:50:25
Downstream 7,840 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) 8.4 dB / 25.0 dB
Line attenuation (Down/Up) 32.3 dB / 19.0 dB
Output power (Down/Up) 11.9 dBm / 1.7 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 / 1
CRC Errors (Down/Up) 405 / 2
HEC Errors (Down/Up) 712 / 0
Error Seconds (Local/Remote) 282 / 3

I've tried connecting directly to the test socket on the NTE5 but still get the same sync/SNR and errors. There is no audible noise on the quiet line test. I haven't yet tried changing the router.

I'm beginning to think that my line is gradually deteriorating. Is this normal ? On what grounds could I raise a fault ? My MSR is 8128 but things haven't got bad enough yet to hit the fault threshold ? If I raise a fault with PlusNet I've read that they will automatically apply interleaving which I don't want. Shouldn't a 32db line be able to sync at 8128 without problems ?

Mike

Have you tried a different filter and/or router?

And ADSL cable.

Have you got any new or replacement electrical or electronic equipment recently? Including TVs, phones and cycle/running machines? (Or have next door?)

Edited by RobertoS (Tue 18-Sep-12 22:25:32)

Thanks guys for your assistance. I've swapped the router for an old Zyxel, changed the filter and ADSL cable.

Here is a comparison of my downstream errors (over 6 hours) - target noise margin is 9db.

BT Home Hub 2 -- Zyxel P2602
Sync rate 7780 -- 7808
CRC errors 26 / hour -- 15 /hour
HEC errors 39 / hour -- 0 / hour ???
Error secs 18 / hour -- 8 / hour

Noise margin on Home Hub is observed to be constant in range 9.0 - 8.1. Noise margin on Zyxel seems to wander randomly between 9-6 (unfortunately it only displays whole numbers).

Not sure what conclusions I can draw for this - doesn't look to me like a router, filter or wiring fault. I've tried turning everything else off in the house bar the router and laptop to eliminate local REIN but it doesn't seem to make any difference.

Stats still seem to be quite a bit worse than they were a year ago which is weird. Given that the Zyxel is a bit better than the HomeHub do you think there is a chance the DLM could now drop the noise margin back to 6db ?

I'd certainly stick with the Zyxel to find out. Unfortunately that's a minimum of 10 days stability, with a probable maximum of 14. Also jot down the error counts once per day at about the same time. Just for long-term comparison if you put the HH back or make any other change later.

I suggest you make sure you can identify (and avoid) that filter and cable. Possibly try them (one at a time) a fair while after/if you get the SNRM drop.

You didn't say anything about possible new noise sources, in my previous post?

Thanks again for the advice. I'll leave the Zyxel alone and see what happens. The HH has maintained sync for over 100 days but the SNRM didn't drop before - hopefully if I can keep the error counts down it might!

Shouldn't be a problem identifying the filter and cable - it was an official BT faceplate filter and quality cable - they are fairly old though so they might have failed.

To answer your question there aren't any new noise sources in my house. Not sure about other properties though - all of the cabling around here runs underground which I had hoped might give me some shielding from noise. Whatever is causing the CRC errors seems to happen throughout the day and night from what I've seen.