Sudden line degradation - line fault? water?

I've had O2 broadband (ADSL2+, STD) on this line for approx 2 months, and am using the supplied Thomson ST780WL model with the 6.2.27.2 firmware. I am experiencing speed problems (sync) as of the last week.

My target SNR margin appears to be 6db up/down and interleaving is enabled downstream. The error rate is generally well under control.

The modem is plugged directly into the master socket via a faceplate filter, so all extension wiring should be isolated from the adsl signal.

For the first ~6 weeks I found that I would typically sync between 3700 and 4700. However if the sync was on the higher side (say> 3900) the modem would typically resync later in the day towards the 3700-3900 mark.

Although there was a general trend of lower snr/speed in the evening closer examination (graphs) suggest there's interference at certain times of day amounting to perhaps an extra 3-4db noise. That may be an expected crosstalk effect.

Around Sun 20th -- maybe later my modem was unable to get a dhcp address. This was remedied via a restart at both ends modem+dslam port and I was back online

A few days later - Sun 27th we had a lightning storm which caused me to loose sync a number of times during the day - log extract below.

Since then I tend to find my modem knocked down to ~2000. Sometimes I look& the SNR margin is 6DB. Othertimes it has shot up to 15-19 dB.

I've done an online BT line check, which was ok, and do not notice any audio difficulties. I also get same results when connected to master socket only.

This suggests I am getting hit by periods of noise bursts of around 9 - 12dB, which is a MASSIVE hit and causes the modem to loose sync. Since I've seen SNR reporting ~6 this looks like a period of noise rather than a sudden burst, but one which generally doesn't last for an extended period. A resync will then get me back up to ~4000 Mbps

Just to re-iterate. There's always been an>element< of this in the 3700-4700 range as mentioned, but here we're plunging down to< 2000 which is a "new feature" I've recently acquired.

Thoughts...
1. I wish the 780WL+O2 would support SRA - it would hopefully "manage" this situation *far* better
2. Any ideas as to cause. I'm pretty sure it's not my house, and the SNR hit is massive. Given the amount of rain could it be water related?

DATA
---
Log for today below:
<173> Apr 28 19:04:48 xDSL linestate down
<173> Apr 28 19:05:18 xDSL linestate down
<173> Apr 28 19:05:41 xDSL linestate up (downstream: 3600 kbit/s, upstream: 922 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 35.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 20:53:36 xDSL linestate down
<173> Apr 28 20:54:06 xDSL linestate down
<173> Apr 28 20:54:29 xDSL linestate up (downstream: 2383 kbit/s, upstream: 922 kbit/s; output Power Down: 16.5 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 20:55:02 xDSL linestate down
<173> Apr 28 20:55:33 xDSL linestate down
<173> Apr 28 20:55:55 xDSL linestate up (downstream: 1942 kbit/s, upstream: 922 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)

** At this point I forced a resync to regain higher speed - notice that after dropping significantly at 20:54 we're back up to 4Mbs again. I may have done this twice - hence the extra resync.

<173> Apr 28 21:23:41 xDSL linestate down
<173> Apr 28 21:24:04 xDSL linestate down
<173> Apr 28 21:24:26 xDSL linestate up (downstream: 4072 kbit/s, upstream: 922 kbit/s; output Power Down: 17.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 dB, Up: 36.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 21:26:37 xDSL linestate down
<173> Apr 28 21:27:02 xDSL linestate down
<173> Apr 28 21:27:25 xDSL linestate up (downstream: 4207 kbit/s, upstream: 918 kbit/s; output Power Down: 18.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 36.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 29 07:29:03 xDSL linestate down
<173> Apr 29 07:29:26 xDSL linestate down
<173> Apr 29 07:29:49 xDSL linestate up (downstream: 3592 kbit/s, upstream: 936 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 35.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 30 05:30:14 xDSL linestate down
<173> Apr 30 05:30:46 xDSL linestate down
<173> Apr 30 05:31:08 xDSL linestate up (downstream: 2804 kbit/s, upstream: 936 kbit/s; output Power Down: 18.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 dB, Up: 34.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 30 09:51:56 xDSL linestate down
<173> Apr 30 09:52:27 xDSL linestate down
<173> Apr 30 09:52:50 xDSL linestate up (downstream: 2030 kbit/s, upstream: 927 kbit/s; output Power Down: 17.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 dB, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)

I also have a log from "day 0" (sorry for bad formatting - I had cut/paste badly)

<173> Apr 27 05:31:46 xDSL linestate down
<173> Apr 27 05:32:16 xDSL linestate down
<173> Apr 27 05:32:39 xDSL linestate up (downstream: 2645 kbit/s, upstream: 932 kbit/s; output Power Down: 18.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.5 dB, Up: 34.0 dB; snr Margin Down: 6.0 dB, Up: 6.0 dB)
<173> Apr 27 08:30:34 xDSL linestate down
<173> Apr 27 08:31:05 xDSL linestate down
<173> Apr 27 08:31:28 xDSL linestate up (downstream: 1964 kbit/s, upstream: 918 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)

* MANUAL RESYNC to regain speed

<173> Apr 27 14:35:56 xDSL linestate down
<173> Apr 27 14:36:29 xDSL linestate down
<173> Apr 27 14:36:51 xDSL linestate up (downstream: 4476 kbit/s, upstream: 932 kbit/s; output Power Down: 18.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 dB, Up: 36.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 06:08:07 xDSL linestate down
<173> Apr 28 06:08:39 xDSL linestate down
<173> Apr 28 06:09:02 xDSL linestate up (downstream: 4535 kbit/s, upstream: 936 kbit/s; output Power Down: 18.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 dB, Up: 36.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 09:38:09 xDSL linestate down
<173> Apr 28 09:38:31 xDSL linestate down
<173> Apr 28 09:38:55 xDSL linestate up (downstream: 3798 kbit/s, upstream: 932 kbit/s; output Power Down: 18.0 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 dB, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 10:01:46 xDSL linestate down
<173> Apr 28 10:02:17 xDSL linestate down
<173> Apr 28 10:02:40 xDSL linestate up (downstream: 3569 kbit/s, upstream: 932 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 35.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 15:53:23 xDSL linestate down
<173> Apr 28 15:53:53 xDSL linestate down
<173> Apr 28 15:54:16 xDSL linestate up (downstream: 2226 kbit/s, upstream: 922 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 dB, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 19:04:48 xDSL linestate down
<173> Apr 28 19:05:18 xDSL linestate down
<173> Apr 28 19:05:41 xDSL linestate up (downstream: 3600 kbit/s, upstream: 922 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 d B, Up: 35.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 20:53:36 xDSL linestate down
<173> Apr 28 20:54:06 xDSL linestate down
<173> Apr 28 20:54:29 xDSL linestate up (downstream: 2383 kbit/s, upstream: 922 kbit/s; output Power Down: 16.5 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 d B, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 20:55:02 xDSL linestate down
<173> Apr 28 20:55:33 xDSL linestate down
<173> Apr 28 20:55:55 xDSL linestate up (downstream: 1942 kbit/s, upstream: 922 kbit/s; output Power Down: 17.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 d B, Up: 33.5 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)

* MANUAL

<173> Apr 28 21:23:41 xDSL linestate down
<173> Apr 28 21:24:04 xDSL linestate down
<173> Apr 28 21:24:26 xDSL linestate up (downstream: 4072 kbit/s, upstream: 922 kbit/s; output Power Down: 17.5 dBm, Up: 12.0 dBm; line Attenuation Down: 61.0 d B, Up: 36.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)
<173> Apr 28 21:26:37 xDSL linestate down
<173> Apr 28 21:27:02 xDSL linestate down
<173> Apr 28 21:27:25 xDSL linestate up (downstream: 4207 kbit/s, upstream: 918 kbit/s; output Power Down: 18.0 dBm, Up: 12.0 dBm; line Attenuation Down: 60.5 d B, Up: 36.0 dB; snr Margin Down: 6.5 dB, Up: 6.0 dB)


Thanks
Nigel Jones

My Dad had a similar problem after a thunderstorm a few years ago with an Efficient Networks EN5861. It turned out that the router had been partially fried in that the damn thing provided a service, but a very poor one. Having tried all the usual things, I eventually drove over with my own router and established that the line/signal etc. was fine.

Then again, it might be something fried elsewhere in the loop.

I started the day pretty good synced at ~4300
-> http://www.flickr.com/photos/cherrybyte/2457357002/

But in the last 30 mins I dropped to ~2500
-> http://www.flickr.com/photos/cherrybyte/2457368102/

During this period I did an online BT line test - no reported problem, and no perceived noise on the line.

and then whilst writing this to <2000
-> http://www.flickr.com/photos/cherrybyte/2456551011/
although note the SNR there is 14.5 db -- showing that the problem was fairly short lived

So I then forced a resync and we can see the speed is back to normal
http://www.flickr.com/photos/cherrybyte/2456560879/

Notice we're back up at 4400 at 6db SNR.

|| Finally whilst adding that last link it happened again. Grrrrrrr....

Additional notes
- When doing ok, the SNR is rock solid, varying over an hour or so by only +/- 0.5 dB, with perhaps a slightly larger general trend towards evening (2-3dB max - not checked closely)
- The range of frequencies being used didn't change much, but from around 300-600 kHz there's a real problem - note the lower occupied bins.

At this point I think I'll try the DG834GT+dgteam firmware, but comments on approack to take with ISP etc welcome. So far I've sent an email to O2 but no response. I've not phoned yet.

My issue is the magnitude of the effect... is that "unusual" and worthy of a trouble ticket/engineer visit, or am I being unreasonable ?

Edited by planetf1 (Thu 01-May-08 17:58:34)

Just checked at end/day, and it's back down to 1876/932 with SNR 19/6.5 -- so very very variable downstream SNR now 13 above normal

I also verified the same behaviour with the dg834gt - actually it's less stable....

A while ago my telephone went dead for voice calls. It turned out that a junction point down the street was under water and this had exacerbated a problem with a poor connection. During that time my broadband service continued unaffected over the same wiring!

Quick update.

Problem still occuring intermittently at an impact of ~12dB. Both modems. Also checked direct to master socket, extensions disconnected and most power in house turned off....

Worst affected appears to be 300-575 KHz probably worst ~440 kHz. Checking frequency allocations that's just about lw/mw -- and as a consequence I don't have a receiver capable of picking up..

Any thoughts on what might cause noise in that range? Could a cable fault be resulting in RF interference

I know the route to the exchange probably goes past many industrial units, although most focus on Mon-Fri, or even Sat, but today is Sunday over bank holiday.

Other thoughts - although none of these a new
- airport ~5 miles away -- but those frequencies differ
- electricity substation next door but one (it's one of those garage sized units)
- Sodium street lights

or what about water pumping kit?

Edited by planetf1 (Sun 04-May-08 21:44:45)

The most likely cause out of what you have mentioned IMHO is:

- electricity substation next door but one (it's one of those garage sized units)


A couple of things to try are a brand new filter faceplate from adsl nation or similar

A new RJ 11 wire

Both with the phone or any other device unattached - make sure no extensions are attached to the new faceplate for the time being also.

Unlikely to be the substation, could be a faulty joint but they usually fail quickly once water gets in, cue smoke, sparks and if a high voltage cable a small hole in pavement.

Thanks. I've tried direct to master socket, a different RJ11 cable, as well as a different adsl filter. (currently using master socket faceplate splitter). My current thoughts are

- I have a second old line. I remember in the past (when the lines were the "other way around") that I had to leave a filter on this else I'd get noise induced. Perhaps because its unterminated? The line should be discon but may just be inactive in sw. I've already added adsl filter, may add old phone to ensure termination ???

- Perhaps mains bourne interference is causing the issue. Maybe getting some form of power filter (surge suppressor, UPS) may help. However there are so many types and until you get up to inline UPSs (noise, price, consumption) it's not clear what mains/broadband filtering they may provide . Can anyone recommend ones that have addressed a similar fault?
- Followon from above, I'm using the regular Speedtouch 780WL PSU. I may try a spare half-decent switch-mode I have to see if that helps.
NOTE: I'm going to open a top level thread specifically on the filter question


- I have called ISP already, but at the time the line was good and whilst helpful all they could do is say the tests were fine, and offer to raise or lower SNRm. I will call again if I have a prolonged bad patch.

As a baseline so far today I had about a 10 min "bad" period -- and I've been at home working (with a monitor running) all day.. That bad patch knocked me for ~13 db SNR. Now recording times in case I can associate with something ....

Going to trawl the blogspace now... meantime have posted to my blog here -> http://cherrybyte.blogspot.com/2008/05/adsl-interference.html