peculiar time-related ADSL line problem

I have a high-speed ADSL line with a BT Voyager 205 router.
With the modem trained at 8Mbps, everything is fine and stable all morning
and afternoon, right up to about 18:15 (give or take 10 minutes), when a
cycle begins wherein the line drops, the modem retrains at a slightly lower
speed and stays that way for maybe 15 minutes before repeating. This carries
on till about 22:30 when everything returns to normal.

The time period of the disruption coincides (I would guess) with the traffic
busy period on the Network, but I can't see how a physical-layer problem
could be caused by the global DSLAM traffic load.

When the ISP reconfigures my port such that the maximum line speed is 6Mbps,
the problem disappears, and line stays up 24 hours a day with no drops.

There is no electrical equipment in my house that kicks in during the
troublesome period, and the line has been tested as ok.

Can anyone shed any light on this ?

In article <dkis2e$5pm$(E-Mail Removed)>, mick
says...
> I have a high-speed ADSL line with a BT Voyager 205 router.
> With the modem trained at 8Mbps, everything is fine and stable all morning
> and afternoon, right up to about 18:15 (give or take 10 minutes), when a
> cycle begins wherein the line drops, the modem retrains at a slightly lower
> speed and stays that way for maybe 15 minutes before repeating. This carries
> on till about 22:30 when everything returns to normal.
>
> The time period of the disruption coincides (I would guess) with the traffic
> busy period on the Network, but I can't see how a physical-layer problem
> could be caused by the global DSLAM traffic load.
>
> When the ISP reconfigures my port such that the maximum line speed is 6Mbps,
> the problem disappears, and line stays up 24 hours a day with no drops.
>
> There is no electrical equipment in my house that kicks in during the
> troublesome period, and the line has been tested as ok.
>
> Can anyone shed any light on this ?
>
>
>
might be noise related. Phone lines in general get noisier in the
evening, and your line could be one of those which suffers.

FR

I had a similar problem except that once the line started failing, it would
then fail every 5 minutes, give or take 10 secs, for a period of time before
returning to normal.

The consistency of the 5 minute fails had me baffled. For weeks I tried
everything I could think of before I tried re-wiring the connection to the
ADSL modem by taking a dedicated feed from a master ADSL line box (bought
from Clarity) that had built-in filtering for the telephone connections and
a separate set of connections for ADSL.

The S/N ratio immediately improved by 10dB and the line stays up for weeks
at a time now. I concluded that the house telephone extension wiring (of
which there is a lot) was the source of the noise and that because it was
close to mains wiring in places, it was picking up additional noise at
certain times of the day.

Hope this helps.


"mick" <(E-Mail Removed)> wrote in message
news:dkis2e$5pm$(E-Mail Removed)...
>I have a high-speed ADSL line with a BT Voyager 205 router.
> With the modem trained at 8Mbps, everything is fine and stable all morning
> and afternoon, right up to about 18:15 (give or take 10 minutes), when a
> cycle begins wherein the line drops, the modem retrains at a slightly
> lower
> speed and stays that way for maybe 15 minutes before repeating. This
> carries
> on till about 22:30 when everything returns to normal.
>
> The time period of the disruption coincides (I would guess) with the
> traffic
> busy period on the Network, but I can't see how a physical-layer problem
> could be caused by the global DSLAM traffic load.
>
> When the ISP reconfigures my port such that the maximum line speed is
> 6Mbps,
> the problem disappears, and line stays up 24 hours a day with no drops.
>
> There is no electrical equipment in my house that kicks in during the
> troublesome period, and the line has been tested as ok.
>
> Can anyone shed any light on this ?
>
>

Thanks for the replies.
I find it strange that the disruptive period is so fixed between those
times. What are the noise sources that predominate at that time ?
Could the presence of other DSL lines in the same DP/cable be a source of
noise ? (I imagine that a lot of DSL users are still using USB modems which
are therefore not always on - i.e the user gets home, powers up the PC and
only then does the modem sync).

In my case, I have no extension wiring at all, and the modem is just 4 feet
away from the (only) socket.

As I write, the modem has been up without interruption (but at 6Mbps) for
over 94 hours, and the CRC failure count is low.

There are a number of things that generate noise of the type that seems to
disrupt ADSL lines. I'm told that a significant contributor is noise from
various types of lighting; in paricular: sodium street lamps, fluorescent
lighting including low-energy bulbs, and the electronic transformers used in
many low-voltage halogen lights.

I guess all these are most likely to be switched on during the times you're
having problems. The consistency of the timings is weird but then so was
the 5 minute line drop I was experiencing with my noise related issue.

"mick" <(E-Mail Removed)> wrote in message
news:dklk6b$sfm$(E-Mail Removed)...
> Thanks for the replies.
> I find it strange that the disruptive period is so fixed between those
> times. What are the noise sources that predominate at that time ?
> Could the presence of other DSL lines in the same DP/cable be a source of
> noise ? (I imagine that a lot of DSL users are still using USB modems
> which
> are therefore not always on - i.e the user gets home, powers up the PC and
> only then does the modem sync).
>
> In my case, I have no extension wiring at all, and the modem is just 4
> feet
> away from the (only) socket.
>
> As I write, the modem has been up without interruption (but at 6Mbps) for
> over 94 hours, and the CRC failure count is low.
>
>