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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Sudden fall and rise in SNR



 
 
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  #1  
Old October 8th 08, 06:53 PM posted to uk.telecom.broadband
nospam
external usenet poster
 
Posts: 82
Default Sudden fall and rise in SNR


Having had a recent 'episode' with ADSL on my line I have been watching SNR
more than I have in the past.

I find someone turns something on and I get an instant SNR drop of about
1.5db (maybe 8 to 6.5) when they turn it off I get an instant rise of
1.5db.

They might turn 'it' on at 6pm then off again at 10 or 11, seen it on early
in the morning once, also seen it on Friday afternoon (half day?).

It isn't anything in this (detached) house. I have a bit of reasonable
twisted pair between a BT faceplate/filter on the master socket and the
ADSL modem so I can't really see it being radio frequency pick up.

Looks like it is injecting noise possibly into the mains or into a phone
line where it couples to other lines in the bundle.

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.
--
  #2  
Old October 8th 08, 07:33 PM posted to uk.telecom.broadband
Brian Gregory [UK]
external usenet poster
 
Posts: 208
Default Sudden fall and rise in SNR

"nospam" wrote in message
...

Having had a recent 'episode' with ADSL on my line I have been watching
SNR
more than I have in the past.

I find someone turns something on and I get an instant SNR drop of about
1.5db (maybe 8 to 6.5) when they turn it off I get an instant rise of
1.5db.

They might turn 'it' on at 6pm then off again at 10 or 11, seen it on
early
in the morning once, also seen it on Friday afternoon (half day?).

It isn't anything in this (detached) house. I have a bit of reasonable
twisted pair between a BT faceplate/filter on the master socket and the
ADSL modem so I can't really see it being radio frequency pick up.

Looks like it is injecting noise possibly into the mains or into a phone
line where it couples to other lines in the bundle.

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.


1.5dB is nothing.

My S/N margin drops by 6dB at night when the night time ionosphere brings in
numerous European medium wave broadcasts. And this is on a line that
underground all the way to the exchange.

--

Brian Gregory. (In the UK)

To email me remove the letter vee.


  #3  
Old October 8th 08, 08:02 PM posted to uk.telecom.broadband
Invalid
external usenet poster
 
Posts: 150
Default Sudden fall and rise in SNR

In message , nospam
writes

Having had a recent 'episode' with ADSL on my line I have been watching SNR
more than I have in the past.

I find someone turns something on and I get an instant SNR drop of about
1.5db (maybe 8 to 6.5) when they turn it off I get an instant rise of
1.5db.

They might turn 'it' on at 6pm then off again at 10 or 11, seen it on early
in the morning once, also seen it on Friday afternoon (half day?).

It isn't anything in this (detached) house. I have a bit of reasonable
twisted pair between a BT faceplate/filter on the master socket and the
ADSL modem so I can't really see it being radio frequency pick up.

Looks like it is injecting noise possibly into the mains or into a phone
line where it couples to other lines in the bundle.

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.


Yes I see a similar reproducible effect, but not as large (my drop is
about 1dB). My SNR drops at about 7:45am and goes up again at about
6:15pm, five days/week, Saturdays sometimes look like weekdays,
sometimes it rises again about 1:00pm (half day!). Sundays can be
nothing, an hour or two or most of the day - but it usually starts
later. The times vary a bit (minutes) each day.

Best I can pin it down to is lighting in an agricultural machinery
workshop about 400m down the road. Its something that gets switched on
when the first person arrives to start work and is switched off when the
last person leaves at night. Talking to the boss the times are roughly
right for their start/stop (they work 8am - 6pm).

It is not a problem for me, because it drops during the day (when SNR is
high anyway) and rises again as it gets dark when the SNR drops off
because (I presume) of pickup of radio broadcasts (all the wiring from
here to the exchange (3km+) is overhead).

If I reboot the router during the day I get 7400-7600 sync speeds with
low/zero error rates (even when they are at work), however at those
speeds come 9 or 10 in the evening (after they have gone home) the error
rate on the line makes it unusable - so I reboot and get 6300-6400 at
which speed the line is much more usable.

I see a really repeatable daylight/dark cycle of SNR. Daylight is 8-9dB.
Dark is 5dB.

Regards
--
Peter R Cook
  #4  
Old October 8th 08, 08:46 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 1,000
Default Sudden fall and rise in SNR

nospam wrote:
Having had a recent 'episode' with ADSL on my line I have been watching SNR
more than I have in the past.

I find someone turns something on and I get an instant SNR drop of about
1.5db (maybe 8 to 6.5) when they turn it off I get an instant rise of
1.5db.

They might turn 'it' on at 6pm then off again at 10 or 11, seen it on early
in the morning once, also seen it on Friday afternoon (half day?).

It isn't anything in this (detached) house. I have a bit of reasonable
twisted pair between a BT faceplate/filter on the master socket and the
ADSL modem so I can't really see it being radio frequency pick up.


then try a different pair of glasses. You have kilometers of unshielded
twisted pair between you and the exchange, and the dominant noise on
your line will normally be MW RF picked up on that.


Looks like it is injecting noise possibly into the mains or into a phone
line where it couples to other lines in the bundle.

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.


Sorry to disappoint you, but its completely normal and not in anyway a
fault that you can lay at your ISP's door, or BT.

They are not responisble for the thousands of millions of bits of
equipment in use all over the country that may or may not generate
interference.

You can try putting a suppressor plug on the modem, and that might cut
down any mains borne noise.

If its reliably repeatable, OFCOM might have something to say though.

someone else reported something similar however..central heating boiler
was surmised.

Try getting your ISP to fix that...;-)
  #5  
Old October 8th 08, 08:47 PM posted to uk.telecom.broadband
nospam
external usenet poster
 
Posts: 82
Default Sudden fall and rise in SNR

Invalid wrote:

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.


Yes I see a similar reproducible effect, but not as large (my drop is
about 1dB). My SNR drops at about 7:45am and goes up again at about
6:15pm, five days/week, Saturdays sometimes look like weekdays,
sometimes it rises again about 1:00pm (half day!). Sundays can be
nothing, an hour or two or most of the day - but it usually starts
later. The times vary a bit (minutes) each day.

Best I can pin it down to is lighting in an agricultural machinery
workshop about 400m down the road. Its something that gets switched on
when the first person arrives to start work and is switched off when the
last person leaves at night. Talking to the boss the times are roughly
right for their start/stop (they work 8am - 6pm).

It is not a problem for me, because it drops during the day (when SNR is
high anyway) and rises again as it gets dark when the SNR drops off
because (I presume) of pickup of radio broadcasts (all the wiring from
here to the exchange (3km+) is overhead).


That's interesting, my 'timing' looks more like domestic usage, maybe an
ADSL or POTS modem they don't keep always on. I can't believe so much SNR
loss from crosstalk between lines is normal. There must be loads of ADSL
going down the same cable. I can 'see' about 20 wireless networks from
here.

I see a really repeatable daylight/dark cycle of SNR. Daylight is 8-9dB.
Dark is 5dB.


My line is all underground and I see about 1.5db variation over the daily
cycle. I can keep 8128 sync though it, the extra 1.5db loss increases the
error rate a bit in the evenings. If I ever get ADSL2+ I'm sure it would
knock out a lump of bandwidth. Just a bit annoying.

--
  #6  
Old October 8th 08, 08:47 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 1,000
Default Sudden fall and rise in SNR

Brian Gregory [UK] wrote:
"nospam" wrote in message
...
Having had a recent 'episode' with ADSL on my line I have been watching
SNR
more than I have in the past.

I find someone turns something on and I get an instant SNR drop of about
1.5db (maybe 8 to 6.5) when they turn it off I get an instant rise of
1.5db.

They might turn 'it' on at 6pm then off again at 10 or 11, seen it on
early
in the morning once, also seen it on Friday afternoon (half day?).

It isn't anything in this (detached) house. I have a bit of reasonable
twisted pair between a BT faceplate/filter on the master socket and the
ADSL modem so I can't really see it being radio frequency pick up.

Looks like it is injecting noise possibly into the mains or into a phone
line where it couples to other lines in the bundle.

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.


1.5dB is nothing.

My S/N margin drops by 6dB at night when the night time ionosphere brings in
numerous European medium wave broadcasts. And this is on a line that
underground all the way to the exchange.

Coo. That must be long. I only get about 3dB...
  #7  
Old October 8th 08, 08:50 PM posted to uk.telecom.broadband
The Natural Philosopher
external usenet poster
 
Posts: 1,000
Default Sudden fall and rise in SNR

Invalid wrote:
In message , nospam
writes

Having had a recent 'episode' with ADSL on my line I have been
watching SNR
more than I have in the past.

I find someone turns something on and I get an instant SNR drop of about
1.5db (maybe 8 to 6.5) when they turn it off I get an instant rise of
1.5db.

They might turn 'it' on at 6pm then off again at 10 or 11, seen it on
early
in the morning once, also seen it on Friday afternoon (half day?).

It isn't anything in this (detached) house. I have a bit of reasonable
twisted pair between a BT faceplate/filter on the master socket and the
ADSL modem so I can't really see it being radio frequency pick up.

Looks like it is injecting noise possibly into the mains or into a phone
line where it couples to other lines in the bundle.

Anyone else seen anything like this, I don't think I have seen anyone
talking about anything similar. Seems whatever 'it' is it must be pretty
faulty and I suppose it is probably near my end but could be anywhere
between me and the exchange.


Yes I see a similar reproducible effect, but not as large (my drop is
about 1dB). My SNR drops at about 7:45am and goes up again at about
6:15pm, five days/week, Saturdays sometimes look like weekdays,
sometimes it rises again about 1:00pm (half day!). Sundays can be
nothing, an hour or two or most of the day - but it usually starts
later. The times vary a bit (minutes) each day.

Best I can pin it down to is lighting in an agricultural machinery
workshop about 400m down the road. Its something that gets switched on
when the first person arrives to start work and is switched off when the
last person leaves at night. Talking to the boss the times are roughly
right for their start/stop (they work 8am - 6pm).

It is not a problem for me, because it drops during the day (when SNR is
high anyway) and rises again as it gets dark when the SNR drops off
because (I presume) of pickup of radio broadcasts (all the wiring from
here to the exchange (3km+) is overhead).

If I reboot the router during the day I get 7400-7600 sync speeds with
low/zero error rates (even when they are at work), however at those
speeds come 9 or 10 in the evening (after they have gone home) the error
rate on the line makes it unusable - so I reboot and get 6300-6400 at
which speed the line is much more usable.

I see a really repeatable daylight/dark cycle of SNR. Daylight is 8-9dB.
Dark is 5dB.


yeah. Ive been at 6dB all day. Its down to 5dB now.

And synching at exactly 4000kbps. Never been on that exact frequency
before....its been


Regards

  #8  
Old October 8th 08, 09:30 PM posted to uk.telecom.broadband
Martin Jay
external usenet poster
 
Posts: 131
Default Sudden fall and rise in SNR

On Wed, 08 Oct 2008 20:50:28 +0100, The Natural Philosopher
wrote:
Invalid wrote:


I see a really repeatable daylight/dark cycle of SNR. Daylight is 8-9dB.
Dark is 5dB.


yeah. Ive been at 6dB all day. Its down to 5dB now.


Mine jumps around, especially at night. Within the past 30 minutes
it's been down to 5 and up to 9.

http://local.onenet.org.uk/stats/. Everything is in red at the
moment, indicating the downstream speed is below 2272, which is the
fixed speed I used to have before going rate-adaptive. Router
probably needs a reboot, but I'm not going to worry about it.
--
Martin Jay
  #9  
Old October 13th 08, 01:53 AM posted to uk.telecom.broadband
nospam
external usenet poster
 
Posts: 82
Default Sudden fall and rise in SNR


If anyone is interested here is a 24hour plot of what I experience.

http://img392.imageshack.us/img392/2...r121008cy4.jpg

The top trace is SNR in db (@8128 sync) the red trace is receive errors per
second the scale for which is 2.5x the SNR db scale, 2840 errors in the
period.

--
 




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