[Durham] ADSL and REIN

Richard Mortimer richm at oldelvet.org.uk
Wed Mar 5 11:17:11 UTC 2014

Hi Richard,

On 04/03/2014 16:18, Richard Patterson wrote:
> Hi All,
> Does anyone have any ideas on how to track down the source of REIN
> (Random Electrical Impulse Noise) which is disrupting my ADSL?
Not really. I'm sure you've thought of all the obvious things. But at 
risk of teaching you to suck eggs...

> I have tried the AM radio tuned to 612khz trick, but that's not
> pinpointed anything...
> I've been monitoring my ADSL SNR Margin for a while, and what I see is
> this normally sits at around 28db, but often suddenly drops to around
> 15db, then slowly reduces from there down to about 4db, then will jump
> back up to 28db.
Ouch. When I've seen that I've often see the line sync frequencies 
change where the modems try to compensate for the poor line quality.

Does the modem also expose stats on the number of transmission errors 
that it has seen/corrected. Obviously that only shows the symptoms but 
if you can monitor that it might allow you to see exactly when the 
problem is occurring.

> I have had 3 BT OpenReach engineers out to "fix" this, without success.
> 1st engineer put the filtered face plate on, the second did a bit of
> stuff, and switched pairs with another line in my house and at the
> exchange.
> The last engineer did a "lift and shift", so my line is connected to
> different equipment in the exchange, but I'm still having bother with it.
Did they send a "Broadband Specialist"? I don't think the "standard" 
guys have the line integrity testing equipment that will allow them to 
see specific frequencies that are at fault.

Of course the fact that you are basically on a totally different circuit 
to the exchange does pretty much rule out issues with an individual wire 
although it isn't impossible.

So a few thoughts:

- have you tried a different modem/filter in your house? I suspect that 
BT have accepted that it isn't your kit otherwise they wouldn't have 
done 3 visits etc.

- are you sure that the exchange/modem aren't just retraining 
themselves. I think that can take 7 to 10 days. I'm assuming that you 
are having some user visible problems other than widely varying margins.

- I've heard of cheap power supplies causing issues in the past. 
Obviously you've done the AM radio trick but have you tried turning 
everything off in the house that you can. Maybe try powering the modem 
from a UPS that is isolated from the mains to rule out direct mains 
interference etc.

- External has anything changed recently between your home and the 
exchange. From memory you don't live too far from the North Shields 
exchange so it would probably be obvious. I do notice that SamKnows say 
that North Shields is/was due to go live with "fibre" broadband on 
1/March so maybe there is a street cabinet that now has AC in it etc.

We had some daytime ADSL disruption here a month or two back. I jumped 
in the car and found a few BT peeps pulling fibre down the conduits on 
the main road. They were obviously disrupting the existing pieces of wet 
string. Thankfully that only last a couple of days and maybe they'll 
even see fit to install some humming cabinets near the end of our street!

> The graph attached shows the last 7 days... at the start of the graph,
> there is little variation on the SNR, but the line was capped at 7Meg,
> with a max speed of just under 8meg. (the scale on the graph is x10 i.e.
> 280 is 28.0)
> Is it possible that the noise which is affecting my adsl is somewhere in
> the 1.1mhz to 2.2mhz range? since there was no noise when i was capped
> at under 8mb (so probably only using up to 1.1mhz)
> If anyone has any ideas, i'd love to hear them.
> also if anyone has any clip on rf chokes i can try on the adsl wire,
> that would be great.

Sorry don't have any.



> Regards
> Richard
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