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Erratic Noise Margin on DSL line

By Tink! ·
The quick run-down is:
We've had problems with the DSL during certain parts of the year where the Noise Margin keeps going really low (-1) and this then causes the CRC errors to add up very quickly up to 30,000 sometimes before the router finally restarts itself. Very recently (last 2 weeks) the DSL has started in again, mostly around Thurs and Fri, and often starting around lunchtime and continuing through the rest of the day.

During normal up-time the SNR Margin usually sits around 13-15. Last year we finally bought a new router. It's still a Netopia brand. But now this problem does not seem to be hardware related.

I've heard that fluorescent lights, electrical outlets and cables can cause interference with the DSL line. The DSL line runs through the ceiling, above fluorescent lights and often near electrical wires/outlets/conduits.

But being that this problem does not seem to be affected by certain things being on or off, but seems to be more of a seasonal issue (more spring/summer than winter), I was wondering what other environmental possibilities there are.

We are a small factory in a large industrial park area. There are many manufacturing plants surrounding us. Someone near us does have an open wireless network connection. My boss' new laptop detects it. We didn't know of this before. Could high traffic on that wireless network possibly cause interefence with our DSL?

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by statykserver In reply to Erratic Noise Margin on D ...

Usually the isp will have a set "total" bandwidth set for an area. It seems like your problem occurs most often when people would be at home so maybe it is a direct result of more people being on and using the bandwidth up around your area. I know this was the case with my last isp and according to them there was nothing they could do about it. Which is why I switched Another thing you could try is ask for another router, if you have the same problem then that is more than likely the case.

Good luck

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by JamesRL In reply to Erratic Noise Margin on D ...

Honestly no.

For one thing, are you sure its your DSL connection, and not anythin to do with your local lan traffic. Your DSL modem connects to a phone line which is probably fairly close to the outside line. Its the local area network cables that probably snake through the ceiling.

First thing to try is an isolation test. During a day when you are having these SNR issues, try this. Unplug all connections to that router, and take a laptop and connect it directly to the router with a fairly short known good cable. If you still have problems then its the DSL line.

Potential issues with DSL - since it shares the same wires as telephone (different frequency), you need filters on all telephony devices. Try replacing all the filters. Try unplugging any faxes etc.

But the more likely culprit are those cables strung overhead. Flouresent lights can definately be a problem - is there one that has a ballast problem - buzzes and has inconsistent light? Fix that.

You can also replace those cables in the ceiling with shielded cables.

James

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by HAL 9000 Moderator In reply to Erratic Noise Margin on D ...

Then there is always the possibility that there is something wrong with the external Phone Lines. You could have a bad connection somewhere that is covered by your Telco and it only acts up under certain conditions.

Like Rain floods the box and shorts out the connection or you have a connection that's been there so long untouched that it has corrosion forming on it and this under the right conditions puts noise on the line and causes the DSL modem to not get a clean signal.

Have you tried plugging in a telephone to this line and listing for any noise on it when the problem is occurring?

I've seen this quite often over here as the telco lines are over loaded and not serviced on a regular basis what happens is they only fix things when you get a total loss of signal other wise you just have to grin & bear it.

Col

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by Tink! In reply to Erratic Noise Margin on D ...

Ok, 1 more thing. We have Tripp-Lite Battery Backups at each desk in the office. They have LED indicators to let you know when there is a "Building Wiring Fault". What the fault is specifically cannot be determined without calling an electrician. We do have at least 1 unit that shows "Building Wiring Fault".

Could this cause an issue with the DSL? Perhaps since the dsl line does run parallel with certain wiring?

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