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Intermittent problem with slow broadband speeds


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I've been having an intermittent problem with slow internet connection speeds over the last month and a half.

Initially after a week of random slow speeds (sometimes the connection was normal and sometimes slow with no pattern to it) I did the bt speedtest which showed a speed of about 400kbps on a line that should have been getting between 2000-4180kbps. My ISP sent me a list of questions for troubleshooting (which I completed), but speeds suddenly became consistently good again and remained so for 10 days before I started having random slow speeds again.

My ISP have said they can find no fault with the connection and would raise it as a fault with BT if I agree to possible engineering charges of £183 if no fault is found. As it is an intermittent problem I am concerned they won't be able to find a fault so am not taking things further with them at this point.

I would like to pursue further troubleshooting myself to see if there is anything at our end of things which is causing the problem.

We do not have a modern BT master socket so I am unable to test the router bypassing our internal wiring.

The connection problems are evident on 2 different computers.

I am currently using a Netgear DG834G with the most up to date firmware and have checked all settings given by the ISP. I am waiting for a replacement Netgear router to test the connection with different equipment. I briefly tried a speedtouch modem which worked for 10 minutes before it disconnected and lost the connection altogether.

One thing I noticed during my investigations so far is that the Noise Margin becomes really low when the speed drops (down between 2db-0db) attenuation remains constant at 39db. When the speed is OK the Noise Margin seems to be around 6db-9db.

Does this show a problem at our end of things and is there anything else I can try?

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When you say you don't have a modern master socket, what do you have? For years now they've had a removable section on the face plate which can be unplugged to allow the router/modem filter to be plugged in directly as here. It's the best way to bypass any extension wiring. If not, unplug all extension filters and see what happens. You do need to prove the internal wiring before risking a ludicrous bill from BT.

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Yes I don't want to have a massive bill and maybe no solution either.

We have an older style BT master socket which is just a 55cm squarish box (branded with the Telecom T) without a removable plate and a single screw in the middle with the wiring coming out of the side . This replaced an even more ancient oblong type. This is why I'm unable to do the bypass testing.

I tried phoning BT quiet line tests and the line was absolutely quiet. Unplugging extension filters doesn't make any difference.

We haven't had any problems with our connection since 2008 and haven't changed anything in our setup.

This afternoon I downloaded a program called routerstats and have been running for about half an hour. Our connection speed seems very high at 6873kbps and noise margin between 3-0db . Download speed around 1210Kbps at the moment.

would it help to leave the router off overnight and renegotiate a fresh connection?

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I have tried a Belkin shielded hi speed modem cable, which didn't reduce the interference, but improved download speeds.

I have now got a replacement router, which I installed about an hour ago. It seems to have solved the problem with the low noise margin and 3-4db spikes of noise, which had been dropping to 0db at times.

It's been running for about an hour and only showing a .20db waver in noise. So it looks like problem solved.

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