Improving Noise Margin & a Possible Bridge Tap

Hello.

I've been connected to a FTTC service (Plusnet) for over 3 years now, speeds generally great at around 23-28Mbit (has been improving over the years!) - this is great as I live around 1.5km from my cabinet. Estimated speeds on a clean line at between 13-21Mbit.

I am currently and have always been plugged in to the master socket (test socket with micro filter at the moment) with a faceplate filter

I recently logged an issue where my router displayed connection speed became 'stuck' at 19999kbps and thought this was unusual as it had never been so low (this figure did actually improve to 22400kbps on the morning just before the engineer visit).

A fault was found and a (non-broadband) Openreach engineer 'fixed' the issue with the line (apparently no dial tone - we never use the land line so were not aware). Unfortunately this fix has made our connection speed even lower (ranges between 13-18Mbit - it has never been this low before!) and more unreliable where the connection appears to drop more often especially in the evenings.

I have told Plusnet but they give the 'It's within expected range' response which is unhelpful considering the connection has been great for the past 3 years!

Interestingly, since this fix, I now notice dslchecker has changed the 'Bridge Tap' part from N to Y which could explain the issues.

Before requesting a further investigation from Openreach and possible incurring a call out charge I have done some investigation to ensure there's no dodgy wiring. We only have one extension which will be removed as this is never used. I have also taken a look at the back of the master socket (Openreach side) to ensure everything is correct, which it is. So ultimately, there's been no changes to our wiring since we've had FTTC.

I have however noticed that this appears to be a very old master socket type, probably 80's. I also noticed that when I touch the area illustrated in this image the Noise Margin will improve by 1-2db (ie, go from 6.2db to 8.1db) - is this normal or does it show the socket is faulty?:

http://joxi.net/Grq7KDXUQd8G82

At the moment I'm a bit perplexed on what to do next. I am beginning to wish I never reported an issue!! Ha!

I currently use a Netgear D6400 router, as I understand it this doesn't give out much in the way of useful stats.

Any thoughts or advice?

Thanks
James

When you say there is an extension which you will remove, is that extension connected to the faceplate of the master socket, or is it connected to a junction box somewhere between the extension socket and the point at which the incoming line reaches the house?

If is is connected to a junction box that is feeding it and the master socket then that is where you need to disconnect the extension by removing its wires. That is the bridge tap point.

Removing the extension socket itself while that connection is present would make no difference. Cutting the wires at the junction box I expect would help but is not the correct solution.

If that Terminal B isn�t properly connected then it obviously needs to be. Is there insulation trapped in it?

Edited by RobertoS (Tue 09-Oct-18 09:30:15)

Thanks Roberto.

The extension runs from the back of the master socket faceplate, so as I'm using the 'test socket' at the moment this extension is not live.

As far as I'm aware, and can see, the phone line enters the house and terminates at the master socket only. There's no other sockets.

Regarding terminal B, I'm sure everything was correct but I'd have to take a closer look tonight.

If there was no dial tone at the test socket previously and no new socket fitted suggests one leg was previously disconnected, and now you mention possible lose screw b, so maybe that has been the problem all along.

NOTE: DSL will work with only 1 wire from a pair connected but a phone will not, thus checking for dial tone is a good test to do.

The age of the master socket should not really matter i.e. nothing too magical about the new ones.

Touching the "B" terminal could also act to provide a path to earth for some of the noise.

I did wonder about that. Possibly wrongly I didn't think for long enough to get anywhere with it.

I checked both terminals last night, nothing incorrect from what I could see, both terminals tight, no insulation trapped.

Just to rule out any issues with the master socket and any internal wiring, I swapped this with a new one (NTE5c with faceplate) while also removing the unused extension wiring (We don't use the land line, so removed them all!). At this stage I can't really see any improvement and my speeds are no better, I also had a couple of disconnects overnight and I rebooted this morning.

Current stats show:
http://joxi.net/v29BDzPU3lPz9A

The downstream noise margin was around 6.5db after rebooting about 8am). It will stay high throughout the day then drop away around 6pm, to around 4db during the evening where it may resync if the db drops low enough.

What is annoying is that up until the engineer fixed a 'fault' I wouldn't drop a connection in days/weeks. Now it appears to be at least 3-4 times a day. I believe it's likely that the recent 'bridge tap' on the line is probably causing the issue - DSLChecker: http://joxi.net/12M94nYhMbo8B2

I guess my next steps are to find a corded phone and try a quiet line test, then logging a fault with Plusnet again.

Cheers
James

Edited by slimj (Wed 10-Oct-18 09:44:43)

From your previous description I suspect the bridge tap diagnosis is spurious.

In reply to a post by MrSaffron:

NOTE: DSL will work with only 1 wire from a pair connected but a phone will not, thus checking for dial tone is a good test to do.

Yes, but it will only work at a much slower rate.

Is anyone else getting a trojan alert when trying to access the screenshots? I'm using the amazing Malwarebytes. ;P

Edited by deleted (Thu 11-Oct-18 16:40:39)

Is anyone else getting a trojan alert when trying to access the screenshots?

No, are you meant to?