cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
Mp22
Beginner
689 Views
Message 1 of 12

BT FTTC with HH5 noise margin decreases gradually until drop out

Hi everyone,
Can anyone help me understand why my HH5 noise margin decreases over a a number of hours until it reaches 0 dB
and then loses sync? After 5 minutes, it reconnects and then starts the process all over again. The time it takes for the noise margin to decrease to 0 dB varies from 30 minutes to 12 hours. The connection speed remains constant at around 74 Kbps downstream and 20 Kbps upstream regardless of the noice margin or the time of day. So I have no issue with losing speed - just connection stability.

I have been suffering with the problem for about 3 years now. When I first switched from BT ADSL to VDSL, the stability was good but then the last 3 years I have been getting regular drop outs. I think it may also be related to the temperature. For the first couple of years of suffering with the issue, I would get maybe 1 drop out per day during winter, but as soon as it becomes hot outside then the dropouts happen much more frequently. On bad days it is less than 1 hour between drop outs. When I called BT in the past (although I haven't for a couple of years), they said that 4 or 5 drop outs a day is what they deem to be acceptable, so they haven't helped.

I have exactly the same issue with a BT HH5 as with a Draytek Vigor 2860 modem/router so I don't think it is the modem/router. The HH5 is connected to the master socket (NTE5a socket + MK2 faceplate) and a couple of weeks ago I disconnected the secondary socket wiring, to no effect.

I have done a quiet line test and that seems fine.

In the last couple of weeks I have been using RouterStatsHub5A to monitor the Noice Margin and shows how it decreases over a period of time until the connection drops. The noise margin always starts at around 16 dB after a drop out and usally decreases to 0 dB gradually. Occasionally it will decrease down to around 1 or 2 dB and then increase again up to 16 dB and then decrease down to 0 dB and lose sync.

Can anyone explain why this happens? Is the issue likely to be house wiring/faceplate or on the BT side? Will switching to NTE5C + MK4 faceplate or changing the cable from BT junction box in loft to master socket to a shielded cable (Cat5e or Cat6) likely to improve stability?

Thanks,
MP

Noise marginNoise marginHH5 detailsHH5 detailsBroadband checker detailsBroadband checker details

0 Ratings
Reply
11 REPLIES 11
Keith_Beddoe
Distinguished Sage
Distinguished Sage
680 Views
Message 2 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

Have you tried connecting it up as shown below, and see if you still get the problem, as it could be the filtered faceplate?

infinity_test.jpg

0 Ratings
Reply
Mp22
Beginner
670 Views
Message 3 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

Thanks for your reply.

I thought I had binned all of my ASDL filters when I swicthed to VDSL about 7 years ago, but I have just found a couple so I will try one. If the filtered facelate is the issue, should I expect to see an improvement immediately or will I have to wait a number of days for sync rate to stabilise like for a new FTTC install?

Thanks.

0 Ratings
Reply
Keith_Beddoe
Distinguished Sage
Distinguished Sage
663 Views
Message 4 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out


@Mp22 wrote:

Thanks for your reply.

I thought I had binned all of my ASDL filters when I swicthed to VDSL about 7 years ago, but I have just found a couple so I will try one. If the filtered facelate is the issue, should I expect to see an improvement immediately or will I have to wait a number of days for sync rate to stabilise like for a new FTTC install?

Thanks.


The sync speed should stabilise right away.

The symptoms you describe can be caused by a poor connection between the faceplate and the test socket, due to oxidisation.

This distorts the broadband signal and causes losses within the frequency range that VDSL operates within. This reduces the overall availability of frequency "slots" which shows up as a reduction of the noise margin.

Once sync is lost, a new set of frequency "slots" is chosen, until again. they become unavailable, and the process starts again.

 

licquorice
Distinguished Sage
Distinguished Sage
662 Views
Message 5 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

That is really weird, what would normally be happening is as line noise increases and your noise margin decreases to unsustainable levels, DLM would kick in and resync your line at a lower speed in an attempt to stabilise the line but you say that you continue to sync at the same speed. I really don't know what could cause such strange behaviour.

Edit. Was typing whilst Keith posted

0 Ratings
Reply
Keith_Beddoe
Distinguished Sage
Distinguished Sage
642 Views
Message 6 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

A drop in noise margin simply means the available bandwidth has reduced, this normally shows in a reduction of the maximum available speed, and can be cause by interference, but a HR connection is more likely, especially as there is a repeating pattern.

0 Ratings
Reply
Mp22
Beginner
600 Views
Message 7 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

Switching to the test socket and microfilter did not prove successful. The noise margin still shows the same pattern of decreasing with time until connection drop, as the image shows.

Assuming it is a HR connection, it would suggest that the oxidation is on the contacts of the test socket - correct? Should I try cleaning the contacts or ordering a new socket and face plate?

Connecting through test socket with micro filterConnecting through test socket with micro filterMax data rateMax data rate

Wall socket and micro filterWall socket and micro filter

0 Ratings
Reply
Keith_Beddoe
Distinguished Sage
Distinguished Sage
590 Views
Message 8 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

If its still doing the same, and also with a different router, then I would suspect an issue either within the cabinet, or the local cable from the cabinet to your home which is picking up crosstalk from another pair, or even a split pair. Its unlikely to be a fault on the master

The cable from the loft to the master socket, may also be picking up interference. I assume there is nothing else connected to the terminal block in the loft?

Are you using any form of powerline adapters on your home network, as they can interfere with FTTC?

What is that Ethernet socket for on the left of your picture?

Also, I can only see one lead coming out of the microfilter, where is your phone plugged in?

0 Ratings
Reply
Mp22
Beginner
581 Views
Message 9 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

Thanks for you reply.

No I am not using powerline adapters. The ethernet socket faceplate has a Cat5e cable running up through the wall into the loft and then across the ceiling and drops down in my office where it feeds a Gigabit switch. One of the Gigabit ports from the HH5 is connected to that ethernet socket.

My phone was connected to the phone plug side of the ADSL filter, but it is currently unplugged to check that having that connected is not making a difference. So there is no land line connected at the moment.

Should my next course of action be to phone BT or is there anything else I can do first?

0 Ratings
Reply
Keith_Beddoe
Distinguished Sage
Distinguished Sage
575 Views
Message 10 of 12

Re: BT FTTC with HH5 noise margin decreases gradually until drop out

Not really sure what to advise.

If your phone line comes from a telephone pole, via a dropwire into the loft, then its possible that is picking up interference, or it could be the section from the loft down into the master socket.

It would be worth making sure there is nothing else which could be causing interference, like the Ethernet switch or its associated power unit.

A good start would be to turn everything else off apart from the home hub, and make sure there is nothing plugged into the HH5 Ethernet ports.

Then connect a computer via wireless, to the home hub, and then monitor the noise margin again over a period of time, so see if its varying. That would leave the home hub as a stand alone unit without any external connections apart from the phone line.

Its just a process of elimination.

0 Ratings
Reply