Overhead cable replacement?

I've purchased a house which, for the first time, has the option of fibre which I'm most pleased with! We haven't moved in yet as the house is being significantly re-worked but I have had Fibre activated (TalkTalk Business Fibre). The speed is fine (67mbps, attenuation 9db) but I was expecting to get the full 78mbps due to being approximately 300m from the cab.

The way I'm connected appears to be underground ducts feeding roadside poles which them distribute to groups of 4-5 houses every 100m or so. My overhead cable is connected to a small metal pole on the gable of my house which appears to provide tension and then goes into a grey BT junction box. The output from this is two cable, one pair that no longer goes anywhere (so I've clipped and tidied) the other par going to the master socket inside the house (approx 5m run).

I'm wondering if the joint is an obvious point of attenuation and if it is worth getting Openreach in to replace the cable with a single run direct to the master socket? Maybe even getting it run underground whilst my builder are still around to prep a trench.

Thoughts?

It is NOT the attenuation that is causing you problems; 9db attenuation is probably about right for 300m line. A line with 15-16dB attenuation can usually provide a full 80Mb service so your 9dB is not an issue. It is more likely to be noise that is the issue.

Can you get your full stats including up and down SNRs.

Are there any other sockets in te house or is it just the master?

No additional socket, VDSL faceplate on master socket to split phone and router - approximately the same stats when using the filter in the box into the master socket. No internal wiring (yet) on the 532 pins.

Upstream line rate 19999
Downstream line rate 67629
Upstream noise safety co-effiicient 15.6
Downstream noise safety coefficient 6.1
Upstream intereave depth 0
Downstream interleave depth 0
Upstream line attenuation 17.5
Downstream line attenuation 8.9
upstream output power 4.3
downstream output power 12.5
Downstream interleave depth none

Edited by deleted (Fri 12-Aug-16 13:15:50)

There is your answer - downstream noise 6.1 dB.

You may have a noise source you can control or it could be crosstalk from other lines.

I thought 6db noise margin was standard for all connections? Or is htat an ADSL only thing?

Yes, you are correct about 6dB being standard. That means (unless set otherwise by DLM) that is what you get at connection time. The reason yours shows you have noise somewhere is explained on this page, which shows how it works .

So is the overhead cable / junction box an obvious source of noise or is it just bad luck for me? The overhead cable is about 25m long (5metres up the pole, 20 metres over the front garden.

Obviously a rock solid 67 mbps/20ms ping is great so I'm not that bothered.

They will not be the source - that will be other devices, cross talk, radio, fridge, motors .... the wires just pick up that and there is no easy or cheap solution. It happens on all lines - just that some are worse than others.

The reason it is rock solid is that the devices have "agreed" a speed based on 6dB (+/- a little) knowing that the amount of noise across the spectrum and in different bands will not significantly affect the successful transmission. The 6dB will move up and down during the day and you speed may move a little to track that.

Thanks for that. I'll save my money and leave the cable alone. Hopefully the crosstalk will disappear once v.fast brings in better measures to defeat.

Changes in SNRM of the kind you describe will only cause a change of Max Attainable, not of sync speed. Unless it changes down dramatically enough to cause a re-sync, which would indicate a serious problem. Changing up does not cause a re-sync at any time.