loss of speed on FTTC upgrade -crosssdtalk?

When we were upgraded to FTTC our ADSL speed of about 9Mbps decreased to about 3.5 V.DSL. BT maintain this is because we are too far from the cabinet, This cannot be as their data indicate that at 2.5Km we should get about 12Mbps. Is there another likely explanation such as crosstalk

I have access to a line that is between 2.5 and 2.7km - mostly overhead and just one point where it could take two routes. That one varies between 2.5 and 3.5 and typically around 3.1Mbps.

In a perfect world you may get 12Mbps - but add in cross talk, external noise, potentially aluminium lines, fine gauge copper, joints, and it will soon drop,

How do you know it is actually 2.5 km?
For 9Mbps ADSL2+ - you will not have been much more than 2.5 km from the exchange, were you on an EO before or is te cabinet close to the exchange?
Can you give the BT Wholesale or Openreach prediction details?
Can you give your router stats?

And what was the guaranteed minimum speed that you were given when you signed up for the VDSL contract?

Thanks for replying, BT tells me a I am 2.5Km away and this is correct. I am sorry but I am not expert enough to answer such technical questions. I would have thought all the other factors that would degrade the signal would have been present before the upgrade. However I understand that going to VDSL may make crosstalk worse. My contract with BT was 4-9 Mbps (minimum of 3) before the upgrade and that is what we had. Now BT tells me i have a line speed of 3.6 max.

Can you go to: https://www.broadbandchecker.btwholesale.com/#/ADSL fill in your line number and then post the result, whilst hiding your line number. The VDSL, ADSL and Observed are te key sections


If you access the BT smart hub under advanced settings you will find details such as Attenuation, Sync speed, Achievable Speed/data rate for both up and down.



Yes, the factors will have been there before but but may not have caused issues with ADSL - different frequencies, power levels and more.

Thanks very much for the help.

The info from the hub is
Data rate:1.167 Mbps / 3.562 Mbps
Maximum data rate:1.167 Mbps / 3.998 Mbps
Noise margin:6.9 / 6.7
Line attenuation:20.0 / 40.7
Signal attenuation:20.0 / 44.8

The key info from the broadband data is

Max observed downstream VDSL 3.76 (after) ADLS 9.94 (before)
upstream numbers are 1.16 and 0.45 respectively

40db attenuation 😳

40dB ties in with around 2.7km of typical line ...so the distances are about right. And just on experience, I would suggest 4Mbps is about all that can be achieved.


The OP needs to post the BT checker results too AND contact BT immediately to express dissatisfaction with the speeds along with a requirement to be returned to ADSL if improvements cannot be made.

This looks as though the cabinet is right next to the exchange as the ADSL figures would suggest a similar line length

In reply to a post by robhughes:

Thanks for replying, BT tells me a I am 2.5Km away and this is correct. I am sorry but I am not expert enough to answer such technical questions. I would have thought all the other factors that would degrade the signal would have been present before the upgrade. However I understand that going to VDSL may make crosstalk worse. My contract with BT was 4-9 Mbps (minimum of 3) before the upgrade and that is what we had. Now BT tells me i have a line speed of 3.6 max.

I would switch back to ADSL if I was you, VDSL is at the very edge of working at that sort of speed so will be a more unstable than your previous ADSL.

It looks like you've gone from an EO line to a cabinet, but your line is far too long for this to help. You need to downgrade back to ADSL.

I think it was asked but I didn't see the answer - what was your speed estimate when you signed up to the new service?

Edited by jpm (Thu 18-Feb-21 16:48:25)

I asked BT to put me back on ADSL and they said min speed would be 500Kbps.Previously it was 3Mbps. I can't take that risk.

I have been arguing with BT since June! They claim it is simply distance. They offered me the option to leave my contract penalty free but the problem is any ISP would have the same problem. It cures their problem but not mine.

In reply to a post by robhughes:

I asked BT to put me back on ADSL and they said min speed would be 500Kbps.Previously it was 3Mbps. I can't take that risk.

Going back to ADSL shouldn't be any different than it was before you switched away from ADSL and you was getting 9Mbps before.

Edit: cleaned my wording up

Edited by deleted (Thu 18-Feb-21 17:00:40)

So where is te evidence to prove they originally quoted 12Mbps?

What does the BT checker say?

The only way to resolve it will be to go back to ADSL and you should see the same figures as before - unless there has been a pair swap.


ALSO: What is the exchange and cabinet number?

Edited by MHC (Thu 18-Feb-21 17:03:09)

Actually, it can become worse, sadly. I was also on EO Line, but until October 2019 when I finally got upgraded to FTTC here in Bishopsgate Exchange, Central London.

In my case while I was with Plusnet ADSL until end of my 12 month contract till January 2020 those 3 months following the cabinet upgrade I experienced a deteriorated ADSL service that seemed to have coincided with the FTTC cabinet upgrade. I was getting stable 12Mbps at 9dB noise margin.

After EO Line was rearranged with a new cabinet upgrade SNR dropped to 7dB and speed to around 11Mbps with multiple disconnections throughout the remaining 3 months, it was a nightmare. This is not a coincidence, as all the 9 months prior to that with Plusnet service was stable and I was getting 12Mbps with 9dB SNR in router stats. 7.8dB was the highest SNR after cabinet upgrade and it would never return back to 9dB ever again.

Anyway, after upgrading to TalkTalk FTTC in February 2020 all these problems resolved on their own, thank God!

I'm lucky that the cabinet is around 320 meters from my property and I get full 80Mbps download and 20Mbps upload last 1 year since being with FTTC so far with no drop-out issues barring TalkTalk maintenance and router firmware upgrades.

While my line length (from the exchange) is approximately 1320 meters. There's a major reduction in copper, so FTTC in my case improved the connection considerably.

Unfortunately the same cannot be said for the OP as it appears that the cabinet is very far away. Fact of the matter is that if you're having a 40dB line attenuation then crosstalk is not the blame, distance is!

In my case cabinet upgrade destroyed my ADSL service, but I don't care about ADSL anymore as the FTTC service turns out to be superb.

Edited by BLaZiNgSPEED (Fri 19-Feb-21 04:42:50)