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)