In reply to a post by candlerb:

Oh yes, it varies by time of year too.

When I was on FTTC, my sync speed was ~35M in winter and ~30M in summer. But some people have reported seeing the trend the other way round.

Not that I check it all the time, but I have not noticed it change at different times of the year. I think it has gone faster because they changed something in the cabinet, that is why my old router can now sync where before it would not sync at all.

There is DLM as a factor too. For example, if DLM decides your line is good enough, it can move you from a 6dB SNR target to a 3dB SNR target, with a corresponding increase in speed. It can take weeks or even months before it decides to do that.

In reply to a post by candlerb:

There is DLM as a factor too. For example, if DLM decides your line is good enough, it can move you from a 6dB SNR target to a 3dB SNR target, with a corresponding increase in speed. It can take weeks or even months before it decides to do that.

Except those on a good line (G.fast) default at 3dB SNR.

Yep all those millions of people. Not 😂

6dB does not necessarily mean a bad line! When I first switched to FTTC (TalkTalk) in February 2020 following the EO Line upgrade in October 2019 I remember syncing at 80/20Mbps at all times for around 6-9 months.

I was having noise margins of 6.40dB for downstream and for upload it was 15.40dB. https://i.imgur.com/0oZtZHE.jpg
I had a line attenuation of 17.90dB! Yet my speeds were always better. After 9 months or so my noise margin has now permanently dropped to 3dB though this time it was still syncing same speeds.

After a year or so due to crosstalk I no longer sync at 80Mbps, more like 74-76Mbps. After 2 years being with TalkTalk FTTC I migrated to BT due to price hikes and thinking that BT might have improved speeds. https://i.imgur.com/UrfEYfh.jpg

Data rate:18.882 Mbps / 74.519 Mbps
Maximum data rate:18.882 Mbps / 77.039 Mbps
Full Fibre (FTTP) Mode:Off
Noise margin:6.1 / 3.3
Line attenuation:10.6 / 16.8

These have been my speeds since joining BT in July. We can see that despite having a lower line attenuation of 16.8dB with BT this time vs 17.9dB with TalkTalk my sync speeds are lower. I have not achieved 20Mbps upload or had speeds any higher than 75Mbps with BT.

This suggests that crosstalk is now showing its negative impact. The only positive we see with this new checker is it gives us speed estimates for FTTC without needing to go to the https://www.broadbandchecker.btwholesale.com site. Checker may show VDSL Range A (Clean) help 80 60 20 16.5 55 Available Available
VDSL Range B (Impacted) help 80 55 20 14.5 46.5 Available Available
or Available now

Superfast Fibre Broadband

55-80 Mbps

download speed
14 - 20 Mbps
upload speed

But the truth is that I have not synced at 80Mbps so far. I won't complain about a few megs. The only change I am seeing is that my line attenuation is 16.8dB as opposed to the 17.90-18.20dB with TalkTalk. This is kinda strange as lower attenuation should indicate shorter line to cabinet. But crosstalk appears to be the biggest cause of this reduction.

Noise margin remaining at 6dB as opposed to 3dB does not mean a lesser stability of the line, it just means there's no crosstalk. Crosstalk means DLM is trying to achieve the higher sync speeds but at 3dB since it's failing to sync at 80Mbps at 6dB.

I've heard and read stories of people where once certain postcodes from a particular cabinet that suffered crosstalk had upgraded to FTTP that relieved crosstalk impact for that FTTC customer as less customers are now overloading the FTTC cabinet. So it is quite possible that if my area or postcodes that were using my cabinet switched to FTTP. FTTC speeds should return back to 80Mbps. But I guess by the time that happens we will all naturally migrate to FTTP and won't care about FTTC.

In reply to a post by candlerb:

There is DLM as a factor too. For example, if DLM decides your line is good enough, it can move you from a 6dB SNR target to a 3dB SNR target, with a corresponding increase in speed. It can take weeks or even months before it decides to do that.

The router I am using at the moment can't show SNR, but at the moment it is synced at 39Mb/s. I know about DLM, I had enough of DLM with ADSL, thankfully it is much better with FTTC.
The problem I have at the moment is with this router, it keeps rebooting for some reason. It has not done so for a couple of days, so maybe it has sorted itself out, we will see.

In reply to a post by zyborg47:

The problem I have at the moment is with this router, it keeps rebooting for some reason. It has not done so for a couple of days, so maybe it has sorted itself out, we will see.

https://vic.bg/jokes/there-was-an-engineer-manager-a...

before the change of the site, it reported we had G.Fast available (i'm currently on 330Mbps G.Fast), now it just says upto 80Mbps, with the FTTH saying build not annouced.

Where I am, half the streets have G.Fast or upto 80Mbps, while others have had FTTH installed. I contacted Openreach and they mentioned it would be around June 2024 when we would be upgraded from G.Fast to FTTH.