Broadband Sync Speed Drop from 8120 kbps to 5728 kbps on Haverhill Exchange



Not sure where to turn now, wonder if any of you have any ideas!

Back on the 16 November 2006 I lost sync with the Haverhill exchange and could not get any sort of stable connection; this was after 2 years of stable sync’d connection of 8120 Kbps – this was with 3 different providers over the period of time (F2S, Zen and the latest NewNet) – all with no sync issues or loss of connection at any time with perfect connection and downloads around a maximum of 7900 Kpbs, so all was good.

I contacted NewNet who I can not fault, as they got onto the case straight away.

The following few days/week my line started to intermittently sync at a rate of 5472 Kbps

NewNet contacted BT and an engineer visit was booked for the sync issue and low speed – which at the time my fault threshold was 6500 Kpbs – so NewNet said that there was problem and BT has to fix it.

The BT engineer came on the 29th November, reporting that there was no problem – all within rates sent by BT and stated that I should be lucky with 5472 Kbps!!

I got back to NewNet and they said this is normal for BT and that they would get back onto them – which they did!
On the 11th December BT altered the B-RAS profile to 6502kbps and also changed the SNR and turned interleaving on.

On the 21st December 2007 the engineer appointment was booked as my sync rate was still less then the fault threshold and I thought that I would get this sorted out once and for all! But one day later, on the 22nd December BT reduced by fault threshold to 4000 Kpbs!! After conversations with NewNet it was decided to let the engineer visit take place and see what happens.

The BT Engineer came out yesterday (4th January 2008) who thought that there was a problem and went of to the exchange. An hour or so later I got a phone call stating that further tests had been done and all was fine.

I got back to NewNet who picked the case up again and said that there was a problem as the fault threshold was 6500 Kpbs when the appointment was booked. The NewNet care manager got onto BT and the final say appears to be from NewNet

"I have just had a conversation with our customer care manager about your case.
He has contacted BT who have come back basically saying that the line is only capable of 5M For Telephone Number *** on Exchange HAVERHILL. We've just tested your line and can confirm your line supports the UK's most complete broadband package, BT Total Broadband and we can confirm that you will be able to reach a maximum download speed of 5.0 (Megabits per second). Even though you were originally able to connect at 7/8M and they have dropped the speed it is within BTs rights to do that. It does not seem there is anything that we can do from where we are, sorry about this."

Can BT do this? I thought broadband and technology was increasing not decreasing? I had a fast sync rate and it has been removed? It seems I am paying for a reduced service, compared to what I had!

Is there any further action that I can do?


Well-known Member
It's a sync problem so not down to the ISP (although the ISP is the correct party to discuss it with).

It may be something has changed between your router & the connection at the exchange. It could be a change made at the exchange, underground, on a telephone pole....once you have ruled out your own internal wiring it could be anything really. If that is the case there is not much you can do about it really.

Have you tried connecting to the test port hidden behind the face plate of your master socket?

Also post your line stats to see if they reveal anything obvious.


I have tried the master socket - same result.

The BT Engineer has also tried the wire before it comes into the house and gets the same sync speed.

The line stats are:

SNR Margin: Down: 15.0db Up:21.0db
Line Attenuation: Down: 33.5db Up: 19.0db

I think it could just be down to BT equipment in the exchange and they do not want to replace it or just to many people on the exchange now - is such a pain as I know the line can do so much more!


Well-known Member
Looks like your downstream SNR is too high for Max ADSL. It should ideally be between 6 to 10 db. Higher SNR offers better stability but at the expense of lower sync. I wonder if you were previously experiencing instability (line drops) that has forced your SNR up? I've seen this problem before but I cant remember the solution (if there is one). I think with certain routers you can manually set target SNR. I'll do some digging and come back to you, or maybe someone else will suggest something in the meantime.

By the way with problems of this nature it would not matter if you were the only person on your exchange or there were a million people on your exchange....the sync would be the same.


Well-known Member
OK, apparently some routers allow you to manually change SNR so have a look around your routers options. If not DMT tool will allow you to change SNR if your router is supported

WARNING: SNR usually increases for a reason. Some change may have taken place resulting in the higher SNR. Your line may no longer be stable if you reduce the SNR.


Looks like I can not manually reduce the SNR - I have a Billion 7404VGO router.

I have just looked at my SNR on downstream and its now 17.5 - is it normal to increase quickly over night?

Never really taken notice of the numbers as before it was rock-solid at the 8mbit mark.


Well-known Member
It can tend to fluctuate a few db in response to local interference, electrical appliances and so on.


Well-known Member
A more detailed response courtesy of RobertoS on Thinkbroadband:
Assuming it happened from something happening on the line, as opposed to BT engineers increasing it in response to a fault report, and as long as they are out of the 10-day training period, then the proper way to fix it is just stay connected.

If the line is stable without a high error rate then the system should automatically drop the "target" SNRM by 3dB after 10 days, and automatically resync the line.

And again after another 10 days, and so on, until 6 is reached or the error rate prevents it dropping further.

(Some people think it is 14 days to drop, but mine dropped during the 10th day, and 10 days is the figure I saw quoted before I experienced it).

Slightly unhappy about your initial post, which has SNRM and attenuation from the router stats, but no actual sync speed. The reason I am unhappy is that each 3dB in "target" SNRM accounts for between 500 and 700kbps. So if they started at 6, a jump to 15 would only lose at most 2Mb of sync - so they could only have started from 7Mb, not the 8 you quote. (Except interleaving may have been turned on which takes another 500kbps - if they were syncing before around 8000 then interleaving was off at that time).

Factors to consider are:

- the only time it is worth recording SNRM is immediately after a sync, as it varies dynamically from then. That is what I mean by "target" SNRM, the value used by the DSLAM to negotiate the speed;

- if their line used to sync at 8150 kbps then the "target" SNRM would be increased from the default 6dB to mop up any spare, so increasing stability. So on a good short clean line at 8150 the SNRM can easily be 15dB - though it looks like that isn't the case here.

Presumably they have tried switching the router off for well over 20 minutes. That is the time for the DSLAM to do a complete cleardown of the line apparently.

Finally, back to the top. Although on some routers the SNRM can be adjusted with DMT or through telnet, if you are wanting the system to fix it properly then I don't recommend this. Reasoning - if the DSLAM sets it to 15 then starts watching errors/stability, and you tweak it down to 6, then the DSLAM may not see any reason to lower the target. On the grounds that (a) the error rates may be fairly high, and (b) the DSLAM set it to 15 and it is now 6 (or even lower at night) so there is high variation so lowering the target would be inappropriate. I could be wrong on that but I know my way works


Great info - thanks!

I actually posted something similar question on thinkbroadband as I wasnt sure which was the best forum for advise (sorry if this is viewed as duplicate).

For reference here is my current line stats and I believe that before the problems interleaving was off.

Up: 448000
Down: 5760000
SNR: Down: 17.5db / Up: 21.0db
Line Attenuation: 33.5 db / 17.0db

I did mention on thinkbroadband the following:

"Interesting when I went to the talk talk web site and keyed my postcode/phone number in to see about the famous free-broadband it says that I can get a speed of 2meg now and 7.1 in March ... whereas samknows reports 5 .... and reports that Talktalk went live in Dec - a couple of weeks after the slow speed occured!

Wonder if this is linked! "

Thanks everyone for help so far!!


Well-known Member
LOL, sorry I didn't realise you had posted there too. Can hardly be considered cross posting though since it's a totally different forum!


Just noticed in your footer you have a link to estimate your download speed... how does that work ? Can I actually use it to show that there is still a problem with my line with my ISP?

Current stats are:

Sync: 5696000
Down Attenuation: 33.5
SNR Margin: 18.0db

As said in the above message its been link this for 5 days+ (from the point of me looking at the attenuation/snr) but I know the sync speed has been the same for much longer... all the way back to November!

Thank again!


Result ! :clap:

After reading around another great forum and website over at thinkbroadband managed to come across a guy that could help - Andrew !!

After detailing my issue/problem my sync is now at 7616 with interleaving on.

Going to see how things go for a week or so and then see if I can get the interleaving turned off which should then push up my sync speed back to the 8120.

All I can say is that this would not have happened without Andrews help - your a star - thankyou! :thumbsup:

Thankyou to the guys here for giving me light at the end of the tunnel as well!


Well-known Member
Glad you got sorted mate :thumbsup: Was that Andrew Ferguson? Would be interested to know what you did in the end to get it sorted.

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