Example of BT Openreach making phone lines worse.

A few years ago BT did lots of work on the main A road that my phoneline comes along. Replacing the "old" wiring.

When this was all done my ADSL sync had gone from 8128 to 3776. BT claim no fault and say the line is perfect.

I know what they did... they didn't use correct pairs (twisted) and connected the wiring just to random wires in the bundle.

The proof of this is tonight we had a power cut, but I am on UPS. Everyone else's connection will have dropped. Hence the crosstalk (the cause of all the problems) is gone. Power failed at 18:12 returned at 18:48

Here is the log.

12.11.2015 18:00:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:01:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:02:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:03:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:04:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:05:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:06:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:07:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:08:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:09:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:10:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:11:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:12:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:13:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:14:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:15:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:16:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:17:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:18:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:19:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:20:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:21:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 28.0 dB
12.11.2015 18:22:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:23:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:24:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:25:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:26:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:27:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:28:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:29:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:30:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:31:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:32:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:33:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:34:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:35:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:36:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:37:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:38:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:39:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:40:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:41:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:42:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:43:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:44:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.5 dB
12.11.2015 18:45:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:46:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 27.0 dB
12.11.2015 18:47:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 26.5 dB
12.11.2015 18:48:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 12.5 dB
12.11.2015 18:49:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.5 dB
12.11.2015 18:50:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.5 dB
12.11.2015 18:51:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.5 dB
12.11.2015 18:52:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:53:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:54:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB
12.11.2015 18:55:00 - C1L1D1T01 | BitrateDN: 3776 kbit/s | BitrateUP: 448 kbit/s | SNRM: 7.0 dB

You can clearly see the rise in SNR, and then when power returns back it goes down again.

So frustrating, but BT refuse to do anything, and charged me the ~£120 call out fee for one of their visits.

And your downstream attenuation is what?

Use of split pairs would provide other symptoms, does your line show any of these ?

38db - It was before and after.

The SNR graph of the tones shows a nice gentle curve so no specific frequencies are suffering, it's just a general large increase in signal noise caused by the crosstalk.

What other symptoms should I be looking for?

Thanks

The lack of noise rejection can impact on the voice side, so you should be hearing issues too I believe, hence why twisted pair was common decades before xDSL was considered.

In addition, given there was a power cut, there could be some serious noise coming from an electrical device somewhere that would not be operating whilst the power was down.

As a start, if I was the OP, I would flip the main breaker in the house (as the router is on UPS) and see if it makes any difference to the noise margin.

And if the noise margin flies up at that point to do a resync and see if the modem is happy to make use of the spare margin.

Possibly worth saying twisted pairs while good are NOT perfect at making xDSL services immune to noise. Some noise sources can still cause problems and that even applies if you go all out and use CAT5E

(edit as phone rang, and pressed post before reading to see if I made sense)

Edited by MrSaffron (Fri 13-Nov-15 13:04:30)

I am either very tired or your second sentence doesn't make much sense?

I think you mean that whilst good at reducing noise they aren't perfect and noise.

Why would they randomly connect to individual wires rather than a specific pair? If they did, then at the other end of the cable the job would be ten times worse trying to locate the two wires used.

And, if a BT tech was found to be working in that way, he would certainly have been dealt with and the terminations remade.