Can a switch mode PS cause this sort of ADSL noise?

Chris Wilson · 18 Jul 2013 at 15:37

Having received a new router from Zen and found it cured some of my ills opf dropped or high noise connections (a Technicolour TG582n) I decided to wire it up properly. My home LAN is wired, no wireless at all. I had been testing with the router connected to the test socket in the BT master socket in the loft via a LONG Ebay purchased cable. I fitted a new latest filtered faceplate with the extra two AB connectors so the wiring to the router socket was hidden. I reconnected the BT installed twisted pair cabling to the AB connectors, and another pair to 2 and 5 for the phone socket in my office. All seemed well for a few hours, but in the night routerstats showed serious noise and the connection speed dropped substantially. Connecting via the extension cable brought a quiet connection again. I decided to follow the BT laid cable and in so doing was forced to recall I had 2 switched mode power supplies on the opposite side of a studded wall, just near the sockets in my office. The cable ran *RIGHT* by them and alongside a mains cable feeding their 13 amp dual mains socket. One is for a Thunderbolt 10 MHz frequency standard, the other for a frequency divider board. I use them in my amateur radio hobby. The Thunderbolt box itself is slso very near the socket and wiring. These supplies runs 24 hours a day, seven days a week and have done for at least 2 years. I decided to turn them off and reconnect the BT wire. All has been quiet since and I am slightly optimistic one may have been the problem. I am perhaps lucky and not had issues with switch mode supplies causing noise that I have been aware of, so could some of the more knowledgeable folk tell me if this screen shot of the noise margin when playing up could be a SMPS gone awry? Thanks!

Tealc · 18 Jul 2013 at 17:45

Could be a REIN fault caused by one of the SMPS. The only way to tell is to do what you've done and see if it makes a difference. If you get a nice clean signal for a while introduce one of the SMPS at a time and monitor. It could even be a problem when they are both in use. So hard to track these faults. I went through a similar thing with my ADSL signal here and swapped a cheapo 12v 1A SMPS that powered router for a homemade linear regulated supply and it cleared most of the issues.

Chris Wilson · 18 Jul 2013 at 21:36

You are right about hard to find! The damned noise is back and both supplies are unplugged. Seriously considering satellite, the neighbours have issues too. The joy of being out in the sticks I guess

Thanks for the replyTealc

Tealc · 19 Jul 2013 at 21:32

Any noise on the line? Make sure you check when you get one of the blips.

I had an issue a while back on a short line that was fine for the most part but two or three times a day would just drop out, often reconnecting at half speed before eventually getting back to full speed. When it was dropping out I could hear cracking and popping on a wired telephone. Called BTO. Engineer came out and changed something on the pole and the problem went away.

You will want to take all other wiring off the main socket while you test. If noise is still there in test socket then it's a line fault. If noise only occurs when your extensions are in use then it's an internal issue. BTO will charge you if the fault is on your side.

What are your line stats?

Chris Wilson · 19 Jul 2013 at 22:36

How can I post the line stats? I believe the issue is on the spur to my office. Currently running the 2 phones in the house and an independent Ebay extension cable direct to the router from the faceplate "router" port on a new master socket. All seems well. I have resistance tested the BT installed line to my office, with one end shorted, and chopped off the ends in case fiddling has flexed and broken a solid core wie juist inside the cable pairings. Seems it's a strange internal fault on the cable to my office from the master socket. I was going to go satellite but I now see Tooway are also having connectivity issues, so feel more obliged to persevere with ADSL. Being in the sticks I accept ADSL won't be perfect, but the situation for the last few months has been ridiculous. I am loathe to have BT in and for them to find an issue withb the internal wiring, so I am very open to further suggestions. Thanks Tealc

Tealc · 20 Jul 2013 at 01:01

Line stats are the things that feature attenuation, line speed, signal to noise margin etc.

Avoid cheap extensions and wire your own with proper twisted pair cable such as CW1308 (think that's the number) or a pair out of cat5e.

bledd · 20 Jul 2013 at 07:33

Paragraph your posts a bit mate, that looks crazy to read.

edit, looks ok on the desktop, was just cramped on my phone, ignore me

Chris Wilson · 20 Jul 2013 at 09:12

Here's a link to a screenshot of the current line stats. Zen organised a bRAS reset late yesterday afternoon and things are fine now I have removed the spur to my office and am using a cheap extension cable from the fascia router port on the ADSL 1.0 master box direct to my router. I am hoping it stays this way and I can rewire from scratch the office socket, probably moving it to an opposite partition wall in case it was picking up RF from something. Thanks for the CAT5 tip, I have a reel of CAT6 and will wire with that if it seems to be the issue.

http://www.gatesgarth.com/routerstats.jpg

Tealc · 20 Jul 2013 at 14:22

You have a fair amount of errors there. Judging by the local being higher this might suggest possible issues in the lower frequencies of the upload spectrum.

Cheap extensions use generally flat untwisted conductors, sometimes even copper coated aluminium rather than pure copper and while these are fine for the low frequencies of voice they do introduce issues in high frequency signals. Flat conductors also act as antenna for all sorts of Interference. A twisted pair works very well at reducing interference and crosstalk and I would assume acts less like an antenna.

Even a small length of poor cabling can make the world of difference. Just 10M of poundshop cable increased my attenuation by 4dB in my old house. That was worth a couple of Mb.