Sunday, 11 October 2009

Don't Flash at Your Router!


I've written before about the range of electrical items that can have a dire effect on your broadband, but every so often you can get caught out, even if you know how these things can cause interference or even repetitive electrical impulse noise (REIN).

The other day, I was trying to help out someone with a broadband problem and thought it would be simplest if I took a photograph of my own broadband set-up to illustrate the point. I was showing him how the use of a timer can help miss spikes of REIN activity. To get the photo, I had to crawl under my office desk and pull out a panel to get at the wiring. Unfortunately, it was fairly dark under there and I had to use flash photography with my little digital camera. As it only has an LCD screen rather than a proper view-finder, the process was a bit hit and miss, so I took half a dozen shots to get one that was half-way decent. Things weren't helped because the camera was playing up and not capturing pictures properly, so I had to resort to a second camera.

Whilst taking the photos, the cameras were within a couple of feet of the router, my PC, the BT Master socket and all sorts of other PC-related electricals.

I was surprised to discover that my SNR margin began to drop very rapidly when I was taking the photos and then I realised that the download speed had dropped through the floor. The trace from RouterStats looked like this:

The SNR margin bottomed out at 9dB and after some minutes, shot up to 21dB. During all this, the IP profile dropped from my usual (pitiful) 1250kbps to 500kbps.

Well, the SNR target had dropped to 12dB by the following morning, but it took a further 15 hours before the IP profile increased again. Surprisingly, this settled at 1500kbps, but it was back to its normal 1250 kbps. So, no harm done in the long term.

There is a lesson here if you are on a long and flakey phone line - don't try flash photography near your router, it may cause the router to lose sync!
Having had some major problems with my own broadband service, I understand how others struggle to get help from BT.

There is a lot of good information out there, but it can be hard to find. So this blog is an attempt to pull some of it together, in one place.

It's a blog that really shouldn't be needed - if only BT and possibly other ISP's in the UK, provided useful customer support.