Lost 5db Margin.

My D/S Attenuation is 23db and power is 19.5 dbm. Been sitting at 11db margin for months now at 8128 sync with no loss of connection. My margin had now dropped to 6.5 db at the same sync. Any ideas why such a dramatic drop ? Doesn't seem to be affecting the connection at all just curious mainly why such a dramatic drop. Any theories ?

My margin had now dropped to 6.5 db at the same sync......why such a dramatic drop. Any theories ?

New item of electrical/electronic equipment (plasma TV, microwave oven, etc.)?
Street lamp?

Is the drop consistent (down by around 5db all the time) or is it fluctuating?

Any better in the test socket (inside the BT master)?

With an attenuation of only 23db, you really should have a higher noise margin (although I note the Tx power from the DSLAM is quite low, so it may have been turned down, as you're on a short line - this could account for the drop in margin).

>>>>>>New item of electrical/electronic equipment (plasma TV, microwave oven, etc.)?
Street lamp?

None of the above that's what's so puzzling. Over Xmas it was 11db and just noticed the drop tonight it's usually 11-11.5db steady day and night. Seem to be fluctuating 6.5-7.5db after a couple of router reboots.

Will have to start monitoring again and see if it's a day/night thing or if this is now the new level of d/s margin. Upstream margin has also dropped from 24db to 22db. Weird - cold, water ingress ? No crackles on the voice side. Margin is the same in the test socket - just a quick test.

Edit: Just unplugged a Freeview box that I just got just in case it was that no difference. CRCs were also low on reboot about 129 for 15 days uptime.

Edited by Banger (Sun 21-Jan-07 02:52:29)

Well either the line quality has gone to pot or the 546 router I'm using has developed a fault. Test socket with everything disconnected shows same symptoms. Will see if I can get a cheap spare router off ebay to test.

Hmmm seems I now have a db swing as shown on the graph, although this is the only time it's peaked at 11db. Have I got a problem ?

Looks like a noise source switching off/on. I have one that when it switches off [not very often] my margin goes straight up by ~8dB.

Looks like I have the same or the router's gone. Before this it was 11db solid all the time :|

Those "blips" seem to be very evenly spaced. Could be a thermostat, or an air compressor motor ? Do you live close to a hospital, or an area where there are engineering companies operating ?

No hospitals or companies, live in a residential area. Weird thing is for a couple of months the SNR was 11db 24/7 then it has dropped to 7.5db 24/7 and the above graph is the only time it has swung like that. Since that graph was taken it has remained at 7.5db 24/7. I'm beginning to suspect the Speedtouch 546.

SNR margin has now dropped to 5db from 8db hope I'm not going to get another fault on my line.