Hi
Am i right in saying that for a fixed line of fixed length, the line attenuation figure should be constant? I appreciate there are many wire junctions between my master socket and the dslam which might cause a variance due to teperature, humidity etc, but sureley this should be practically immesurable?
Yes and no.
No if looking at the typical attenuation figure shown on router stats. This is because attenuation reported by routers is an average over all the tones received. If you make some improvement to your line that for example reduces the noise on it, perhaps remove some bad extension wiring, you might easily see attenuation go a bit higher, this is good in that case, as it means you are receiving more higher frequencies and as higher frequencies are attenuated more, your average reported by the router will go up. This is exactly the same reason when people switch to ADSL2+ that uses higher frequencies that attenuation reported goes up. Depending on your line, sometimes you might see quite a few more higher frequency tones than at other times, so this fluctuates the average attenuation. For a lot of people the tones they receive do not change much so the attenuation figure seems fairly static.
Yes it shouldn't change much if you are BT testing the line or are using a tool that provides attenuation statistics from your router at a set frequency. The test BT or the ISP will do to check attenuation is different from your router as it reports the figure at a set frequency. This should be consistant all the time, although may still vary a few db up and down.
If your router supports the DMT tool, it usually gives you an attenuation figure at 300KHz, similar to the readings BT might have, and this will remain pretty constant unless something physical happens to the line.
Regards
Phil
Edited by deleted (Sat 30-May-09 08:44:11)
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