I get the same results with only the router plugged into the test socket of the master socket with all other extensions disconnected and nothing else switched on in the house.
Also the ring wire is not connected.
On the quiet line test yesterday using an old wired phone I could hear a small amount of crackling but very little.
When the router speeds are very low I can hear the router making quiet screeching noises on the phone (but not if I use our dect cordless ones) that obviously you shouldn't hear. Turn the modem off and it stops and then back on and once it starts to try and sync the noises appear again.
The noises are the kind of thing I'd expect if the microfilter was playing up but I've tried this with three routers and six microfilters and the problem is the same so I'm pretty sure the problem is not related to an internal issue.
I'll try the idea above with the am radio to see if I can find an interference source.
I actually have vague recollections that I used to be able to hear the radio when using the phone when we first moved in about 7 years ago and BT came and fitted a filter where the cable enters the building before the master socket and it stopped the radio on the phone line.
Edited by StuB (Wed 02-Feb-11 22:10:08)