what causes widely fluctating SNR?

I'm with Be and normally synch at 23 to 24Mb with downloads around 18-19Mb/s. I am using a netgear dg834n router with a line attenuation of 18db down.

Over the last week I have started to see the download synch speed bump downwards from say 23400 to low 22Mb. Looking at the connection stats indicates that my snr can vary from 5.9 down to 1db within a matter of seconds. Looking at the DMT tool shows me that at some times I can see over 8000 crc errors within the space of an hour.


My line was previously stable for the few months I've been with Be until last week.
Is there anything I could be checking to solve this issue as atm I'm not so happy with this connection.

You have been around here long enough to have done the basics (I presume), checked at the NTE test jack, etc. Tried borrowing a different router, to rule this out ? Any noise present on a quite line test ?

As Zarjaz said check all the physical setup:

Make sure that you are not using any extensions.
Make sure that you have all the sockets that you are using filtered with nothing before the microfilter at all.
Try the bt test socket if you have one.
Try another router.