Guys
This may be more about ADSL than Draytek, but interested if anyone else has seen this before.
Previously had a Netgear DG834 on BT broadband, sych at about 5.5mb and SNR of 6dB. Upgraded to 2820n with BT WAN1 and virgin WAN2, all nice and stable.
Recently noticed ADSL SNR had leapt up to 22dB sych drop to 1mb. Rebooted and got back to 6-8dB and 5.2 sync. Decided to montor SNR via SNMP using Paessler PRTG freebie and noticed the SNR varying during the day from 6-10dB based on time of day - lower at night increasing in the day.
This variation isn't a one off as I've graphed 2 months now and the cycle is daily. Then two days ago, another jump to 20dB etc. Rebooting the router gets back to 6-10dB. Tried BT line tests and speed checker, nothing reported as faulty.

Any advice or feedback?

The decrease in noise margin durning darkness is normal as the frequencies that ADSL uses are subject to more interferrence during darkness (i believe something to do with the ionosphere being more reflective when its dark but may be making that bit up! lol). This bit of fluctuation is normal

The sudden drops in sync speed and then massive noise margin indicate that something is suddenly injecting lots of noise onto your phone line, causing the modem to re-sync at a lower, more robust, speed. (the normal target noise margin is 6dB) Once the noise stops your noise margin returns until you reset/re-sync the modem to the exchange swapping that margin back for sync speed.

Hope this helps :lol:

As rxt_ian says this all sounds perfectly normal, street lights etc will cause interference to ADSL thats why it always drops at night.
The odd big spike does happen, could be just a bloke at the exchange resting on a board, who knows.
My adsl is exactly like this so no need to worry.
I also would expect that a longer line, like mine is makes it worse as well as more cable to pick up interference.