'Noisy' SpeedTouch 585v6

Long story short, I've had BT checking my line quality as part of another fault, and they've determined that my router is generating noise on the line. They had me swap it out for the old frog USB modem that came with my original Engineer install of ADSL back in 2001, and although that doesn't work very well (only syncing at 3Mbit+ compared to the 4-5Mbit of the 585, and repeatedly dropping sync, line noise was reduced).

Is this a problem anyone else has come across with this router, or could I just have a bad unit? The connection itself seems to be fine, holding a sync of 4533+ on a 6-9dB margin, with reasonably low FEC and CRC counts, but seems to have a lot of errored seconds. For example in the last 24 hours DMT is showing 479 errored seconds. Is this something that will cause the exchange to lower my sync, even though the connection is holding up fine?

I would change the router if I could be reasonably sure it would be an improvement, but the SpeedTouch has been the best performing router I've had on this line, so I'm doubtful.

479 errored seconds in 24hrs wouldn't concern me as being excessive. I can't speak though about what BT are seeing.

Most newer routers have switch-mode power supplies these days, and they are prone to noise generation when they go faulty. You can tell whether you have a linear or a switch-mode supply by the weight - linear supplies had a large iron-cored transformer inside, which made them quite heavy.

obviously noise would be considered reduced on a lower synch, I expect if the speedtouch synched at 3meg it would be the same.

I wouldnt read too much into error counts, the main thing is how the line itself performs, if you get no packet loss, retransmits etc. then be happy with it and just turn a blind eye to the reported errors.

Your 585 was dropping synch and such tho so I would suggest putting it back in and manually increasing the snr margin a few db (in DMT) and see how it goes.

Mmm consider this...

Is the noise because of the router, or because it is running the ADSL closer to the limits, and thus you will see the odd error. 479 errored seconds in 24 hours, when there are 3600 errors per hour is not that massive.

What are the full stats for both the 585 and frog modem?

I did raise this with support, that if the sync was lower then wouldn't the line quality be different anyway, but I didn't get a clear answer regarding that.

I basically do what you've suggested, which is use DMT to tweak the sync to the best usable profile, ie a sync of 4544+, to get a 4000 profile.

Stats for the frog, I have no idea, the taskbar utility that controlled it was very basic. It seemed unable to work reliably with MAX anyway, but it was the only other working device I had available to test their theory.

The 585 stats are downstream attenuation 50dB and currently synced at 4608 with a 7dB SNR margin. There appears to be some leeway though, since I can sync above 5000 on a good day, although it's not reliable enough to hold that sync long enough for a profile rise, so I generally limit it to maintain a 4000 profile.

Syncing lower doesnt change the line quality that is relatively constant, what has changed is the number of bits you are trying to use to carry the ADSL signal.

Use less (lower sync) and chances of hitting an error are less.