Thanks for that, Azzaka. Shame that BT only set the SN target in 3dB steps...
Anyway, here's an update on my line, which I was leaving alone at 7680kbps...
- Ran overnight at 7680, SN margin range 6.5 to 5.5dB
- Mid-morning yesterday: re-sync'd from peer to 8000 when the SN margin went up to7.5dB
- Mid-evening yesterday: re-sync'd to 7680 when the SN margin dropped to 5dB
- 5.00 this morning: re-sync'd from peer to 7808 for no obvious reason (SN margin range 5.5 to 6dB for previous several hours)
- mid-morning today: re-sync'd from peer to 8000 for no obvious reason (SN margin range 6 to 6.5dB)
Interpretation of this: I don't have a clue what's going on; just wish I could combine the line stability of the TG585v7 with the DG834v3's tenacity at holding sync with very low SN margins.
Having watched this passively, I have just used ftp to upload a config file (user.ini) with this line in the [ adslpots.ini ] section:
[ adslpots.ini ]
config modemoption=30000000200000000600000000000000
then, having confirmed that the new file was in fact on the modem, I went into the CLI and did
:config load flush = enabled filename = user.ini
Long, long wait. Reboot. Same old story: sync at 8000kbps with 8.5dB SN margin, and :adsl debug modemoptioninfo shows the unmodded settings. So I'm laying this one to rest; life is too short.
However, the huge bursts of 100,000's of FEC errors have not happened since I put a clip-on ferrite toroid on the DC power line into the modem yesterday - though I'm not assuming cause + effect just yet.
All the same... since it was the high error rate that was the original concern, if the ferrite does turn out to have got the errors down to an acceptable level, does it matter if the line re-syncs quietly from time to time? As there's no way the line will hold an IP profile of 7000 but doesn't look like syncing down (to coin a phrase) below the 6500 threshold, the answer is: probably not,
unless this will upset the secure VPN to which we're being migrated in a few weeks' time.
Yet another long post -- sorry. But I think that's the end of the saga, at least until the VPN arrives...
Thanks, folks.
rwm32