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I've recently replaced my ageing BTOR fibre modem with a Draytek Vigor 130 and it appears to be working okay but it's reporting upstream and downstream SNR of 6dB that goes down to 4dB then to 5dB then back to 6.
From what I've read, anything below 7dB means that I shouldn't be getting any broadband service yet I am.
Is the Vigor 130 wrong?
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I've recently replaced my ageing BTOR fibre modem with a Draytek Vigor 130 and it appears to be working okay but it's reporting upstream and downstream SNR of 6dB that goes down to 4dB then to 5dB then back to 6.
From what I've read, anything below 7dB means that I shouldn't be getting any broadband service yet I am.
Is the Vigor 130 wrong?
Ah, I've just read this
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With the Vigor 130 you can also tweak the SNR value to get a potentially faster sync. I found this helped increase my sync:
https://www.overclockers.co.uk/forums/threads/drayte...
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| > vdsl status
---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Running Mode : 17A State : SHOWTIME DS Actual Rate : 68416000 bps US Actual Rate : 20000000 bps
DS Attainable Rate : 81427400 bps US Attainable Rate : 24229471 bps DS Path Mode : Interleave US Path Mode : Fast
DS Interleave Depth : 997 US Interleave Depth : 1 NE Current Attenuation : 12 dB Cur SNR Margin : 2 dB
DS actual PSD : 0.-5 dB US actual PSD : 0.-4 dB NE CRC Count : 42 FE CRC Count : 5526
NE ES Count : 10 FE ES Count : 4560 Xdsl Reset Times : 0 Xdsl Link Times : 1
ITU Version[0] : fe004452 ITU Version[1] : 41590000 VDSL Firmware Version : 05-07-06-0D-01-07 [with Vectoring support]
Power Management Mode : DSL_G997_PMS_L0 Test Mode : DISABLE
-------------------------------- ATU-C Info --------------------------------- Far Current Attenuation : 10 dB Far SNR Margin : 7 dB
CO ITU Version[0] : b5004946 CO ITU Version[1] : 544eb206 DSLAM CHIPSET VENDOR : < IFTN > |
I am however connected to an ECI cabinet. I found with stock I couldn't get past 64 mbps, with the SNR tweak I got the full 80 mbps near enough, but then as time went out got banded back down to 73 mbps and since it dropped back to around 68 mbps, probably due to the higher error count. Still slightly more than the original sync from stock though, I haven't noticed any major issues, although it is a backup line for failover not always in use.
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Just ignore the rubbish it the article you linked it is totally wrong. I have seen it quoted before as the absolute gospel truth in another forum but it is just nonsense.
FTTC lines can run at 3db or less quite happily. I have 80/20 sync speeds and 1.8dB noise margin downstream. This has been running for over 33 days with no downstream errors and will continue to do so until the next power cut. 
As for the Draytek I would always go for a Broadcom chipset modem as they are generally better on most lines and give more understandable stats. I will leave you to figure out which are the upstream and downstream, or is it near end and far end data, it is confusing and I think even Draytek are confused because I have heard that some figures are wrongly identified. 
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From what I've read, anything below 7dB means that I shouldn't be getting any broadband service yet I am. Not all VDSL/VDSL2 systems are the same, so if your information is not from the UK about specifically the Openreach deployment it is likely wrong.
Openreach systems can go down to a target SNR margin of 3db, and you can see numbers lower if the noise increases and reduces the margin at the time you inspect the statistics. As long as you have some margin and the modem at your end, and the DSLAM at the cabinet stay in sync, you will stay connected. If you get disconnected, DLM (dynamic line management) will intervene and change the target SNR margin.
21 years of broadband connectivity since 1999 trial - Live BQM
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With the Vigor 130 you can also tweak the SNR value to get a potentially faster sync. I found this helped increase my sync:
...
I found with stock I couldn't get past 64 mbps, with the SNR tweak I got the full 80 mbps near enough, but then as time went out got banded back down to 73 mbps and since it dropped back to around 68 mbps, probably due to the higher error count.
Every line really is different, if you play the SNR tweaking game you are at increased risk of DLM intervention. If the noise floor is *perfectly* flat and correctly measured then you can in theory run on 1dB margin. The reality is that the amplitude of the noise will vary and some lines have problems even with a 6dB margin because there are noise spikes more than 6dB above the floor, whereas others can be perfectly stable at 2dB. Luck of the draw...
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Not all lines can, especially long lines, but yes I have found some can run quite happily on very low noise margins...
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If you get disconnected, DLM (dynamic line management) will intervene and change the target SNR margin.
Not always, it can take several resyncs in a 24 hour period (sometimes longer) for DLM to change the target. 
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I am running my v130 on an eci line at 5db (offset -5). Has lifted my sync back to where I was when I had a zyxel om my line which just seemed to lose DS sync over time. 5db for around 30 days with no intervention from dlm.
Using munin to gather stats from the v130. Works a treat.
Sky Fibre Pro - Billion 880nl V1 (bridge mode) + Opnsense with ipv6 - ECI cab, G.INP disabled April 2016
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I am running my v130 on an eci line at 5db (offset -5). Has lifted my sync back to where I was when I had a zyxel om my line which just seemed to lose DS sync over time. 5db for around 30 days with no intervention from dlm.
Using munin to gather stats from the v130. Works a treat.
How are you running Munin?
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joconnell
