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3dB SNR is Plain Daft

Community Veteran
Posts: 5,702
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Registered: 23-09-2010

3dB SNR is Plain Daft

Reading back through the posts I know I'm not the only one who has had this. I noticed my line had dropped twice during the night and had reconnected with a "snr Margin Down: 3.0 dB" which is plain daft.
I know my line has improved recently from the wide SNR fluctuations it used to have but it still wavers up and down by around 3db probably like most lines.
So as was asked on a previous post what's the point as it's bound to keep dropping. 6 was OK so why screw things up by changing to 3?
My experience with the "magic" DLM shows me that contrary to what's said, the DLM is there to introduce instabilities into stable connections.
I assume if the line drops a few times too many it will end up back on 6 anyway?

3 REPLIES
Steve
Seasoned Pro
Posts: 6,802
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Registered: 13-07-2009

Re: 3dB SNR is Plain Daft

Can your router keep connection with a SNR of 3? Mines can, Some routers can keep connection with an even lower SNR than that.
If life gives you lemons, make lemonade.
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Re: 3dB SNR is Plain Daft

Contrary to the usual advice, while your target is low you should always resync during the evening/night when the noise margin will be at it's lowest. That way you should always keep enough margin to avoid the drops.
jelv (a.k.a Spoon Whittler)
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Community Veteran
Posts: 5,702
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Registered: 23-09-2010

Re: 3dB SNR is Plain Daft

Quote from: jelv
Contrary to the usual advice, while your target is low you should always resync during the evening/night when the noise margin will be at it's lowest.

That's true. My usual max connection speed lately is around 7500 which gave me an ip speed of 6500 in old money. The first drop at night reconnected me at just over 9000, which lasted around 4 hours, but the second drop in the early hours of the morning reconnected at the usual speed and the SNR has now risen up to 6.5 so it should hold OK.
But that's what it would have been at the usual 6 anyway.
And no, 3 won't hold if it starts at the best midday time. (It will hold at 1 but the SNR varies around 3)
Pity there's no way to zero the routers various error counts, other than switching off, because the counts become vast and meaningless when the connection drops due to the SNR running below zero. That said some of the Thompson readings have always been suspect and a bit impossible.
I suppose at 3 the router will always connect at a good better than usual speed it's just a question of how long it will hold it for and how many times (maybe) the line will drop. I guess only time will tell.