7800N: Large SNR Drop at Night

[arobertson676]

I bought the 7800N to improve the SNR level at night, but it doesn't look like much is happening:



Any ideas?

By the way, PhyRe is enabled.

[Tomken]

Probably everyone's SNRM drops as the evening wears on and mine is sitting at 2.5dB at the moment from a 6dB Interleaved Profile, but the beauty of the 7800N with its Broadcom chipset is, that it will maintain the connection and I've seen mine down as low as 0.4dB, with the only symtom being some lag.

I've found that PhyR tends to keep my SNRM lower than perhaps it would be and Billion Tech Support don't advocate that it is enabled, so I no longer use it.

What is the comparison SNRM drop with PhyR disabled to when it is enabled ?

While the write up (according to Broadcom) at http://www.spaldwick.com/broadband/billion-7800n praises PhyR's virtues, I've never found this to be the case

[tinytim]

There's certainly nothing wrong with a drop in SRNM to 6dB as that's a normal setting for many ISPs anyway. BT & O2 run at that as the default , while Sky's is 7dB.

Who are you with if your default is 10dB?

[arobertson676]

The problem is that I really want to try the router at 6dB but I don't think it is going to hold.

[Tomken]

You must have a decent Attenuation if you're getting almost 8meg on that SNRM so I think you should be okay to tweak it down to 6dB, but you'll only find out by trying it.

After you have tweaked it, check the stats via telnet and if it remains stable with a reasonably low error count and without any lag, then you're in business and you could ask your ISP to properly change your profile.

You could drop that margin down by 3dB and still be fractionally above 6, which is usually deemed to be the minimum for a stable connection and if at some point in time after/if you've had your ISP change it, then going into the tweaking page and entering the value 150, will revert it back to what you have now if you encounter any problems.

My Attenuation is 49 - 50dB, syncing at approx 6.6meg and stable even when dropping well below the 6dB margin, which is something my ISP's supplied routers could never achieve.

[arobertson676]

I am on a 40dB attentuation. Where do you get the 8Mb figure from?

[Tomken]

I am on a 40dB attentuation. Where do you get the 8Mb figure from?

From the right hand side of the graph, if I understand it correctly (?)

Check your possible speed on this http://www.kitz.co.uk/adsl/max_speed_calc.php I wasn't too far out

These calculations are based on a 6dB Profile, have a shufty around the rest of the site, it's quite informative.

Edit... Just had another look and see that it's syncing a 6368.

[admin]

Drop in SNR at night is normal and is usually caused by interference. There are a lot more electrical appliances running at night and they could cause drop in SNR. Well at long as your SNR doesn't drop below 6dB then you should be ok.

[tinytim]

Drop in SNR at night is normal and is usually caused by interference. There are a lot more electrical appliances running at night and they could cause drop in SNR. Well at long as your SNR doesn't drop below 6dB then you should be ok.

That's why you can gain SNR or speed by re-syncing between 11am & 2pm as that's when interference is at it's lowest.

I've had great gains when we've had local power cuts as my routers' the first thing to come on.