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Sync speed & Noise margin
This is a discussion on Sync speed & Noise margin within the Sky Broadband help forums, part of the Sky Broadband help and support category; Be glad you have that!...
- 13-09-06, 01:54 PM #81
Be glad you have that!
- 13-09-06, 02:12 PM #82
I have been having the same problem,
I have been through to Tier 3 on many occasions they just advised to drop the speed on my line and then i would leave it and then the next night the same thing would happen, I would then call them back and then they would reduce my speed again and then the next day the same.
Have been on 1mb for about a week and going to ask them to max it out again and see what happens seems to be the common theme to what has been happening here!
Speeds drop and connection freezes and have to restart router and then go through the process again!
- 13-09-06, 04:26 PM #83
Annie, so what have they actually done to your line?
- 13-09-06, 05:13 PM #84
As in the PM.
They moved me over to ADSL and not ADSL2+ and capped at 8Mb though I'll never get more than 4Mb.
Apparently ADSL should be more stable.
I've heard reports of Duff exchange equipment in the London area so I can only cross my fingers and wait until 7pm/8pm.
Wish me luck.
- 13-09-06, 05:15 PM #85
Is there any way the end user can tell if they're on ADSL2+, as opposed to ADSL?
- 13-09-06, 07:36 PM #86
Could someone please help me understand how ADSL noise margin relates to ADSL2+ noise margin and what sort of prediction my current noise margin offers for a Sky Max connection.
I am currently using UK Online 8Mb service and my Actiontec router is currently reporting my SNR Margin as 3 downstream and 7 upstream. This is actually reasonably good, I have seen it as low as 2 down & 3 up.
From reading various threads this would appear to be catastrophic and an ADSL speed predictor I tried (can't remember the URL) says that I should expect 512Kb connection speed at best. Well, I hardly ever get disconnects and am typically synced at 7200Kbs down and 768 up (this is my current sync speed). Speed test sites typically show my effective download speeds at about 6500Kbs so the sync speed seems correct.
What gives with my low SNR figures? Is this something different to the noise margin that you all talk about here? Should I be worried? Maybe it's just a case of my Actiontec router mis-reporting the figures?
I'm 1.6km from my exchange, as the crow flies, but there is also a major road running almost dead straight between me and the exchange and, since I suspect BT like to lay their wires along roads and pavements, I suspect my wire length is pretty close to 1.6km too. My internal wiring is lousy and will be optimized if/when I go Sky Max. Right now my Actiontec is plugged into an extension socket rather than the master socket and, even then, it is connected to the extension socket via a 5 metre ADSL cable. When I go Sky Max I'll get my builder to drill a hole in a wall into the cupboard with my master BT socket in so that I can site the ADSL router right next to the master socket and run an ethernet cable to it. I think I'll also cut the orange ring wire since I've seen good reports of that helping sync speeds.
- 13-09-06, 07:41 PM #87
- 13-09-06, 08:14 PM #88
Julian: For ADSL fixed speed, the higher the SNR the better. For ADSL Max/ADSL2+, the lower the better. However, with a lower SNR you can get disconnections. This becomes a bigger problem at night when most peoples SNR drops quite a few db. If it goes too low the connection will drop. The more SNR you have the slower speed you get, and vice versa.
You can outright choose what kind of line you want - fast or stable. If you have hacked the firmware, you should be able to find a middle ground which provides a fast enough speed, but with as high enough SNR to keep your connection stable throughout each day.
- 13-09-06, 09:17 PM #89
Now I'm confused. Why is a poorer SNR figure better for ADSL Max ?
I can see how the higher attenuation figure you have, the slower speed you get. I would have thought the higher the signal/noise ratio, the better and faster the possible connection speed whatever type of ADSL you have.
Hope the answer isn't too technical if anyone wants to reply.
- 13-09-06, 09:27 PM #90
OK here is my under standing of it. I am new to this and so forgive me I am sure someone will correct me if I am wrong.
Attenuation does indeed affect max possible speed, but SNR plays a part in this way: When you reboot your router, it makes contact with the exchange and begins negotiating your speed. It does this by working from your SNR. The ISP sets a target usually between 7 and 9db. The negotiation reaches the highest speed it can around the target SNR. If you regularly get unstability at that speed the ISP can raise the SNR target effectively lowering your connection speed, but increasing stability.
Low or dropping SNR can cause loss of signal, either intermitent or requiring a reboot. Your SNR will always sync lower on ADSL due to this negotiation process. As for the drop outs some routers work on low SNRs better than others, from the post we have seen about drop outs the Sky router is not one of the better ones in this respect.
I hope this makes sense.