UK ADSL Broadband Internet Connection Tips and Tweaks - Page 8
UK ADSL Broadband Internet Connection Tips and Tweaks
By: Mark Jackson - January 17th, 2011 : Page 8 -of- 8
"if an Upstream SNR fluctuates a lot (e.g. drops by several points, such as from 7db to 4db) then this could cause interuptions"

router broadband adsl phone connection22. Keep an eye on your routers Signal to Noise Ratio (SNR) Margin (dB)

SNR (power ratio between a signal and the background noise) is explained, in a very basic way, here:

However, generally speaking, if an Upstream SNR fluctuates a lot (e.g. drops by several points, such as from 7db to 4db) then this could cause interuptions with your connection and could indicate a problem on your line. It can also occur when your ISP is trying to get more speed out of your line than it can handle. Some routers will allow you to force the SNR higher (there are various different highly technical methods for this), which will drop your line speed but could improve stability.

The ISP may also be able to help and we recommend contacting them first. We have found that line stability can often be improved when an ISP forces the 'Connection Speed' artificially lower (e.g. from 12,000Kbps [13Mbps] to 10,000Kbps [10Mbps]). Obviously this is annoying if your line is already slow but if you have a fast connection and don't need all the speed then it may be worth trying. Then, even if the SNR is still unstable, you may find that your line is more reliable.

23. DMT Tool - SNR Margin (dB) Speed Tweak.

This is a clever GERMAN made tool and ONLY for use by advanced users who are actually familiar with how ADSL broadband works. It allows owners of certain specific routers/modems (e.g. SpeedTouch) to tweak, among many other things, your Downstream target SNR margin. The DMT Tool is version specific, so for example the one required for the bebox (ISP BE Broadband) is DMT 7.35.


Why is tweaking your Downstream SNR important you ask? In our previous home the line was quite poor but we knew it was capable of more than the current ISP claimed. By using DMT Tool we were able to adjust the ISP's SNR setting for our line from around 14dB to 10dB, which resulted in a noticeable jump in download speeds.

Be warned, this tool does not work on all lines and with all routers, it can in fact cause more problems than it solves, especially if you are not familiar with the technology. This is the reason why we never suggest it in public. For the unfamiliar it is a risky piece of software to use.

Note: The user interface will usually switch to English after the first time you shut it (DMT Tool) down and load it up again, when it's identified your router as Annex A.


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