cancel
Showing results for 
Search instead for 
Did you mean: 

Can Somebody Please Explain Noise Margin & Attenuation P

N/A

Can Somebody Please Explain Noise Margin & Attenuation P

Hi all

I see everybody here going on about Noise Margins & Attenuation but what do the figures actually mean ?

here is what my router reports

Operation Data Upstream Downstream
Noise Margin 24 dB 14 dB
Attenuation 54 dB 44 dB


so what does it all mean ? Is higher or lower dB better?


Dave
7 REPLIES
N/A

Can Somebody Please Explain Noise Margin & Attenuation P

Have a look here, it may help:-

http://www.kitz.co.uk/adsl/linestats.htm
N/A

Can Somebody Please Explain Noise Margin & Attenuation P

Thanks a lot for that it was very helpful


so it looks like I have had it then

:-(
N/A

Can Somebody Please Explain Noise Margin & Attenuation P

Having just read the information on the link you posted. may I just make sure that I have things straight I have according to the Members centre "Your current broadband speed is 8000 Kbps".But if I have read the information correctly then with SNR (margin on my router) ratio fluctuations like this..... each figure is 15 seconds apart the time taken for the router to refresh the information.This is only a small sample as I spent 20 minutes watching the updates so in actual fact there are 40 items I wrote down but during that time the highest I got was 9db

7db 6db 6db 5db 6db 6db 6db 5db 6db 4db 5db 6db 5db 1db 3db 1db 1db 1db

Then I have not a hope of having a stable connection at anywhere near 8000 Kbps.

Am I correct in this assumption or have I got the whole thing wrong?
shellsong
Grafter
Posts: 2,191
Registered: 03-08-2007

Can Somebody Please Explain Noise Margin & Attenuation P

The thing is that the SNR and relevent synch rate are interrelated so, for example, when I was on 2Mbps before MaxDSL the downstream SNR was about 28dB but now on MaxDSL the synch rate is 8Mbps (8128Kbps) and the SNR is about 14dB

So the SNR figures are more or less meaningless without the relevent synch rates

For a doubling of the synch rate the SNR will reduce by 6-7dB normally

As for downstream attenuation, that is related to a combination of line quality and length and it is usually possible to get a rough estimate of actual line length in Km by dividing it by 14dB, so my 35dB attenuation means my actual line length is about 2.5Km

Mind you I looked at my stats just now and realised that the downstream attenuation is about 5dB lower than it used to be so maybe there's a frequency based aspect of that I didn't know about (or a sneaky BT engineer removed about 400metres of my line while my back was turned!) :lol:
Community Veteran
Posts: 3,364
Thanks: 15
Registered: 06-04-2007

Can Somebody Please Explain Noise Margin & Attenuation P

Quote

so it looks like I have had it then


What is your current line speed, I guess it is 1Mb (=1152kb/s)?

If so, your line statistics are similar to mine before MaxDSL. I now vary from 2 to 2.5Mb, but I also have to put up with the router disconnecting once a day which can be more annoying than it sounds if it happens whilst using the connection.

SW.
--
3Mb FTTC
https://portal.plus.net/my.html?action=data_transfer_speed
N/A

Can Somebody Please Explain Noise Margin & Attenuation P

Isn't there a 'Signal to Noise Ratio' vs 'Noise Margin' issue here though as the two aren't really the same?

I've been running on a 6k sync speed for the past two weeks on a download Noise Margin of 3 - 5dB and attenuation of about 30dB.

(I think previously i even had a sync of 6.5 with a noise margin of about 1.5) Cheesy
N/A

Can Somebody Please Explain Noise Margin & Attenuation P

Quote
Quote

so it looks like I have had it then


What is your current line speed, I guess it is 1Mb (=1152kb/s)?


SW.



It would be great if it was its in fact just below 500k