Line Quality: Noise Margin & Line Attenuation

[surfgate]

I have been reading up and trying to understand Noise Margin and Line Attentuation and how these affect my ADSL line quality. I referred to this earlier post:

http://mybroadband.co.za/vb/showpost.php?p=1239914&postcount=7

and a few others. I also ran the RouterStats diagnostic tool. My 4mb line (Netgear DG834GT) has been randomly disconnecting for the last 2 weeks - after being very stable for about 4 yrs. Telkom have tested it (on site as well) and confirmed all is 100%. Yesterday it kind of stabilised to about 6 or 7 disconnects a day. Crazy thing is my upstrean stats are:

Noise Margin = 6db
Line Attenuation = 29db

According to what I have read, a Noise margin of 6db should be pretty much unusable. Something is not right - but I need help figuring this out. Anyone out there add some insights?

 

[[OUPA]MrNutz]

hi Surfgate - welcome to myadsl.

an SNR margin of 6 is going to give you problems !

i would suggest you try a few things first:

-remove EVERY telephone/fax/filters/non adsl related device possible from the line , and then monitor the SNR margin again.

-secondly - is your voice quality of the line CLEAR without any humms/clicks/pops?

-have you tried shortening the length of your adsl line to the wall socket? (replacing cable)

obviously just small steps - but it is a start.

ps: how does your routerstats graph look - can you maybe upload a 1 hour sample?

 

[surfgate]

Hey MrNutz,

Wierd - I posted a detailed reply with links to the graphs and when I submitted at the end it said that a moderator needed to review the response first. Any idea how long that process takes? and why it is needed?

 

[[OUPA]MrNutz]

send me a pm with your details+links ect

 

[semaphore]

I had the same issues with my 4mbit bad snr's and what not, i lowered it to 1024 and my line is stable and perfect, i am going to move it to 2mbit just havnt had the time.

 

[Jonno2343]

Hmmm....
I just checked my modem and it says this:

Item Downstream Upstream Unit
SNR Margin 6 31 dB
Line Attenuation 39 9 dB
Data Rate 384 128 kbps

I'm guessing it's not too great right?
Is there anything I can do to lower it, although I'm not really having problems.

 

[Kalvaer]

I have been reading up and trying to understand Noise Margin and Line Attentuation and how these affect my ADSL line quality. I referred to this earlier post:

http://mybroadband.co.za/vb/showpost.php?p=1239914&postcount=7

Hey that post looks mighty familiar... Its the same as mine back in 2005 http://mybroadband.co.za/vb/showpost.php?p=193137&postcount=8 (Granted.. I originally got the data from BT)

Anyway,I'll put my head on the block and say that the problem is your SNR. Most modems/routers will automatically try force a reset when the SNR drops below 6. It could be due to a number of things. Its usually though, the distance from you to the exchange, or really bad lines. In SA.. 90% of the time I would say its the line quality.

In my case back in 2005 it was copper rust on the joins in the boxes on the poles. Once they cleaned them all up, it was perfect and has been ever since... It took me about 6 months though to get one of the "top" techies out with a diagnostics machine and he was able to pick up voltage spikes and drops and tell the other techies where to go in order to clean the lines

TOUCH WOOD!!!!!! of course.. and lets hope my line stays as it is.