SNR and Line Attitude

charlieharper

charlieharper

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What is

SNR Margin

:
30.0 23.0 db

Line Attenuation

:
46.5 21.0 db

and how does it work.

How would I know if its good or bad?
I think this also indicates if you have noice on your line.

Thanks
 
SNR is the indication of noise on your line. The higher the number the better. 10dB and lower and you will potentially start getting slower speeds and loss of sync.

Attenuation can give you an indication of the length of you copper line. Again, the lower the number the better. A line with 46dB would probably be about 4Km to the exchange
 
marine1 said:
But shouldnt the Attenuation be the same for up and down then?
Click to expand...
No, it is different, dont ask how it works, but thats the way it is.

In short, your noise margin is good and "attitude" not so good / too high.
What speed is your line syncing at though?
 
Mine?
DSP FirmwareVersion DMT FwVer: 3.6.0.1_A_TC, HwVer:T14F7_1.0
DMT Status Up
Operational Mode ADSL G.Dmt
Upstream 512 kbps
Downstream 3072 kbps
Noise Margin (Upstream) 10.0 db
Noise Margin (Downstream) 7.0 db
Attenuation (Upstream) 31.5 db
Attenuation (Downstream) 63.5 db
 
Thats why you dont sync at 4096 marine1.
Too much noise downstream and too little of a noise margin
 
I got the same spec as marine1, though I can only sync at 2048. I am only 3.1km away from the exchange, I think it also has to do with the type of copper in your area. Some areas got really thin diameter copper suitable for voice which makes for bad attenuation. Thicker copper has less resistance and better attenuation. Trying to get Telkom to fix mine but I think it's a losing battle on the 30 year old infrastructure.
 
marine1 said:
But shouldnt the Attenuation be the same for up and down then?
Click to expand...


Just_Ice said:
No, it is different, dont ask how it works, but thats the way it is.
Click to expand...

Will try and explain. Frequency and attenuation are related.

The more bandwidth you have to pump through a wire the higher the signal frequency required.

The problem however is that higher frequencies get attenuated more than lower frequencies, thus higher frequencies = higher attenuation.

So your ADSL downstreem (which has a high speed/frequency) attenuation will always be higher than your upstream (which has a lower speed/frequency) attenuation.

Attenuation uses a logrithmic scale, every 3dB equates to HALVING your signal strengh.

There are many factor at play here that are inter related like impedance, resistance, frequency, physical copper properties etc.
 
erm..

can someone tell me how I can get these readings? I'd like to test my line and see what mine looks like..

:)
 
aborg said:
I got the same spec as marine1, though I can only sync at 2048. I am only 3.1km away from the exchange, I think it also has to do with the type of copper in your area. Some areas got really thin diameter copper suitable for voice which makes for bad attenuation. Thicker copper has less resistance and better attenuation. Trying to get Telkom to fix mine but I think it's a losing battle on the 30 year old infrastructure.
Click to expand...

The copper diameter is pretty much the same. The problem lies with the age of the copper the diameter of the jumpers used along the path. A good start would be for you to ask Telkom to replace all the jumpers along your cable route.

As for 'old' copper, not much you are going to achieve there unless a whole bunch of people on the same cable biatches or the criminals do you a favour and steal it :D Mind you, if one takes into consideration the amount of copper theft in this country we should all pretty much have new copper by now :p
 
Thx ponder, I'll mention that to the techie when he phones again. What do these jumpers look like physically? Could a 'dry' connection be a problem with these?

@HTC_guy you can find this info on your router.
 
Hi all...

My stats are:

Downstream Upstream
SNR Margin 29.0 dB 12 dB
Line Attenuation 40.5 dB 17.0 dB
CRC Errors 0 0
Latency Fast Fast

I'm currently syncing and my line is stable at:

Upstream 512000
Downstream 1024000

I've tried asking Telkom to increase my sync to 2Mbps but I always have hassles. The line will sync at that speed but I am unable to connect using the ISP username and password.

Any ideas why? From the numbers it seems I could at least get 2Mbps or is my attenuation too high?

UPDATE:

I just got Telkom to increase my line speed to 2Mbps, i couldn't wait :D And all is working.

Here are my stats after the upgrade:

Downstream Upstream
SNR Margin 23.0 dB 11.5 dB
Line Attenuation 31.5 dB 17.0 dB
CRC Errors 0 0
Latency Fast Fast

Line speed:

Upstream 511800
Downstream 2043900

Really weird line speed, suppose the router negotiated the best speed it could :)
 
Last edited:
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