# Thread: Understanding SNR and Attenuation Rates

1. For those of us who use noise margins :

2. Hi all.

We have about 4 phone jacks in the house.
The one I connect the ADSL to gives me an attenuation of 61db and a SNR of around 11.
If I connect the ADSL to another jack, I get similar readings.
Is this definitive proof that high attenuation is simply due to distance from exchange, or is there a "core / master" jack in the house that all the lines go to, and that one might be 'faulty'?

Do telkom charge to come out and re-do the wiring?

3. XperiAnce:
The attenuation reading will influence the SNR. The downstream attenuation changes by about 14dB/km.

So extending the telephone line in your home would barely make any difference. If you extend it by 50m, then it could change like 0.7dB.

First see what the attenuation values are when you don't connect any telephones or filters - just the ADSL.
If it is still that high, then you're most likely too far from the DSLAM/Exchange to get a fast ADSL connection (meaning you'd be stuck on like 384kbps - 512kbps).

You can ask Telkom to tell you how far you are from the DSLAM, which you can then take to estimate what your downstream line attenuation would be like by multiplying the km's by 14dB/km

4. Thanks for the update Pada.

I'm also looking at my work line and the stats are as follows (4MB):

Parameters
Downstream Upstream
SNR Margin 23.5 dB 1.4 dB
Line Attenuation 15.0 dB 7.5 dB

Now the downstream values are fantastic, but the upstream SNR Margin of 1.4dB, is that something to worry about?

Below is a traceroute, which is ugly as you can tell:
C:\Users\Michael>tracert www.mweb.co.za

Tracing route to www.mweb.co.za [196.2.63.110]
over a maximum of 30 hops:

1 2 ms 1 ms 1 ms 192.168.1.200
2 2 ms 2 ms 2 ms 10.0.0.254
3 628 ms 271 ms 235 ms 41-133-86-1.dsl.mweb.co.za [41.133.86.1]
4 375 ms 130 ms 142 ms 197-80-4-94.jhb.mweb.co.za [197.80.4.94]
5 214 ms 212 ms 225 ms vl-92.vic-hscore-2.mweb.co.za [196.22.189.3]
6 91 ms 85 ms 96 ms tengig0-7-0-2.12.vic-p-2.mweb.co.za [196.22.169.242]
7 86 ms 70 ms 58 ms TenGigE0-0-0-0.cpt-p-1.mweb.co.za [197.84.4.34]
8 156 ms 166 ms 196 ms vlan11.cpt-hscore-1.mweb.co.za [196.28.178.99]
9 292 ms 284 ms 362 ms 196.28.178.66
10 314 ms 313 ms 92 ms cte-core-sw2.vwol.net [196.41.144.35]
11 165 ms 195 ms 173 ms www.mweb.co.za [196.2.63.110]

Trace complete.

5. XperiAnce:
Could you get hold of your line speed too?

I see that your latencies are very erratic, which could either be due to your work download/uploading lots of data while you're doing the trace route, or it could be due to an unstable connection (low SNR).

6. This is my line stats after a line upgrade:

Operational Mode G.Dmt
Annex Type AnnexA
Upstream 512000
Downstream 4096000
SNR Margin(Upstream) 29 dB
SNR Margin(Downstream) 28.0 dB
Line Attenuation(Upstream) 2.5 dB
Line Attenuation(Downstream) 4.0 dB
Line speedtest

Test conducted on 08 Augustus 2012 03:49:12 PM

Upload Speed: 322 kbps (40.3 KB/sec transfer rate)

Latency: 301 ms
This is after a hell lot of phone calls to Telkom. Persistence does pay off!!!

7. SNR Margin (0.1 dB): 302 140
Attenuation (0.1 dB): 250 140
Telkom reckons I am not able to get to 10Mbps - I beg to differ. These kinds of stats should get me at least above 7Mbps? No?

8. you will easy get 10mb

9. I wish I could get 10Mb - but it seems as though Telkom may never upgrade the exchange.

10. Hi.
I would like to know if this is any good.
Downstream/Upstream
Line Coding(Trellis): On/On
SNR Margin (dB): 423/190
Attenuation (dB): 320/190
Output Power (dBm): 5/-14
Attainable Rate (Kbps): 10016/928
Rate (Kbps): 384/128
D (interleaver depth): 1/1
Delay (msec): 0.13/0.25

Thanks

11. Kaze6129:
Your stats are great, except for your current line speed of course (384kbps ADSL is rather slow).

The SNR Margin & Attenuation values are actually displayed in 0.1dB units, meaning that 423 SNR margin is actually 42.3dB SNR margin.

The Attainable Rate values give you a pretty good indication of what kind of line speed you can get with your ADSL line. You should be able to get 50-80% of that attainable rate without having stability issues I suppose.

12. hmmm.. I have a Trendnet TEW-635BRM Router and I can't find the SNR or attenuation values anywhere. all I can find is the connection speeds.

Anyone know how I could measure these values? Or am I just not looking hard enough? (pretty sure the router interface just doesnt display that info )

13. Noise Margin(dB)
Downstream: 28.4
Upstream: 14

Attenuation(dB)
Downstream: 22.5
Upstream: 8.5

God-like Upstream Attenuation, and fair Upstream Noise Margin...

What's with the major difference (Especially with Attenuation) ?

---

Originally Posted by mulacasto
hmmm.. I have a Trendnet TEW-635BRM Router and I can't find the SNR or attenuation values anywhere. all I can find is the connection speeds.

We have the same modem ;P

14. Can anyone explain to me why my Attenuation is so high, when I am around 500-600 metres from my exchange in Stellenbosch central.

Edit: According to the first post, my SNR margin rates should be extremely good?

Here is a local speedtest result as an additional reference.

15. Originally Posted by Reelix

We have the same modem ;P

I'm confused. That's the only info it will display. Do you mean for me to click on 'ADSL Details'?
Because that yields this:

No SNR or Attenuation

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