How to measure SNR?

Sconsey

Hi,
Maybe a dumb question but does anyone know of a way to measure SNR (noise) on a line other than through the modem interface? I am hoping there is some application that I can install.
I got a new modem (beacuse of noise problems on my line) and I can't find the SNR anywhere on the modem interface....following is a cut and paste from modem DSL status page:
DSL Status
Connection Status Connected
Upstream Rate (Kbps) 384
Downstream Rate (Kbps) 2912
US Margin 16
DS Margin 3
Modulation MMODE
LOS Errors 0
DS Line Attenuation 55
US Line Attenuation 63
Path Mode Interleaved

I doubt 'DS Margin' is SNR because it's way too low.

Anyhow, any ideas on how to measure SNR?

Thanks,
Sconsey

CuLT

Maybe new firmware for your router? Doubt a program based on the PC would be able to do it, as all it would be doing is maybe telenetting to your router and running the programs. And if the programs to do it were there, you'd almost certainly be able to use them via the web interface.

kaizersoze

Can't be done from a pc based program afaik. I've seen SNR referred to as "US Margin" & "DS Margin" on some modem readings before so it looks like thats it. Your line attenuation is very high aswell. You could have something in the house causing interference or a dodgy filter or just a crap phoneline.
Who is your ISP?
What make and model is the modem?
How far are you from the exchange?

watty

US = Upstream = Signal to head end/Exchange etc
DS = Downstream = Signal to customer

So DS margin = SNR - minimum SNR for operation. 3dB doesn'yt sound too good. 6dB or more is fine. BUt I'm no expert on DSL signal levels.

You could buy a different ADSL modem. But what is point?

Ping someplace good like heanet with 1300 byte packets continously for a few minutes to see packet loss.

Download from them a big file to see speed.

If packet loss is high and speed is low then SNR is poor. If speed is high and no packet loss then SNR good.

This is simplistic, but at end of day as a user the data performance is what counts not he the lines engineering data.

Blaster99

The modem will lower the speed until it works so those tests are pointless. The fact that the modem synchs at 2912kbps with that SNR is remarkable. I bet over time that your DS speed will drop as the modem adjusts to noise.

Sconsey

Thanks for the replies,

I checked later and the DS Margin had increased to 10 which sounds more reasonable. I got D-ling DSL G604T because I read it is good on noisy lines.

I was online for about four hours last night (addicted to WoW!) and only got disconnected once which is a big improvement from my other modem (the Creative modem that UTV internet supply). So it looks like the new modem can help keep connection when noise is bad, I am amazed that it was able to maintain a connection based on the figures it was reporting from the earlier message!

Thanks all for your comments.

philologos

Just out of interest this one is mine 1st one is downstream 2nd one is upstream, are those noise margin, line attenuation good?

Noise Margin 21.4 dB 17.0 dB
Line Attenuation 24.0 dB 17.0 dB

Sconsey

Well I'm no expert but your noise marging looks good anyway, I have read that 10dB is the cut off point (lower is bad, higher is good).

The line attenuation looks good too, I think that you need less than 30dB to reliably support a 2Mb line so you should be OK.

Note: I am referring to downstream figures only, I don't think upstream figures are as important.

watty

Blaster99 wrote:

The modem will lower the speed until it works so those tests are pointless. The fact that the modem synchs at 2912kbps with that SNR is remarkable. I bet over time that your DS speed will drop as the modem adjusts to noise.

Well if you get a high speed and no packet loss, it isn't pointless to kn ow that.