SNR vs Noise Margin

MY Cr^^*y SSE router, a "MediaAccess TG589vac" does not seem to display the SNR..

I can see the following:

Line Rate (D)20 Mbps (U)55.4 Mbps
Output Power (D)4.7 dBm (U)4.7 dBm
Line Attenuation (D) 0 dB (U) 0 dB
Noise Margin (D) 6.9 dB (U)6.3 dB

When we moved into the house, a new build 300m from the Cab we were getting 80/20mbps.
Following a number of power cuts by the buildders we well to less than half this on the Download.. Eventually, I managed to get it back up to aoru nd 68 -70 and was happy at that..

Last week a storm took out the power again, my 70mb fell to 55mb..

I waited until a few days had passed to show the line was stable, switches off PPP, and then shut down the router.. left it 30mins and brought it back up..

The power output fell from 5.2 to 4.7, and the Noise Margin didnt see, to change.. I know rebooting the router should be done when the SNR is at its best, but with only Noise Margin is that when its high or low?

Assuming Noise Margin being high is best?

What about power output? Lower the better as there is low noise on the line?

Thanks for the advice.

Noise Margin (D) 6.9 dB (U)6.3 dB

^^ SNR Margin

Edited by j0hn83 (Tue 29-Aug-17 14:30:38)

I don't think you'll ever see the SNR, just the SNRM (noise margin). I suppose it's best to reboot when the snrm is highest but as your connection is controlled by DLM, it's probably best to leave it to DLM to manage your connection. Except on the odd occasion that you've synced low for some reason and the snrm will be unusually high, as it's currently around the target of 6 probably best to leave it.

The line has likely been banded (sync is capped) due to too many disconnections. The SNRM being stuck above 6 also suggests this.

Stop resyncing. All you will do is make it take even longer to return speeds to normal. DLM acts in its own time, no manual resync will fix it, no matter the time of day.

You're also in a new build, so it's reasonable to assume crosstalk is increasing as more people move in and take up services.

Thanks for all the replies..

We did have Openreach out and they did say the line wasn't capped at that time. But that could have changed.

I monitored the connection daily for 8 months. It never seems to be managed and unless there is some power issue the speed is always the same.

We did see the speed drop as people move in, but the biggest difference is the power cuts.

So I want the SNRM to be low?
Is there any thing i can do to help?

When my deal with my ISP ends and I change, does the new connection with the new ISP all start over? Or is it going to remember the disconnections from when this was a building site?

thanks again

What you want your SNR to be, is exactly what it's target is , usually 6db. Unless Your purchased speed is less than the line can provide, in which case your SNR may appear as higher than the target.

A change of provider should see the connection back to 'out of the box' settings.

Thanks...

so closer to 6 the better.

Think I might need to switch at the end of this.

Who are you currently with ?

Looks to me as though you just need a DLM reset.

SSE broadband... all in (LR, Calls, BB, etc) £21..

Been ok..

Reading your 1st post again, I've just got even more confused.
The download/upload figures appear to be mixed up.
I've no idea if the SNRM figures are also mixed up.

Do you have another modem with more detailed stats?

just taken these now :

Data Transferred
1110.37 MBytes 118.54 MBytes
Output Power
4.7 dBm 4.7 dBm
Line Attenuation
0 dB 0 dB
Noise Margin
7 dB 6.3 dB

Before each there is a up arrow, and then a down arrow on the second.

Those aren't connection speeds

Full set:

DSL Uptime
1 days 21 hours 13 minutes 47 seconds
DSL Type
VDSL2
DSL Mode
Interleaved
Line Rate
20 Mbps 55.4 Mbps
Data Transferred
1197.11 MBytes 1171.56 MBytes
Output Power
4.7 dBm 4.7 dBm
Line Attenuation
0 dB 0 dB
Noise Margin
6.9 dB 6.3 dB

Looks fine to me (without an attenuation showing anyway)

Edited by ukhardy07 (Tue 29-Aug-17 18:39:59)

Did you mix up the upstream/downstream in the 1st post?
The most recent stats suggest:
Upstream - 6.9dB
Downstream - 6.3dB

Which looks correct. The Upstream is above the 6dB target as you are at the 20mb package limit. The downstream being 6.3dB is close enough to 6dB, and actually what my line syncs at every time.

Speed loss is likely due to crosstalk, interference from neighbouring lines. Probably not banded with 6.3dB snrm but watch the "Line Rate 55.4 Mbps" figure after the next couple resyncs and see if it changes.

Sorry, Yes, now I look I put the U and the D at the wrong place.

I'm on the "up to 80mb" package..

Before the storm, i was on 61.86mbps.. It has been like that since May..

So when the upstream and downstream values are lower, closer to 6, that's better?

Is that the time to reboot...

You're probably not missing much over that 5mbit you've lost. I think just forget about it and look forward to newer tech in a few years to give a big boost (gfast, etc).

I very much doubt you'd notice the difference between 61mbit and 56mbit. Especially over wifi or similar.

very true.

Just the principal