MyFRITZ! Reading SNR or SNR Margin

[Craig Ball]

Hi all, my Fritzbox 7530 started resynching on Thursday and after multiple restarts it appears DLM has kicked in and slowed down my line. I suspect noise on the line, which I am trying to get to the bottom of.
I am struggling to interpret the statistics on the MyFRITZ! user interface. Both DSL information and statistics bar graphs report SNR = 7 (was 18 on Thursday). On the spectrum graph it shows SNR doesn’t drop below 18. Does anyone know if the values are SNR or abbreviated SNR margin?

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[UK Sentinel]

A screen dump of the stats would be handy, as this usually shows CRC’s /ES etc.

 

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[Craig Ball]

Hi UK Sentinel, here’s a screen dump of the stats. It doesn’t show anything prior to Friday am reboot. Please let me know if any other screenshots will help. Many thanks.

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[UK Sentinel]

Is there anything like this on your 7530

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[Craig Ball]

Hi, yeah just got these from the GUI on my laptop…..

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[Craig Ball]

….here’s the rest of the screenshot

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[Grisu]

For sure something happened to your line. Noise, bad contacts, wet lines, bad modem DSL-input driver or whatever.

SNR is what it is, the difference between signal and noise.
SNR margin would be how much you have spare and you could use it for higher sync (or let it be for better SNR with less lost bits)

Now you have 6dB SNR and thats needed for reliable transmission, your line wont get faster as it is running on its limit right now.
If you get back 15dB you could go faster by reducing SNR and DLM would step up again.

 

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[Craig Ball]

Thanks Grisu, that’s what I feared. Prior to this I was getting a stable 54.5Mbit/s (a whisker below the Vodafone minimum speed guarantee). Our internet gets hammered throughout the day with us both working from home, driving CAD applications on Remote Desktop and constant Skype calls; it never skipped a beat in the 7 months since I got the Fritzbox. The weather turned on Thursday and that’s when it started to go pear shaped.

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[Grisu]

But 54 to 45 is not that much, keep cool.

And you got zero CRC (what is even too good).

You could get much more with vplus/supervectoring (35b) if it is available at your location.

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[UK Sentinel]

Your line does seem to not show to many problems from a CRC perspective after the line synch change, you are getting a few so maybe worth trying a quite line test with your telephone to see if there is any crackling on the line that you can hear.

In UK, if you are connected to a broadcom exchange (cab) usually your SNR downtream (receive) is 3dB and as yours is 7, then this is most likely why your synch rate has changed from 55 to 45 (ish) and G.inp is off which does not help and should be On for Broadcom cab if line is good etc.

Has the 7530 updated recently ?

Either way, give it a few days and see if the original 55Mb returns and keep an eye or your SNR (signal to Noise Ratio) values ?

 

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[UK Sentinel]

Just a thought, when you have a moment, take a look at below page and let us know what face-plate you have ?

BT Master Sockets and Face Plates Mini Wiki

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[Craig Ball]

Morning, thanks for the help. The faceplate is a Mk4, it was installed by Openreach 2 years ago in efforts to reach the minimum speed guarantee, but still fell just short. The 7530 plugs straight into it with 8 metres of  quality (solid core/twisted pair) cable.

The line speed increased slightly overnight to 50Mbit/s, I guess that’s DLM still settling.

I don’t recall the router updating recently and it seems to indicate being up to date.

Should I be looking for the downstream SNR going from 7 towards 3 for an improvement? I think this is where I am getting confused.

Thanks

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[UK Sentinel]

Good that you have at least the Mk4 faceplate.

The connection between Faceplate and Fritz!Box sounds  long, but I am sure you are aware of this.

Yes, the higher the SNR, the more stable the connection, but likewise at the cost of synch rate (speed) – huewei street cabinets support the Broadcom chipset in UK, these cabinets also support G.inp which is an error correction solution that allows your SNR to be lower and thus have a higher synch rate (speed) etc.

Look under the Overview tab on the router to see what the exchange you are connecting to is ?

 

 

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[Craig Ball]

Thanks, I looked in the overview tab on the mobile app and it’s not obvious to me the type of exchange. I did however discover a website that identifies the cabinet by landline number and it says it is an ‘ECI’?

Think I’ll head out to Argos and buy myself a cheap corded phone to test the line for noise.

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[UK Sentinel]

ECI means you do not have a Broadcom based cab so you will not have G.inp available to yourself.

So your SNR values will not change down to 3, maybe 5 or 6 if you are lucky .

Enjoy your shopping trip.

 

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