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Discussion topic: Extremely low downstream SNR Margin

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This message was authored by: Suzie10

Extremely low downstream SNR Margin

Hello,

 

I'm not really experiencing any issues with my broadband. However, I have noticed something odd when checking the router statistics page. 2 days ago, the power in my home got cut due to the fire at the Hayes electrical substation. It was out for a few hours. Once the power returned, I logged in to my router and saw that my download sync speed increased.

 

Usually, I get around 70Mbps download and around 19-20Mbps upload. SNR is always around 3dB on the downstream and 6dB on the upstream. After the power cut,. however,  the download speed rose to 79999 kbps and 20000 kbps upload. The downstream SNR margin now reads 0.1dB and the upstream is 5.1dB which is why the speed went up. This is quite strange. I've had a power cut before (was sometime in 2024 and was a local issue) and this didn't happen, so not sure why it happened this time.

 

I've not noticed any differences with my broadband. It's not unstable or anything like that. Everything is working as normal. Throughput speeds have gone up slightly on the download (used to be around 62-64Mbps, now it's around 68-73Mbps). I was expecting the router to reboot and re-sync back to what it's usually at, but it hasn't so far.

 

 
I'm guessing on the next reboot/re-sync it'll go back to the usual readings. I'm just curious if anyone has seen this before/knows what caused it to happen. It's nice to have a small speed boost, but I know it won't last because the SNR margin looks wrong/way too low. 
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This message was authored by: jamesn123

Re: Extremely low downstream SNR Margin

Posted by a Superuser, not a Sky employee. Find out more

Hi @Suzie10 

Your SNR can dip below 3dB if the line is stable & of good quality, however I have never seen an SNR dip that low. You may find the line becomes a unstable at such a low SNR but it should automatically come back up if that is the case.

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