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preston55
Aspiring Contributor
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Message 1 of 4

Lowering Noise Margin drops 100Mb max DR to 60Mb, why?

We've been lucky to generally get an 80Mb down rate, and BTHH5 showing a max data rate of around 100Mb. e.g. image 1. What I've noticed recently is that the noise margin is getting reduced from around 10 to 3 or so, and then the max reported data rate drops to below 70. I get that the exchange automatically adjusts the noise margin, but if a noise margin around 10 is giving rates that comfortably allow 80Mb to be delivered, why is the margin dropping and with it the max data rate? Shouldn't the exchange be leaving the noise margin well alone?

bt-hh-1.PNGExcellent speeds after HH bootbt-hh-2.PNG3 days later, NM dropped and with it max speed

 

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Distinguished Sage
Distinguished Sage
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Message 2 of 4

Re: Lowering Noise Margin drops 100Mb max DR to 60Mb, why?

There is something wrong possibly with hub the noise margin does fluctuate during a day as does the attainable speed but actual stats constant the fluctuations in margin may be 0.1/0.5 but not like shown in your stats
Try a factory reset of hub and see if that fixed it


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preston55
Aspiring Contributor
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Message 3 of 4

Re: Lowering Noise Margin drops 100Mb max DR to 60Mb, why?

Thanks for the reply. The noise margin was back at up at 11 this morning, giving max speed around 97Mb, and then I noticed that the line had dropped and reconnected which is what brought it back up.

Since then and as you said, it's fluctuated around 0.1 or so. Before resetting I'm going to see if the margin plummets again in a day or two and whether there's any pattern to that.
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Techwizz
Aspiring Expert
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Message 4 of 4

Re: Lowering Noise Margin drops 100Mb max DR to 60Mb, why?

Don't think there's a problem with the Hub.

Firstly, the exchange isn't doing anything, you're getting mixed up with ADSL and VDSL. On VDSL, DLM is intergated into the DSLAM in the cabinet, whereas on ADSL it's in the exchange. DLM isn't changing the noise margin, because the drop occurs without a resync. It's simply a noise source turning on and off. That noise source could be within your property, but it may not be. Do you know of anything that turns on when the NM drops and off when it increases? It could also be a crosstalker (another connection to the cabinet) that is connecting/disconnecting.

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