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[Busa]

As per the attached my line seems to be suffering from sudden step changes in SNR random times throughout any 24 hour period, see attached.

This is also related in sudden changes to the max attainable line rate.

I've had multiple pair swaps carried out over the last 3 months and other than losing tones above 2200 nothing has changed other than my connection rate has dropped.

Can anyone suggest what is going on with my line please as both PlusNet and Openreach will not/cannot find a fault?

[attachment deleted by admin]

[WWWombat]

With FTTC, your line is more susceptible to interference from other subscribers. This interference is known as crosstalk, and can accumulate (from many other subscribers) to reduce your line speed by tens of Mbps.

As takeup increases, this interference increases, and speeds decreases. All of this is known to happen, but the impact to any one line is random in terms of both the time it happens, and the size of the speed drop.

That gradual increase in noise, and decrease in speed, is what you see when those subscribers leave their modems turned on 24 hours a day, as most people do.

However, if one of your "disturbers" has a habit of turning their modem on and off during the day, then you see step changes in SNRM in the way you do. Anything from 0.5dB up to perhaps 3dB.

And, because the "max attainable" value is calculated from the current SNRM, whenever the SNRM undergoes a step change, so does the max attainable.

[Busa]

Thanks for the info although AFAIK my cabinet was already fully subscribed, I was one of the first, if not the first on it some 4 years ago and this was not happening until Openreach started fiddling with my line back in April of this year.

Even changing pairs has failed to make a difference apart from increasing my attenuation and reducing my speed! Openreach also informed me that I don't suffer from crosstalk but if I actually do then I must have a weird neighbour with erratic sleep patterns if they are switching their modem on and off at all times of the day and night.

[ejs]

It's only about 0.5 dB, it could be almost any electrical device outputting a little interference while it's on, the SNRM is there to allow for changes in the amount of interference.

[NewtronStar]

Sudden drops of SNRm came from my VDU (monitor) by 1.0 dB the worst was the RPi HDMI to VGA converter the SNRm would drop by 2.0dB when plugged in the HG612 was set-up in bridge mode to HH3a then HH5a and then the BB2 all showing sudden drops of SNRm with these devices.

Now this is weird once I purchased the Billion 8800NL and set it up just using it as an all in one unit these sudden SNRm drops have completely disappeared