ADSL Attenuation and SNR

[John]

For various reasons I managed to get Demon to remove me from the ADSLMax
upgrade in the first week of October. So I am still on plain vanilla
512Mbps ADSL, which is steady, synchronised at all times now (as far as
my router logs inform me) and acceptable for the business and private
use I do.

Out of curiosity, today I looked at my router interface to see the stats
and other information. I see one has changed, and that is the stats for
the down stream attenuation (all other data is still the same).

Before the exchange was ADSLMaxed my downstream attenuation was reported
as 63.5 dB whenever I looked. The Noise Margin varied between 8.5 dB and
15.0 dB.

Today my router stats reported the downstream attenuation as 15.5 dB,
and the Noise Margin in the same range (actually 12.5). The upstream
attenuation and Noise Margin is exactly the same as it has always been.

Looking at the figures right now, the downstream attenuation is 15.5 dB
and the Noise Margin is 10.1 dB.

Out of curiosity ...
Why is this so different for the downstream attenuation?

What has caused the change, other than the change to ADSLMax to which I
am not tuned in?

[Chris Bell]

Post by John
Out of curiosity ...
Why is this so different for the downstream attenuation?
What has caused the change, other than the change to ADSLMax to which I
am not tuned in?

Why should it stay the same? The hardware was apparently in place before
the upgrade to ADSL Max, so it was probably a software change, and it
changed the way the available bandwidth was utilised. If you have opted for
a further change, to a fixed maximum data rate, it may well be attained in a
different manner from before, using a different mix of frequencies.

[John]

Post by Chris Bell

Post by John
Out of curiosity ...
Why is this so different for the downstream attenuation?
What has caused the change, other than the change to ADSLMax to which I
am not tuned in?

Why should it stay the same? The hardware was apparently in place before
the upgrade to ADSL Max, so it was probably a software change, and it
changed the way the available bandwidth was utilised. If you have opted for
a further change, to a fixed maximum data rate, it may well be attained in a
different manner from before, using a different mix of frequencies.

The figures are so different as ti be very noticeable. The line length
(>8km) and wiring has not changed, so why the change in attenuation?

The old downstream figures were right on the margin for 1Mbps ADSL
connection speeds. The current figures, subject to SNR reductions, look
like being OK at up to 3Mbps.

Just interested in an explanation, if possible!

[Tony]

Post by John

Post by Chris Bell

Post by John
Out of curiosity ...
Why is this so different for the downstream attenuation?
What has caused the change, other than the change to ADSLMax to which I
am not tuned in?

Why should it stay the same? The hardware was apparently in place before
the upgrade to ADSL Max, so it was probably a software change, and it
changed the way the available bandwidth was utilised. If you have opted for
a further change, to a fixed maximum data rate, it may well be attained in a
different manner from before, using a different mix of frequencies.

The figures are so different as ti be very noticeable. The line length
(>8km) and wiring has not changed, so why the change in attenuation?
The old downstream figures were right on the margin for 1Mbps ADSL
connection speeds. The current figures, subject to SNR reductions, look
like being OK at up to 3Mbps.
Just interested in an explanation, if possible!

I'd suspect a sensor error first! Have you rebooted the router and
re-checked?

[John]

Post by Tony
I'd suspect a sensor error first! Have you rebooted the router and
re-checked?

Yes! Several times for other reasons, with the same figures reported.

This has only happened since October, and was consistent before October
reporting the, what I regard, as the old higher figures.

It is not important, just noticeable!

[PhilT]

Post by John
Today my router stats reported the downstream attenuation as 15.5 dB,
and the Noise Margin in the same range (actually 12.5). The upstream
attenuation and Noise Margin is exactly the same as it has always been.

its either broken or getting duff info from the exchange. Not uncommon
and occasionally has been exploited to get around the checker.

Phil