MaxDSL - Why do I get different Attenuation and Noise Margin

[MikeWill34]

Hi,

Pre Max DSL the stats from my router were :-

ADSL Link: Downstream, Upstream
Connection Speed: 2272 kbps, 288 kbps
Line Attenuation: 3 db, 0 db
Noise Margin: 26 db, 24 db

Post MaxDSL the stats are now :-

ADSL Link: Downstream, Upstream
Connection Speed: 8128 kbps, 448 kbps
Line Attenuation: 4 db, 0 db
Noise Margin: 8 db, 19 db

When the 17070 BT Check still worked it said I was 250m from the
exchange.

Can anyone explain the change please?

Using the ADLS Guide Speed Checker :-

On Day 1 (Friday, 08 September 2006, 23:47) I got EXACLTLY 5Mbps
http://www.adslguide.org.uk/tools/speedchart.asp?id=115775580252012019644
Now on Day 2 (Saturday, 09 September 2006, 22:19) I am getting EXACLTLY
2Mbps
http://www.adslguide.org.uk/tools/speedchart.asp?id=11578366886329058834

I expected to get very close to 8Mbps due to my proximity to the
excahge (250m)
Our house is only 15 years old so I would expect the BT wiring in the
street to be in good condition.

Regards
Mike Williams

[PhilT]

Post by MikeWill34
Pre Max DSL the stats from my router were :-
ADSL Link: Downstream, Upstream
Connection Speed: 2272 kbps, 288 kbps
Line Attenuation: 3 db, 0 db
Noise Margin: 26 db, 24 db
Post MaxDSL the stats are now :-
ADSL Link: Downstream, Upstream
Connection Speed: 8128 kbps, 448 kbps
Line Attenuation: 4 db, 0 db
Noise Margin: 8 db, 19 db

you have traded the noise margin for the extra speed. The higher
frequencies used at the higher speed will give slightly higher
attenuation.

The noise margin wasn't fantastic to start with, given you could almost
run ethernet rto the exchange from your location. Maybe a review of the
wiring and filtering would get you a better margin.

Phil

[MikeWill34]

Hi Phil,

I have just checked by connecting the router (and filter) directly to
the "hidden" socket in the NTE5 and my downstream noise margin is
exactly the same. The upstream noise margin gets a little better (up
to 21)

I had already disconnected the orange bell wire (3) from all internal
wiring.

I Think it may be time to start pestering Demon to get BT to look into
this.

Regards
Mike

Post by PhilT

Post by MikeWill34
Pre Max DSL the stats from my router were :-
ADSL Link: Downstream, Upstream
Connection Speed: 2272 kbps, 288 kbps
Line Attenuation: 3 db, 0 db
Noise Margin: 26 db, 24 db
Post MaxDSL the stats are now :-
ADSL Link: Downstream, Upstream
Connection Speed: 8128 kbps, 448 kbps
Line Attenuation: 4 db, 0 db
Noise Margin: 8 db, 19 db

you have traded the noise margin for the extra speed. The higher
frequencies used at the higher speed will give slightly higher
attenuation.
The noise margin wasn't fantastic to start with, given you could almost
run ethernet rto the exchange from your location. Maybe a review of the
wiring and filtering would get you a better margin.
Phil

[PhilT]

Post by MikeWill34
I Think it may be time to start pestering Demon to get BT to look into
this.

as a comparison my office line is ~750m long and has 11 dB attenuation
with 13-15 dB of SNR margin at 8128 kbits/s.

Phil

[MikeWill34]

Phil,

I am happy with my attenuation figure of 4db, but you are getting a
significantly better Noise Margin (mine is 8db). I would have expected
to get a much better margin as my line is approx a third the length of
yours.

Regards
Mike

Post by PhilT
as a comparison my office line is ~750m long and has 11 dB attenuation
with 13-15 dB of SNR margin at 8128 kbits/s.

[PhilT]

Post by MikeWill34
I am happy with my attenuation figure of 4db, but you are getting a
significantly better Noise Margin (mine is 8db). I would have expected
to get a much better margin as my line is approx a third the length of
yours.

agreed. My office stats :-


Downstream Upstream
SNR margin 16.1 15.0 dB
Line attenuation 11.4 11.0 dB
Errored seconds 0 4
Loss of signal 0 0
Loss of frame 0 0
CRC errors 0 4
Data rate 8128 832 kbps
DSLAM (0.5 km) ALCATEL NETWORK

[Iain]

Post by MikeWill34
Hi Phil,
I have just checked by connecting the router (and filter) directly to
the "hidden" socket in the NTE5 and my downstream noise margin is
exactly the same. The upstream noise margin gets a little better (up
to 21)

Your problem is not the noise margin, youre getting an 8meg sync, which is
as good as it will get. The slow adsl speed test sounds like your BRAS
profile is stuck at 2 Meg. More noise margin would be nice, but wont
improve the speed test result.

[MikeWill34]

Sunday, 10 September 2006, 15:56 Back up to 4.5Mbps

http://www.adslguide.org.uk/tools/speedchart.asp?id=115790012581437417395

Post by MikeWill34
Hi,
Pre Max DSL the stats from my router were :-
ADSL Link: Downstream, Upstream
Connection Speed: 2272 kbps, 288 kbps
Line Attenuation: 3 db, 0 db
Noise Margin: 26 db, 24 db
Post MaxDSL the stats are now :-
ADSL Link: Downstream, Upstream
Connection Speed: 8128 kbps, 448 kbps
Line Attenuation: 4 db, 0 db
Noise Margin: 8 db, 19 db
When the 17070 BT Check still worked it said I was 250m from the
exchange.
Can anyone explain the change please?
Using the ADLS Guide Speed Checker :-
On Day 1 (Friday, 08 September 2006, 23:47) I got EXACLTLY 5Mbps
http://www.adslguide.org.uk/tools/speedchart.asp?id=115775580252012019644
Now on Day 2 (Saturday, 09 September 2006, 22:19) I am getting EXACLTLY
2Mbps
http://www.adslguide.org.uk/tools/speedchart.asp?id=11578366886329058834
I expected to get very close to 8Mbps due to my proximity to the
excahge (250m)
Our house is only 15 years old so I would expect the BT wiring in the
street to be in good condition.
Regards
Mike Williams