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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Noise and attenuation



 
 
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  #1  
Old September 24th 04, 07:54 PM posted to uk.telecom.broadband
Geoff Venn
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Posts: 1
Default Noise and attenuation

My connection shows
local line attenuation 63 dB
remote line attenuation 31.5dB
Local SNR Margin 7.5dB
Remote SNR 17dB

I live a long way from the exchange and BT only recently agreed to connect
me despite the long wire length to the exchange.
My question is that sometimes whewn I connect I get Local SNR Margin of 2
or 3 dB and sometimes 7 or 8.
How does this happen? Is it unusual to connect with 3dB and still get
braodband running. It works OK at the lower levels but drops out
occasionally.
Geoff

  #2  
Old September 24th 04, 08:11 PM posted to uk.telecom.broadband
Kráftéé
external usenet poster
 
Posts: 126
Default Noise and attenuation

Geoff Venn wrote:
My connection shows
local line attenuation 63 dB
remote line attenuation 31.5dB
Local SNR Margin 7.5dB
Remote SNR 17dB

I live a long way from the exchange and BT only recently agreed to
connect me despite the long wire length to the exchange.
My question is that sometimes whewn I connect I get Local SNR
Margin of 2 or 3 dB and sometimes 7 or 8.
How does this happen? Is it unusual to connect with 3dB and still
get braodband running. It works OK at the lower levels but drops
out occasionally.
Geoff


Anything below a SNR of 6db can cause you all sorts of problems, slow
speends, drop outs etc....

Have you tried disconnecting all extension wiring & pluging into the master
to see what your results are? If it does make an improvement there are a
few things you could try. Now if you're using the only telephone socket on
the line it becomes more problematic...


  #3  
Old September 24th 04, 08:17 PM posted to uk.telecom.broadband
Geoff Venn
external usenet poster
 
Posts: 2
Default Noise and attenuation

On Fri, 24 Sep 2004 20:11:14 +0100, Kráftéé wrote:

Geoff Venn wrote:
My connection shows

Whats odd is that I can reboot the router, without touching anything in
the house, and get a "clean line" at 7 or 8dB. Is there an external
influence at work here?
Geoff

local line attenuation 63 dB
remote line attenuation 31.5dB
Local SNR Margin 7.5dB
Remote SNR 17dB



Anything below a SNR of 6db can cause you all sorts of problems, slow
speends, drop outs etc....

Have you tried disconnecting all extension wiring & pluging into the master
to see what your results are? If it does make an improvement there are a
few things you could try. Now if you're using the only telephone socket on
the line it becomes more problematic...


  #4  
Old September 25th 04, 05:02 PM posted to uk.telecom.broadband
David G
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Posts: 101
Default Noise and attenuation

Geoff Venn wrote:

My connection shows
local line attenuation 63 dB
remote line attenuation 31.5dB
Local SNR Margin 7.5dB
Remote SNR 17dB



Sorry to side track this, but could someone explain the relevance of
these figures please.

--
Regards


David G
(remove r u n)
  #5  
Old September 25th 04, 08:16 PM posted to uk.telecom.broadband
Geoff Venn
external usenet poster
 
Posts: 2
Default Noise and attenuation

On Sat, 25 Sep 2004 14:20:12 +0100, Brian Morrison wrote:

On Fri, 24 Sep 2004 20:17:40 +0100, in article
Geoff Venn
wrote:

Thanks Brian, that explains it. I've noticed that using the phone can
cause changes in the SNR that can persist and which change if I reboot.
Geoff

What you're seeing is that the retraining deals with the noise that is
appearing by adjusting the frequency bin usage to minimise the effect of
that noise spectrum at that point in time. If the noise subsequently
changes its spectral characteristics, then the modem will see the SNR
decline and the error rate will increase. At some point this process
leads to a line drop and another retraining cycle.


  #6  
Old September 25th 04, 09:25 PM posted to uk.telecom.broadband
Alex Heney
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Posts: 1,607
Default Noise and attenuation

On Sat, 25 Sep 2004 17:02:12 +0100, David G [email protected]
wrote:

Geoff Venn wrote:

My connection shows
local line attenuation 63 dB
remote line attenuation 31.5dB
Local SNR Margin 7.5dB
Remote SNR 17dB



Sorry to side track this, but could someone explain the relevance of
these figures please.


Local means downstream (i.e. the figures relevant to data coming from
the internet to your PC), while remote means upstream (i.e. relevant
to data going from your PC to the internet).

Attenuation is the loss of signal, expressed in Decibels (dB). Until
the 6th, you generally could not get 512K ADSL if the downstream
attenuation was more than 60dB. The lower the figure, the stronger the
signal you are getting.

SNR is Signal-to-Noise Ratio, again expressed in dB. With this one,
the higher the value the better. I've seen suggestions that anything
under 10 is likely to cause problems, and anything under about 5 is
likely to be unworkable.
  #7  
Old September 25th 04, 10:04 PM posted to uk.telecom.broadband
RChick
external usenet poster
 
Posts: 13
Default Noise and attenuation


"David G" [email protected] wrote in message
...
Geoff Venn wrote:

My connection shows local line attenuation 63 dB
remote line attenuation 31.5dB
Local SNR Margin 7.5dB
Remote SNR 17dB



Sorry to side track this, but could someone explain the relevance of these
figures please.

--
Regards


David G
(remove r u n)


I would like to ask where you can obtain these readings my modem/router
(Netgear DG814) does appear to show them anywhere

Regards

Roy


  #8  
Old September 25th 04, 10:55 PM posted to uk.telecom.broadband
David G
external usenet poster
 
Posts: 101
Default Noise and attenuation

Alex Heney wrote:

Local means downstream (i.e. the figures relevant to data coming from
the internet to your PC), while remote means upstream (i.e. relevant
to data going from your PC to the internet).

Attenuation is the loss of signal, expressed in Decibels (dB). Until
the 6th, you generally could not get 512K ADSL if the downstream
attenuation was more than 60dB. The lower the figure, the stronger the
signal you are getting.

SNR is Signal-to-Noise Ratio, again expressed in dB. With this one,
the higher the value the better. I've seen suggestions that anything
under 10 is likely to cause problems, and anything under about 5 is
likely to be unworkable.


Thanks

--
Regards


David G
(remove r u n)
  #9  
Old September 26th 04, 02:44 AM posted to uk.telecom.broadband
David Wood
external usenet poster
 
Posts: 88
Default Noise and attenuation

In message , RChick
writes
I would like to ask where you can obtain these readings my modem/router
(Netgear DG814) does appear to show them anywhere


Some ADSL equipment, including your DG814, doesn't give such
information.



David
--
David Wood

  #10  
Old September 26th 04, 09:06 AM posted to uk.telecom.broadband
Reg Edwards
external usenet poster
 
Posts: 168
Default Noise and attenuation

At what frequency is local line attenuation measured?


 




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