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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.

Line noise margin variation?



 
 
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  #1  
Old January 3rd 05, 07:13 PM posted to uk.telecom.broadband
Gareth
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Posts: 75
Default Line noise margin variation?

My line noise margin varies between 25 and 14 (or lower).

Does this indicate a faulty line or is variation during the course of a
day - and a few minutes - part of normal line function?

Gareth.


  #2  
Old January 3rd 05, 08:11 PM posted to uk.telecom.broadband
Sunil Sood
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Posts: 1,590
Default Line noise margin variation?

"Gareth" wrote in message

My line noise margin varies between 25 and 14 (or lower).

Does this indicate a faulty line or is variation during the course of
a day - and a few minutes - part of normal line function?


Its nothing to worry about.

Regards
Sunil


  #4  
Old January 6th 05, 05:49 AM posted to uk.telecom.broadband
Peter M
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Posts: 1,496
Default Line noise margin variation?

On 4 Jan 2005 , in uk.telecom.broadband, "Grant" wrote:

"Brian Morrison" wrote in message


Typically I have an SNR margin of 33-35dB, but occasionally it falls
to 10dB.


Highest I've ever seen here is 16dB. Right now, it's 9.5dB. Average is 11dB.


Must be a distance thing. Happily I am ~ 30 minutes walk to the exchange
so the figures I have are usually good (and I wish I had some note of the
figures before the BT guy changed the pair back to the exchange, sometime
in December, to be able to compare with the figures today)...


ADSL STATUS (My Plus.Net connection)

Showtime Firmware Version: 2.28b
ADSL Startup Attempts: 1
Elaspsed Time: 0 days 20 hours 7 minutes 35 seconds

SNR Margin 39.8 25.0 dB
Line Attenuation 34.1 21.0 dB
Errored Seconds 0 0
Loss of Signal 0 0
Loss of Frame 0 0
CRC Errors 0 0
Data Rate 576 288 kbps

Only 20 hours as I rebooted it after making some forwarding changes.



ADSL STATUS (My UKFSN connection, using Tiscali's network)

Showtime Firmware Version: 3.27
Startup Attempts: 1
Max Tx Power: -38 dBm/Hz
CO Vendor: ALCATEL_NETWORK
Elaspsed Time: 61 days 15 hours 46 minutes 28 seconds

SNR Margin 29.6 25.0 dB
Line Attenuation 34.1 21.0 dB
Errored Seconds 195 2
Loss of Signal 0 0
Loss of Frame 0 0
CRC Errors 391 2
Data Rate 2272 288 kbps


--------------------------------------------------------------------

For anyone interested, the later firmware for the Conexant / PTI /
DabsValue router (v3.27) has no diagnostic test display within the
browser UI, which is a bit of a shame, IMO. Peter M.



--
PlusNet http://tinyurl.com/24ymz - I recommend them and save some cash.

My other ISP : UK Free Software Network http://www.ukfsn.org
UKFSN passes all profits to Free Software projects in the UK.
  #5  
Old January 6th 05, 08:31 PM posted to uk.telecom.broadband
Phil Thompson
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Posts: 2,720
Default Line noise margin variation?

On Thu, 06 Jan 2005 20:21:36 +0000, Brian Morrison
wrote:

I am very surprised that I get such a high SNR at this
distance, apparently the modems tend to run out of measuring capability at
between 35 and 40dB SNR anyway.


SNR + attenuation is often around 70, if you get 80 then the
interference level must be nice and low. Enjoy !

Phil
--
Splenda - the only sweetener made from chlorine :-)
  #6  
Old January 6th 05, 10:45 PM posted to uk.telecom.broadband
robert w hall
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Posts: 242
Default Line noise margin variation?

In article , Phil Thompson
writes
On Thu, 06 Jan 2005 20:21:36 +0000, Brian Morrison
wrote:

I am very surprised that I get such a high SNR at this
distance, apparently the modems tend to run out of measuring capability at
between 35 and 40dB SNR anyway.


SNR + attenuation is often around 70, if you get 80 then the
interference level must be nice and low. Enjoy !

Phil


So anyone at greater than 7.5km/75db is demonstrably stuffed???

(Hey Phil, I feel we're exchanging similar posts in two different
forums, the other being demon.service, at about the same time...)
Bob

--
robert w hall
  #7  
Old January 6th 05, 11:52 PM posted to uk.telecom.broadband
robert w hall
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Posts: 242
Default Line noise margin variation?

In article , Phil Thompson
writes
On Thu, 06 Jan 2005 20:21:36 +0000, Brian Morrison
wrote:

I am very surprised that I get such a high SNR at this
distance, apparently the modems tend to run out of measuring capability at
between 35 and 40dB SNR anyway.


SNR + attenuation is often around 70, if you get 80 then the
interference level must be nice and low. Enjoy !

Phil



This is a rather limited rule of thumb IMHO Phil.

(I thought it was quite useful until I tried applying it :-))
Looking at a few data for Berkeley and Falfield exchanges, the value for
the sum seems to vary between 75 and 90, and that's a pretty wide range
in SNR.

You _might_ expect there was a correlation of the form
atten + a. SNR = b
where a might be of order 2ish
that might be more serviceable.
--
robert w hall
  #8  
Old January 7th 05, 09:41 AM posted to uk.telecom.broadband
Phil Thompson
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Posts: 2,720
Default Line noise margin variation?

On Thu, 6 Jan 2005 23:52:48 +0000, robert w hall
wrote:

Looking at a few data for Berkeley and Falfield exchanges, the value for
the sum seems to vary between 75 and 90, and that's a pretty wide range
in SNR.


that is huge, what is the 90 made up of - not 70 attenuation and 20
SNR I hope (envy !)

The "70" came from observing reports from people on longish lines. If
the attenuation exceeds 65 then the inteference level has to be pretty
low to get a decent SNR but this does happen reasonably often.

The time to worry is when you see 50 attenuation and 8 SNR on a 512k
line.

Phil
--
Splenda - the only sweetener made from chlorine :-)
  #9  
Old January 7th 05, 06:19 PM posted to uk.telecom.broadband
kraftee
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Posts: 1,069
Default Line noise margin variation?

Phil Thompson wrote:
On Thu, 6 Jan 2005 23:52:48 +0000, robert w hall
wrote:

Looking at a few data for Berkeley and Falfield exchanges, the value
for the sum seems to vary between 75 and 90, and that's a pretty
wide range in SNR.


that is huge, what is the 90 made up of - not 70 attenuation and 20
SNR I hope (envy !)

The "70" came from observing reports from people on longish lines. If
the attenuation exceeds 65 then the inteference level has to be pretty
low to get a decent SNR but this does happen reasonably often.

The time to worry is when you see 50 attenuation and 8 SNR on a 512k
line.

Phil


No the time to worry is when you see 0db line loss & -65db snr on the
line.....

Yes it still synched up, just, but was un-usable....


  #10  
Old January 7th 05, 11:24 PM posted to uk.telecom.broadband
Grant
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Posts: 230
Default Line noise margin variation?

"kraftee" [email protected]& die.com wrote in message


No the time to worry is when you see 0db line loss & -65db snr on the
line.....


Coo. I'm currently dreaming of a 0dB loss.

Operation Data Downstream
Noise Margin -8.5 dB
Output Power 16 dBm
Attenuation -64 dB

Finally got round to complaining to Pipex today. Watch this space.


 




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