A Broadband and ADSL forum. BroadbanterBanter

Welcome to BroadbanterBanter.

You are currently viewing as a guest which gives you limited access to view most discussions and other FREE features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload your own photos and access many other special features. Registration is fast, simple and absolutely free so please, join our community today.

Go Back   Home » BroadbanterBanter forum » Newsgroup Discussions » uk.telecom.broadband (UK broadband)
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

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.

Lies, damn lies and router noise margin statistics



 
 
Thread Tools Display Modes
  #1  
Old July 4th 05, 04:09 PM posted to uk.telecom.broadband
Grant
external usenet poster
 
Posts: 230
Default Lies, damn lies and router noise margin statistics

[Didn't intend it to but this turned into a bit of an opus. So, summary:

Don't believe what your modem tells you. Two different makes can't even get
close to agreeing what the noise margin is for a given line]


For the last ten months I've been using a 3Com 3CRWE754G72-A ADSL modem
router. For an average of two hours a day, the noise margin drops low enough
that I'm disconnected - see www.mason.sh/3com.gif for a graph of the last
four months, sampled every ten minutes, showing the noise margin reported by
the 3Com.

The drop outs are almost exclusively between the hours of 10pm and 1am.

Given that I don't expect to get too far with Pipex or BT when I ask for
a engineer to visit at 10.30pm to check out a line that's 6.6km from the
exchange as the wire goes, in an area where the neighbours are being turned
down for ADSL left, right and centre and when the line was previously
delivered via TPON, I've been prepared to put up with it and revert to
dialup when needed.

However, reading recent posts on here about the ability of Vigor and Zyxel
kit to better handle poor line conditions, I thought I'd give them a try.

So with the help of ebay and for the grand sum of twelve quid delivered, I'm
now the proud owner of a Zyxel 645R ADSL router. Plug it in yesterday, get
it
all configured (telnet only, cool....) and bingo, I'm connected. Spend ten
minutes on Google trying to find out how to get some line stats out of it
and with the help of the Italian equivalent of utb, I find out 'wan adsl
line near' is the required syntax:

relative capacity occupation: 29%
noise margin downstream: 19.5 db
output power upstream: 12.0 dbm
attenuation downstream: 66.5 db

Hmmm. Two minutes ago when I disconnected the 3Com, it was claiming 13dB and
given I've *never* seen it higher than 15.5dB, where does 19.5dB come from?

Also points towards the 3Com not being able to handle integers higher than
63 for
attenuation - I'm so used to looking at "-63dB" it's interesting to see what
it really is.

Change back to the 3Com and it really does think that 13dB is what it's
hearing.

Skipping forward to 10.15pm last night and the line goes dead - 3Com reckons
4dB
is all I've got. Swap over to the Zyxel and.........

9dB and a working connection.

Zyxel keeps the line up for another 30 minutes before it reckoned the line
was below 6dB at which point it dropped the line too.

Now, just need to get hold of a Vigor for twelve quid as well :-)





  #2  
Old July 4th 05, 05:02 PM posted to uk.telecom.broadband
David G. Bell
external usenet poster
 
Posts: 25
Default Lies, damn lies and router noise margin statistics

On Monday, in article

"Grant" wrote:

[Didn't intend it to but this turned into a bit of an opus. So, summary:

Don't believe what your modem tells you. Two different makes can't even get
close to agreeing what the noise margin is for a given line]


[snippage]

So with the help of ebay and for the grand sum of twelve quid delivered, I'm
now the proud owner of a Zyxel 645R ADSL router. Plug it in yesterday, get
it
all configured (telnet only, cool....) and bingo, I'm connected. Spend ten
minutes on Google trying to find out how to get some line stats out of it
and with the help of the Italian equivalent of utb, I find out 'wan adsl
line near' is the required syntax:

relative capacity occupation: 29%
noise margin downstream: 19.5 db
output power upstream: 12.0 dbm
attenuation downstream: 66.5 db

Hmmm. Two minutes ago when I disconnected the 3Com, it was claiming 13dB and
given I've *never* seen it higher than 15.5dB, where does 19.5dB come from?


The obvious question is whether you were using the same lead between
modem and wall-socket. And, even if you were, my own experience with
other stuff would have me wondering if there was something about the
physical connectors. (And the damaged lead I had recently didn't look
obviously damaged.)

Doesn't sound quite right for a long-term problem...

--
David G. Bell -- SF Fan, Filker, and Punslinger.

"I am Number Two," said Penfold. "You are Number Six."
  #3  
Old July 4th 05, 05:10 PM posted to uk.telecom.broadband
Phil Thompson
external usenet poster
 
Posts: 519
Default Lies, damn lies and router noise margin statistics

On Mon, 4 Jul 2005 16:09:51 +0100, "Grant" wrote:

Hmmm. Two minutes ago when I disconnected the 3Com, it was claiming 13dB and
given I've *never* seen it higher than 15.5dB, where does 19.5dB come from?


there are 256 frequency bands in an ADSL connection. A modem with a
different connecting strategy might use more of them with less bits
carried on each, that would potentially give a higher margin.

3com kit has let people down before on dodgy lines eg guy with useless
connection on 3com buys Zoom X3 and achieves reliable connection.

http://www.yarwell.demon.co.uk/plot.html and
http://www.yarwell.demon.co.uk/ADSL%20Status.htm illustrate the point
about strategy. I don't even know if all kit reports the same thing -
is the margin an average, the worst value, at a particular frequency
or what ?

The hard bit is pinning down what is due to the line and what to the
kit !

Phil
  #4  
Old July 4th 05, 07:08 PM posted to uk.telecom.broadband
Nigel Molesworth
external usenet poster
 
Posts: 28
Default Lies, damn lies and router noise margin statistics

On Mon, 4 Jul 2005 16:09:51 +0100, Grant wrote:

see www.mason.sh/3com.gif for a graph


How did you do that?


--
Nigel M
  #5  
Old July 4th 05, 09:58 PM posted to uk.telecom.broadband
Grant
external usenet poster
 
Posts: 230
Default Lies, damn lies and router noise margin statistics

"Nigel Molesworth" wrote in message

On Mon, 4 Jul 2005 16:09:51 +0100, Grant wrote:

see
www.mason.sh/3com.gif for a graph

How did you do that?


Scheduled Perl script that logs in to the router admin page, grabs the noise
margin figure and sticks it in a text file as well as HH:MM:YYYY:MMD.

Excel macro sucks text file in and voila.


  #7  
Old July 4th 05, 10:34 PM posted to uk.telecom.broadband
Alt Beer
external usenet poster
 
Posts: 15
Default Lies, damn lies and router noise margin statistics


"Grant" wrote in message
...
[Didn't intend it to but this turned into a bit of an opus. So, summary:

Don't believe what your modem tells you. Two different makes can't even

get
close to agreeing what the noise margin is for a given line]


For the last ten months I've been using a 3Com 3CRWE754G72-A ADSL modem
router. For an average of two hours a day, the noise margin drops low

enough
that I'm disconnected - see www.mason.sh/3com.gif for a graph of the last
four months, sampled every ten minutes, showing the noise margin reported

by
the 3Com.

The drop outs are almost exclusively between the hours of 10pm and 1am.

Given that I don't expect to get too far with Pipex or BT when I ask for
a engineer to visit at 10.30pm to check out a line that's 6.6km from the
exchange as the wire goes, in an area where the neighbours are being

turned
down for ADSL left, right and centre and when the line was previously
delivered via TPON, I've been prepared to put up with it and revert to
dialup when needed.

However, reading recent posts on here about the ability of Vigor and Zyxel
kit to better handle poor line conditions, I thought I'd give them a try.

So with the help of ebay and for the grand sum of twelve quid delivered,

I'm
now the proud owner of a Zyxel 645R ADSL router. Plug it in yesterday, get
it
all configured (telnet only, cool....) and bingo, I'm connected. Spend ten
minutes on Google trying to find out how to get some line stats out of it
and with the help of the Italian equivalent of utb, I find out 'wan adsl
line near' is the required syntax:

relative capacity occupation: 29%
noise margin downstream: 19.5 db
output power upstream: 12.0 dbm
attenuation downstream: 66.5 db

Hmmm. Two minutes ago when I disconnected the 3Com, it was claiming 13dB

and
given I've *never* seen it higher than 15.5dB, where does 19.5dB come

from?

Also points towards the 3Com not being able to handle integers higher than
63 for
attenuation - I'm so used to looking at "-63dB" it's interesting to see

what
it really is.

Change back to the 3Com and it really does think that 13dB is what it's
hearing.

Skipping forward to 10.15pm last night and the line goes dead - 3Com

reckons
4dB
is all I've got. Swap over to the Zyxel and.........

9dB and a working connection.

Zyxel keeps the line up for another 30 minutes before it reckoned the line
was below 6dB at which point it dropped the line too.

Now, just need to get hold of a Vigor for twelve quid as well :-)


I have just upgraded to different firmware version on my DSL-504 router and
get very different s/n ratio 12dB on one firmware and 25 dB on the other.
All same hardware just different firmware. Looking in the include files
which comprise the compiled firmware load, there are entries such as TX gain
RX gain and other settings. If the default gain settings are different
which they more than likely would be with different makes of router then you
will definitely get different s/n ration figures reported.


  #8  
Old July 4th 05, 11:00 PM posted to uk.telecom.broadband
Bill
external usenet poster
 
Posts: 61
Default Lies, damn lies and router noise margin statistics

Grant wrote:


relative capacity occupation: 29%
noise margin downstream: 19.5 db
output power upstream: 12.0 dbm
attenuation downstream: 66.5 db

Hmmm. Two minutes ago when I disconnected the 3Com, it was claiming 13dB and
given I've *never* seen it higher than 15.5dB, where does 19.5dB come from?



The 3com has 4 times as much noise in its' front end ? Does not move to
cleaner bands in the same way ?

Bill
  #10  
Old July 4th 05, 11:49 PM posted to uk.telecom.broadband
Phil Thompson
external usenet poster
 
Posts: 2,720
Default Lies, damn lies and router noise margin statistics

On Mon, 4 Jul 2005 23:01:26 +0100, "Grant" wrote:

Was that the router that needed a firmware upgrade because they had the SNR
and attenuation figures reversed?


Dlink, yes.

Phil
--
Tiscali - dialup speeds at Broadband prices, see
http://bbs.adslguide.org.uk/postlist...&Board=tiscali

AOL - the unlimited ISP of choice for heavy downloaders.
 




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Variable Noise Margin - causes? Grant uk.telecom.broadband (UK broadband) 12 May 27th 13 02:18 PM
BBC lies! Ian Bland uk.telecom.broadband (UK broadband) 6 April 15th 04 12:00 AM
BBC lies! Jonathan Buzzard uk.telecom.broadband (UK broadband) 1 April 5th 04 01:43 AM
BBC lies! Alex Heney uk.telecom.broadband (UK broadband) 0 April 1st 04 01:31 AM
BBC lies! Anton Gysen uk.telecom.broadband (UK broadband) 0 April 1st 04 01:02 AM


All times are GMT +1. The time now is 10:51 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.Content Relevant URLs by vBSEO 2.4.0
Copyright 2004-2019 BroadbanterBanter.
The comments are property of their posters.