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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.

Critic my noise margins/attenuation please



 
 
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  #1  
Old October 7th 05, 08:48 PM posted to uk.telecom.broadband
tarzan
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Posts: 27
Default Critic my noise margins/attenuation please

from my conexent results i have (512 connection)

up down

NM +24dB +3.7dB
ATT +25dB +44.1dB
BPF 232 54

crc error 1 0
HEC 0 1

max TX psd -38dBm/hz

how do these look and if bad how can i get them right?
i have slow/eratic speeds and dropped lines

  #2  
Old October 7th 05, 11:05 PM posted to uk.telecom.broadband
Phil Thompson
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Posts: 2,720
Default Critic my noise margins/attenuation please

On 7 Oct 2005 12:48:41 -0700, "tarzan" wrote:

how do these look and if bad how can i get them right?
i have slow/eratic speeds and dropped lines


the 3.7 dB margin on the downstream is rubbish, should be at least 20
if not 30 with only 512k service on the line.

If you have a split faceplate master socket like shown at
http://www.clarity.it/telecoms/adsl_faceplate.htm#part3 then try again
in the test socket at the back of the master.

If you don't have one of those, unplug everything else from the phone
system and see if it gets better.

Phil
--
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http://bbs.adslguide.org.uk/postlist...&Board=tiscali

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  #3  
Old October 7th 05, 11:26 PM posted to uk.telecom.broadband
Bill
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Posts: 61
Default Critic my noise margins/attenuation please

tarzan wrote:

from my conexent results i have (512 connection)

up down

NM +24dB +3.7dB
ATT +25dB +44.1dB
BPF 232 54

crc error 1 0
HEC 0 1

max TX psd -38dBm/hz

how do these look and if bad how can i get them right?
i have slow/eratic speeds and dropped lines



I'd expect a better noise with that atten. Likely you have a source of
noise getting on your the line.
Any dodgy wiring, extensions, Sky boxes, DECT phones etc about ?

Bill
  #4  
Old October 8th 05, 08:35 AM posted to uk.telecom.broadband
SteveB
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Posts: 42
Default Critic my noise margins/attenuation please

Your downstream noise margin should be more like 30dB not 3.7dB. Most
routers will be unreliable once you get below about 9dB. Try the usual
disconnecting everything (phones etc), just have the router only plugged
into the BT master socket, also try it without any microfilter in case
that's faulty. Try switching all mains appliances and non tungsten lights
in the house off, try moving leads around while you look at the noise
figures, you may have a dodgy lead.

I've just had an ISP arranged BT engineer visit to fix an intermittent
noise/disconnection problem that had got worse over a 2 month period, and my
problem was actually two it seems. One was an ancient street cable he
swapped over to a new one, that got me 6dB less attenuation. The other was
noise generated in my house by mains adapters running the router, switch and
a cordless phone and the fix for these was to wind 4 turns of the DC output
leads round ferrite rings (I did this after the visit). The 2 fixes
together gave me about 8dB improvement in noise margin. The orange ring
wire can be disconnected in the BT master socket (see
http://yarwell.blogspot.com/2005/08/adsl-tweaking.html) to improve some home
systems but mine was already disconnected it seems by the BT engineer that
fitted my ADSL in the first place 2 years ago when it was swapped over from
ISDN so I had nothing to gain there. I now get 44dB attenuation and 24dB
noise ratio on a 2MB connection, 512K used to be about 35dB noise ratio and
the figures are close on two routers I have (D-Link DSL-500 and Safecom
SAMR-4110).





 




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