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Standard User domb
(newbie) Wed 07-Nov-12 09:13:07
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Two ADSL lines in same property very different line stats


[link to this post]
 
Hello Folk

I have two Talk Talk LLU lines in the same property, here are the line stats from them. Both have been fixed at a 6db non DLM profile, hence the fairly high number of upstream errors.

You may notice there is a 9-10db difference in attenuation between each pair. Both lines have the same routers, termination (filtered faceplate on master socket, no extensions). I have also tried swapping routers and cabling around, so this is clearly a line issue.

It is my understanding that if line length is the same (approx 3km) attenuation for each pair should be the same, unless:
a) they are routed differently
b) different material e.g copper vs alu.
c) there is a fault on B.

I find G.DMT modulation works best on these lines (I assume the higher ADSL2 frequences are getting attenuated).

Anyone have any thoughts? Would Openreach investigate this? Considering both lines are performing higher than the BTw and TalkTalk estimate (3.8 megabit/s), I fear not.

Why the two lines you might ask? Line B was installed first, then Line A to allow me to VPN bond these using my VPS. As Line A has twice the downstream anyway I never bothered.

Line A (will hold solid for days):
ADSL synchronization status Up
ADSL up time 1 Days 20:00:15
Upstream line rate (kbit/s) 960
Downstream line rate (kbit/s) 7520
Line standard G.DMT
Channel type Interleaved
Upstream SNR (dB) 7
Downstream SNR (dB) 7
Upstream line attenuation (dB) 26.5
Downstream line attenuation (dB) 53.5
Upstream output power (dBmV) 12.5
Downstream output power (dBmV) 20
Upstream CRC 25355
Downstream CRC 633
Upstream FEC 27555
Downstream FEC 21

Line B (resyncs a fair bit, probably as I have asked for too agressive a profile):
Upstream line rate (kbit/s) 800
Downstream line rate (kbit/s) 4512
Line standard G.DMT
Channel type Interleaved
Upstream SNR (dB) 7
Downstream SNR (dB) 7
Upstream line attenuation (dB) 31.5
Downstream line attenuation (dB) 62.5
Upstream output power (dBmV) 12.5
Downstream output power (dBmV) 19
Upstream CRC 330
Downstream CRC 15
Upstream FEC 30942
Downstream FEC 84

Result of BTw checker for postcode:
Your exchange is ADSL enabled, and our initial check on your postcode indicates that your line should be able to have an ADSL broadband service that provides a fixed line speed up to 1Mbps. However due to the length of your line the 1Mbps service may require an engineer visit who will, where possible, supply the broadband service.

Our check also indicates that your line currently supports an estimated ADSL Max broadband line speed of 2.5Mbps; typically the line speed would range between
1.5Mbps and 5Mbps.

Cheers

Edited by domb (Wed 07-Nov-12 09:22:19)

Standard User yarwell
(sensei) Wed 07-Nov-12 09:58:50
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Re: Two ADSL lines in same property very different line stat


[re: domb] [link to this post]
 
as you say, both are performing well above what one would normally expect given the attenuation. The upstream attenuations are also different, perhaps there are two E-side cables feeding your PCP and you have one line on each. Different routings are fairly unlikely but different wire gauge, material or number of joints are possible.

--

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Standard User domb
(newbie) Wed 07-Nov-12 12:21:37
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Re: Two ADSL lines in same property very different line stat


[re: yarwell] [link to this post]
 
Yes, that is what I was also considering. Its a mid 80s build, the first line was the original telephone line, the second was a new pair. I guess the E side cable is different.

Cheers


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