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Line Attenuation

Community Veteran
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Registered: 14-07-2009

Line Attenuation

According to the ADSL Exchange and Line Checker here http://www.kitz.co.uk/adsl/adslchecker.php I live 2km from my telephone exchange as the crow flies and over 5 km by road.  My router reports the line attenuation as around 38 dB, my line currently syncs at 6880 kbs, my IP profile is 6000 kbps and download speed measurements usually achieve in excess of 5000 kbps.  I am very happy with this!!!
However, someone who lives not very far away (and is NOT a Plusnet customer) suffers an attenuation of 60 dB, syncs at 500 -800 kbps and has an IP Profile of 135 kbps.  The result is utterly dreadful for broadband performance.
I tried to find a figure for attenuation vs. distance for typical BT copper cable and found a suggested figure of 14 dB/km (with a wide error margin).  If this were true it would imply that my telephone line takes a fairly direct (and cross-country) route from the exchange in that I see less than 3 km worth of attenuation.  But what should I make of my friends 60 dB attenuation figure?  As the crow flies they live closer to the exchange than I do.  Could their phone line follow a completely different and much longer route or is there just a very bad connection somewhere?         
26 REPLIES
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Registered: 11-01-2008

Re: Line Attenuation

Are you both on the same exchange? And is your friend plugged into the master socket?

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Community Veteran
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Registered: 14-07-2009

Re: Line Attenuation

My friend and I (and the whole of my locale) are on the same exchange.
Despite the fact the my friend's house is about 15 years old he has lived there since it was built, it does not have a BT Master Socket with a detachable faceplate.  The BT cable comes out of the ground in a standard BT sheath, through the house wall and into a dual phone socket with a BT 'T' symbol on it.  I carefully unscrewed the entire face plate but their is no test socket behind and no demarcation between the internal and external wiring.  I don't know how this could have come about and whether BT would be prepared to rectify it.   
Community Veteran
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Registered: 15-06-2007

Re: Line Attenuation

Have a look here http://www.broadband-notspot.org.uk/coverage-map.html#5,50.66948354087614,-2.146453857421875,all,2 and see it there is a not-spot or a slow-spot shown in your area.
There is a big not-spot near me for no obvious reason
Community Veteran
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Registered: 02-10-2008

Re: Line Attenuation

When you say your friends lives not far away - how far approximately and in which direction compared to the exchange.
I don't know when master sockets were first introduced - but my house is older than 15years and has one.
I thought BT always put in the cable to the master socket and then the builder put in any extension wiring - so I wonder why no master socket ?
Community Veteran
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Re: Line Attenuation

My friend lives about 300 m away as the crow flies and about 450m by road.  This is in the direction toward the telephone exchange as the crow flies.  The area is not a 'Not Spot' unless this is confined to a few tens of houses on a particular street.
I'm sure the house should have a BT Master Socket, but for whatever reason it does not.  The socket that should be the master socket has a T symbol on it whilst the extension sockets are not marked.  Perhaps the BT engineer came to wire the house at the end of the day, found he was out of Master Sockets and put in whatever he had to hand?         
Lurker
Grafter
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Registered: 23-10-2008

Re: Line Attenuation

The T symbol is the mark of ownership by BT and is the demarcation point/master socket.
It was replaced by the piper branding when BT rebranded, and then subsequently by 'Openreach' branding now.
Community Veteran
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Registered: 02-10-2008

Re: Line Attenuation

Then maybe your friend has a problem then !
Community Veteran
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Registered: 14-07-2009

Re: Line Attenuation

Yes, my friend does have a problem!
His next-door-neighbour has the same lack of BT Master Socket but, apparently, much better broadband speeds.
AOL, his ISP say they have it on file that BT reported the line was unlikely to sustain more than 250 kbs but neither they nor BT seem to have done anything about this.  Surely if it's a bad line you go looking for a bad connection en route, not just shrug your shoulders?
This isn't a Plusnet problem but I would be very interested if anyone from Plusnet can explain how a bad broadband line is dealt with.  How do you motivate an engineer to test the line with the same thoroughness that they would for a bad voice telephone line?   
itsme
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Re: Line Attenuation

They are master sockets, just not a master socket with a removable part  Wink As far as I know there  was not a dual split master socket. So I believe what have been fitted is a LJU5/1A http://www.telephonesuk.co.uk/line_jacks.htm The split master sockets have been fitted since the mid to late 80's, mine was fitted 1989.
Attenuation is a function of length, material (copper or alumimuim) and quality of joints.
itsme
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Re: Line Attenuation

Quote from: Oldjim
Have a look here http://www.broadband-notspot.org.uk/coverage-map.html#5,50.66948354087614,-2.146453857421875,all,2 and see it there is a not-spot or a slow-spot shown in your area.

This made me smile. BT main research facility at Martlesham Heath is in a slow spot of 2m or less and just outside of 1m or less. Why as the exchange is not that far away and properties on the same exchange further away get higher speed, all down to experimenting with aluminium cables I believe.
Community Veteran
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Registered: 02-10-2008

Re: Line Attenuation

Perhaps ironic, but maybe they have their own exchange and a very wideband WAN ?.
It's an impressive place - I went to a conference there a a few years ago now............
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Re: Line Attenuation

Quote from: itsme
They are master sockets, just not a master socket with a removable part  Wink As far as I know there  was not a dual split master socket. So I believe what have been fitted is a LJU5/1A http://www.telephonesuk.co.uk/line_jacks.htm The split master sockets have been fitted since the mid to late 80's, mine was fitted 1989.

Judging from the picture of the inside it is an LJU4/1A Master IDC - I remember the two capacitors.  My friend told me his house was 15 years old but perhaps he lost a decade?
Is Aluminium widely used for telephone wiring and is all copper wiring the same diameter? 
pierre_pierre
Grafter
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Registered: 30-07-2007

Re: Line Attenuation

Aluminium, ask somebody who lives in Miton Keynes what they think of it Sad Sad
Not spot, pic one the notspot although close to Braintree is actually on the Chelmsford Exchange, pic2, the Braintree Exchange is just by the B in the name
Community Veteran
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Registered: 02-10-2008

Re: Line Attenuation


Since when was Boreham inside the Chelmsford bypass - as was
http://www.samknows.com/broadband/mapping/mapping.php?ecode=EABOR