ADSL Attenuation 62dB - any thoughts?

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rwbj
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ADSL Attenuation 62dB - any thoughts?

Post by rwbj » Tue Jul 15, 2008 9:29 pm

Hi,

My BB speed in my new house is a paultry 1Mb (having been used to 6.5Mb in my old house) Looking at the attenuation figures, they are 32/62dB and sn ration of 8/16dB. Having looked for the master socket in the house, I find that there isn't one. Instead, there is a grey box on the outside of the house where the BT line comes in from underground.
Leading out of the back of the box are 3 connections. One is routed internally into the lounge, one is routed externally around the house and through the wall into the kitchen and one is routed internally through the garage and then externally up to the master bedroom. I suspect that splitting the signal at this point may have something to do with the high attenuation and low sn ratios. The cabling looks like it was done by a previous owner of the house as the wiring isn't great, some of the wires have 180 degree kinks in them, not great for signal integrity.
I have a few questions for the forum:

Is this the likely cause for the slow internet speeds?
Who owns the grey box? Can I just open it up and rewire it myself?
(I was thinking of quickly disconnecting the kitchen and master bedroom wiring and checking the results.)

Many thanks for any input given.

RWBJ
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SyBorg
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Post by SyBorg » Tue Jul 15, 2008 9:50 pm

welcome on board.

I would certainly think the wiring isn't helping :shock:
It all sounds a bit odd, there should be a master socket that is that point of ownership change from BT to you. Playing with the wiring without being sure is asking for trouble if you end up needing to get BT involved, but then maybe as you are new in the house now is the time to give them a call. If you don't mind the call out fee you can rightly claim ignorance if it was a botch job from the previous owners and get the wiring sorted (at least to have one clear NTE5 master socket installed).

Having said that have you taken the face plates off the three sockets you do have to see if there are additional components in there that might indicate if one of them is supposed to be the master? There are several different types.

Have you read the networking post pages.php?page=44 ? It has some links for things to check in terms of wiring.
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Re: ADSL Attenuation 62dB - any thoughts?

Post by mstombs » Tue Jul 15, 2008 9:58 pm

rwbj wrote:Is this the likely cause for the slow internet speeds?
definitely won't be helping, the 'modern' NTE5 master sockets have been around a long time

Code: Select all

Who owns the grey box? Can I just open it up and rewire it myself
The grey box on the outside should just a conversion from external to internal cable. There should be a master socket indoors which contains a few components to allow BT to test the line etc. Extensions should be wired to the customer side of the master socket.

It used to be illegal to tamper with the GPO side of the telephone circuit. - that includes the grey box and the back of the master socket. Nowadays I suspect the biggest cost at risk will be a a charge for a full callout/rewire and repair if you get disconnected/cutoff!

If you have just taken over the line I would call up BT and report a voice fault - don't you get noise and intermittent drops on calls? and get them to fix the basic wiring before moving onto ADSL issues.
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Post by rwbj » Tue Jul 15, 2008 11:54 pm

Ok, I have looked at things a little bit closer.

There is a 'master' style socket is in the lounge. I removed the faceplate and tried the internal socket, but got no ADSL connection when plugged into it. In fact, the only wires in the socket run directly into the faceplate.

As there is only one set of wires going into this box, the other sockets in the house are split off elsewhere. As mentioned in the previous post, this appears to be at the grey box outside.

From what I know, the way it should work is that the external cable comes into the master box and is wired to the internal socket and all extensions run from faceplate around the house and unpluggind the face plate should unplug any extensions. Clearly this is not how I am wired up!

Am I correct in my thinking?

Removing the two extensions from the grey box should help and then rewiring them back to the master socket would be the correct way to have the cables wired.

Does that sound correct?


Many thanks,

RWBJ
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Post by mstombs » Wed Jul 16, 2008 12:25 am

I'm sure its linked in the above mentioned FAQ, but a good guide to what it should be is in

http://www.wppltd.demon.co.uk/WPP/Wirin ... phone.html

which seems to agree with your explanation.

A single pair is used by the telephone company to the master socket.

The advice in that document is now somewhat superceded, most devices do not need the ring wire connected, so internal connections also revert to a single pair.

Is the master socket a genuine BT logo one - it seems as though yours is only wired as an extension - cable cos also use a similar but subtly different box. Genuine BT ones are not officially sold anywhere. they are only fitted by Openreach employees.
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Post by rwbj » Wed Jul 16, 2008 7:50 am

Thanks for the info.

Having looked at the links, it would seem that I am correct and that it has been incorrectly wired up.
The 'Master' socket does look like it is a genuine BT socket. It has the old style BT logo with the T in a circle with dots as the the right hand side of the T piece.
I think I will have a closer look at the grey box this morning. The two extensions running from is are currently not in use, so disconnecting them will not cause me any problems. If it improves the attenuation, I can always run the extension cabling to the 'master' socket and rewire it properly. ts quicker and easier than getting BT out to look into it.

Will let you know what happens...

RWBJ
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Post by rwbj » Wed Jul 16, 2008 8:02 am

Quick update.

Inside the grey box isn't exactly tidy, spagetti junction box! However, the crux of it is, there are 3 extensions running from it. Looking at the wiring, the three lines comming out of the box have just 2 wires connected, so no ring line, which is fine.
These 2 connections each comprise of the 3 extension wires bared and twisted together and then screwed into the juncton box. (These extensions do use paired wires in the extension cable)

Right, gotta get the kids ready for school right now. So I will unravel the wires and disconnect the 2 extensions later this morning.

Cheers,

RWBJ
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Post by rwbj » Wed Jul 16, 2008 9:49 am

Update.

Ok I removed the extension circuits so that the cabling runs
BT>Grey box>'master' socket

Reset the router and checked the values. Still 62dB attenuation and sub 1Mb speeds.

Noddy question, I assume that resetting the BT home hub would instantly change the attenuation value although it might take time to adjust the speed upwards? Is that correct?

Looking at the cable to the 'master' socket, it runs directly behind the house's main fuse board. Could this cause a problem?
(I remember in my old house having a dimmer switch that killed the internet when used!)

I will try one of the other sockets later and see what I get from them.

Cheers,

RWBJ
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Post by rwbj » Wed Jul 16, 2008 10:09 am

Update:

Tried one of the other sockets, same attenuation - 62dB
I am guessing that I am not going to get any better than that.
We are just under 5km from the exchange, so maybe that is all I am going to get from my line.

The only other thing I can think of trying to rule out internal cabling is to wire the modem directly into the grey box. I've got some UTP around somewher, if I can find a BT socket or an extension lead that I can sacrafice, i might try that later.

If anyone has any other ideas, I would be grateful for them!

Cheers,

RWBJ
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Post by mstombs » Wed Jul 16, 2008 10:29 am

If the wiring is OK, the attenuation should just be a function of cable distance from the exchange (there's a few online checkers). The dodgy extensions would be expected to have more effect on the noise and dropouts, and yes as you say with BT it should increase the margin, then over time they upgrade the speed profile.

You do have filters on any phone outlets? UTP is supposed to be better than phone cable, slightly thicker cores plus tight bonding/twisting of pairs - but again should really only be tackling noise/interference - typically in the AM radio frequency range.

62 attenuation is at the limit of adsl, it didn't seem right in your first post - time to meet your neighbours and see what they can get - at similar distance from exchange.
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Post by rwbj » Wed Jul 16, 2008 10:36 am

The only socket in use is the 'master' one and the phones are directly plugged into the home hub. The other sockets have nothing at all plugged into them.
I just changed the micro filter that the home hub went into and again, no change to the attenuation.

You mentioned online checkers for distance to the exchange - do you have any URLs for good ones?

I'll pop next door later and see what speeds they are achieving.

Thanks,

RWBJ
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Post by rwbj » Wed Jul 16, 2008 10:46 am

Sorry, should have googled for one first. Found a couple of distance calculators. (aint google great!)

3.1km as the crow flies
4.3km as the car drives

So I may just be stuck with lousy speeds.

I just checked my previous address, it was only 48 metres away from the exchange, no wonder it flew.

Thanks,

RWBJ
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Post by jerky2 » Mon Aug 04, 2008 9:40 pm

I would like to make a question related to the problem of bad signal.
I am using the Dlink g624t router and my downstream line attenuation is around 60 db and the reason is long distance from the provider ~5 Km.
My router runs the latest dlink firmware. Is it possible that running Routertech firmware could make my connection speed any better?
My line is theoreticaly 24Mbit ADSL2+, i have downgraded to ADSL G.dmt to achive ~1.2Mbit sync.
I haven't tried your fw yet because i already have enough trouble with wiring trying to get the best from my line...
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Post by SyBorg » Tue Aug 05, 2008 1:04 pm

It's possible that it will help. 2.6 includes updated drivers for the ADSL sync which may help with stability/performance but to be honest you won't know until you try it. If you are going to give it a go make sure you have a copy of your current firmware in case you want to go back (and read all the instructions carefully of course)
We learn something every day, and lots of times it’s that what we learned the day before was wrong.
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Post by jerky2 » Tue Aug 05, 2008 4:36 pm

Thanks for your reply, I will probably try 2.6 in a few days and post my results. For the time being I 'll still collect data to create some reference statistics because my connection is still new (1 month old).
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