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Standard User Mr_Grumpy
(newbie) Thu 17-Mar-11 20:47:04
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ADSL2 Sync Speed halved.


[link to this post]
 
Around christmas, my sync speed dropped from around 2500kbps to around 1200kbps.

I've got a Netgear DG834G v5 Router plugged into a microfilter into the master socket, and 1 phone plugged into the microfilter. No other cabling is attached.

I've called Demon numerous times, only to be told that it is deemed an "acceptable speed" for my line. Recent checks on other ISPs suggest a speed of around 2.0Mbps will be achievable (but they don't guarantee it!). I have some evidence from old speedtest history from 10th December 2010 where my download was 1.97Mb/s and it's now less than 1.0Mb/s, but that didn't really help with the argument.

The stats I get from my router are:

ADSL Link Downstream Upstream
Connection Speed 1208 kbps 595 kbps
Line Attenuation 48.0 db 31.0 db
Noise Margin 9.10 db 6.5 db

Any suggestions as to how I can get this back to an acceptable level?

Thanks
Paul
Standard User RobertoS
(sensei) Fri 18-Mar-11 09:44:50
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Re: ADSL2 Sync Speed halved.


[re: Mr_Grumpy] [link to this post]
 
A big problem somewhere on your line.

Ignore the estimates form other ISPs, they all come from one or other of three (or so) BT databases. These vary between being wildly inaccurate, and auto-adjusting over time to the actual being achieved. You seem to be seeing the latter effect.

The attenuation on your line indicates a potential connection speed of well over 3.5Mbps. Possibly over 5Mbps. The higher than usual downstream noise margin perhaps indicates a long-running instability, and is costing you around 1Mbps.

Please can you get the stats with the filter plugged into the test socket, on the wall at the back in this pic, without the phone connected to the filter. In fact, preferably with the phone(s?) unplugged from mains power as well if they are that kind.

Have you recently changed anything like the phones or the router? TV, anything?

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.
Standard User Mr_Grumpy
(newbie) Fri 18-Mar-11 18:19:01
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Re: ADSL2 Sync Speed halved.


[re: RobertoS] [link to this post]
 
Thanks for the reply.

I've just plugged the filter in to the socket you described, and removed the phone from the filter, rebooted the router and got the following, very similar, results:

ADSL Link Downstream Upstream
Connection Speed 1215 kbps 611 kbps
Line Attenuation 47.5 db 31.5 db
Noise Margin 9.05 db 6.0 db

Can I tweak the noise margin or does that get set automatically?

The router was changed about 3 months earlier than the problem started, so probably not related, although the old router (DG834G v3) does sync at a slightly higher speed (about 150bps higher). Nothing else has changed, although it was around the time when we had the very cold weather (-15degC) that the problem started.

BT have tested the line and say there's no fault though.

Thanks for your help

Paul


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Standard User uno
(fountain of knowledge) Fri 18-Mar-11 18:32:00
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Re: ADSL2 Sync Speed halved.


[re: Mr_Grumpy] [link to this post]
 
I will take a guess here. You are on Demon's ADSL2+ LLU service.

This works VERY VERY poorly with the v5 router that you have. Although maybe not to blame completely, this won't be helping.

Matt

-
uno Broadband
t: 0808 221 8642
Official Maidenhead, Milton Keynes & Manchester Speedtest.net Host
Standard User Mr_Grumpy
(newbie) Sat 19-Mar-11 10:58:11
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Re: ADSL2 Sync Speed halved.


[re: uno] [link to this post]
 
Interesting observation.

I've just dug out my v4 router and get a different set of stats.

ADSL Link Downstream Upstream
Connection Speed 1266 kbps 715 kbps
Line Attenuation 59.5 db 31.5 db
Noise Margin 9.3 db 5.8 db

I'll leave this one connected for a bit and see if this improves things.

Thanks
Paul
Standard User RobertoS
(sensei) Sat 19-Mar-11 14:53:07
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Re: ADSL2 Sync Speed halved.


[re: Mr_Grumpy] [link to this post]
 
The differences are not significant, which probably rules out a router problem. Small variations in sych speed every time you connect are normal, and the noise margin varies 24/7. Not a lot during the day, but often quite a bit after dusk until after dawn.

You don't use a plug-in extension lead to connect the router to the socket do you?

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.
Standard User XRaySpeX
(knowledge is power) Sat 19-Mar-11 16:19:45
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Re: ADSL2 Sync Speed halved.


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
The differences are not significant, which probably rules out a router problem.
Don't you think the Down Attn. increase is significant, and surprising?

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 16 Meg LLU BB
Standard User RobertoS
(sensei) Sat 19-Mar-11 19:12:33
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Re: ADSL2 Sync Speed halved.


[re: XRaySpeX] [link to this post]
 
In reply to a post by XRaySpeX:
Don't you think the Down Attn. increase is significant, and surprising?
Whoops! I compared two or three times, and completely missed that!

I think I would trust the v4, which suggests perhaps he had a pair change around Christmas, for some reason.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.
Standard User RobertoS
(sensei) Sat 19-Mar-11 19:18:53
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Re: ADSL2 Sync Speed halved.


[re: Mr_Grumpy] [link to this post]
 
You didn't have any line faults around Christmas did you? What was the BT engineer called for, just this? Did he say he had done anything, like a pair swap?

Did you change anything electrical/electronic?

What stats do you get with the v3 in the test socket?

Adding a filter to the Sky box connection to the splitter is worth a try with one of the other routers, not the v4. Just be careful about swapping routers several times in one day. With the ADSL faceplate back on of course. Some Sky boxes can need double filtering, and there is no guarantee that the filter in the ADSL faceplate hasn't died.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

Edited by RobertoS (Sat 19-Mar-11 19:22:13)

Standard User Mr_Grumpy
(newbie) Sun 20-Mar-11 19:41:11
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Re: ADSL2 Sync Speed halved.


[re: RobertoS] [link to this post]
 
Thanks for your help so far.

I've not had any engineer visits that I'm aware of, and we don't have a sky box plugged into the phone.

I can't find the v3 router - just the v4 & the v5 - so can't try that. I think I have a generic ebuyer router somewhere too, but don't know how to get the stats on that?

Paul
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