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Standard User Metallifux
(learned) Fri 28-Mar-14 12:43:03
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Noise margin on FTTC


[link to this post]
 
I'd like some feedback from any telephony engineers on here as to what might be happening to my line. When the telephone line is active the downstream noise margin and max data rate nose dive. This doesn't happen all of the time so can be a bit of a pain when booking engineers. I have however captured it on video, you 'll need to increase the settings on youtube to make it readable.

https://www.youtube.com/watch?v=O-OMNvw_iew
Standard User Zarjaz
(knowledge is power) Fri 28-Mar-14 13:11:27
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Re: Noise margin on FTTC


[re: Metallifux] [link to this post]
 
Maybe a duff filter, or more likely a minor HR on the pair. Could even be something as simple as duff crimps in the cabinet. DLM knows you have a problem, looks like your target SNR is at 9db.

This isn't a self installed service is it ? Or maybe a poor installation by a contractor ?

Standard User Metallifux
(learned) Fri 28-Mar-14 13:44:05
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Re: Noise margin on FTTC


[re: Zarjaz] [link to this post]
 
No filtered face plate has been swapped out by Openreach unfortunately at the time the line wasn't misbehaving itself. I think I'll just have to ring BT and get another engineer booked.


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Standard User Computerman142
(regular) Fri 28-Mar-14 13:52:38
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Re: Noise margin on FTTC


[re: Zarjaz] [link to this post]
 
I just thought I would test mine, I have a VDSL faceplate but when press the dial button the noise margin also goes down not a great deal, just from 6db to 5.3-5.4db ish. Is this a normal range or do I have the same issue as Metallifux?

http://www.speedtest.net/my-result/2859828308
My best ever result- upload is more than it should be. but more the better. Also ping is a bit high

MYSEL

TalkTalk 40/2 FTTC - Currently getting 26.5Mbps
Standard User adslmax
(knowledge is power) Fri 28-Mar-14 14:04:34
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Re: Noise margin on FTTC


[re: Computerman142] [link to this post]
 
checking mine as mine is 15.1db noise margin. Pick up the phone up and dialing it, the noise margin stay at 15.1db.
Standard User Computerman142
(regular) Fri 28-Mar-14 14:06:22
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Re: Noise margin on FTTC


[re: adslmax] [link to this post]
 
Lucky you, that must mean I have some sort of issue I guess.

http://www.speedtest.net/my-result/2859828308
My best ever result- upload is more than it should be. but more the better. Also ping is a bit high

MYSEL

TalkTalk 40/2 FTTC - Currently getting 26.5Mbps
Standard User Computerman142
(regular) Fri 28-Mar-14 14:23:34
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Re: Noise margin on FTTC


[re: adslmax] [link to this post]
 
Think I made it better, As per your recommendation of the MK2 faceplate, I replaced it back for the original and the noise went from 6.3db to 6 - 5.9db when I pressed dial so much better but still not like yours.

http://www.speedtest.net/my-result/2859828308
My best ever result- upload is more than it should be. but more the better. Also ping is a bit high

MYSEL

TalkTalk 40/2 FTTC - Currently getting 26.5Mbps
Standard User WWWombat
(fountain of knowledge) Fri 28-Mar-14 15:36:18
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Re: Noise margin on FTTC


[re: Computerman142] [link to this post]
 
My three values stay the same, at 7.0dB.
Standard User MHC
(sensei) Fri 28-Mar-14 21:05:47
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Re: Noise margin on FTTC


[re: Computerman142] [link to this post]
 
Not necessarily. A small change can be expected - by initiating a call you are changing the impedance that load the filter, that will effect the apparent impedance of the filter as seen from the line which in turn will have an effect on the VDSL signal and noise. On some phone/filter/line combinations the net effect might be zero whereas on others it could be 1 dB or so. Changing the faceplate/filter has demonstrated this. Using the very old GPO style phones also causes a significant change in some cases.

The OP however, does appear to have a problem that needs sorting.


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C


taurus excreta cerebrum vincit
Standard User Computerman142
(regular) Fri 28-Mar-14 21:09:48
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Re: Noise margin on FTTC


[re: MHC] [link to this post]
 
OK thank you MHC so nothing to worry about. In comparison to mine yes I think he has a problem.

http://www.speedtest.net/my-result/2859828308
My best ever result- upload is more than it should be. but more the better. Also ping is a bit high

MYSEL

TalkTalk 40/2 FTTC - Currently getting 26.5Mbps
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