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Standard User NBK
(experienced) Wed 31-Dec-14 11:41:41
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SNR margin...


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Hi.
Just a quick query, is it normal or a bit odd for SNR margin to be negatively affected when using a phone connected to a microfilter? (by a couple of db)
Also a secondary question somewhat related...
with the BT VDSL faceplate, does that completely isolate extension wiring from the VDSL connection or would noise generated by extension wiring still negatively affect the VDSL stats/speed?

Thanks smile
Standard User RobertoS
(elder) Wed 31-Dec-14 12:23:58
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Re: SNR margin...


[re: NBK] [link to this post]
 
Mine (when on ADSLx) used to drop by about 1.5dB when the phone was in use. A bit less on FTTC.

Re your VDSL faceplate question, that depends on whether it was an Openreach engineer that fitted it, in which case it shouldn't unless they unusually cocked up. If it was a subcontractor such as Kelly's or Quinn's who often cock it up, or a self-install, the wiring can negatively affect VDSL, more so than it did ADSLx. We need to know more about where the extensions are wired from - from the line reaching the building to the sockets.

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Standard User NBK
(experienced) Wed 31-Dec-14 12:37:29
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Re: SNR margin...


[re: RobertoS] [link to this post]
 
Well I've actually been fiddling about...
test socket with ADSL connected, no crackling on quiet line test.
extensions connected but ADSL modem not, no crackling on quiet line test
extensions connected and ADSL modem connected, slight crackling on quiet line test.

Anyways
Drop wire -> BT extenal junction box -> short run to master at upstairs front -> long external run to first extension upstairs rear -> external extension downstairs rear -> dodgy internal extension downstairs front -> internal extension upstairs front.


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Standard User MHC
(sensei) Wed 31-Dec-14 12:47:57
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Re: SNR margin...


[re: NBK] [link to this post]
 
As RobetoS says, yes the SNR can be affected as can the attenuation/signal level.

The filters are cheap and any change to the termination impedance will affect the overall line impedance and the actual filter characteristics and thus how any noise is picked up or transmitted. 2dB is fairly high however nothing to worry about unduly.


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Standard User NBK
(experienced) Wed 31-Dec-14 14:21:33
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Re: SNR margin...


[re: RobertoS] [link to this post]
 
Hi Roberto.
One more thought...
Does the VDSL/FTTC faceplate BT install work the same/a similar way to the original pre-self install ADSL faceplates?
I had an ADSL v1.0 faceplate lying in a drawer from when I originally got ADSL many years ago (nildram 512/256 for £50 a month...ow) and that has
a) lowered the attenuation from the extension wiring
b) stopped any crackling/noise when the extensions are connected.
c) given me better upload speed than i've ever seen since I was switched to sky from Be.

If the VDSL faceplate works the same way (does a similar thing) I can hopefully assume that come install day I won't have an issue?
I'm not at all sure though.
Thanks smile
Standard User ian72
(eat-sleep-adslguide) Wed 31-Dec-14 14:51:56
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Re: SNR margin...


[re: NBK] [link to this post]
 
Apart from maybe an update of electronics there should be little difference between the ADSL faceplate and the VDSL. For self installs people will still potentially use ADSL filters which work fine with VDSL as well.
Standard User TheEulerID
(member) Wed 31-Dec-14 15:58:36
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Re: SNR margin...


[re: NBK] [link to this post]
 
If a VDSL faceplate is fitted properly (which means extensions are connected to the filtered output), then it will, to all intents and purposes eliminate interference from those extensions.

Note that if an unfiltered extension is added for VDSL purposes, it really ought to use twisted pair cable or performance will suffer.
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