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[ColinS]

So, whatever the differences are in terms of VDSL2 performance, information-wise they don't seem to have 'filtered' through to engineers yet.

 

[guest]

As the frequency increases, I speculate that the 'shunt effect' becomes more significant and thus the signal is further attenuated.

ASCII Art

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^ B-wire ^                  |
                                |
                               O  <--- Surge arrestor, acting as a frequency dependent shunt, applies a load across the pair.
                                |
                                |
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^ A-wire ^

Its a bit more complex than that as the signal is differential.

The spark gap will be seen (by VDSL2 frequencies - certainly 30a) from the FTTC cab as a discontinuity in the transmission line so you will end up with reflections back down the line. Depending on the length of the line this may or may not be an issue.

More seriously than that you will increase noise at the EU-side as the the spark gap acts as a shunt. That will shunt some of the signal to the other input of the VDSL2 modem but it'll be slightly out of phase so it will appear as out of phase noise to the modem. This is never going to be good.

Edit - in theory the shunt effect shouldn't be that much of an issue, but theory assumes a perfectly balanced pair.

[ColinS]

The spark gap will be seen (by VDSL2 frequencies - certainly 30a) from the FTTC cab as a discontinuity in the transmission line so you will end up with reflections back down the line. Depending on the length of the line this may or may not be an issue.

Which may be the cause of (some of) the phantom 'bridged taps' that have been reported on some people's lines (even BS)

in theory the shunt effect shouldn't be that much of an issue, but theory assumes a perfectly balanced pair.

However Longditunal AC inbalance (<50dB) occurs as a fault every so often, although this is tested at installation and should be investigated and corrected if it is seen.  AIUI >60dB is what they should be looking for and <50dB red flags it.

[guest]

The spark gap will be seen (by VDSL2 frequencies - certainly 30a) from the FTTC cab as a discontinuity in the transmission line so you will end up with reflections back down the line. Depending on the length of the line this may or may not be an issue.

Which may be the cause of (some of) the phantom 'bridged taps' that have been reported on some people's lines (even BS)

in theory the shunt effect shouldn't be that much of an issue, but theory assumes a perfectly balanced pair.

However Longditunal AC inbalance (<50dB) occurs as a fault every so often, although this is tested at installation and should be investigated and corrected if it is seen.  AIUI >60dB is what they should be looking for and <50dB red flags it.

Could be for bridged taps, I have no idea of the test equipment used.

In terms of balance, the shunt should be of trivial importance but that would assume perfect balance which doesn't exist with all the junctions on a normal line. It all depends on the phase shift really and I don't know enough about VDSL front-ends to make a judgement on that.

[snadge]

Guess what,  so did one of the sfi's that came to mine saying it was old and no good, I'm assuming for the same reason :-)  so he swapped it out

Sent from my Sony Xperia Miro on Tapatalk

[guest]

Oh BTW snadge, Sky DLM seems to have finally set a speed for me in the MyBroadband section - 21Mbps down and 1.3Mbps up. Did yours ever update?

[snadge]

Oh BTW snadge, Sky DLM seems to have finally set a speed for me in the MyBroadband section - 21Mbps down and 1.3Mbps up. Did yours ever update?

nope - if you recall it was almost through line training when that BT Engineer caused my line to go funny, so then Sky reps reset it to 18Mb (when testing the line) as thats what speed I told them I was getting, so once fixed it stuck at that, Iam currently testing the new Sky Hub v2 and iam getting 18,010k which is exactly what i got when I was fixed to he 18Mb profile in April last year, and when I did try to go above with my DG834Nv1 when the line was fixed it would not ...so I know Iam on the 18Mb profile (as opposed to 18Mb being the fastest I can get whilst on a 20Mb profile...like I was before), I wouldnt mind being on the 20Mb profile because since the changes sky have made my DG834N has gone from 15.5Mbps to 17.6Mbps sync, so I wouldnt mind seeing what the 2504N/HUB gets as these were always about 1.5-2.0Mb higher than the DG834N -> should hit 19Mbps easily I reckon, if not more?

heres what MY SKY says now:

Line connection testing completed on 18/06/2012, resulting in the following settings:

Download speed setting
Your connection has been set to a download speed of up to 4.1Mbps .

Upload speed setting
Your connection has been set to an upload speed of up to 0.5Mbps .


sorry to have gone off topic slightly

[guest]

I never had an entry before, this one appeared last week despite the testing finishing in March 2013.

Currently sitting at 16Mbps with a 10dB margin, seems best with all the BT OR peeps about.

[snadge]

Well I stripped my NTE5 down (it was installed last year by BT Broadband Engineer and its Openreach branded one, printed on top)

I found that

A) it did have a 26A surge arrestor installed

B) it does not appear to have some form of RF3 or similar installed.

here are photos of the faceplate, as you can see it has the 22mH Bellwire Choke - but doesnt have anything else installed alongside it? I dunno if its built into the 22mH choke or resides on the other section where the 26A Surge Arrestor is (which looks identical to previous picture with Surge Arrestor on)

[snadge]

...to further add.... ive learned that it was the BT i-Plate that has both RF3 filter and 22mH choke

so, are all new NTE5's Openreach branded? (the ones with no 26A) so the only way to tell is to open it up? - if one hasnt got a soldering iron then I supposed cutting it out would be ok yes?

edit:
 I have been doing a bit research on the whole "filtering" issue, SIN346 is a set of requirements by BT that manufacturers must work to when creating ADSL filters.. there are different revisions of SIN346, Iam unsure as to what the latest revision is but Ive read that SIN346 v2.6 saw the introduction of ADSL2+ and apparently the NTE2000/NTE2005 filtered faceplates are advertised as v2.2 ready??? (in other words ADSL1 only)...im reading of someone who once had issues getting an NTE2005 to work on ADSL2...  I know my NTE2000 worked on my ADSL2+ connection quite well, but then I recently installed an SSFP (which is obviously built too newer SIN346 revision) and my speeds have gone up...although I can not be 100% sure the speeds went up before or after installation of the SSFP, I will have to track back and see if I can find out because sky have been upgrading DLM and ISAM firmwares which have made enhancements to my speed previously

apparently if the phone port is not filtered properly it can cause the ADSL signal to reflect back into the line and cause problems..is this correct? i know you can get "bridged taps" that affects VDSL but according to this user on plusnet forums it can, he also talks about 'loading' , 'return loss' & other stuff and why its important to have a filter thats manufactured to SIN346 (and version/revision according to service its used on) otherwise you can have these problems.

so according to that it would be important to have a filter thats been designed to work with a given service.


SIN346 history:

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SIN 346 Issue 2.7 - BT ADSL Interface Description

Issue 2.7 of SIN 346 has been updated from the previous issue in order to remove explicit support for ADSL2.

Published 13/2/08
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SIN 346 Issue 2.6 - BT ADSL Interface Description
This SIN has been updated to cover 21CN versions of ADSL, the possibility of ADSL 2 plus and CPE filters to ETSI standard TS101 952.

Published 03/02/06
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----------------------------------------------------------------------------
SIN 346 Issue 2.5 - BT ADSL Interface Description
The SIN has been updated to be compatible with a new repair process for problem lines.

Published 11/8/04
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SIN 346 Issue 2.4 BT ADSL Interface Description
This Supplier Information Note describes the interface presented at the end of an ADSL line at the end customer premises. The issue reflects the changing situation regarding the compatibility of ADSL lines and Redcare.

Published 7/11/03
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----------------------------------------------------------------------------
SIN 346 Issue 2.3 - BT ADSL Interface Description
An Operations and Maintenance section has been added recommending that end-user CPE support F5 loopback. The clause on CPE approval requirements has been removed and Figure 6 amended

Published 11/8/03
----------------------------------------------------------------------------


----------------------------------------------------------------------------
SIN 346 Issue 2.2 - BT ADSL Interface Description
This supplier information note (SIN) describes the interface presented at the end of an ADSL line at the end customer premises. It is one of a family of SINS relating to ADSL delivered services. This issue includes editorial changes to clarify topology options and source of CPE ADSL filter specification requirements

Published 11/07/02
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----------------------------------------------------------------------------
SIN 346 Issue 2.1 - BT ADSL Interface Description
This supplier information note (SIN) describes the interface presented at the end of an ADSL line at the end customer premises. It is one of a family of SINS relating to ADSL delivered services. This issue includes editorial changes to clarify topology options and source of CPE ADSL filter specification requirements

Published 02/10/01
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[c6em]

Latest is 2.10
Mod list as below................
an available from http://www.sinet.bt.com/

V2.8
March 2010   
Updated to add support for Annex M. minor changes to section 5 and to referencing ITU-T Recommendations

V2.9
March 2011
Ammendment to Section 5 to reflect status of the product referred to

V2.10
Oct 2011
Minor corrections & addition of low power mode.

[Black Sheep]

...to further add.... ive learned that it was the BT i-Plate that has both RF3 filter and 22mH choke

I have to say, I thought all along you were referring to the i-Plate ??

[ColinS]

...to further add.... ive learned that it was the BT i-Plate that has both RF3 filter and 22mH choke

I have to say, I thought all along you were referring to the i-Plate ??

Seems even SFI's get confused then eh, BS? 

[snadge]

...to further add.... ive learned that it was the BT i-Plate that has both RF3 filter and 22mH choke

I have to say, I thought all along you were referring to the i-Plate ??

no I was referring to the faceplate of the new NTE5 as I think it was me that said that I read they had both installed..but it was my mistake, when i rechecked it was the i-Plate that had both installed...sorry

@ Black Sheep -  can you confirm that the newest/all BT supplied NTE5's are Openreach 'printed' on the top of the box (grey print)..? if so then I guess the only way to tell if you have the 26A then is to open it up...

@ c6em - I dont see any mention of VDSL in those SIN346 logs...? would have thought there was a revision which extended it to include VDSL..?

@ ANYONE - can anybody tell me the difference between passive (capacitor) and active (transistor) filters..? ive heard active ones arent as good or can fail quicker yet ADSLnation say that their filters are better than Pressac filters, well they rate theirs 5/5 and pressac 4.5/5

[Black Sheep]

Ha ha, Colin and Snadge. Not confused, I meant that from Snadge's description early in the thread, he was describing an i-Plate. But it was interesting to watch everyone smash their own NTE5's up to see what was inside. 

Yes Snadge, the very latest NTE's have the 'Openreach' logo printed on, as opposed to the previous embossed logo.