Technical Discussion
  >> DSL Hardware Discussion


Register (or login) on our website and you will not see this ad.


Pages in this thread: 1 | 2 | 3 | 4 | 5 | 6 | [7] | (show all)   Print Thread
Standard User meditator
(fountain of knowledge) Wed 13-Jul-16 15:56:50
Print Post

Re: Whats involved with a fibre self install?


[re: Banger] [link to this post]
 
Yes, I hope the info I've provided is useful.

Looking again at the photos I took, I began to wonder whether the double-choke I mentioned was in shunt (across) with the AB terminals, rather than spurring off as series chokes. A shunt arrangement would mean that it'd be a transformer of a kind. But after then re-checking my Mk3 faceplate with an ohmmeter I was able to confirm that it's definitely not a shunt inclusion. Indeed, if it were, the choke(s) would rapidly burn out as soon as the 45 - 50v DC appears on the dropline AB terminals for the phone (the chokes are made from very fine-gauge wire).

Here's another practical issue to consider. For anyone thinking of acquiring a Mk3 plate to use and who might already be using an earlier issue NTE5 with brass threaded fixings (I mean the outer pair of holes, not the inner pair) do take care to obtain the correct machine screws. Suppliers of the plate often provide a set of screws - some self-tappers, others threaded - but invariably supply the wrong size, for the threaded ones. What you'll need instead are a pair of M3 x 35mm long machine screws, either countersunk head or cheesehead. The 35mm includes the head of the screw. These can be bought quite cheaply from various suppliers on Amazon, if necessary. If you don't have the correct length of machine screws you won't be able to hold all three faceplate components together. The NTE5 main body of course is normally fixed to the surface-mount or flush backbox with a short pair of M3.5s (not M3s), using the inner pair of holes. If you don't happen to have threaded inserts as the outer fixdowns of the NTE5 ensemble, really your only option is to use the self-tappers but, if you do that, in time the fixdown may well loosen and then fail to keep all three sections together. And if you're especially unlucky you might even crack the surrounding plastic. If you force the self-tappers into the threaded inserts, the fixdown is kinda ruined for good. So I'd advise that you avoid all of that; if you've threaded inserts get the correct screws. I've always felt it was a bad move when Openreach stopped using the brass threaded inserts, and in fact in other respects the general quality of all these components has, in my view, dropped quite noticeably in recent years. The same sort of care re screws would need to be taken if instead you choose to use a Clarity or an ADSL Nation faceplate. Clarity seems to have stopped trading but they used to make a specific point of supplying correct screws for their faceplate. The Clarity faceplate is, I believe, still available from Solwise.
Standard User Arksun76
(newbie) Wed 13-Jul-16 16:44:11
Print Post

Re: Whats involved with a fibre self install?


[re: meditator] [link to this post]
 
I didn't know about the length of them, though I had heard some people say when they bought the MK3, that the supplied screws weren't the correct thread type for their particular NTE5.

However the one that I bought off Amazon came with 2 sets of screws so that wasn't an issue. I guess some people are selling them with just 1 set and others with 2 sets of screws.
Standard User Banger
(eat-sleep-adslguide) Wed 13-Jul-16 19:47:18
Print Post

Re: Whats involved with a fibre self install?


[re: meditator] [link to this post]
 
Yes very useful indeed.

The ADSLNation plate I currently have came with machine screws so that was extremely handy. Can't remember what I did with the original fittings.

Tim
www.xilo.net & freenetname
Billion 7800 on 24 Meg LLU
http://www.thinkbroadband.com/speedtest/results.html...


Register (or login) on our website and you will not see this ad.

Standard User meditator
(fountain of knowledge) Thu 14-Jul-16 10:31:31
Print Post

Re: Whats involved with a fibre self install?


[re: Banger] [link to this post]
 
Getting back to the extra little filter that's now incorporated into the Mk3 faceplate - the filter that now operates on the A and B lines going to the modem - I think I've now fathomed its nature. It is a 'double-choke' of a kind but more accurately is a pair of toroidal windings. One winding comes from the A side of the incoming dropline, the other winding comes from the B side. The output sides of these windings then go to the two innermost pins on the RJ45/RJ11 jack-socket on the front top of the faceplate, as well as to the user-usable IDC. That central pair is then the pair that go to the modem. The two windings are put on to the toroidal core in opposite directions. This is what electrical engineers regard as a passive 'common-mode rejection device'. The idea is that any sporadic noise impulses picked up on either the A or B side of the Openreach dropline will get induced into the other side, but because the windings are wound in anti-phase, the impulses will then largely cancel each other out.

This little toroidal filter will have been designed to curb only the upper parts of the ADSL/VDSL spectrum, I feel sure, and my guess is that it was added by Openreach to assist lines that are plagued with transient noise picked up on the A or B line at or in the vicinity of the user's premises. For already noise-free lines, I don't see that inclusion of this tiny bit of filtering would cause an increase in speed performance, as I believe some people elsewhere on the Web have claimed. After all, it amounts to a series inductance on each side. In my view, it'd either leave the speed unaffected or would cause a small decrease in speed. However, for those lines where there's a lot of sporadic noise around (and the modem as a result disconnecting regularly), it could well clean up the AB pair sufficiently to recover a bit of increased speed.

Actually, while looking at the bits of tracking on the Mk3's circuitboard associated with this toroidal filter, I noticed that the pin connections on the RJ45/RJ11 are different to what they are in the Clarity faceplate. That's to say, on the Mk3, the A side connects via its winding to contact 4 on the RJ45 (looking into the RJ45/RJ11 jack-socket), whereas on the Clarity the A side connects to contact 5. Now, it's many, many years since I last considered the TIA pinouts on RJ45 connectors but I do recall that at one stage it was said that some modems were sensitive to input polarity. However, I can only conclude from what I've now found that contacts 4 and 5 are interchangeable nowadays, as far as modems are concerned. In other words, the modem connection must surely be a completely balanced arrangement and is not polarised in any way. The fact that some modem manufacturers appear to supply RJ11 modem leads with straight-through connections end-to-end but others supply a lead with the connections in them crossed over would seem to support the idea that these days it doesn't matter about polarity. If anyone here has superior knowledge on this, do please comment.

Edited by meditator (Thu 14-Jul-16 10:39:48)

Standard User richi
(regular) Fri 15-Jul-16 10:27:27
Print Post

Re: Whats involved with a fibre self install?


[re: meditator] [link to this post]
 
Thanks for the info, meditator. I've just gone and bought one for £9.50 from an Amazon Marketplace seller, Plutodirect. Worth a try to fix my occasional SHINE issues.

3 km line on THTG: 14500/1020 Mb/s with Pulse8
Pages in this thread: 1 | 2 | 3 | 4 | 5 | 6 | [7] | (show all)   Print Thread

Jump to