Copper Clad Steel "CW1308"

[Peter Crosland]

He stated he had shortened the drop wire that is the BT side of thinngs. He may well know what he is doing but if he does have to get BT involved then they have every right to charge him.

[Peter Crosland]

Don't be silly! The point I was making is thta even people as expereinced as the OP have no right to interfre with BT property. In my expereince BT can, and wiil, charge if they have to put right what the customer has done. My comment was aimed more at those with less experience who might be tempted to try something similar. As for repeatedly Power cycling the modem repeatedly that will simply make matters worse by making the exchange equipment lower the speed.

[Dave Liquorice]

I very much doubt it. A resonance such as that would just remove (or enhance) a fairly narrow bit of bandwidth, not the 1 MHz or so that was clobbered here.

Yes it also doesn't use carriers with lots of "noise" like those that match the carriers of resonably strong MF transmissions:

That's from 2009, the upper end is now much better between 80 and 100 symbols/carrier and the only really noticeable notches are at 693 R5 Live and 810 R.Scotland.

A power cycle will force a retrain of the modems each end, no need to repeat it. Indeed if you do the system might notice and knock back your BRAS rate, you then have to wait for that to, hopefully, automagically recover.

[The Other Mike]

Could you not use jelly filled IDC's, conected to a short length of proper copper to remove the chance of corrosion?

Someone working for Openreach might let you have a handfull for a beer token

[fred]

In article , The Other Mike writes

In a similar vein I was going to suggest a screw terminal to IDC junction box (mini BT style) with vaseline or silicone grease on the screwed conns. IDC for the copper.

I note the scotchloks are only specified for copper conductors so a jelly smeared screwed connection may be more reliable.

[Andy Wade]

Hmm, it might only be 3-5 microns - that's a common sort of plating thickness for appearance and protection. Fakers won't use any more copper than they have to. For most of the current to flow in a copper layer it needs to be several skin-depths thick - two or three, anyway - and that means hundreds of microns at the frequencies of interest, so the steel will have an adverse effect. This is becoming an academic discussion though; I don't the RF resistance of the conductors is very relevant...

Hypothesis: as some contributors have said, the steel won't work well in IDC (incl. jelly-crimp) connectors - you won't get reliable low-resistance connections. If connection resistances are different in the A & B wires it will have an unbalancing effect on the line - allowing the common-mode broadcast interference to enter the wanted signal path. (Discuss.)

You could try a common-mode filter (choke) such as the BT80A-RF3 (or an iPlate, which contains the CM choke component as the aforesaid block terminal.

I don't buy any of this stuff about resonant antenna lengths. We're talking about a 3m change where the wavelengths of the interfering signals are 100s of metres.

[Peter Crosland]

AIUI, and I am open to correction, the choke in the latest front plate is wired to reduce RF pick up on the bell wire not the incomimg line. As for the resonant antenna length that is what we are talking about the total physical length. Altering that can make a difference. The worst mistake anyone can make in fault finding is to say that "It can't be that".

[Andy Wade]

Not quite sure what you mean by "the latest front plate" but in the iPlate it's both. There's a bifilar-type common-mode choke for the thro' line pair (pins 2 & 5) and a separate 22mH inductor in series with the bell-wire (pin 3). The details are all in BT's patent, no. GB2445212.

[Graham.]

I would expect a tone tracer to pick up hash from an ADSL twisted pair at more than two inches. Same if the line was carrying BRI. Likewise an Ethernet cable. Perhaps my tone receiver is more sensitive than yours.

[tony sayer]

Me neither .. after all its survived miles of BT's best string then for a few feet of cable to screw it over;?..

[The Natural Philosopher]

what can happen is that other stuff feeds in to the line post domestric install point - for example a cable chafing and contacting a steel bulding frame or some such, or a notch filter formed out of some equipment in the house.

[Dave Liquorice]

Yers, the dropwire does have three steels in it or if not steel damn hard and strong, they have brassed look. I just picked up the (copper) pair that BT are feeding from the pole top. If I'd found them using the steels I would have got 'em out to fix it, I'm not into climbing poles...

[Dave Liquorice]

interfering

With paralleled extension wiring and multiple filters all manner of resonant stubs can exist. Though at the likely lengths the effective frequencies are going to be around tens of MHz rather than up to 1 MHz.

Not the case here, dropwire > NTE > single pair through house > filter > ADSL modem and POTS.

[Dave Liquorice]

I wouldn't that indicates "leakage" from the balanced pair which shouldn't happen to any great extent and when you have 20 50 200 pairs all bundled together lots of mutal interference.

Having just played around a bit more it may just be detecting the general 50 Hz induced mains buzz/hum. Every wire I approach is "humming", be that phone, ethernet, mains. Even wires that are not connected to anything but a much lower level compared to wires that are in use...

[Peter Crosland]

I was referring to the latest version that BT fir for customers that have FTTC service. I have not had the opportunity to look inside but I was assured by an experienced BT engineer who is broadband trained, that there was not an equivalent inductor to that fitted to the RF3 in the latest version of the NTE5. So now there are two directly conflicting accounts.

[Dave Liquorice]

You don't know how close you are to the orginal problem with that statement.

When I repodged one of the junctions the other night I sort of noticed that the ends of the unused pairs where "close" to one of the screw terminals. Had a fiddle, deliberatly connected one wire from one of the unused pairs to the A wire of the line. Instant speed drop and lots of MF interference. Remove it and modem doesn't notice, at least not in a few minutes time frame. Manual resync good speed, bung the wire back on instant drop... So that's the orginal problem solved. B-)

That night it still wasn't as good as it was though, left it through last night as well and again a larger than normal drop in SN ratio. The daytime symbols/carrier plot shows big dips at 693, 810 and 1053 kHz, 45 dB loss and a SN ratio varying. from 8 down to 3 dB. Stable sync at a tad over 6000. Night SN was getting down to 0 dB, that's not how it was.

This morning swapped out the CCS for a copper pair in one of the Cat5's. Still a large dip at 693 kHz, the one at 810 has more or less gone and 1053 is now much broader (there are three MF stations close together around there) and not as deep. 44 dB loss and much more stable SN at 6 dB and (daytime) sync a tad over 7000. That's more like it.

Will be interesting to see what happens tonight, I expect it will resync down to something over 6000 as that was "normal". At this stage it very much looks like CCS knocks the edge of ADSL for what ever reason. This is about 10 yards of CCS in between the NTE and about 40 yards of internal, proper, CW1308 that runs on a convoluted route through the house to filter/ADSL modem and POTS equipment. Single pair only all the way.

I noticed CCS "telephone cable" in one of CPCs offer flyers the other day, Pro-Power 100m 3 pair white £8.00. By comparison Pro-Power 100 m

3 pair white CW1308 (copper) £26.94. For the CCS they do quote a conductor resistance of

[fred]

In article , Dave Liquorice writes

[Andy Wade]

Ah, googling "vdsl faceplate" is quite revealing. There is indeed a new i-plate style filtered faceplate for VDSL (FTTC) and ADSL. This looks like the death-knell for the microfilter - and about time too. Using the interstitial concept opens the door to a (legit) self-installed filtered faceplate installation. FTTC self-install must be on the way...

According to

it does provide common-mode filtering, in addition to the longitudinal low-pass filtering for the phone o/p. There are three double-wound coils visible in the photo, neatly colour-coded for correct insertion on the PCB.

[Andy Burns]

[tony sayer]