Modern electronics and radio interference

Depends on the frequency used. Certainly with HF frequencys because the overhead telephone cabling is basically a f****ng great long wire antenna.

Even an 'open circuit' can, under freak conditions still pass the ADSL signals while the phone might appear dead.

True, but not germane to the point. That open circuits by themselves do not create intermodulation.

Yep, that's what happened to mine while I was still on adsl. And the phone service was completely dead with the adsl still working fine. And it doesnt take freak conditions, just no DC path.

TNP's point, AIUI, is that a corroded circuit might act as a semi-conductor under the right circs. Nothing to do with semi-conductors elsewhere.

I was thinking the same:

I've seen both copper oxide and selenium rectifiers in old radios.

And copper is generally the preferred conductor for telephone wires. I get tired of correcting so many of TNP's assertions.

There is no doubt that corroded circuits can generate intermodulation distortion. However, an rf driver which is highly linear when loaded with the expected load impedance might become very non-linear when its output is open circuited as the output voltage will approximately double and it will be working well outside its intended operating range. As for the other comments - I have heard noise on an analogue phone which I attributed to some kind of intermodulation effect from adsl. It might however been caused by non-linearities in the electronics of the phone itself rather than corroded connections. I have also experienced a non-working analogue phone with working adsl. The adsl download speed was roughly halved however. It took BT 5 days to fix this. They had spent a whole weekend miswiring the local exchange while making preparations for VDSL. John

In my day,we used Selenium rectifiers as a matter of course. They stink like a fart when overheated.

Thank you for confirming my assertion in this case, that a corroded copper oxide joint acts like a rectifier.

Probably. Long time since I saw one.

Correct. It happened here when a neighbour had trimmed a tree. One of four lines severely damaged but the rest of the drop wire left intact and in place. The BT engineers could see a small reflection on the line and had narrowed it down to the drop-wire - but it looked so OK that they left without solving the problem.

And that afternoon I needed to call 999. A real Sod's law case. Must have been that final, frustraded shake of the drop wire by the engineer that severed the final strands of the conductor.

PA

The connections in a punch-down block are gas-tight.

There's not supposed to be any oxide.

Similarly, for things that don't involve punch-down blocks, there are gel-connectors, where the metals are protected by whatever is in the gel.

Telecom does seem to have some idea of chemistry.

Now, when telephone wiring gets inside a home, we switch to consumer grade materials. Now you can have oxide (as I had here), on a telephone connector box near the floor.

This is why, if you have issues with ADSL, you should consider the possibility it is the house wiring doing it. I got improved signal quality when I removed the previous rats-nest of house telephone wiring.

For my boss, his bad signal was caused where the ADSL cable went through the concrete foundation. That's the wire he had to replace

Paul

HomePlug AV2

It does not look like they've stopped.

They've even mixed Wifi and PLC in the same plastic box.

The connections in a punch-down block are *supposed to be* gas-tight.

The metals are *supposed to be* protected,

And Openreach engineers who serviced my line on upwards of a dozen occasions *always* talked about 'remaking corroded connectors'.

I don't see what there is any argument. Connectors fail, air and water get in, the copper corrodes and you get crackles and partial rectification. That partial rectification ends up mixing RF down into the audio band as broadband 'hiss' and generally muddying up the carrier bins the broadband wants to use spilling their contents over into other bins, which reduces the signal to noise ratio.

Ergo if you have low attenuation but high noise, its 99% of the time a corroded connector.

The only other fault I had was in the exchange DSLAM. But they are in the warm and dry and generally reliable as are the frames used to do the final connection to them.

I have now had a written detailed breakdown of the work carried out by Openreach to resolve my Internet connection issue ( upload speed is now flaky but adequate for my use).

It seems to include several termination remakes but the solution of by-passing a section of faulty overhead is not recorded.