Sending a signal with one strand of wire.

A capacitor, by definition, has two conductors mutually isolated.
Having a single wire, totally isolated from everything else, including ground, is pretty much just as good as having no wire at all. You can send a signal using electromagnetic radiation but you don’t need a wire for that. If you want to have an actual flow of current you need to have two conductors of which one can be ground and the other can be any conductor isolated from ground. That does not detract from the concept that you need two conductors.

Coax cable has two conductors of which the shield is “at rest” and the central conductor “does all the work”. In other words, you do not have currents going in opposite directions but only the central conductor carries AC. This is called an “unbalanced” line.

With parallel conductors both conductors conduct in opposite directions and this is called a balanced line. To adapt a balanced line to an unbalanced line you use a balun.

He could be on a battery, in which case, gee whiz, no earth ground.

Well, my first thought would be “trip wire”, which is purely mechanical (spring loaded switch). Is there reason to believe it’s more sophisticated than that?

Doesn’t need one. At least not what one would normally think of as an Earth ground; for a FET circuit as I outlined, the leakage current through the air, through the table and/or through the user’s body is sufficient. There is a return path, but you don’t need to specifically supply one.

In normal (e.g. CATV) operation, a coax has currents flowing in both directions. One way on the center conductor, and the other way on the inside of the outer conductor. It can be unbalanced when you connect it to, say, a dipole antenna, because current can also flow on the outside of the outer conductor.

Bear_Nenno, I think you have to assume that yes, it can be used as a primitive command wire. I can’t prove that it could, but it seems plausible to me that there would be enough opportunity for current to flow through a single wire, with the circuit completed through capacitive coupling through the terminal device to the ground, to trigger an IED.

Exactly. Their isolation is equivalent to the lack of a return path.

It is possible, even in a perfect nonconducting vacuum. In the device on my end, I have something that strips electrons off of an isolated electrode, and shoves them onto the wire. I now have a positive charge on the electrode inside my handset, and a negative charge distributed along the wire. At the other end of the wire, put something that can detect the charge. Presto, there’s your signal.

That said, though, the amount of charge at the far end of the system would be absolutely minuscule, for any reasonable length of wire and charging device, and I doubt that it would actually be possible to detect it. It’d be much more practical to communicate in other ways: Completing the circuit through the ground or another wire, or tugging on it, or sending mechanical waves down the wire (the good old two-cans-and-a-string telephone), etc.

Right. Put another way, the isolation between the device and Earth ground represents the dielectric in a capacitor. The Earth is one conductor in this cap; the control wire is the other.

OK… maybe I’m misunderstanding it then.

Will a gold leaf electroscope, floating in a vacuum, signal a charge delivered to it along a single wire?

I should think so, yes. How long that wire can be before leakage bleeds the charge off to the point the leaves can no longer be pushed apart, I have no idea, however. I assume if the wire is also in vacuum, that can pretty well approach infinity, but we’re getting out of the range of my expertise here.

The wire is not running along the ground. It went up an existing pole about 20 feet and then across the street to another pole. From there it went from pole to pole until it was out of sight. The poles are normal electric poles. But this is definitely not an electricity wire. It’s just a single strand of bare copper wire. But it’s tide off every so many feet. So there is no way to tug on it or something like that. It’s definitely not mechanical.

Why do you say it is not electric? What makes you think that? Is it insulated? If it goes into the ground uninsulated then it seems it cannot carry electricity. But you have to be sure. It may be insulated and just look like it’s not. If it is resting on insulators but then goes down it just may be an old wire which has fallen at one point. It is really difficult to guess when you do not give details.

I think he means it’s not an electric power line, based on it being only “thread-thick”.

Maybe some of this gives you ideas.

Think of one of those touch lamps as a device receiving a command. Attach a insulated wire to that and when the wire is touched the lamp would go on. Add a high voltage from something like a piezoelectric starter for a grill and you could send a spark for a ways. The outside of the copper does tarnish and there is copper wire with enamel coating, both of which are insulators. A dry wood pole is also a good insulator. In other words I’m saying it could be isolated from grounding enough to treat it as insulated wire that will have little voltage drop the whole length of the wire. The wire could be a long antenna for transmission or receiving of radio waves. There are so many things a thin wire could be put to use for. Unless you find more pieces to the puzzle I don’t think you can determine what this is for.

I’m sure I recall reading about a true single-wire transmission scheme that operated with no ground return - when you apply a charge to a conductor, I think I’m right in saying that (subject to resistance, etc), that charge affects all of it - obviously if there’s no ground at the other end, you can’t pour charge in continuously, but you can modulate the adding and removing of it, and because that charge has to be distributed along it, that causes a measurable effect at (or near) the other end.

That’s my very non-technical understanding of it, anyway. If we can get an electroscope to signal at the end of a long single wire, then we can modulate whatever we did to cause that effect, enabling a signal to be sent.

The question is just too obscure and vague. There are worlds of difference between

  • Can I make something which when touched by a person will send a signal to a very short distance?

  • There is a long single wire hanging from posts. What could this be used for?

If you want any kind of meaningful answers you have to formulate your question well and provide all the details. It is bad enough that half the posters don’t know too much about the subjects we post about, if you make it worse by making the question vague and incomplete then you can get really crappy answers.

Are you having reading comprehension issues? The OP was clear in his first few posts. i.e. “There is a single strand of bare copper wire that is used to activate IEDs, how does this work electrically if normally a dual wire setup is required to send a signal?”

IED are set off by what appear to be single strand bare wires. According to the story these are used in pairs so there probably another single wire tracing a different route that is simply missing.

It makes total sense if they’re used in pairs. I’ve never seen the second one, so it’s always bugged me to think about. I keep going back and forth in my head from “I guess you can do it with one,” to “no way, you need two wires to send a signal”…
So after months of occassionaly thinking about it, I decided to post a question here. Thanks everyone!

This would have been my guess - just use it as a range booster for a simple radio switch. But from astro’s link it looks like my guess is wrong - again.

I’ll just add, the wire is unlikely to be uninsulated. It is probably the copper from a transformer or similar, coated with shellac so it still looks like bare copper but is insulated.