A random wire is exactly that—a piece of wire that’s as long as you can possibly make it. One end of the wire attaches to a tree, pole or other support, preferably at a high point. The other end connects to the random-wire connector on a suitable antenna tuner. You apply a little RF and adjust the antenna tuner to achieve the lowest SWR. That’s about all there is to it.
Random-wire antennas seem incredibly simple, don’t they? The only catch is that your antenna tuner may not be able to find a match on every band. The shorter the wire, the fewer bands you’ll be able to use. And did you notice that the random wire connects directly to your antenna tuner? That’s right. You’re bringing the radiating portion of the antenna right into the room with you. If you’re running in the neighborhood of 100 W, you could find that your surroundings have become rather hot—RF hot, that is! We’re talking about painful “bites” from the metallic portions of your radio, perhaps even a burning sensation when you come in contact with the rig or anything attached to it.
Random wires are fine for low-power operating, however, especially in situations where you can’t set up a vertical, dipole or other outside antenna. And you may be able to get away with higher power levels if your antenna tuner is connected to a good Earth ground. (A random-wire antenna needs a good ground regardless of how much power you’re running.) If your radio room is in the basement or on the first floor, you may be able to use a cold water pipe or utility ground. On higher floors you’ll need a counterpoise.
A counterpoise is simply a long, insulated wire that attaches to the ground connection on your antenna tuner. The best counterpoise is 1/4-wavelength at the lowest frequency you intend to use. That’s a lot of wire at, say, 3.5 MHz, but you can loop the wire around the room and hide it from view. The counterpoise acts as the other “terminal” of your antenna system, effectively balancing it from an electrical standpoint.