I've tried everything from #18 stranded to #10 solid. The difference can be measured, but in real life it means nothing.

If you're ground mounting, just as a Butternut vertical, let me offer this suggestion.

Find an electrician, telephone, or cable TV guy. Ask if they would save some ends for your you from jobs. Keep in mind, since it's wire you can take (2) 10-foot pieces and solder them together for (1) 20-foot radial. A buddy of mine gave me a whole box of scrap romex 12-2 that he had left over from a wiring job, so my wire cost was zero. Use a box cutter "carefully" to just put a slit in the center, and you can usually peal back the wires out of the jacket. Don't worry about taking off the black or white insulation.

I typically build with 10 to 40 radials. You could do the broadcast method and use 120, but I don't think you would see any appreciable difference. My butternut is installed with just 12 and it works just fine.

Trim your grass as close as you possibly can, to the point where you scalp it. Then, drive down your mounting pipe where the antenna will mount, and right next to it (by about 3") a copper ground rod.

Lay out your radials. Don't worry if some are longer than others. My back yard is rectangular, so radials that go to the corners are the longest. Lay them from the ground rod, and tie the wire onto the ground rod. You'll clamp them later. What I do to keep them straight is at the opposite end I'll tie the wire onto a 3-penny nail and press it into the ground. This just keeps the wire straight.

Using a flat spade, dig a slot next to the extended wire. Push down into the ground about 2", and then wiggle the spade back and forth till you have sort of a "V" in the ground. When you have this slot dug, you can then push the wire into the bottom of the "V" and press down on the dirt with your foot, and the dirt holds the wire in place.

When you get to the end where the nail is, remove the nail, and bury the end.

One all the wires are in the ground, dress down the end where the ground rod is located. All wires should come up, bare, into a clamp. If you have about 6"-9" of wire left, this can be the ground jumper to the antenna.

After all the wires are connected to the rod, and you have your jumper in place, coat the connection with Vasoline or spray it with WD40. You just want to keep that connection clean from corrosion.

The last step makes mama happy. Throw down a heavy application of grass seed over the area where the radials are located. After a while, the grass will take hold and grow, and then nobody will know you have radials in the ground. You can also mow over them, as long as they were stuffed down in the slit you made with the shovel. If you get the wires down at least 2" you'll be OK.

Also, what I did is make a 1' x 1' square piece of landscape timber, and the antenna and ground rod are inside the square. Then I filled it with pea gravel. A bag of that stuff is $2.49 at Lowes. This makes it look nice, and then when I'm trimming the grass with a weed-wacker, I don't hit the antenna or the ground rod/wires.

I've got two of these installations, on put in about 1988, and the other in 2000. Both cooking along just fine. And the cool thing is nobody but me knows the radials are under the ground.