How to Build a Discone Antenna

Scribe a 42-inch-diameter circle and a 14-inch-diameter circle on the sheet metal, using the drafting compass. Press the middle compass needle into the metal, leaving an indentation to designate the centers of the discs. Cut these discs from the sheet using the tin snips.

Cut a radial line through the 42-inch disc from the outside to the center. Work the circular metal into a cone shape, wearing work gloves. Set the compass to a 60-degree angle, and place it inside the cone at the tip. Shape the cone until the inner angle is 60 degrees, matching the compass. Temporarily duct-tape the cone to this shape.

Drill three evenly spaced holes through the sheet metal along the seam of the outside of the cone. Insert machines screws through these holes and tighten the nuts, securing the cone permanently. Make sure the inner angle of the cone remains at 60 degrees.

Drill a 1/8-inch hole completely through the top of the cone, slightly below the tip. Snake the U-bolt through the holes so that both threads stick up.

Poke a small hole through the center of the 14-inch disc using the metal point of the compass. Position the disc on top of the U-bolt threads. The center hole should be directly above the tip of the cone. Mark the position of the U-bolt threads on the disc. Drill a 1/8-inch hole through the disc at each mark.

Cut the tip off the cone, leaving a 1/4-inch hole at the top.

Cut the connector from one end of the coaxial cable. Remove 1 inch of insulation from this end. Slice down the side of the braided sheath, and pull it back over the cable housing. Strip 1/4 inch of plastic insulation from the inner copper wire.

Thread the stripped end of the coaxial cable through the bottom of the cone, and up through the small hole in the tip. Spread the braided sheath around the outside edge of the cone, and solder it to the metal. Make sure the base of the copper wire is flush with the top of the cone.

Cut a 4-inch-diameter disc from the plastic bottle. Cut small holes in the plastic to accommodate the U-bolt threads and center coaxial wire. Slide the plastic disc over the U-bolt. This will insulate the cone from the copper disc.

Mount the 14-inch copper disc on the U-bolt, making sure the coaxial copper wire pokes through the center hole. Tie a loop of twine around the U-bolt threads, and tighten the nuts, securing the disc to the cone. The twine should be clamped under the U-bolt nuts. Bend the copper wire against the top of the disc, and solder it in place.

Hang the cone from the twine. Connect the free end of the coaxial cable to the external antenna jack on your VHF radio.