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How to Build a VHF Ground Plane With Thin Copper Sheets

If you're a boater seeking to improve your VHF marine-band radio signal, a ground-plane antenna made from copper sheets may be an effective option. The discone antenna design can be built using copper sheet metal shaped into a cone, with a ground-plane disc mounted at the tip. The discone's compact, bell shape may provide a stronger signal, and can be mounted as a decorative item on your boat.

Things You'll Need

Copper sheet metal, 5 feet square
Coaxial cable with connectors, 50-ohm, 10 feet long
Drafting compass
Tin snips
Work gloves
Duct tape
Power drill and 1/8-inch metal-cutting bit
3 machine screws with nuts, 1/8 inch diameter, 1/4 inch long
U-bolt and nuts, 1/8-inch diameter, 1 1/2 inches long
Permanent marker
Wire-stripping tool
Utility knife
Soldering iron and solder
Small piece of twine
Plastic 2-liter soda bottle

Instructions

- 1
  Scribe 13-inch- and 37-inch-diameter circles on the sheet metal. Press firmly on the middle compass needle to mark the center of each circle in the metal. Cut the two discs from the sheet metal.
- 2
  Cut a radial slit in the 37-inch disc from the outside edge to the center point. Shape the disc into a cone. Adjust the compass to a 60-degree angle, and set it inside the cone's tip. Work the cone to a 60-degree angle at the tip, matching the compass. Duct-tape the cone at this angle.
- 3
  Drill three equally spaced holes along the seam on the outside of the cone. Fit machine screws through the holes, and fasten the nuts. Make sure the cone remains shaped to 60 degrees. Remove the duct tape.
- 4
  Drill a 1/8-inch hole through the cone, slightly below the tip. Snake the U-bolt through the holes so that the threads stick up. Cut the tip from the cone, leaving a 1/4-inch hole in the top.
- 5
  Cut the connector from one end of the coaxial cable. Strip 1/2 inch of insulation from this end. Slice down the side of the braided sheath, and pull the sheath back over the cable housing. Strip 1/2 inch of plastic insulation from the inner copper wire.
- 6
  Thread the stripped end of the coaxial cable through the bottom of the cone, and out through the tip. Spread the braided sheath around the cone's outer edge, and solder it in place. The coaxial copper wire should point up at the center of the cone.
- 7
  Poke a small hole through the center of the 13-inch disc using the compass point. Set the disc on the U-bolt threads with the center hole directly above the coaxial copper wire. Mark the thread positions on the disc. Drill 1/8-inch holes through the disc at these marks.
- 8
  Cut a 4-inch-diameter disc from the plastic bottle. Cut small holes in the plastic disc to accommodate the U-bolt and the center copper wire. Slide the disc over the U-bolt and wire. This will insulate the disc from the cone.
- 9
  Mount the 13-inch metal disc over the U-bolt and center wire. Tie a loop of twine around the U-bolt threads. Tighten the nuts on the U-bolt, securing the twine and disc to the cone.
- 10
  Hang the antenna from the twine. Connect the coaxial cable to your VHF radio's antenna jack.

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