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DIY Hi-Gain VHF Repeater Antenna

A VHF repeater can extend local ham radio coverage by converting transmissions to a separate frequency and resending the signals, transmitting to distant radio receivers. Repeaters tend to be mounted at high elevations to maximize the transmission and reception coverage areas. A high-gain repeater antenna will extend the range of the repeater and provide local hams with long distance communication capabilities -- coverage that is otherwise inaccessible.

Things You'll Need

Electrical wire, 20-gauge, 10 feet long
Wood dowel, 1/2-inch diameter, 2 inches long
Twin-lead cable, 300-ohm, 20 inches long
Coaxial cable with connectors, 50-ohm, 10 feet long
Ring terminal lug, 20-gauge
Eye bolt, nut and washer, 1/8-inch diameter, 1 1/2 inches long
PVC tube, 1-inch diameter, 100 inches long
2 PVC tube caps, 1-inch diameter
PVC glue
Silicone sealant
Power drill, 1/8- and 1/2-inch bits
Soldering iron and solder
Electrical tape
Wire-stripping tool
Utility knife
Tape measure
Small piece of twine

Instructions

- 1
  Drill an 1/8-inch hole through the dowel, 1/2 inch from the end. Thread 38 5/8 inches of electrical wire through the hole. Wrap the remaining wire tightly around the dowel 13 times. After the 13th turn, drill a 1/8-inch hole. Thread the remaining wire through the hole. Trim the excess wire to 38 5/8 inches. Wrap electrical tape around the dowel to secure the wire in place.
- 2
  Strip 1/2 inch of insulation from one end of the electrical wire.
- 3
  Strip 1/2 inch of insulation from one end of the twin-lead wire pair. Twist the wires together and solder the connection. This will be the bottom of the antenna.
- 4
  Measure 1 1/2 inches from the solder point and remove 1/4 inch of insulation from both sides of the twin-lead cable. These exposed segments will be the feed line contact points.
- 5
  Measure 16 11/16 inches from the twin-lead solder point and trim the cable to this length. Cut a 1/2-inch gap from the right side of the trimmed end of the cable, leaving 1/2 inch of the exposed left wire sticking out from the end of the cable.
- 6
  Solder the exposed end of the electrical wire to the left wire at the end of the twin-lead cable. Wrap the solder point with electrical tape.
- 7
  Cut the connector from one end of the coaxial cable. Remove an inch of insulation from this end. Slice down the side of the braided sheath and twist the braid into a wire. Remove 1/2 inch of the plastic insulation, exposing the inner copper cable.
- 8
  Solder the twisted braid to the right side of the exposed twin-lead wire segments. Solder the coaxial copper wire to the left exposed segment. Wrap electrical tape around the connections to protect the solder joints.
- 9
  Crimp a ring terminal to the free end of the electrical wire.
- 10
  Drill a 1/8-inch hole in the center of one PVC cap and a 1/2-inch hole in the center of the other cap.
- 11
  Attach the eye bolt to the cap with the 1/8-inch hole. Thread the free end of the coaxial cable through the cap with the 1/2-inch hole.
- 12
  Tie the ring terminal end of the electrical wire around the eye bolt nut. The antenna should be fastened to the inner side of the PVC cap. Mount the antenna inside the PVC tube and glue the cap to the tube. Glue the other PVC cap to the open end of the tube, sealing the antenna inside. Seal the drill holes in both caps with silicone sealant.
- 13
  Hang the antenna from the eye bolt. Connect the free end of the coaxial cable to the repeater's external antenna jack.

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