How to Build a Collinear VHF Vertical Antenna

Written by adam quinn
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How to Build a Collinear VHF Vertical Antenna
Boost your marine radio's signal strength with a collinear VHF antenna. (sport fishing boat image by Wimbledon from Fotolia.com)

The U.S. Coast Guard recommends that boats be equipped with a VHF radio for distress calls and general communication. Channel 16 of the marine band is the standard channel that boaters should monitor, and should use for emergency calls and initial contact when hailing other boats. A collinear antenna's stacked-coil design will boost your radio's transmitting distance across open water by boosting the signal's strength.

Skill level:
Moderate

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Things you need

  • Twin-lead cable, 300 Ohm, 20 inches long
  • Electrical wire, 20 gauge, 10 feet long
  • Wood dowel, 1/2 inch thick, 2 inches long
  • Coaxial cable, 50 Ohm, 10 feet
  • Coaxial connector
  • Ring terminal lug, 20-gauge, solderless
  • Power drill and 1/8-inch bit
  • Wire-stripping tool
  • Utility knife
  • Tape measure
  • Electrical tape
  • Pliers
  • Permanent marker

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Instructions

  1. 1

    Measure 3/8 inch from the end of the dowel and drill two 1/8-inch holes through the dowel, 1 1/16 inches apart.

  2. 2

    Measure and mark 38 5/8 inches from the end of the electrical wire. Thread this length of wire through a hole in the dowel, and then tightly wrap the electrical wire around the dowel 13 times. After the 13th turn, thread the remaining length of wire through the second hole.

  3. 3

    Measure the electrical wire from the second dowel hole, and trim it to 38 5/8 inches. Strip 1/4 inch of insulation from the wire end. This end will be soldered to the twin-lead cable.

  4. 4

    Strip 1/2 inch of insulation from one end of the twin-lead cable. Twist the wires together, securing the connection with solder. This will be the bottom point of the antenna.

  5. 5

    Measure 16 11/16 from the solder point, and trim the twin-lead cable to this length. Strip 1/2 inch of insulation from the left wire of the trimmed end.

  6. 6

    Measure 1 1/2 inches from the solder point, and remove 1/4 inch of insulation from both twin-lead wires. This will be the connection point for the coaxial feed line.

  7. 7

    Solder the end of the electrical wire to the exposed left wire of the twin-lead cable end. Wrap this connection with electrical tape to protect the solder joint.

  8. 8

    Strip 1 inch of insulation from the end of the coaxial cable. Slice down the side of the braided insulation, and twist the braid into a wire. Remove 1/2 inch of plastic insulation from the inner copper wire.

  9. 9

    Solder the coaxial copper wire to the exposed wire segment on the left side of the twin-lead cable. Solder the twisted braid to the right wire segment. Wrap electrical wire around the solder joints.

  10. 10

    Crimp a ring terminal to the free end of the electrical wire. Hang the antenna from the ring terminal.

  11. 11

    Crimp a connector to the free end of the coaxial cable that will fit the external jack on your radio receiver. Connect the antenna to the radio.

Tips and warnings

  • Weatherproof the antenna by mounting it inside a length of PVC tube, capping the ends.

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