If you need to extend the range of your boat's marine radio transceiver, a high-gain vertical antenna may be a viable solution for your over-the-water transmitting. The VHF marine band is used for emergency or general communication, by the coast guard and pleasure-boater alike. Channel 16 is monitored for distress calls, and used to hail another craft. Once a non-emergency call is established, the interchange is switched to an agreed upon channel. Build a VHF vertical antenna with a collinear coil to boost your radio's range.
- Skill level:
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Things you need
- Twin-lead cable, 300-ohm, 20 inches long
- Wood dowel, 1/2 inch thick, 2 inches long
- Electrical wire, 20-gauge, 10 feet long
- Coaxial cable with connectors, 50-ohm, 10 feet
- Ring terminal lug, 20-gauge, solderless
- Power drill and 1/8-inch bit
- Wire-stripping tool
- Utility knife
- Tape measure
- Electrical tape
- Small piece of twine
Measure 1/2 inch from the end of the dowel, and drill 1/8-inch hole. Thread 38 5/8 inches of electrical wire through the hole. Wrap the excess wire tightly around the dowel 13 times. After the 13th turn, drill a 1/8-inch hole through the dowel and thread through the remaining wire. Measuring from the second hole, trim the remaining wire to 38 5/8 inches. Wrap electrical tape around the dowel to secure the wire turns.
Remove 1/2 inch of insulation from one end of the twin-lead cable. Twist the wires together, and solder the connection. This point will be the bottom of the antenna.
Measure 16 11/16 inches from the solder point, and trim the twin-lead cable to this length. Remove 1/2 inch of insulation from the left wire of the trimmed end. Remove 1/2 inch of both insulation and wire from the right side of the trimmed end. The left exposed wire should stick out 1/2 inch from the twin-lead end.
Strip 1/2 inch of insulation from one end of the electrical wire. Solder this end to the left wire of the twin-lead cable. Wrap electrical tape around the connection to protect the solder joint.
Measure 1 1/2 inches from the bottom twin-lead solder point, and remove 1/4 inch of insulation from both the left and right wires.
Cut a 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 twist the braid into a wire. Strip 1/4 inch of plastic insulation from the inner copper wire.
Solder the twisted braid to the right side of the exposed wire pair on the twin-lead cable. Solder the coaxial copper wire to the left side. Wrap electrical wire around this connection to protect the solder joint.
Crimp a ring terminal to the free end of the electrical wire, and tie a loop of twine to the ring. Hang the antenna from the twine loop.
Connect the free end of the coaxial cable to the external antenna jack of your VHF radio.
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