How to Make an Efficient VHF Antenna
The VHF radio band has become a standard in recreational boating communication. Originally developed for emergency and official marine correspondence, with the increase of pleasure boating, VHF radio is also used for friendly conversation on designated channels. Whether for emergency use or a social interchange, a VHF radio needs an efficient antenna. Build this antenna from a few parts obtainable from your local electronic store and hop on the airwaves during your next pleasure cruise.
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Things You'll Need
- Twin-lead cable, 300-ohm, 5 feet long
- Coaxial cable, 50-ohm, 6 feet long
- Soldering iron and solder
- Wire stripping tool
- Utility knife
- Electrical tape
- Coaxial cable crimping tool
Instructions
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1
Strip 1/2 inch of insulation from one end of the twin-lead cable. Twist and solder together the exposed twin-lead wires to form the bottom of the antenna.
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2
Measure 50 5/16 inches from where the soldered wires meet, and cut the twin-lead cable.
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3
Strip 1/4 inch of insulation from both twin-lead wires, 1 1/4 inches from where the soldered wires meet. These exposed wire segments will be the connection for the coaxial feed line.
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4
Measure and mark 16 3/4 inches from the soldered wires. Cut out a 1/4-inch section from the right twin-lead wire. Cut both the insulation and wire, leaving a gap on the right side of the cable.
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5
Strip 1 inch of the outer plastic sheath from a coaxial cable end. Pull the inner braided sheath back over the cable. Strip the inner plastic insulator, exposing 1 inch of the inner copper wire.
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6
Solder the coaxial copper wire to the left exposed feed line segment of the twin-lead that you stripped earlier. Solder the braided sheath to the right exposed feed line segment. This right feed line segment should be on the same side as the 1/4-inch gap in the wire.
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7
Secure the soldered coaxial cable end to the twin-lead cable with electrical tape. This will take the stress from the solder points.
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8
Crimp a connector to the other end of the coaxial cable appropriate for the external jack of your VHF receiver.
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9
Cut a small hole at the top of the antenna in the insulation between the twin-lead wires. Tie the antenna to a coat hanger with a piece of twine threaded through this hole. Hang the antenna either at your home or on your boat.
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Tips & Warnings
Apply silicone sealant to where the coaxial cable is soldered to the twin-lead to prevent moisture from seeping into the cable.
References
- Photo Credit antennes bateau image by Marc Rigaud from Fotolia.com
