If you cannot afford an expensive commercial antenna, a long piece of wire and a homemade antenna tuner may be sufficient for transmitting and receiving on the amateur radio bands. An antenna tuner transforms the antenna's impedance, or resistance to electrical current, to a level that matches the radio transceiver. A long-wire antenna can be tuned to resonate at multiple short wave frequencies, maximising the power and distance at which the transceiver can operate. Communicate with amateur radio hobbyists around the world with an efficiently tuned antenna.
- Skill level:
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Things you need
- Plywood board, 6 inches square, 1/2 inch thick
- Variable capacitor, 365 pf, air type
- PVC pipe, 1 inch by 3 inches
- Magnet wire, 24-gauge, 5 feet
- Electrical wire, 16-gauge, 18 inches long
- 2 machine screws, 1/4 inch by 1 inch
- 4 machine screw nuts
- Alligator clip
- Wire-stripping tool
- Power drill, 1/4- and 1/8-inch bits
Drill two 1/4-inch holes side by side in a corner of the board. Insert screws through the bottom of the board, threads facing up. Secure a nut on each screw.
Drill two 1/8-inch holes in the PVC pipe, 1/4 inch from one end. Thread the magnet wire through the holes. Wrap the wire tightly around the tube 150 times, twisting the wire into a loop every 10 turns. Drill two 1/8-inch holes after the 150th turn, and thread the wire through the holes to keep the wire from unravelling.
Sand the insulation from the twisted wire loops to expose the wire contacts. Trim back the magnet wire, leaving 2 feet of excess wire at one end of the tube. Place a small amount of epoxy in the drill holes of the PVC pipe, permanently securing the wire ends in place.
Epoxy the PVC pipe to the board, standing it vertically in a corner adjacent to the screws. Epoxy the capacitor to another corner of the board, with the tuning knob facing out.
Cut the electrical wire into three 6-inch lengths, and strip 1/2 inch of insulation from the ends. Solder a wire to the rear frame of the capacitor, and twist the other end around a screw. This screw will connect the ground wire.
Solder another wire to a metal tab on the side of the variable capacitor. Twist the free end of the wire around the empty screw. This screw will connect the antenna.
Crimp the alligator clip to one end of the remaining 6-inch wire. Twist the free end around the antenna screw, and clip the other end to a loop on the PVC pipe.
Attach the antenna and ground wires to the corresponding screws. Tighten a second nut to each screw, securing the wires in place.
Strip 1/2 inch of insulation from the end of the excess magnet wire, and connect the wire to the external antenna jack of your radio transceiver.
Tune the antenna by adjusting the capacitor knob and attaching the alligator clip to different loops on the PVC pipe.
Tips and warnings
- Ground the radio and the tuner to a cold water pipe.
- Hang the antenna outdoors for better reception.
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