If you've ever lost your GPS signal while hiking under a canopy of trees or in a canyon, you may appreciate the need for an external antenna. A GPS receiver's accuracy is dependent upon the strength of the satellite signals. An external antenna can provide increased signal reception, circumventing sources of interference. Build this compact antenna and remain on course during your next hiking trip.
- Skill level:
Things you need
- GPS receiver with external antenna jack
- Plastic container, 227gr
- Aluminium baking tin, 9-inch diameter
- Circuit board, blank, glass epoxy, one-sided copper-clad, 1/16 inch thick
- Copper wire, insulation removed, 14-gauge, 8 inches long
- Coaxial cable, 50-ohm, 6 feet long
- Epoxy, fast-drying
- Mini saw, high-speed
- Utility knife
- Soldering iron and solder
- Permanent marker
Cut the copper wire into two 4-inch segments. Bend each wire 90 degrees at the centre.
Cut two 2-inch-long strips of circuit board 1/4 inch wide using the mini saw. Measure 1/8 inch from the end of one circuit board strip, and remove a 1/16-inch cross-section of copper using the utility knife. Place the knife tip at the top centre of the cross-section and pull the knife upward at a 45-degree angle, slicing off a small triangle of copper. This circuit board strip will be the active side of the antenna, and the other strip will be the ground side of the antenna.
Epoxy the two circuit board strips together with the copper sides facing out.
Cut a 4-inch-diameter circle from the bottom of the baking tin. Measure and mark the centre of the circle. This will be the base plate.
Drill or melt a small hole in the side of the plastic container through which the coaxial cable can be fed.
Strip 1/2 inch of outer insulation from the end of the coaxial cable. Slice through a side of the braided insulation and twist it into a wire. Strip 1/4 inch of the plastic shield from the inner copper wire. Thread this end of the coaxial cable through the hole in the plastic container.
Stand the sandwiched circuit board antenna perpendicular in the centre of the base, cross-section end down. Solder the antenna to the base plate, making sure to keep it standing at a 90-degree angle. Fix solder between the active side of the antenna and the base plate only.
Measure and mark a line 1 3/4 inches from the base plate to a point on both sides of the standing antenna.
Align the 90-degree corner of the bent copper wire at the 1 3/4-inch mark on the ground side of the standing antenna. One leg of the copper wire should be pointing down, parallel to the antenna, and the other leg should be lined up with the mark, perpendicular to the antenna. Tilting the bottom leg out from the antenna at a 45-degree angle, solder the wire to the strip, maintaining this angle.
Solder the remaining bent copper wire to the active side of the antenna using the same procedure as the ground side.
Trim the horizontal legs of both copper wires to 1 1/2 inches from the centre of the antenna strip. Trim the angled vertical legs to 1 13/16 inches from the centre of the antenna strip. Taking care not to break the solder joints, gently bend the vertical legs until the tips are 1/2 inch above the base plate.
Saw the excess circuit board from above the horizontal copper wire legs.
Solder the coaxial copper wire to the active side of the antenna above the cross-section. Solder the twisted braid wire to the antenna below the cross-section.
Seat the base plate in the lid of the plastic container, and fit the container on the lid.
Crimp a connector to the free end of the coaxial cable appropriate to the external antenna jack of the GPS receiver.
Tips and warnings
- An 227gr cream cheese container is suitable for the antenna enclosure.
- A second pair of hands may be needed when soldering the copper wires to the antenna at the 45-degree angle.
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