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How to Make an HF Antenna

High frequency, or HF, antennas are used by radio enthusiasts, the military, boat captains, aircraft pilots and television stations to receive and transmit signals. As Eric Johnson of New Mexico State University points out, HF signals provide global coverage, making it ideal for long distance communications. An HF antenna must be matched to the frequency of the signal it receives or transmits, but this can result in some types of antennas occupying up to 15 acres. Other designs are more compact.

Things You'll Need

Single strand insulated or bare copper wire
Tape measure
Wire cutters
Plastic terminal block
Electrician's screwdriver
Duct tape

Instructions

- 1
  Determine the frequency to which the antenna will be tuned. Divide 468 by the frequency, in MHz, to obtain the approximate length for a simple dipole antenna. For example, the popular 10m HF band has a center frequency of 28.30 MHz, so a dipole antenna must be 16.54 feet long -- 468 divided by 28.3 equals 16.54.
- 2
  Add 12 inches to the length of the antenna determined in Step 2. Cut a length of single strand insulated or bare copper wire to the resultant length. Fold the wire in half to determine the center point -- dipole antenna consist of two equal length wires, each half the length of the total antenna -- then cut the wire in half. For example, the wires for a 16.54 feet long dipole are both 8.27 feet long because 16.54 divided by 2 equals 8.27.
- 3
  Strip the insulation, if present, from the final 1/2-inch of one end of each wire. These are the ends that form the center point of the antenna. Insert the stripped ends into separate terminal holes in a plastic terminal block, then tighten the retaining screws with an electrician's screwdriver. Cover the terminal block with duct tape to prevent moisture, dirt and insects from getting between the wires.
- 4
  Mount the joined wires on a suitable frame to form a straight line with the terminal block in the middle. The ends of the dipoles can be bent out of line if space is limited. The mounting can be vertical or diagonal.
- 5
  Attach a length of coaxial 50-ohm or 75-ohm antenna cable to the terminal block and run the cable back to your tuner. The polarity of the connection is not important.

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