How to Make a Simple Antenna for FM Radio

Most store-bought radios have an internal antenna or an antenna made of a metal rod that telescopes into the radio. Neither of these give you good reception on the AM or FM band. If you listen to FM radio regularly, you can make a fixed antenna that will improve your reception. One of the simplest types of antenna you can build is a dipole antenna, which consists of two pieces of wire in line with one another and connected to a central feed.

Difficulty:

Moderately Easy

Instructions

Things You'll Need

• Stiff wire, 60 inches
• Ruler
• Calculator
• Wire cutters
• Plastic dog bone insulators
• Screws
• Wood block
• 300-to-75 ohm matching transformer
• Coaxial cable with F-type connectors

1. Calculate the length of the antenna. The formula for calculating antenna length in feet is 468/f, where f is the center frequency. The FM band runs from 88 to 108 MHz, and dipole antennas amplify a center frequency with the amplification factor decreasing on either side of the center frequency. Therefore, you need to use 98 as the center frequency to maximize your antenna function. The total length of the antenna is 4.77 feet, with each piece 2.39 feet.

2. Cut the stiff wire into two straight pieces each 2.39 feet long. Strip an inch of insulation from one end of each piece. Place a plastic dog bone insulator over the end and loop the wire through the holes.

3. Insert the screws into the wood block spaced an inch apart. Leave half an inch of the screw protruding from the wood.

4. Bend the noninsulated ends tightly around the screws and align the wires straight.

5. Place the terminals of the transformer around the screws and tighten the screws.

6. Connect the other end of the transformer to the coaxial cable.

References

• University of Hawaii; Antenna Design Length; 1999