How to Make a Powerful Homemade FM Antenna

This rooftop antenna demonstrates stacking to increase signal strength.

Antennas receive electromagnetic waves. The transference of electric current and the electromagnetic waves is a continuous flow. FM is an anagram for frequency modulation. FM technology focuses on transmitting the highest quality sound from FM radio stations to radio receivers. You can make an FM antenna easily. Understanding the continuous flow of electromagnetic waves and electricity will help you get strong signal strength from the homemade FM antenna.

Things You'll Need

• 3 meter long wire
• Antenna
• Insulating tape
• Radio lead wiring
• Wire strippers
• Duct tape
• Staple gun
• Staples
• Utility knife

Instructions

1. Determine the frequency of the FM channel you want to receive; the higher the frequency the shorter the length of wire to the antenna. As an example, an FM channel with a frequency of 95 to 98 needs a length of wire of 2.5 to 3 meters. The mathematical equation for this calculation is λ = v/f. You can also call the radio station and ask what the frequency is.

2. Select an antenna rod. This can be any piece of metal from a wire coat hanger to a car antenna to a rebar.

3. Splice the protective coating back 1 inch off the end of the wire. Use a pair of wire strippers for this task. A utility knife can easily cut too deep and splice the wire, making the wire useless. Wrap the exposed wire around the material you selected to use as an antenna. For this project we will use a wire coat hanger. Wrap the wire around the hanger as tightly as you can.

4. Pick up the other end of the wire and split the wires, separating the two colors. Be careful not to cut through the wires; just cut back the protective coating and pull the wires apart.

5. Arrange the split wires against a wall and staple them to it with a staple gun. The location on the wall is not important. You may want to take into consideration the aesthetic value of the placement of the wires. You can also use duct tape to attach the wires to the wall.

6. Increase the strength of the FM antenna by stacking the front-to-back ratio. What this means is that you need to build 2 antennas; one for the front and one for the back ratio. The desired signal will arrive at the front antenna before it reaches the back antenna, which means the wire has to be 25 percent longer on the front antenna than the back antenna. By cutting the wire to the front antenna 25 percent longer, the desired signal arrives at the output terminal from both antennas at the same time. This boosts the power of the FM antenna.

Tips & Warnings

• FM radio antennas have a tendency to attract external interference. The more stacking you do, the less the interference will bother your FM reception.

• Rooftop antennas attract lighting; make sure to ground any antenna placed on a rooftop.

References

• Fcc.gov: FM and TV Channel / Frequency conversions
• Kyes.com: Fundamentals of Antennas
• Kgnu.org: Help with KGNU's FM signal

Resources

• Read this Article in Spanish
• Weru.org: Improving Your Reception