How to Calculate the Length of a Folded Dipole Antenna for 80 MHz

Written by brendan conuel
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How to Calculate the Length of a Folded Dipole Antenna for 80 MHz
The frequency 80MHz is close to that of FM radio. (radio image by Claudio Calcagno from

A folded dipole antenna is one of the simplest models of antenna designed for picking up electromagnetic radiation signals. It uses a single loop of wire bent back in on itself. Typically a folded dipole antennae resembles long, thin ovals. Calculating the optimal antenna length to pick up a certain frequency signal is fairly straightforward because antenna physics demand that the total length of wire used in the antenna be equal to one wavelength of the type of electromagnetic radiation it will be picking up. This means that the total length of the antenna (from tip to tip) should be equal to half the desired wavelength. By converting frequency (80MHz in this case) into a wavelength, you can thus obtain your antenna length.

Skill level:

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  1. 1

    Note the wavelength-frequency relationship for electromagnetic radiation:

    λ = c/f

    where λ is wavelength (in meters), c is the speed of light (about 2.998 x 10^8m/sec), and f is the frequency (in Hz).

  2. 2

    Convert the frequency 80MHz to Hz. One MHz is equal to 1 million Hz, so the following relationship holds:

    80MHz = 80 x 10^6 Hz = 8 x 10^7 Hz

  3. 3

    Plug 8 x 10^7 Hz in for f and 2.998 x 10^8m/sec in for c in the wavelength equation from Step 1. It should look like:

    λ = (2.998 x 10^8m/sec)/(8 x 10^7 Hz)

    Solve for λ. You get a value of about 3.747 meters.

  4. 4

    Divide your λ value by 2 to obtain the tip-to-tip length of your folded dipole antenna. You should get about 1.874 meters--a little under six feet, two inches.

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