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How to Calculate VHF Radio Antenna Length

An antenna's length determines the radio frequencies it receives.
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In radio frequency (RF) terminology, the Very High Frequency (VHF) range is the signal spectrum from 30 to 300 megahertz (MHz). To receive a specific VHF signal, you simply need a dipole antenna. Comprised of two lengths of wire or other conductive metal, a dipole antenna's shape allows the incoming signal's electromagnetic field to induce an alternating current (AC) within the antenna's material. To ensure the best possible reception of a given frequency, the total length of the antenna must be equal to one-half of the signal's total wavelength.

Decide which frequency you want the antenna to receive. Express the frequency in megahertz (MHz).

Multiply this frequency by 1,000,000 to convert its units to hertz (Hz).

Divide 299,792,458 meters/second (m/s, the speed of light) by the frequency in hertz (Hz). This will give you the signal's wavelength in meters.

Divide this wavelength by 2. This result represents the combined length in meters of the entire dipole antenna.

Divide by 2. This is the length that each of arm of the antenna must be in order to properly receive the signal.

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