EMC Question of the Week: June 14, 2021

Array of resonant dipole antennas

The length of a resonant half-wave dipole is  

  1. slightly less than a half-wavelength
  2. exactly one half-wavelength
  3. slightly more than a half-wavelength
  4. independent of the wavelength


The best answer is “a.” The length of a half-wave dipole antenna is slightly less than a half-wavelength at its resonant frequency. The precise length depends on the diameter of the dipole wire, but is typically about 0.47λ to 0.48λ. Thicker wires have lower resonant lengths.

The figure on the right shows an array of resonant dipoles used for direction finding. 

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