Antennas

Quarter Wave Ground Plane (1)

  • A half wave dipole cut in half and standing on a mirror would look like a full dipole
  • The mirror can be the earth, a metal sheet or a number of radials as shown above
  • Feed point impedance is about 35Ω and is unbalanced
  • At the base of a quarter wave antenna the RF current will be high and the voltage will be low (similar to the centre of a half wave dipole)
  • It can be fed with coaxial cable, the inner to the vertical radiator and the outer to the radials