Which of the following is a type of OCFD antenna?

  1. A dipole fed approximately 1/3 the way from one end with a 4:1 balun to provide multiband operation
  2. A remotely tunable dipole antenna using orthogonally controlled frequency diversity
  3. A folded dipole center-fed with 300-ohm transmission line
  4. A multiband dipole antenna using one-way circular polarization for frequency diversity