A top-loaded, inductively-coupled small antenna for HF ground wave transmission

An electrically small, top-loaded, inductively coupled antenna is proposed for HF ground wave transmission. An inductively coupled feed structure is used to step up the input resistance. The top loading is used to achieve small size and self resonance. The dimensions of the inductive coupling structure and the multi-armed, spherical helix top loading are designed using a genetic algorithm to ensure maximum coupling to HF ground waves. An antenna with a kr of 0.2 has been designed, built and tested at 30 MHz. The transmission performance shows improvements over a previous-generation antenna.