A reduced size helical antenna

Conventional axial mode helix antennas offer wide bandwidth, high gain, and circular polarization. They are in widespread use at UHF frequencies. Their physical size, however, can become excessively large at lower frequencies. In this paper we present a new design of the helical antenna, termed the stub loaded helix (SLH), which offers a substantial size reduction over a conventional axial mode helix without sacrificing performance. For the same number of turns, a stub loaded helix offers a 4:1 reduction in overall size while maintaining comparable gain performance. The usable bandwidth ofthe stub loaded helix is less than the conventional helix design (25% versus 50%) due to reduced axial ratio performance of the stub loaded helix.