An antenna comprising: a hollow conductive chamber having an upper end and a lower end, wherein the lower end is open; a shorting strap electrically connected to the upper end; a conductive center member running through the chamber and electrically connected to the shorting strap; a conductive ground plane having a top surface and a bottom surface, wherein the top surface is separated from the lower end of the chamber by a gap; and a first solid insulator connected to the chamber and the top surface of the ground plane such that the first insulator fills the gap and fills the lower end and an interior portion of the chamber.