An ultrawideband (UWB) antenna has been developed for operation in the 60 MHz to 18 GHz frequency range. This antenna is a new type--an offset bicone/dipole design that allows for vertically polarized omnidirectional coverage over an instantaneous 300:1 bandwidth. Numerical electromagnetic simulations with the finite-element method (FEM) were used to investigate the antenna concept and optimize geometry prior to fabrication. Measurements both outdoors and in an anechoic chamber confirm the antenna's performance.