A linearly-polarized ultrawideband dipole array antenna has been developed for coverage in the VHF/UHF frequency range for communications or radar applications. The antenna design utilizes a horizontally polarized array of thick tubular dipole elements above a ground plane. Numerical electromagnetic simulations were used to analyze and optimize the antenna parameters prior to fabrication. Measurements of a 24-element ultrawideband dipole array prototype in an anechoic chamber demonstrate the antenna's return loss and gain pattern performance over a wide bandwidth.