We present in this paper the design and realisation of two autonomous, ultra wideband radiation sources consisting of a high gain broadband antenna driven by two subnanosecond pulsed power sources. Each one is made of a Marx generator and a pulse forming device based on the use of gaseous spark gap. The main pulsed source is a ten stage subnanosecond Marx generator which delivers pulses in the range of 250 kV/1.5 J, with a 300 ps rise time, subnanosecond pulse duration at a pulse repetition frequency of 350 Hz. The antenna combined with the pulsed source is a travelling wave antenna called Valentine antenna. Some mechanical modifications were made to improve the dielectric strength of this radiation element. A 3D model of the antenna, on a time domain electromagnetic software, was first performed to study the influence of these modifications on the main radiating characteristics of the antenna. Its high gain and its capability to radiate short pulses without dispersion allow us to achieve a high measured figure of merit.