We present in this paper the design and realisation of two autonomous, ultra wideband radiation sourcesconsisting of a high gain broadband antenna driven by two subnanosecond pulsed power sources. Each one ismade of a Marx generator and a pulse forming device based on the use of gaseous spark gap. The main pulsedsource is a ten stage subnanosecond Marx generator which delivers pulses in the range of 250 kV/1.5 J, with a300 ps rise time, subnanosecond pulse duration at a pulse repetition frequency of 350 Hz. The antenna combinedwith the pulsed source is a travelling wave antenna called Valentine antenna. Some mechanical modiflcations weremade to improve the dielectric strength of this radiation element. A 3D model of the antenna, on a time domainelectromagnetic software, was flrst performed to study the in°uence of these modiflcations on the main radiatingcharacteristics of the antenna. Its high gain and its capability to radiate short pulses without dispersion allow usto achieve a high measured flgure of merit.PACS numbers: 84.70.+p, 07.57.Hm, 84.30.Ng