The design process and construction method of a strip line is described for measuring radiated susceptibility of vehicular components having electrical cables more than 2 min length. he characteristic impedance of the trip line was determined 90$Omega$ to obtain the field uniformity of $leq$${pm}$3 dB in the frequency range from 100 kHz to 500 MHz. Tapered coaxial lines were used instead of the traditional lumped circuit element for the impedence matching units, therefore, the strip line has high power capability. Using these techniques, the field uniformity and power capability of a strip line could be considerably improved.