In Electronic Warfare, and more specifically in the domain of passive localization, accurate time synchronization between platforms is decisive, especially on systems relying on TDOA (Time Difference Of Arrival) measurements. This paper investigates this issue by presenting an analysis in terms of synchronization performance of an experimental passive localization system based on off-the-shelf components. This system is detailed, as well as the methodology used to carry out the acquisition of real data. This experiment has been realized with two different kinds of clock. The results obtained in the two cases are compared through the analysis of their Allan time deviation. The choice of this metric is explained and its properties are discussed in the scope of an airborne bi-platform passive localization context. Conclusions are drawn regarding the overall performance of the system.