I. Introduction
In 2010, the CNRS (French National Center for Scientific Research) and the GdR Ondes (French research network about waves) initiated an inventory of French anechoic chambers, designed for Antenna measurements and/or Radar Cross Section (RCS) measurements. No less than 49 facilities were identified and described [1]. Common research topics were also exhibited among which measurement uncertainties. Finally, the GdR Ondes has created a Working Group, piloted by the CNRS and the CEA (French Atomic Energy Commission) which first aim was to organize a national interlaboratory comparison of RCS measurements inspired by the European framework ACE on antennas [2] and to the work conducted in the frame of National RCS Measurement Facility Certification Program (see [3] for example). The nine laboratories listed in the author affiliation joined this group.