AbstractTwo full-sized mock-ups of the all-metal antenna supports (AMSs) for a center conductor of an ITER ICRF antenna are designed, fabricated, and tested to confirm the high-voltage capability of the antenna. The RF voltage stand-off achieved at the AMSs, i.e. 55 kV at 60 MHz, meets the requirement of the ITER ICRF system. In addition, the RF characteristics of the pair of mock-ups connected by a coaxial line are measured to determine the optimum coaxial line length between the two AMSs in the antenna system. This work is carried out as R&D on the ITER engineering design activity (EDA).