Experimental measurements on reduced‐scale mock‐ups allow validating the electrical properties and RF numerical optimization of the ITER ICRF antenna. Frequency response in the different regions of the antenna is described and key parameters for performance improvement are given. Coupling is improved by acting on the front‐face geometry (strap width, antenna box depth and vertical septa recess). The 4‐port junction acts as a frequency filter and together with the service stub performs pre‐matching in the whole frequency band. Influence of the Faraday screen on coupling is limited. The effect of voltage limitation on the maximum total radiated power is given. The importance of a good decoupling network and of grounding is emphasized. Finally the control of the antenna wave spectrum is performed by implementing feedback controlled load‐resilient matching and decoupling options and control algorithms are tested.