This paper presents a new process for additively manufacturing purely metallic antennas based on Fused Deposition Modeling (FDM), with a proprietary filament developed using a hot extrusion method and composed by a mix of rounded shape copper powders with particle sizes in the range from 20 to 80 mu m embedded in a polymeric matrix, to accomplish the desired antenna shape; followed by a post-processing stage involving de-binding to remove the base polymer and a further sintering process for obtaining a purely metallic component. This new process is validated by means of a prototype antenna consisting on a modified tri-band cactus monopole that is manufactured and measured, exhibiting results in agreement with standard and alternative additive manufacturing techniques reported in the literature.