Retlectarray (RA) and transmitarray (TA) antennas that use the element-rotation technique require the radiation from the feeding antenna to be circularly polarized (CP). A CP axially corrugated horn antenna is developed as a feeding element for CubeSat RA and TA antennas. The CP operation is enabled using a septum polarizer. The all-metal geometry is attractive for space applications and allows the horn to be 3D printed in aluminum in a single piece. A prototype of the feed chain was fabricated using the Direct Metal Laser Sintering (DMLS) technique. The results of 3D simulations and VNA/far-field measurements of the feed chain arc presented in this paper.