Spacecraft entering a planetary atmosphere are surrounded by a plasma layer containing high levels of ionization due to the high temperatures on the shock layer. The high electron number densities cause attenuation and rotation of the emitted signal, leading to communication blackout. This work presents experimental measurements of radio signal attenuation and Faraday rotation due to an ionized plasma flow. These measurements are conducted at the VKI Plasmatron using circularly polarized directive horn lens antennas with a waveguide orthomode transducer. Clear attenuations are observed when the signal is propagating through the plasma, and Faraday rotation measurements show a good agreement with the theoretical estimation.