English: 111.5 MHz Reflective array antenna at Fort Monmouth, New Jersey, USA, used by the US Army Signal Corps, 1946, in Project Diana to bounce a radar signal off the Moon. It consists of 64 half-wave dipoles in an 8x8 array in front of a flat reflective screen, and had a gain of 24 dB and a main lobe beamwidth of about 15°. It was driven by a 50 kW modified SCR-271 radar set that produced quarter-second pulses. The echoes took about 2.5 seconds to return. The antenna could be rotated in azimuth only so the experiment could only be done at moonrise and moonset as the moon passed through the antenna's horizontal beam. It was the first demonstration that artificial radio signals could penetrate the ionosphere. From [1]