File:Radar antennas on USS Theodore Roosevelt SPS-64.jpg

Summary
AN/SPS-46(V)9 radar antenna on the USS Theodore Roosevelt aircraft carrier. This is an X-band (8-12 GHz) marine navigational radar similar to types on civilian ships, used to detect other ships in the vicinity. It has a peak power of 7 kW, a range of somewhere around 35 nautical miles. This type of antenna is called a slot antenna and radiates a narrow vertical fan-shaped beam of microwaves, about 15° high and 2.2° wide. A motor in the housing below rotates the bar-shaped antenna to scan the beam around the horizon. http://commons.wikimedia.org/wiki/File:Radar_antennas_on_USS_Theodore_Roosevelt_SPS-64.jpg