At the very top of the building are antennas with airline warning strobe lights that flash 40 times a minute. Visible to pilots over great distances, the lamps are changed about every 18 months by a climber who scales the antenna towers. New digital antennas were recently installed for Chicago’s major television stations so they can broadcast high-definition TV.
West antenna tower height = 294'-5" (from 109 roof level to top of strobe light)
East Antenna tower height = 290'-7" (from 109 roof level to top of strobe light)
Tower Bases = 12' diameter solid wall steel cylinders