The STU-4 series shipboard tilt units are modular electromechanical systems for lowering and raising dual shipboard communication antennas. These units and the single antenna variants (STU-3 series) have over 90% commonality of components.

The drive element is a two-stage planetary gear assembly. The STU-4HD uses a 2-horsepower brakemotor, while the STU-4LW uses a 1-horsepower brakemotor. The electrical controls are located in the pedestal for local operation, while an optional remote control will operate up to three units at a maximum of 1,200 feet away. A manually operated handcrank provides emergency control in the event of electrical failure. Tilt angles may be preset to any angle from vertical through 115, and powered rotation from vertical to 90 horizontal takes only 20 seconds. All units may be tilted inboard to expedite antenna maintenance, removal or installation. Converting from dual to single antenna configuration is accomplished by removing one
support arm. Provisions for mounting antenna tuners and couplers are available in rotating elements, permitting antenna feedwire lengths to be kept to a minimum. Compression pads are activated at vertical and horizontal limits to reduce shock and vibration loads from being transmitted to the rotating elements. Cam operated limit switches control the vertical and horizontal positioning. An overtravel limit switch removes all power to the drive motor in the event of limit switch failure. These units are designed to withstand loads of 1,000,000 in/lb, and are normally used where green water loads are a major concern. Manual crank versions are also available.

Optional equipment includes the C-11549 remote control unit and ID-2371 remote indicating unit.