AN/FPS-35

The AN/FPS-35 frequency diversity radar was a long range search radar used in the early 1960s. It was one of the largest air defense radars ever produced, with its antenna and supporting structure mounted on one of the largest rolling-element bearings in the world (with a ball pitch of 12 ft 7 inches in diameter.).

Classification of radar systems
Under the Joint Electronics Type Designation System (JETDS), all U.S. military radar and tracking systems are assigned a unique identifying alphanumeric designation. The letters “AN” (for Army-Navy) are placed ahead of a three-letter code.
 * The first letter of the three-letter code denotes the type of platform hosting the electronic device, where A=Aircraft, F=Fixed (land-based), S=Ship-mounted, and T=Ground transportable.
 * The second letter indicates the type of equipment, where P=Radar (pulsed), Q=Sonar, and R=Radio.
 * The third letter indicates the function or purpose of the device, where G=Fire control, R=Receiving, S=Search, and T=Transmitting.

Thus, the AN/FPS-35 represents the 35th design of an Army-Navy “Fixed, Radar, Search” electronic device.

Overview
Sperry Corporation built 12 long range radars (picking up objects 200 miles away) in the 1960s to succeed existing Semi Automatic Ground Environment (SAGE) to provide enhanced electronic countermeasures (ECM). The systems operated at 420 to 450 MHz. The antennas weighed 70 to 80 ST and had numerous problems. The concrete tower bases were 84 ft high and 60 ft square in side dimensions.

The prototype was developed at the Thomasville Aircraft Control and Warning Station in Thomasville, Alabama.

The 85 foot enclosed radar towers that supported all 12 of the FPS-35 antennas were prominent landmarks. All these radar towers were of the same basic design with 10 made primarily from concrete and two based on a steel frame structure (Baker and Finley). Only the radar tower at Baker has been demolished.

The 23 radar towers used by the AN/FPS-24 and the AN/FPS-35 radar sets were of similar designs (concrete or steel frame) and were designed under the direction of the Rome Air Development Center (RADC). The radar tower at Thomasville has an RADC plaque next to the one from the Sperry Corporation. Only the AN/FPS-35 tower at Baker included a radome to protect the antenna. This radome was attached to a separate steel tower called a Radome Support Structure (RSS) that surrounded the radar tower to its full height of 85 feet. With the antenna, the structure's total height is 150 feet.

Montauk tower
All of the radars have been dismantled except for the one at Camp Hero State Park on the eastern tip of Long Island in Montauk, New York. It was the last to operate (January 1981) and the radar tower is the only one that still has an antenna on the roof and contains some of the radar set equipment and cabinets. The antenna was repaired with parts from the Sault Ste. Marie station after it closed in October 1979. The Montauk antenna is very corroded and can not be rotated.

The structure was listed on the National Register of Historic Places in 2002. Fishermen on the Atlantic Ocean and Block Island Sound lobbied to save it since the massive radar tower was a better daytime landmark than the Montauk Point Lighthouse.

The 150-foot tower dominates the environs and can be seen from as far away as Charlestown, Rhode Island, to the east (22 miles) and Orient Point, New York (20 miles) to the west.

The Montauk radar has worked its way into an urban legend that it was used in time travel experiments called the Montauk Project.

List of towers

 * AL Thomasville 31.9382°N, -87.7502°W
 * CA Boron 35.0823°N, -117.5823°W
 * MI Sault Ste. Marie 46.4565°N, -84.3878°W
 * MI Selfridge 42.6275°N, -82.83°W
 * NV Fallon 39.4054°N, -118.7224°W
 * NY Montauk 41.0622°N, -71.874°W
 * ND Finley 47.5161°N, -97.8687°W  (steel tower, present)
 * ND Fortuna 48.9042°N, -103.8665°W
 * PA Benton 41.3574°N, -76.293°W
 * VA Manassas 38.6288°N, -77.4385°W
 * WI Antigo 45.04833°N, -89.23389°W
 * OR Baker 44.58639°N, -117.78722°W  (steel tower, demolished)