Historic California Posts, Camps, Stations and Airfields
Point Reyes Headland Radar Site
(SCR-682 Radar Set No. 1, Harbor Defenses of San Francisco)
US Army Corps of Engineers Sacramento District History (Corrected) (1993)

On 7 May 1943, the War Department acquired 1.00 permit acre from the U.S. Coast Guard, then under the Navy Department. The total acreage acquired was 1.00.
The site was known as Point Reyes Lighthouse and as Point Reyes Lighthouse Reservation, CA. The actual radar site was known ar Seacoast Radar No. 1, Harbor Defenses of San Francisco. The site provided data for the detection and targeting of potential seaborne threats. The site was equped with the SCR-682 Transportable Microwave Seacoast Artillery (Radar) Set. Defensive armament consited of two M2 .50 caliber Machine Guns, one to the west of the radar set and the other to the east.
It was situated 30 miles northwest of San Francisco in Marin County. Improvements were not listed in historical documents.
On 26 September 1952, 1.00 permit acre was relinquished to the Department of Treasury. (All information above was compiled from the real estate map of the site, below.)
SCR-682 Transportable Microwave Seacoast Artillery Set
Description: Transportable Seacoast Artillery microwave radar.
Uses: Used by 155-mm and 8-inch railway battalions. PPI gives indication of surface craft and low-flying planes. Uses IFF (Identification Friend or Foe) RC-282.
Performance and Siting: Set covers 360°. For a height of 100 feet, range will average 50,000 yards or greater. At times, under favorable conditions, very much greater maximum ranges will be achieved from sufficient heights of site. Minimum range is about 500 yards. Azimuth accuracy is on the order of ± 2 degrees depending somewhat on the range scale in use. The range accuracy thus may be considered ± 3 per cent of the range scale in use. The range scales are 10,000; 4,000p; 160,000; and 320,000 yards. Set should be sited not less than thirty feet above the surrounding terrain and preferably at least 100 feet above sea level. The optimum height of site is between 150 and 500 feet.
Transportability: A transportable version of the SCR-582, the SCR-682 can be carried in two standard 2-1/2-ton 6x6 cargo trucks.
Installation: Set normally is operated form a portable tower furnished with set. The operating components are located near the tower in a Shelter HO-17 or housing constructed by the using troops from materials obtained locally. No transportation is furnished with the set.
Personnel: One man operates the set and another plots the position of detected targets. These men relieve one another every thirty minutes to reduce fatigue. For 24-hour operation a chief of section, five operators, two power plant operators, and one maintenance man are required.
Power: Requires about 1.28 KW, 120 V, 60 cycles, single phase.
Report of Completed Works - Seacoast Fortifications

Radar Coverage Map
Site Map
Corps of Engineers Real Estate Map
Other Online or Printed Histories
Harbor Defenses of San Francisco - A Field Guide 1890 to 1950


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Updated 8 February 2016