Almaden Air Force Station

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Almaden Air Force Station (1958-1980) - A Cold War Air Force Radar Station first established in 1958 on Mount Umunhum, Santa Clara County, California. Initially assigned a Permanent ID of M-96, later a Sage ID of Z-96. Abandoned in 1980.


Established 24 Jun 1957 and became operational on 21 Mar 1958 as Almaden Air Force Station manned by the 682nd AC&W Squadron. The station initially had both a Ground-Control Intercept (GCI) and early warning mission. The early warning mission involved tracking and identifying all aircraft entering their airspace while the GCI mission involved guiding Air Force interceptors to any identified enemy aircraft. Controllers at the station vectored fighter aircraft at the correct course and speed to intercept enemy aircraft using voice commands via ground-to-air radio.

Initial equipment in 1957 included the FPS-20 search radar and a single FPS-6A height-finder. The FPS-20 was located on an arctic type tower designated as building 103 just west of the operations building (Bldg 100). The antenna was enclosed in a radome. The FPS-6A was located on a temperate tower (Bldg 125) just north of the Operations Building. A second FPS-6A height-finder radar was also installed on a temperate tower (Bldg 107) in 1958.

A new SAGE addition was built onto the operations building (Bldg 100) in 1959 and the FST-2 Coordinate Data Transmitter (CDT) was installed there in preparation for automated SAGE System operation.

SAGE System Transition

The transition of the manual GCI system to the automated SAGE system began with the installation of the FST-2 coordinate data transmitter and search radar upgrades. The FST-2 equipment digitized the radar returns and transmitted the digital returns to the SAGE direction center. Under the SAGE System, interceptor aircraft were directed to their targets by the direction center computers and controllers, greatly reducing the need for local controllers and equipment at every radar station.

The FST-2 was a very large digital system using vacuum tube technology. Over 6900 vacuum tubes were used in each FST-2 requiring 21 air-conditioned cabinets, 40 tons of air conditioning, 43.5 kva of prime power, and usually a large new addition to the operations building. The FST-2B modification added two more cabinets but with newer solid-state (transistor) technology to process coded responses from aircraft transponders.

SAGE System Operation

Almaden Direction Centers
From To Organization Direction Center Notes
1 Jul 1960 1 Aug 1963 SFADS Beale SAGE Direction Center DC-18
1 Aug 1963 1 Apr 1966 LAADS Norton SAGE Direction Center DC-17
1 Apr 1966 15 Sep 1969 26th AD Adair SAGE Direction Center DC-13
15 Sep 1969 19 Nov 1969 27th AD Luke SAGE Direction Center DC-21 Interim Organization
19 Nov 1969 1 Apr 1980 26th AD Luke SAGE Direction Center DC-21 Site Deactivated

The site began operation as a SAGE site 1961 initially feeding the Beale SAGE Direction Center DC-18.


The site was reconfigured in 1962-1963 to support a new long-range search radar, the FPS-24. The FPS-24 was housed in a four-story concrete building (Bldg 102) east of the Operations building. The FPS-6A height-finder radar in building 107 was upgraded to an FPS-90 in the spring of 1963. A MPS-14 mobile height-finder radar was placed in a temperate tower designated as building 108. At the end of the reconfiguration, the site had an FPS-24 search radar (Bldg 102), an FPS-90 height-finder (Bldg 107) and an MPS-14 height-finder (Bldg 108). The remaining FPS-20 and FPS-6A radars and towers were removed (Buildings 103 and 125).

The new search radar interfered with the operation of the Ground to Air Transmitter/Receiver (GATR) site located nearby in building 110. The GATR site was relocated to nearby Mount Thayer.

When the Beale SAGE Direction Center DC-18 closed in 1963 Almaden AFS was connected to the Norton SAGE Direction Center DC-17 until it closed in 1966. Control of Almaden AFS then shifted to Adair SAGE Direction Center DC-13 until it closed in 1969 and finally to Luke SAGE Direction Center DC-21.

The FST-2B was replaced with a more up-to-date coordinate data transmitter, the solid state FYQ-47 in May 1972. The FPS-90 height-finder radar was deactivated on 1 Oct 1976 and removed.


Almaden AFS and the 682nd were deactivated on 1 Apr 1980.

Almaden AFS Major Equipment List
Search Radar HF Radar Data Systems
Unit Designations
  • 682nd Aircraft Control & Warning (AC&W) Squadron (1958-1961)
  • 682nd Radar Squadron (SAGE) (1961-1974)
  • 682nd Radar Squadron (1974-1980)
682nd Assignments
  • 1 Dec 1953 - Activated at Geiger Field, WA, assigned to the 4702nd Def Wg.
  • Jan 1954 - Moved to Kirtland AFB, NM and transferred to 154th AD.
  • 13 Jul 1954 - Moved to Hamilton AFB, CA and transferred to 28th AD.
  • Sep 1957 - Moved to Almaden AFS, CA.
  • 1 Jul 1960 - Transferred to San Francisco ADS.
  • 15 Jan 1961 - Redesignated from AC&W Sq to 682nd Radar Sq (SAGE).
  • 1 Aug 1963 - Transferred to LA ADS.
  • 1 Apr 1966 - Transferred to 26th AD. (at Adair AFS)
  • 15 Sep 1969 - Reassigned to 27th AD. (Temporary)
  • 19 Nov 1969 - Reassigned to 26th AD. (at Luke AFB)
  • 1 Feb 1974 - Redesignated 682nd Radar Sq.
  • 1 Oct 1979 - Assigned to TAC.
  • 1 Apr 1980 - Deactivated.

Almaden Air Force Station Partial Commanders List (edit list)
Assumed Relieved Rank Name Cullum Notes
1958~ Lt. Colonel Herzenber, Albert P. N/A
1960 1962 Lt. Colonel Joyce, Kenneth B. N/A
Lt. Colonel Poskie, David L. N/A
1975~ Major Aftosmis, Charles N/A
1976-05 1978-07 Major Giles, Harry G. N/A
1980~ Major Skinner, Charles R. N/A

Physical Plant

The physical plant of the site was divided into the main site, a cantonment area, a housing area and a radio site. The main site housed the operations buildings, the radar towers, and the backup generators. The cantonment area was below the main site and housed the enlisted barracks, the bachelor officer's quarters, the orderly room, the dining hall, the motor pool and other support buildings.

Just below the cantonment area was a small 27 unit housing area for married personnel. Leased housing units were also available in San Jose.

A separate Ground to Air Transmitter/Receiver (GATR) radio site on nearby Mount Thayer housed the radio equipment for directing aircraft intercepts. The original GATR site was relocated to Mount Thayer because of interference from the high powered FPS-24 radar.

Almaden Air Force Station Composite Plan.

Almaden AFS Structures (edit list)
Number Building Exists Notes
100 Operations/FST-2 No 1957 addition 1959
102 Radar Tower FPS-24 Yes 1961
103 Radar Tower FPS-20 No 1957
105 Fallout Shelter No 1961
107 Radar Tower FPS-6A, FPS-90 No
108 Radar Tower MPS-14 No 1962
110 Old GATR/Training Bldg No 1957
112 Power Generation No 1960
114 Sheet, Pipe & Paint Storage No 1965
115 Security Sentry House No 1964
118 Diesel Fuel Pump No 1957
119 Civil Engineering Maint. Shop No 1957
120 Old Powerhouse, Warehouse Supply & Equipment No 1957
200 Water Pump Station No 1957
205 Bachelor Officers’ Quarters No 1957
207 Squadron Headquarters Orderly Room No 1957
211 Motor Pool No 1960
212 NCO Open Mess No 1957 addition 1975
213 Dispensary No 1957
215 Fire Hose House No 1957
217 Bowling Alley No 1961
225 Airman’s Dining Hall No 1957
230 Commissary No 1957 addition 1967
233 Barracks No 1957
245 Recreation No 1957
250 Auto Maintenance Storag No 1958
275 Swimming Pool No 1957
276 Bath House No 1966
303 Paint Storage No 1958
510 Fourplex Apartment No 1958
511 Fourplex Apartment No 1958
512 Fourplex Apartment No 1958
513 Fourplex Apartment No 1958
514 Fourplex Apartment No 1958
515 Triplex Apartment No 1958
516 Commander’s House No 1958
517 Triplex Apartment No 1958
700 Communications Transmitter/Receiver (GATR Building) No 1962
715 Security Sentry House No 1966
722 Security Sentry House No 1966
TELCO No 1957

Current Status

Part of the Sierra Azul Open Space Preserve but not open to the public. The opening has been rescheduled for 2017. Except for the FPS-24 tower the main site has been leveled.

Location: Mount Umunhum in Santa Clara County, California. Zoom in to see location details. The GATR site is located on Mount Thayer.

Maps & Images

Lat: 37.16045 Long: -121.8979

  • Multi Maps from ACME
  • Maps from Bing
  • Maps from Google
  • Elevation: 3,478'

See Also:


  • Cornett, Lloyd H. & Johnson, Mildred W., A Handbook of Aerospace Defense Organization (1946-1980), Office of History ADC, Peterson AFB, Colorado, 31 Dec 1980, 179 pages, Pdf, page 160.
  • Winkler, David F., Searching the Skies: the Legacy of the United States Cold War Defense Radar Program, USAF Hq Air Combat Command, 1997, 192 pages, Pdf, page 105.
  • USGS Geographic Names Information System (GNIS) Database Entry: 2107695


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