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facilities:microwave:oak_hill [2026-05-10 21:16] – J. B. Crawfordfacilities:microwave:oak_hill [2026-05-11 18:48] (current) – J. B. Crawford
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 ====== Oak Hill Microwave Station ====== ====== Oak Hill Microwave Station ======
  
-Oak Hill is a distinctive microwave site located on Communications Hill in San Jose, California. Many will recognize Oak Hill for the unusual concrete tower, which sits above an underground building that is semi-hardened at most. Much about the history of Oak Hill is obscure, including the reason for the unusual construction. Functionally, Oak Hill was a microwave station and likely also exchanged microwave traffic with an L-carrier cable that runs north-south through California.+Oak Hill is a distinctive microwave site located on Communications Hill in San Jose, California. Many will recognize Oak Hill for the unusual concrete tower, which sits above a partially underground building. Much about the history of Oak Hill is obscure, including the reason for the unusual construction. Functionally, Oak Hill was a microwave station for connectivity to the San Jose CO and likely also exchanged microwave traffic with an L-carrier cable that runs north-south through California.
  
 ^ Built    | 1972 | ^ Built    | 1972 |
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 | San Jose | North | WLEL | | San Jose | North | WLEL |
  
-This list is probably incomplete and confusing, the routes seem to have changed over time. A [[https://groups.io/g/coldwarcomms/message/4739|mailing list post]] from Wayne M H also gives the following:+This list is probably incomplete and confusing, the routes seem to have changed over time. A [[https://groups.io/g/coldwarcomms/message/4739|mailing list post]] from Wayne M H also gives the following. I am not familiar with the maps referenced.
  
   The map I have that seems post-1979 shows Oak Hill with a MW path to   The map I have that seems post-1979 shows Oak Hill with a MW path to
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 Oak Hill didn't just serve microwave, the 1979 route map appears to depict a north-south L-carrier cable passing through. Other mailing list posts suggest that this cable was rerouted to appear at Oak Hill during the later part of the 1970s, as AT&T continued to relocate more equipment to the remote site. It is not thought that there was ever power feed equipment at Oak Hill, due to its close proximity to the San Jose CO, but Oak Hill may have had equipment to exchange groups or supergroups between the cable and microwave. Oak Hill didn't just serve microwave, the 1979 route map appears to depict a north-south L-carrier cable passing through. Other mailing list posts suggest that this cable was rerouted to appear at Oak Hill during the later part of the 1970s, as AT&T continued to relocate more equipment to the remote site. It is not thought that there was ever power feed equipment at Oak Hill, due to its close proximity to the San Jose CO, but Oak Hill may have had equipment to exchange groups or supergroups between the cable and microwave.
 +
 +Another point of interest about the Oak Hill site is the presence of early encryption equipment, documented by interior photos at Long-Lines.net (see below). Similar equipment appears at some other microwave sites (including, reportedly, Bernal Heights) and is thought to be an artifact of a Cold War program in which AT&T encrypted select microwave links near possible Soviet/Russian intelligence collection centers. The equipment in the Bay Area was presumably in response to the Consulate General of Russia in San Francisco, which included apparent SIGINT equipment on the roof. The "For Future Use" stickers on the encryption equipment (apparently present at other sites as well) calls into question how far the deployment of this encryption system ever got.
  
 ===== Construction ===== ===== Construction =====