[Milsurplus] AN/URR-30 or R-571/URR - what is it?

[Nick England]

I found the following reference to a Navy manual for an AN/URR-30 (R-571)
receiver mde by National - does anyone know anything about it? given the
XN-1 designation, maybe a prototype only?
cheers,
Nick KD4CPL
www.virhistory.com/navy 

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Instruction book for radio receiving set AN/URR-30 (XN-1) : consisting of
radio receiver R-571 (XN-l)j accessories / Bureau of Ships, Navy Department.
[Washington, D.C.]: Bureau of Ships, Navy Dept.; Maiden, Mass.: National
Company, Inc., 1953. 1 v. (various pagings) : ill. (some folded); 28 cm. 87
p. "NAVY NAVSHIPS 91947" "Approved by BUSHIPS: 1 June 1953" "Contract NObsr
57305" United States. Navy. -- Handbooks, manuals, etc. Radio -- Receivers
and reception -- Handbooks, manuals, etc. United States. Navy Dept. Bureau
of Ships. National Company. (Malden, Mass.).