NDB Oslo-Gardermoen *SOK :
no recording available
see here the multi-QSL version from the collection of Rudi Renkwitz (2005), verifying RS-336, RSY-378, SAD-348, SF-283, SLB-414, and SOK-387
in 2009, Bernhard Hein received this nice multi-QSL for 6 NDBs: ASK-360, BVK-362, HD-414, SLB-414, SOK-387, and UTH-366
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Callsigns:
GR
HR
SOK
Frequencies Morse Telegraphy:
387.