NDB Rotterdam *RM :
no recordings available
this communication sheet from Rotterdam airport dates from 1979, listing *RM on 274.5 kHz (Rudy van Dalen)
here is a fine QSL-card, confirming *RM actually on 318 kHz (Rudy van Dalen, 1988)
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Callsigns:
RM
Frequencies Morse Telegraphy:
274.5
318
374.