in this recording of *KBA-431 from 2004 you have *GBL-429
Giebelstadt (429 kHz) in the background
see this QSL-card from the files
of Dieter Pohlmann (2009)
here a look at the navigation systems
placed close to the Baden Airpark airport (rb, 2012)
------------------------------------------------------------
Callsigns:
KBA
Frequencies Morse Telegraphy:
431