this signal could be received
daytime on nearby island of Menorca (rb, 2013)
very detailed QSL letter
from the collection of Patrick Robic (2012)
although this picture looks like a maritime NDB, it is a true
aeronautical one (Jean-Luc Wauquier, 2022)
------------------------------------------------------------
Callsigns:
SGO
Frequencies Morse Telegraphy:
356