An antenna 3 of an electromagnetic probe 1 used in investigation of geological formations GF surrounding a borehole WBH comprises a conductive base 31 and a first antenna element 32. The conductive base 31 comprises an opened non-resonant cavity 33. The first antenna element 32 is embedded in the cavity 33 and goes right trough the cavity. The first antenna element 32 is comprised of a center-split half-coaxial wire so as to define a symmetrized antenna radiation pattern.
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