Ultra-low profile low frequency antenna including a magnetic core made of a soft-magnetic non-electro conductive material, the magnetic core having coil winding channels in three intersecting axial directions orthogonal to each other, defining X-axis, Y-axis and Z-axis orthogonal to each other wherein: the magnetic core include a flat central region and four corner protuberances spaced apart to each other around said central region, said corner protuberances defining therebetween a X-coil winding channel surrounding the central region around the X-axis, and a Y-coil winding channel surrounding the central region around the Y-axis; and a Z-coil winding channel surrounds the magnetic core around the Z-axis, said Z-coil winding channel being defined by a discontinuous groove confined between two parallel surfaces which are perpendicular to the Z-axis providing a rectangular cross section, said discontinuous groove including four partial grooves each included in one of the corner protuberances; a X-coil is wound around the X-axis contained within the X-coil winding channel, a Y-coil is wound around the Y-axis contained within the Y-coil winding channel, and a Z-coil is wound around the Z-axis contained within the Z-coil winding channel; and the X-coil, the Y-coil and the Z-coil being made of conductive wire, and each having a conductive wire entry and a conductive wire exit connected to a respective connection terminal, the magnetic core has a flattened drum-like shape; characterised in that the thickness of the magnetic core in the Z -axis direction is of less than 1,2 mm; each partial groove is narrow and deep with the width of each partial groove in the Z-axis direction being equal or less than 0,4 mm and the depth of each partial groove in a radial direction being perpendicular to the Z-axis direction at least two times the width thereof; and the Z-coil is wound within said Z-coil winding channel inserted in said narrow deep groove and extending radially from 1/3 to 2/3 of the depth of the groove, such that the outer edge of the Z-coil wound in the Z-coil winding channel is at a distance of the entrance of the groove so that the parallel surfaces extent in cantilever beyond said outer edge. the magnetic core include a flat central region and four corner protuberances spaced apart to each other around said central region, said corner protuberances defining therebetween a X-coil winding channel surrounding the central region around the X-axis, and a Y-coil winding channel surrounding the central region around the Y-axis; and a Z-coil winding channel surrounds the magnetic core around the Z-axis, said Z-coil winding channel being defined by a discontinuous groove confined between two parallel surfaces which are perpendicular to the Z-axis providing a rectangular cross section, said discontinuous groove including four partial grooves each included in one of the corner protuberances; a X-coil is wound around the X-axis contained within the X-coil winding channel, a Y-coil is wound around the Y-axis contained within the Y-coil winding channel, and a Z-coil is wound around the Z-axis contained within the Z-coil winding channel; and the X-coil, the Y-coil and the Z-coil being made of conductive wire, and each having a conductive wire entry and a conductive wire exit connected to a respective connection terminal, the magnetic core has a flattened drum-like shape; characterised in that the thickness of the magnetic core in the Z -axis direction is of less than 1,2 mm; each partial groove is narrow and deep with the width of each partial groove in the Z-axis direction being equal or less than 0,4 mm and the depth of each partial groove in a radial direction being perpendicular to the Z-axis direction at least two times the width thereof; and the Z-coil is wound within said Z-coil winding channel inserted in said narrow deep groove and extending radially from 1/3 to 2/3 of the depth of the groove, such that the outer edge of the Z-coil wound in the Z-coil winding channel is at a distance of the entrance of the groove so that the parallel surfaces extent in cantilever beyond said outer edge.