Abstract: A data transaction card having a substrate supporting a chip module coupled to opposite ends of a coil antenna wound so as to form a substantially integral number of main loops and having a supplementary loop having an active area that is different from an active area of the main loops. In one embodiment, the data transaction card has a substantially rectangular substrate having major and minor edges, which supports a substantially rectangular coil antenna having a major dimension that is substantially equal to a dimension of the major edge of the substrate. The coil antenna is positioned relative to the substrate so that a footprint of the coil antenna does not overlap an area of the substrate that is reserved for embossing data therein.