Modeling and characterizing low frequency antennas in realistic environments is considered as one of the most difficult computational problems. This complexity arises mainly from the multiscale nature of low-frequency scenarios. In this article, we present a block meshing technique with TLM to accurately represent the geometry of thin-wire antennas. This enables us to accurately compute its input impedance and radiated power. Numerical simulations are presented to show the efficiency and the accuracy of the proposed approach, with comparisons with regular fine meshing and MoM.