The radiation characteristics of a monopole antenna that consists of one-half of a bow-tie dipole antenna, made of optically transparent conductive thin film and mounted above a ground plane, are investigated. The antenna is measured for several films with different sheet resistivities. It is found that the gain lowering of the antenna varies from 4.4 dB to 0.2 dB at 2.4 GHz and the efficiency of the antenna increases from 46% to 93% at the same frequency, as the sheet resistivity