Electron Bernstein Emission (EBE) diagnostic system using Ordinary (O) - eXtraordinary (X) - Bernstein (B) mode conversion process has been developed for determining electron temperature profiles at overdense plasmas in a helical-axis heliotron device, Heliotron J. Ray-tracing calculation results show that the O-X mode conversion window is accessible with a current ECH/ECCD launcher and transmission system. The EBW radiation from the core region is expected to be measurable by adjusting the magnetic field strength. Effect of density fluctuation on O-X mode conversion efficiency is also discussed. Based on the calculations, a multi-channel radiometer of Ka-band range has been designed, assembled and tested.