Abstract: The high-frequency (HF) polarimetric antennas reduce channel fading in applications such as over-the-horizon (OTH) radar and diversity reception systems. Polarimetric antennas can be equipped with different numbers and types of antenna elements and polarization diversity is required in antenna design to evaluate reception performance in the HF fading channel, i.e., the channel with time-varying wave direction, polarization, and the possible presence of multi-paths. However, it is difficult to generate ground waves with time-varying fading, and multi-paths in the time-varying sky wave impede direct polarization diversity. Communication or OTH radar signals help to resolve multi-paths but require computationally intensive steps such as channel equalization or pulse compression. A simple and reliable method is proposed to address this problem using the sky wave, which is based on the maximal-ratio-combining (MRC) of multipath sine waves. Multi-paths of the sine wave are correlated with each other and can be viewed as synthesized into a sine wave in a short time, and the performance of antennas can then be compared by the output signal-to-noise ratio (SNR) of the MRC. Simulation validates the proposed method and an experiment over a link length of about 700 km further compares typical polarimetric antennas that have 2 or 3 elements. The simulation shows that the antenna with 2 orthogonal elements significantly outperforms the 1 linear wire antenna and approaches the performance of the antenna with 3 elements as the elevation angle increases. The experiment shows similar results with unknown and time-varying elevation angles.