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Electromagnetic waves in the FM broadcasting frequency band have been observing at our eleven observatories in Japan. We have been frequently observed anomalous FM radio waves due to reflection by the ionospheric sporadic-E layer, and due to the tropospheric duct propagation. For large amounts of data observed in years, it is important to classify them automatically. Thus, we propose a method to classify above two FM radio waves based on their propagation characteristics. We evaluated the method using data observed at Hiroshima and Aso from 2005 to 2010. As a result, we confirmed that the classification method worked correctly.