Measurements on FM waves from Japan and Korea for estimating overreach interference sources of terrestrial TV waves

In western Japan, UHF band terrestrial digital TV waves have been sometimes affected by co-channel overreach interferences from Korea. To evaluate the co-channel interferences, we have proposed a new method monitoring both RSSI (Received Signal Strength Indicator) and CNR (Carrier to Noise power Ratio) of the digital TV waves and RSSI of FM broadcasting waves at the same time and we installed the measurement system at KIT (Kyushu Institute of Technology) in Fukuoka prefecture. At the measurement point, there are some candidates of overreach interference sources transmitting TV waves with same frequency, not only in Korea but also in Japan. In this study, we tried to estimate the overreach interference sources based on our proposed method monitoring FM waves transmitted from stations nearby the several candidates of interference sources. From the measurement results, it was found that the main overreach interference was from Korea, and that the main factor of the interference was an atmospheric duct propagation occurred over the sea.