Repeaters can cover hundreds of kilometers, such as the 438.500 MHz channel covering Tangshan to Dalian, Tangshan to Shijiazhuang, and Tangshan to Beijing – these are all normal operations.
1、Regarding repeaters:
If the repeater is at a height of 800 meters, it can normally provide stable communication between two or three cities outside this city. If someone also stands at a height of 800 meters and operates the same repeater from a very distant location, it may be possible to communicate several hundred kilometers away.
2. Regarding direct frequency, the height is the determining factor. The connection between Miaofengshan and Baizhou, and Baizhou to Tianjin, are perfectly normal. Given that Miaofengshan has a very high altitude and Baizhou is located near Tianjin, this is entirely reasonable.
3. Regarding abnormal propagation, there are many ways for it to occur. Atmospheric ducting is one example; you can search for more details. When referring to "abnormal propagation," this typically refers to situations where normal communication is not possible, and radio stations use phenomena like atmospheric ducting to establish communication. For example, on the frequency of 438.5 MHz, it's possible to communicate between Beijing and Dalian, Beijing and Shijiazhuang (both communicating with Dalian), Beijing and Handan, and even between Beijing and Henan. I have personally experienced receiving signals from a repeater station in Tangshan, Shandong, which can be received on the ground near Dongying, and sometimes, ground-based stations in Shandong can communicate with the Tangshan repeater. In my opinion, these are all normal occurrences.
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