The future of high frequency broadcasting

Since the end of World War II, the number of daily frequency hours used by high-frequency (HF) broadcasting (also known as shortwave and band 7, 3-30 MHz) has tripled. Approximately 35000 daily frequency hours are carried in an HF spectrum that can barely accommodate half that amount. As a consequence, congestion is severe, and interference levels intolerably high. Attempts to remedy this situation by planning the high-frequency bands date back to 1947, but, thus far, they have not been successful. International planning conferences in 1984 and 1987 have shown a possibility for agreement; another conference is tentatively scheduled for 1992. Some broadcasters have attempted to solve their congestion problems by moving out-of-band, sometimes expanding their services int bands allocated to other services, such as amateur radio, fixed, aeronautical, and mobile. It is feared this trend will continue. The attempts that have been made to plan the HF bands in an effort to alleviate congestion are described and the outlook for the remainder of the 20th century is discussed     

The Problem of Congestion in High-Frequency Broadcast Bands

The usefulness of the high-frequency spectrum for international broadcasting is in serious jeopardy. A rapid increase in the number of transmitters operating in the broadcast bands between 3 and 30 MHz has resulted in a corresponding increase in co-and adjacent-channel interference levels. At present, a condition of extreme congestion exists, with many channels over-loaded by a factor of three during certain peak broadcast periods.