History of Ground Wave Propagation Prediction Curves for AM Standard Broadcast

The history of the FCC curves is traced from the early 1930's, when the Federal Radio Commission and later the FCC faced an intensifying need for technical information concerning interference distances. A family of curves satisfactorily meeting this need was published in 1940 based on theory. Methods for calculating these curves were reexamined recently in connection with the planned expansion of the AM broadcast band, and the resulting ground wave curves are a more precise representation of the mathematical theory.