June 1980 | NTIA Technical Report TR-80-42
Abstract: The chronological development of the available methods for predicting medium frequency sky–wave strengths is presented with a brief discussion of each method. Measured field strengths for 36 medium frequency sky–wave paths are compared with the predicted field strengths from several different prediction methods. Based on the rms errors between observations and predictions, the 1938 Cairo Curves provide the best estimates of the sky–wave field strengths for very long paths worldwide. A new prediction method developed for use in North and South America only, provides improved estimates of the sky–wave field strengths for paths ‹3500 km.
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