Institute for Telecommunication Sciences
the research laboratory of the National Telecommunications and Information Administration

Arthur D. Spaulding

Abstract: In the MF band, interfering signals from one or more broadcast stations can be received. During nighttime periods, this interference is caused by fading signals, propagated from distances of more than about 200 miles. It is the purpose of this report to provide the techniques needed to properly determine the degree of interference from one or more distant broadcasting stations. Computer algorithms are developed which determine the actual overall fading distribution of one or a combination of two fading signals, when the short–term fading of each is represented by a Rayleigh distribution and the long–term fading of median values is given by a log-normal distribution. Also, a simple approximate means of determining the distribution of the median value of a signal given by the sum of any number of fading signals is given. This approximate method is accurate only for the smaller percentage points. It is found that the techniques described here lead to somewhat higher values for the sum of the signals than previous methods.

Keywords: MF fading; fading signals; signal interference

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Institute for Telecommunication Sciences
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Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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