A Method of Predicting the Interference Margin for Non-Directional Beacons

摘要

The purpose of this report is to describe a new method for determining the electric field strength produced by a Non-Directional Beacon (NDB) as a function of the important parameters involved which include distance, frequency, ground conductivity, and effective isotropic radiated power (EIRP). This method enables the determination of the coverage area within which the signal level from the NDB exceeds some critical value, usually 70 microvolts per meter (peak power). Applied to another NDB which might cause interference to the first, correcting for frequency difference to account for receiver selectivity, one can determine at any point the interference margin, (i.e., the amount by which the desired NDB signal exceeds the undesired and potentially interfering signal). This interference margin must be at least 15 dB for satisfactory operation. The scope of this report includes frequencies from 190 to 535 kHz. (Author)