Short Range Skywave Field Strengths From Tall AM Broadcast Towers

Calculations of mediumwave skywave field strengths within 100 km of an AM broadcast station using a 186 degree tower are presented. The analysis is novel in that the high vertical elevation angle radiation from the tower is calculated using a method of moments technique. The results show that skywave field strengths are several times stronger than predicted when using the FCC tower radiation formula, and that within 100 km the 10 percent time skywave field strength can in some cases be of comparable amplitude to the groundwave signal amplitude. An analysis of the resulting signal envelope amplitude and phase fading statistics is also presented.