Effects of antenna elevation and inclination on VLF/LF signal structure

The report analyzes the effects of antenna elevation and inclination on the structure of air-to-air VLF/LF communication signals for frequencies between 15 and 40 KHz. Considered are (1) propagation broadside to the horizontal component of trailing-wire transmitting antennas, and (2) ambient and moderately disturbed daytime ionospheric conditions and ground conductivities of 0.001 and 0.00001 mhos/m. The calculations use full-wave methods, and fully account for the vertical inhomogeneity of the ionosphere and the curvature of the earth. Numerical results are given for the excitation factors, height-gain factors, and attenuation rates of the first few TM and TE modes. Mode summations are carried out, and detailed plots are given for field component versus distance for antenna altitudes between 0 and 40 kft.