Radio wave propagation
Here are the main things which affect EM wave communications.

Polarization
The orientation of E flux is the polarization of the EM wave. If E flux lines are parallel to earth’s surface, you have horizontal polarization. If E flux lines are perpendicular to surface, you have vertical polarization. Polarization can be inclined at any angle between the horizontal and vertical.The orientation of E flux lines sometimes rotates as wave travels through space. This is circular polarization if E-field remains constant intensity. If E-field intensity is more intense in some planes than in the others, the polarization is elliptical. Rotating polarization is either clockwise or counterclockwise, viewed as wavefronts approach you. This is sense of polarization