What is meant by 'propagation' in radio communications?

Propagation in radio communications refers to the transmission of signals through space. This encompasses how radio waves travel from the transmitter to the receiver, including the various physical phenomena that affect the signals, such as reflection, refraction, diffraction, and scattering. These factors can influence the range and quality of the signals received, making propagation a pivotal aspect of effective radio communication.

Understanding propagation is crucial for amateur radio operators as it helps them determine the ideal frequencies and times to transmit, based on the behavior of radio waves under various atmospheric conditions and at different times of the day. For instance, certain frequencies may propagate better during the day while others may perform better at night due to changes in the ionosphere.

The other options refer to different concepts that are not directly related to the traveling of radio signals. Generating electrical signals involves creating signals, modulation refers to altering a signal's characteristics for transmission, and encryption involves securing data but does not relate to how signals propagate through space.