Short answers, pulled from the story.
Guglielmo Marconi invented the first practical antenna in the summer of 1895 near Bologna, Italy. He suspended a simple wire from a wooden pole to create a device that could send radio waves across vast distances. This invention transformed the antenna from a laboratory curiosity into an industrial product.
A half-wave dipole antenna consists of two elements arranged end-to-end, each approximately one-quarter of a wavelength long. It creates a standing wave where the current peaks at the feed point and the voltage drops to a minimum. This design allows the antenna to resonate effectively at a specific frequency.
The ground acts as a reflector that creates an image of the antenna to either reinforce or cancel the signal. Vertical polarization is preferred for terrestrial broadcasting because the reflected wave adds in phase with the direct wave. Horizontal polarization suffers from cancellation at ground level, making it less effective for terrestrial communication.
The Yagi-Uda antenna features a single driven element and passive elements that create a highly directional beam with limited bandwidth. The log-periodic dipole array maintains performance over a very large bandwidth through a self-similar design with progressively shorter elements. Engineers choose between these designs based on whether they need narrowband directionality or wideband operation.
Electrically short antennas have a radiation resistance that plummets with the square of the antenna length, making power transfer difficult. They often require loading coils to resonate at lower frequencies, which results in reduced bandwidth and increased heat loss. The laws of electromagnetics dictate that an antenna must be a significant fraction of a wavelength in size to be efficient.