Foundations Of Amateur Radio

Foundations of Amateur Radio After recently talking about noise, today I want to discuss gain, specifically antenna gain. When you say that your antenna has 18 dBi gain, what does that mean? This entire discussion starts with an isotropic radiator or antenna. It's often described as the perfect antenna, but rarely is there any description on how that actually works, so I'd like to start there. Before we dig in too much, it's worth remembering that an isotropic antenna is a thought experiment, it cannot physically exist, but it's a useful tool for comparing antennas. Antennas have a physical size. There's often a direct relationship between the size of the antenna and the frequencies for which it works best. A lower frequency means a longer wavelength and corresponding large antenna to handle that radio frequency. In contrast, an isotropic antenna is infinitesimally small and responds equally well for all frequencies. Similarly, unlike an actual antenna, an isotropic antenna is symmetric in all directions