What is an ideal antenna?

An ideal antenna for amateur radio is a theoretical construct that has perfect characteristics such as no losses, 100% efficiency in converting electrical energy into electromagnetic waves and vice versa, and completely uniform radiation in the desired direction. In practice, there is no antenna that achieves this ideal state because every antenna has certain limitations in terms of efficiency, bandwidth, size and radiation characteristics. For amateur radio operators, the "ideal" antenna is therefore one that is best tailored to their specific needs, taking into account the frequency range, local environment, available space and intended use. This often includes compromises between size, gain, bandwidth and multi-band capability.