📘 Definition
Antenna gain (measured in dBi — decibels relative to an isotropic radiator) quantifies how much an antenna focuses transmitted or received energy in a particular direction. A high-gain antenna (e.g., 40+ dBi) produces a narrow beam that concentrates energy, dramatically increasing the effective signal power over long distances — essential for deep-space communications and GEO satellite links. A low-gain antenna (e.g., 0–3 dBi) radiates nearly omnidirectionally, useful for telemetry and emergency communications where precise pointing isn't guaranteed. The trade-off: higher gain requires more accurate pointing (via the ADCS), and the beamwidth shrinks as gain increases.
dBi (decibels isotropic)
Unit
0–6 dBi (omnidirectional)
Low Gain
20–50+ dBi (narrow beam)
High Gain
Higher gain = narrower beam
Trade-Off