Antenna Gain & Isotropic Radiators
Concentrating Energy in the RF Space
The Isotropic Ideal
To measure how well an antenna focuses energy, we need a reference point. This is the Isotropic Radiator—a theoretical point source that radiates energy equally in all directions (a perfect sphere).
Antenna Radiation Pattern Simulator
Inverse Square Law & Energy Concentration
Inverse Square Law: Signal power density decreases with the square of distance (1/d²). High-gain antennas concentrate energy in a specific direction, achieving greater range in that direction at the cost of coverage elsewhere. EIRP = TX Power + Antenna Gain - Cable Loss.
Conservation of Energy
High gain comes at a cost. Because an antenna cannot create energy, high gain in one direction must mean a loss of energy in all other directions. This results in narrow Beamwidths.
- Omni-directional: Radiates in a 360° 'donut' (toroid). Low gain (2-5 dBi).
- Directional (Yagi/Patch): Higher gain (10-15 dBi), narrow arc.
- Paraobolic Dish: Extreme gain (30+ dBi), laser-thin beam.
Effective Isotropic Radiated Power (EIRP)
Regulation (like the FCC or CITC) doesn't just look at the radio's power; it looks at the EIRP—the actual power emitted into space after antenna gain is added.
Conclusion
Understanding gain is the difference between a functional wireless link and a system that generates massive interference with zero performance. Choose your 'focus' wisely.