Plain-language answer: The reactive near field is the closest region, where stored electric and magnetic energy dominates over outward radiation.
Why it changes the path
Nearby conductors can detune the antenna, carry induced current, or create high local voltage and current without representing transmitted far-field strength.
What to observe
Tune only in the final surroundings, keep bodies and metal clear, and use probes designed for local E- or H-field work.
The common mistake
Using a close field-strength reading as an antenna gain measurement.
Planning boundary
Propagation models and field regions depend on frequency, geometry, terrain, atmosphere, polarization, antenna pattern, and measurement distance. Use them to plan and compare—not to guarantee a contact or installed range.
