Start here: Radiation resistance is the equivalent feed-point resistance that would dissipate the same power the antenna radiates. It is a model quantity, not a physical resistor.
Why this changes a real station
Radiation resistance competes with conductor, ground, matching, and other loss resistance; efficiency depends on how much accepted power reaches each.
What it looks like in practice
A low radiation resistance can make ordinary connection or ground loss a large percentage of the total, especially in electrically short antennas.
What to do next
Evaluate it at the stated feed point and frequency, keep loss terms separate, and do not infer efficiency from SWR alone.
Evidence boundary
Keep frequency, reference plane, antenna geometry, losses, measurement method, and safety conditions attached to the conclusion. A match, a DC check, or one field symptom does not prove efficiency or identify the complete RF path.
