Which statement best describes radiation resistance in an antenna?

Which statement best describes radiation resistance in an antenna?

• A. It is the portion of input resistance attributable to radiated fields
• B. It is the load resistance due to the antenna mount
• C. It is the DC resistance of the feed line
• D. It is the impedance mismatch reflection coefficient

Answer: (A)

Radiation resistance is the part of an antenna’s input resistance that comes from energy being radiated as electromagnetic waves. It represents the real power that leaves the antenna as radiation, as if the antenna were a resistor through which that power is dissipated by emission of waves. The rest of the input impedance is made up of reactive energy stored near the antenna or resistive losses in the materials, which do not contribute to radiation at that instant. This description fits best because it distinguishes the power actually radiated from other effects like mounting losses, the DC resistance of the feed line, or reflections due to mismatch. The load from the mount isn’t about radiated power, the DC feed line resistance isn’t what radiates, and the reflection coefficient describes how much power is reflected back due to impedance mismatch—not how much power the antenna radiates.

Radiation resistance is the part of an antenna’s input resistance that comes from energy being radiated as electromagnetic waves. It represents the real power that leaves the antenna as radiation, as if the antenna were a resistor through which that power is dissipated by emission of waves. The rest of the input impedance is made up of reactive energy stored near the antenna or resistive losses in the materials, which do not contribute to radiation at that instant.

This description fits best because it distinguishes the power actually radiated from other effects like mounting losses, the DC resistance of the feed line, or reflections due to mismatch. The load from the mount isn’t about radiated power, the DC feed line resistance isn’t what radiates, and the reflection coefficient describes how much power is reflected back due to impedance mismatch—not how much power the antenna radiates.