If the ohmic resistance of a miniloop antenna is 2 milliohms and the radiation resistance is 50 milliohms, what is the antenna efficiency?

Antenna efficiency is found by dividing the radiation resistance by the total resistance, which is the sum of the radiation resistance and the ohmic resistance. Working in milliohms does not change the math, as the units cancel each other out during division. The total resistance here is 50 milliohms (radiation) + 2 milliohms (ohmic) = 52 milliohms. To find the efficiency, divide 50 by 52, which yields 0.9615, or 96.15%. The distractor 52% is simply the sum of the two numbers used as a percentage, and 25% comes from improperly dividing 50 by 2. Always remember the correct formula: Efficiency = R_rad / (R_rad + R_loss).