Radiation Resistance vs. Antenna Resistance

The terms 'radiation resistance' and 'antenna resistance' are sometimes used interchangeably by amateurs, but they shouldn't be, because they have distinctly different meanings. Radiation resistance is equal to the power radiated by an antenna divided by the square of the rms (effective) antenna current at a specified point in an antenna. That point usually is the point where RF power is supplied. In contrast, antenna resistance is equal to the power supplied to an entire antenna circuit divided by the square of the rms (effective) antenna current at a specified point. The difference between the power-values used in the two calculations is the loss power, because the antenna resistance calculation includes not only radiated power, but also power lost in RF conductor resistance, eddy current loss, insulator leakage loss, dielectric loss, corona loss, ground resistance loss, and any other power loss. ©2005 Tigertek, Inc. All rights reserved.

• July Fact-of-the-Day Index