Radio frequency, or RF, is a frequency or rate of oscillation within the range of about 3 Hz and 30 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves. Since most of this range is beyond the vibration rate that most mechanical systems can respond to, RF usually refers to oscillations in electrical circuits.

Special properties of RF electrical signals
Electrical currents or waves that oscillate at RF have properties that arise out of electromagnetic forces that do not affect direct current signals. One such property drives the RF current to the surface of conductors, known as the skin effect. Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor. The degree of effect of these properties depend on the frequency of the signals.