Definition

Any FREQUENCY at which electromagnetic RADIATION of energy is useful for communication. Radio frequencies are usually classed as very low, below 30 kilohertz; low, 30-300 kilohertz; medium, 300-3,000 kilohertz; high, 3-30 MEGAHERTZ; very high, 30-300 MEGAHERTZ; ultra high, 300-3,000 MEGAHERTZ; super high, 3,000-30,000 MEGAHERTZ; extremely high, 30,000-300,000 MEGAHERTZ.