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The RADIATION FIELD contains E and H fields that are propagated from the antenna into space
in the form of electromagnetic waves. The E and H fields of the radiation field are in phase with each
other.
A HARMONIC FREQUENCY is any frequency that is a whole number multiple of a smaller basic
frequency. For example, a radio wave transmitted at a fundamental frequency of 3000 hertz can have a
second harmonic of 6000 hertz, a third harmonic frequency of 9000 hertz, etc., transmitted at the same
time.
A VERTICALLY POLARIZED antenna transmits an electromagnetic wave with the E field
perpendicular to the Earth's surface. A HORIZONTALLY POLARIZED antenna transmits a radio
wave with the E field parallel to the Earth's surface.
A WAVEFRONT is a small section of an expanding sphere of radiated energy and is perpendicular
to the direction of travel from the antenna.
RADIO WAVES are electromagnetic waves that can be reflected, refracted, and diffracted in the
atmosphere like light and heat waves.
REFLECTED RADIO WAVES are waves that have been reflected from a surface and are 180
degrees out of phase with the initial wave.
