PART A: RADIO WAVE PROPAGATION
The distance traveled by a radio wave during a single cycle is known as a wavelength. A
wavelength can be expressed in any unit of measure. However, it is normally expressed in
meters. The number of complete waves that move past a given point in one second is called
frequency. A unit of frequency is called Hertz (Hz). One unit is equal to one cycle per
second Figure 1-1). The radio wave's strength or intensity is called its amplitude.
The radio wave, which is electromagnetic in nature, consists of an electrical field (E field) and
a magnetic field (H field). Each field supports the other, and neither can be propagated by
itself. Table 1, lists frequency bands, their designators, and the commonly accepted limits of
each band.
The direction of the E field of a radio wave, relative to the ground, determines the polarization
of the wave. Polarization can either be horizontal, vertical, or a mutation which adopts
portions of vertical and horizontal. The later results in a circular or hybrid form of a wave. If
a whip or other vertical type transmitting antenna is used to propagate radio waves, the
transmitted wave is considered to be vertically polarized. If the transmitting antenna is
horizontal, relative to the earth's surface, the transmitted wave is horizontally polarized.
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