TC 9-64 _________________________________________________________________________
that of the E field is produced. The variations in magnetic field intensity, in
turn, produce another E field. Thus, the two varying fields sustain each
other, resulting in electromagnetic wave propagation.
2-15. During this radiation process, the E and H fields are in phase in time
but physically displaced 90 degrees in space. Thus, the varying magnetic field
produces a varying electric field; and the varying electric field, in turn,
sustains the varying magnetic field. Each field supports the other, and
neither can be propagated by itself. Figure 2-4 shows a comparison between
the induction field and the radiation field.
Figure 2-4. E and H Components of Induction and Radiation Fields
2-16. An energy wave generated by a transmitter is called a radio wave. The
radio wave radiated into space by the transmitting antenna is a very complex
form of energy containing both electric and magnetic fields. Because of this
combination of fields, radio waves are also referred to as electromagnetic
radiation. The discussion that follows explains the earth's atmosphere and its
effect on radio waves. All the principles of wave motion that were discussed
in chapter 1 also apply to radio waves.
alone. The term applies to all equipment that generates signals in the form of
electromagnetic energy.
2-6
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