5. Summary. In this lesson, you learned about the fundamentals of radio wave propagation,
modulation, and propagation characteristics through different media.
a. A cycle is one complete positive and negative alternation of current or voltage.
b. A wavelength is the distance an electromagnetic wave travels during the cycle.
c. Amplitude in the magnitude of energy of a wave, as measured from zero.
d. Frequency is the number of complete positive and negative cycles completed in a given
period, normally per second.
e. The electromagnetic spectrum is the entire range of electromagnetic waves arranged in the
order of their frequencies.
h. Polarization is the direction of a radiated signal, either horizontal or vertical.
i. AM is modulation in which the amplitude of a carrier wave is varied above and below its
normal value in accordance with the intelligence of the signal being transmitted.
j. FM is the process of varying the frequency of a carrier wave, usually with an audio
frequency, in order to convey intelligence.
k. Reflection is the turning back of a radio wave from an object on the surface of the Earth.
Radio waves can also be reflected off the ionosphere.
l. Refraction is the bending or change in direction of a radio wave passing into another
medium.
m. Diffraction is the bending of the path of waves when the waves are met with some form of
obstruction.
n. Absorption is the removal of energy from a radiated field by objects which retain the energy
or conduct it to ground. Loss by absorption reduces the strength of a radiated signal.
SS0130
1-14
Previous Page
