2-14
Q10. What is one of the major reasons for the fading of radio waves which have been reflected from a
surface?
THE EFFECT OF THE EARTH'S ATMOSPHERE ON RADIO WAVES
This discussion of electromagnetic wave propagation is concerned mainly with the properties and
effects of the medium located between the transmitting antenna and the receiving antenna. While radio
waves traveling in free space have little outside influence affecting them, radio waves traveling within the
Earth's atmosphere are affected by varying conditions. The influence exerted on radio waves by the
Earth's atmosphere adds many new factors to complicate what at first seems to be a relatively simple
problem. These complications are because of a lack of uniformity within the Earth's atmosphere.
Atmospheric conditions vary with changes in height, geographical location, and even with changes in
time (day, night, season, year). A knowledge of the composition of the Earth's atmosphere is extremely
important for understanding wave propagation.
The Earth's atmosphere is divided into three separate regions, or layers. They are the
TROPOSPHERE, the STRATOSPHERE, and the IONOSPHERE. The layers of the atmosphere are
illustrated in figure 2-10.
Figure 2-10.—Layers of the earth's atmosphere.
TROPOSPHERE
The troposphere is the portion of the Earth's atmosphere that extends from the surface of the Earth to
a height of about 3.7 miles (6 km) at the North Pole or the South Pole and 11.2 miles (18 km) at the
