LESSON 2
PROPAGATION OF RADIO WAVES
TASK
The soldier will identify the principles of propagation of radio waves, microwave multichannel systems
and microwave multichannel radio antennas.
CONDITIONS
Given information and diagrams about the principles of propagation of radio waves, microwave
multichannel systems, and microwave multichannel radio antennas.
STANDARDS
Demonstrate competency of the objective by responding to 85 percent of the multiple-choice test
covering the principles of propagation of radio waves, microwave multichannel systems and microwave
multichannel radio antennas in lesson two.
REFERENCES
FM 11-65 and FM 24-21.
Learning Event 1:
PROPAGATION OF RADIO WAVES.
1.
The atmosphere. Wave propagation deals with the properties and the nature of the atmosphere
through which radio waves must travel from the transmitting antenna to the receiving antenna. The
atmosphere is not uniform, but varies with the altitude, geographic location, time of day or night, season,
and year. A knowledge of the composition and properties of the atmosphere aids in the solution of
problems that arise in planning radio communications paths and in predicting the reliability of
a. Troposphere. The troposphere is that portion of the earth's atmosphere extending from the
surface of the earth to heights of approximately 6 1/2 miles (10 km). Within the troposphere, the
bending of radio waves by refraction causes the radio horizon to exceed the optical horizon.
Tropospheric refraction (reflection caused by sudden changes in the characteristics of air in a lower
atmosphere) affect the received signal at distances beyond the radio horizon.
b. Stratosphere. The stratosphere is that portion of the earth's atmosphere lying between the
troposphere and ionosphere about 6 1/2 miles to 30 miles (10 to 48 km) above the earth. The
temperature in this region is nearly constant.
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