a. The Troposphere.
The troposphere lies
from
the
earth's
surface to a height of approximately 6.8 miles.
b. The Stratosphere.
The
stratosphere
lies
between
the
troposphere and the ionosphere.
It is also called the isothermal
region. Its height is from 6.8 miles to 30 miles above the earth.
c. The Ionosphere. Because it is the furthest layer away, it is
ionized the most by the sun. It extends from approximately 30 to 250
miles above the earth. The ionosphere has several layers which have
varying levels of ionization.
3.
Frequency Classifications. Not only does each atmospheric layer
vary in ionization levels, but certain bands of frequencies have
unique propagation characteristics.
The lower frequencies have
different characteristics from the upper frequencies.
It is
important to understand how each band of frequencies travels from the
transmitter to the receiver.
Table 1.
Frequency band coverage.
*1kHz = 1 kilohertz = 1,000 hertz or 1 kHz
**1MHz = 1 megahertz = 1,000,000 hertz or 1 MHz or 1,000 kHz
***1GHz = 1 gegahertz = 1,000,000,000 hertz or 1 GHz or 1,000 MHz
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