(3) The high frequency band (3 to 30 MHz) is used for short
distance communication.
At these frequencies, the local terrain
absorbs more and more of the signal as the frequency increases,
decreasing the ground wave range.
Long distance communications is
possible using sky wave.
(4) The very high frequency band and higher bands (30 MHz and
over) are used for line of sight communication. Only the direct wave
component of the ground wave is usable.
The range can be increased
by raising the height of the antenna. Sky wave communication is not
possible because the frequencies pass through the ionosphere and are
not reflected.
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