Harris RF-7800W Student Manual page 12

Directional – Radiation Pattern
Directional Antennas use Horizontal Polarization
Pros
Directionally focuses radio signals for improved communication
Greater transmitting distance (military planning range 1500 miles)
Cons
Difficult installation and mounting
Requires large area for setup
Long-range radio communications take place in the high-frequency (HF) range of
1.6 to 30 MHz. Different portions of this band are allocated to specific radio
services under international agreement.
Directional antennas focus the RF energy in a particular direction. As the gain of
a directional antenna increases, the coverage distance increases, but the
effective coverage angle decreases. For unidirectional antennas, the lobes are
pushed in a certain direction and little energy is on the back side of the antenna.
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