Telenetics OM-AMPS-100, Инструкция по установке, эксплуатации и обслуживанию

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Section 5
External Antenna Guidelines
OMEGA Installation, Operation, and Maintenance Manual 47
5
Introduction
This section provides guidelines about using an external antenna
with OMEGA. If you will not be using an external antenna, you
can skip this section
General Guidelines
The following guidelines provide general topics about using an
external antenna with your OMEGA.
High Voltage Areas
To avoid any damage, serious injury, or possible death, never
install an antenna near high-voltage power lines. Telenetics
recommends that you provide lightning protection for all external
antennas.
RF Signal
Antennas cannot amplify an radio-frequency signal. Rather, they
are designed to concentrate the radiated signal in a specific pattern
or focus it in a particular direction. The range of an antenna can be
increased by concentrating or focussing the signal.
Gain
An antenna’s gain is one of its identifying characteristics. Terms
such as unity gain, 3dB gain, and 9dB gain are common. The
amount of gain of an antenna is based on that of a true omni-
directional antenna. This type of antenna radiates the transmitted
signal in all directions. If the radiated power were visible, it would
resemble a sphere encompassing the antenna.
An omni-directional antenna is described as having unity gain. A
3dB gain antenna has a greater range. This type of antenna is also
referred to as omni-directional because the signal is transmitted in
all directions. However, the signal is concentrated in a horizontal
plane, so instead of a spherical “image”, its radiated power image
resembles a disk. With this type of RF signal concentration, a 3-
watt 3dB gain antenna has the equivalent range of a 6-watt unity
gain antenna and is said to have 6 watts of Effective Radiated
Power (E.R.P.).