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Configure and test the Orion-900, 900MHz ISM band radio indoors first before
installing and mounting antennas.
The Power Over Ethernet Injector is not a waterproof unit, and should not be exposed
outdoors without protection or you may void your warranty.
Chapter 3 Antenna and RF Tutorial
Selecting Antenna Type
There are a vast number of antenna types designed for various general and special purposes, but
despite the huge variety, all designs essentially address two concerns, directionality and gain. These
selection criteria are discussed in the following paragraphs, along with a third criterion, polarization.
Directionality
An antenna may be designed to receive and transmit in all directions. Such antennas are
omni-directional. An example of an omni-directional receiving antenna would be a television antenna
in a metropolitan area where each television station transmits its signal from a different location
relative to the receiver. Similarly, a centrally located television transmitter would use an
omni-directional transmitting antenna.
The sensitivity and power of an omni-directional antenna are unfocused; that is, they are spread
through a wide volume of space, so the advantage of being able to communicate in all directions is
traded off for limited sensitivity and power.
If it is determined that all signals of interest are coming from a definable direction, the
omni-directional antenna can be replaced by a directional or sectoral antenna, which increases
sensitivity and power by focusing the beam in the desired direction.
In practice, even omni-directional antennas take advantage of directionality by focusing their
sensitivity and power in the horizontal plane. Rather than waste performance by sending signals into
space or into the ground, the horizontal omni-directional antenna redirects its power and sensitivity
from these directions, increasing performance in the horizontal plane.
In point-to-point applications, where the direction of communication is known and fixed, a highly
focused directional antenna can be used to provide maximum sensitivity and power. In addition,
because of its decreased sensitivity in all directions but the desired one, the directional antenna
improves performance by rejecting signals not coming from the desired direction. This provides an
effective increase in signal-to-noise performance.
A sector antenna has a wider “spread” than a directional (generally between 60 to 120 degrees) which
makes it a cross between an onmidirectional and a directional. This is useful in a point to multipoint
configuration where multiple sites are grouped in the same general area. The installer can then
make use of the higher sensitivity and power but also take advantage of the wider beam pattern and
improved front to back ratio.
