Viper SC+™ IP Router for Licensed Spectrum PN 001-5008-000 Rev. C
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2.6.
SELECTING ANTENNA AND FEEDLINE
Viper can be used with a variety of antenna types. The exact style used depends on the physical size and layout. Viper
has been tested and approved with antennas having a maximum gain of 10 dBi.
2.6.1.
ANTENNA GAIN
Antenna gain is usually measured in comparison to a dipole. A dipole acts much like the filament of a flashlight bulb: it
radiates energy in almost all directions. One bulb like this would provide very dim room lighting. Add a reflector
capable of concentrating all the energy into a narrow angle of radiation and you have a flashlight. Within that bright
spot on the wall, the light might be a thousand times greater than it would be without the reflector. The resulting bulb-
reflector combination has a gain of 1000, or 30 dB, compared to the bulb alone. Gain can be achieved by concentrating
the energy both vertically and horizontally, as in the case of the flashlight and Yagi antenna. Gain can be also be
achieved by reducing the vertical angle of radiation, leaving the horizontal alone. In this case, the antenna will radiate
equally in all horizontal directions, but will take energy that otherwise would have gone skywards and use it to increase
the horizontal radiation.
The required antenna impedance is 50 ohms. To reduce potential radio interference, the antenna type and its gain
should be chosen to ensure the effective isotropic radiated power (EIRP) is not more than required for successful
communication.
2.6.2.
TYPES OF ANTENNAS
A number of FCC-approved antennas have been tested for use with the Viper. Similar antenna types from other
manufacturers may be equally acceptable. It is important to follow the manufacturer’s recommended installation
procedures and instructions when mounting any antenna.
Table 11 Antenna Types
Omni (Vertical Collinear)
Yagi
Vertical Dipole
Omni-Directional Antenna
In general, an omni-directional antenna should be used at a master station and Relay Points. This allows equal coverage
to all of the remote locations. Omni-directional antennas are designed to radiate the RF signal in a 360-degree pattern
around the antenna. Short range antennas such as folded dipoles and ground independent whips are used to radiate
the signal in a ball shaped pattern while high gain Omni antennas, such as a collinear antenna, compress the RF
radiation sphere into the horizontal plane to provide a relatively flat disc-shaped pattern that travels further because
more of the energy is radiated in the horizontal plane.
