User manual

Chapter Two Installation
Page 13 © January 2011
Where antennas are mounted on elevated masts, the masts should be effectively earthed to avoid
lightning surges. For high lightning risk areas, surge suppression devices between the module
and the antenna are recommended. If the antenna is not already shielded from lightning strike by
an adjacent earthed structure, a lightning rod may be installed above the antenna to provide
shielding.
2.2.1 Dipole and Collinear antennas.
A collinear antenna transmits the same amount of radio power in all directions - as such that are
easy to install and use. The dipole antenna with integral 15 ‘ cable does not require any
additional coaxial cable, however a cable must be used with the collinear antennas.
Collinear and dipole antennas should be mounted vertically, preferably 3 feet (1 metre) away
from a wall or mast to obtain maximum range.
2.2.2 Yagi antennas.
A Yagi antenna provides high gain in the forward direction, but lower gain in other directions.
This may be used to compensate for coaxial cable loss for installations with marginal radio path.
The Yagi gain also acts on the receiver, so adding Yagi antennas at both ends of a link provides
a double improvement.
Yagi antennas are directional. That is, they have positive gain to the front of the antenna, but
negative gain in other directions. Hence Yagi antennas should be installed with the central beam