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2.1.6 Mechanical Installation of the Antenna
A solid mechanical installation of the antenna is the base of a quality link. An
outdoor mounted antenna is exposed to extreme weather conditions. Metal
brackets oxidize, and vibrations will cause slack on connections. Therefore, the
mechanical connection between the antenna and its carrier needs to be solid.
Use locktite on screws. The connector between the cable and the antenna needs
to be sealed with threading tape. Corrosion on the connector will cause signal
losses due to changing impedance of the connection.
Outside mounted antennas are lightning strike sensitive. Lightning strikes always
are common at highest and smallest point, typically an antenna. The antenna
cable will then conduct the enormous amount of energy towards the bridge. If no
lightning arrestor is placed in-between the antenna cableand the bridge, the
bridge unit will be damaged, or worse, set on fire. Therefore, always use a
lightning arrestor.
When placing the antennas the following points should be kept in mind:
•
Place the antenna above conducting objects and in the clear
•
Place the antenna always on the edge of a roof or mounted on a wall
•
With an outdoor installation of the antenna, always use a lightning arrestor
•
Make sure that the mounting of the antenna can handle high forces. Wind can
cause misalignment or even permanent damage
•
Keep the cable length between the antenna and the bridge limited to the
minimum. Every meter of cable causes signal loss
•
Antenna cable should be a low noise cable such as LMR-400
