Altai Technologies Ltd. All rights reserved
A8n Series Super WiFi Base Station Installation Guide
TPS13-002_rev1.0
External Lightning Protectors
1)
Lightning Rod
A lightning rod (air terminal) neutralizes the downward lightning strike by launching an
upward ionized path. The lightning current will follow this path and is thus diverted
away from personnel and electronic equipment. The lightning rod must be
constructed of steel with a pointed tip and welded to a ground conductor.
The lightning rod must be installed at top of the mounting post or tower higher than
the highest portion of equipment it protects. For A8n base station installation, the 4-
sector antennas are usually the highest points and usually protrude away from the
post. Suppose the horizontal distance from the post to the top outer most point of
antenna is d, the minimum height of the tip of lightning rod above the highest point of
antenna (H) is recommended to be at least 2d such that a cone of protection of 60
degree is ensured around the pole or tower. In areas of high lightning activities, the
height H should be increased to 5d.
2)
Ground Conductor
A ground conductor is a metal strip or rod usually made of copper or similar
conductive metal linking the lightning rod to the earth. The prime purpose of the
ground conductor is to conduct lightning current from the lightning rod to the earth
termination. It also provides connection to a metal grounding plate so that the
equipment under protection can be connected to at the shortest distance possible.
A ground conductor must be installed straight and vertical without bends such that it
connects to the earth termination at the shortest and direct path. As a rule of thumb,
a minimum 50 mm
2
in cross sectional area or AWG 0 copper conductor is
recommended for the ground conductor. Aluminum or iron conductor can also be
used but with poorer conductivity. Minimum cross sectional area of copper,
aluminum and iron ground conductor are 16, 25 and 30 mm
2
respectively.
The connection between the ground conductor and the earth must be no higher
than 5 ohms. This is achieved by grounding to special grounding bars in the case of
post mounting or to the steel reinforcement bars at the concrete base of the tower in
case of tower mounting.
3)
Grounding Plate
A grounding plate is a metal plate welded to the post or tower which provides a
common grounding connection placed at a short distance from the equipment and