User's Manual

Chapter Two Installation
Man_455U Rev 1.0 Page 13
as “3M 23 tape”, with a final layer of PVC insulating tape.
Where antennas are mounted on elevated masts, the masts should be effectively earthed to
avoid lightning surges. Although the 455U module is fitted with surge protection, additional
surge suppression devices are recommended if lightning surge problems are experienced. 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 3dB/6dB Collinear antenna.
A collinear antenna transmits the same amount of radio power in all directions - as such they
are easy to install and use. For marginal radio paths, the following lengths are the
recommended maximum for the coaxial cable to the antenna. RG58 -10 metres RG213 -
20 metres. Note that this applies to marginal paths only - if the radio path has a strong radio
signal, then longer lengths of cable ( and hence more cable loss) can be tolerated. If more
than 20 metres of cable is required for a marginal path installation, then a low loss cable such
as 10D-FB, or a higher gain antenna should be used. Collinear antennas should be mounted
vertically, at least 1 metre away from a wall or mast.
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
1m minimum
COLINEAR
ANTENNA
MAST
EARTH STAKE
IF GROUND CONDITIONS ARE
POOR, INSTALL MORE THAN
ONE STAKE
INSTALL AERIAL ABOVE
LOCAL OBSTRUCTIONS
ANT
455U
SURGE
ARRESTOR
(OPTIONAL)
COAXIAL CABLE
WEATHERPROOF
CONNECTORS WITH
“3M 23” TAPE
STRESS RELIEF LOOP
PROVIDE GOOD
GROUND
CONNECTION TO
MAST, MODULE
AND SURGE
ARRESTOR
GND
455U
Antenna installed
with drain holes
down
Coax feed looped
at connection
90
o