905U-G Wireless Gateway
User Manual
Page 29
©September 2004
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 should be installed above the
antenna to provide shielding.
3.2.1
Dipole and Collinear antennas.
A collinear antenna transmits the same amount of radio power in all directions - it is easy to
install and use. The dipole antenna with integral 15 ft (5m) cable does not require any
additional coaxial cable, however the other collinear antennas do not have integral cable and
an external cable length must be connected - such as the CC10 or CC20 cable kits..
Collinear and dipole antennas should be mounted vertically, preferably no less than 2 ft (0.6
metre) away from a wall or mast to obtain maximum range. The CFD890 dipole antenna is
the preferred antenna for use in industrial plants and factories.
3.2.2
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.
1m minimum
COLINEAR
ANTENNA
MAST
EARTH STAKE
IF GROUND CONDITIONS ARE
POOR, INSTALL MORE THAN
INSTALL AERIAL ABOVE
LOCAL OBSTRUCTIONS
ANT
905U
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
for best performance
