Westermo RM-505U-K - Manual (Page 21)

man_505U-K_1.4.doc Dec 2008
    ELPRO Technologies Pty Ltd 2008 Page 21
“3M 23 tape”, and finally with another layer of PVC UV Stabilised insulating tape. The first
layer of tape allows the joint to be easily inspected when trouble shooting as the vulcanising
seal can be easily removed.
Where antennas are mounted on elevated masts, the masts should be effectively earthed to
avoid lightning surges. Where the antenna is mounted outside of an industrial plant
environment, a coaxial surge diverter is 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.
3.2.1 Dipole antenna.
A unity gain dipole is the normal antenna for use on unlicensed channels. As it does not
provide any gain, then the power transmitted from the antenna will be the same as the power
out of the module, and hence will not exceed the permitted power of the unlicensed channel.
Dipole antennas should be mounted vertically, at least 1 metre away from a wall or mast for
maximum performance.
3.2.2 Yagi antenna.
Yagi antennas are directional. That is, they have positive gain to the front of the antenna,
but negative gain in other directions. This may be used to compensate for coaxial cable loss
for installations with marginal radio path.
Yagi antennas should be installed with the central beam horizontal and must be pointed
exactly in the direction of transmission to benefit from the gain of the antenna. Also note that
Yagi antennas normally have a drain hole on the folded element - the drain hole should be
505U