User manual

905K Radio Telemetry Module User Manual
 ELPRO Technologies Pty Ltd 2010 Page 26
3.2.1 Dipole and Collinear antennas.
A collinear antenna transmits
the same amount of radio power
in all directions - as such that
are easy to install and use. The
dipole antenna with integral 15
‘ cable does not require any
additional coaxial cable,
however a cable must be used
with the collinear antennas.
Collinear and dipole antennas
should be mounted vertically,
preferably 1 metre away from a
wall or mast to obtain
maximum range.
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 located on the bottom of the
installed antenna.
The Yagi antennas may be installed with
the elements in a vertical plane
(vertically polarised) or in a horizontal
plane (horizontally polarised). For a two
station installation, with both modules
using Yagi antennas, horizontal
polarisation is recommended. If there are
more than two stations transmitting to a
common station, then the Yagi antennas
should have vertical polarisation, and the common (or “central” station should have a dipole or
collinear (non-directional) antenna.
905U
Antenna installed
with drain holes
down
Coax feed looped
at connection
90
o
Coaxial surge
diverter