Chapter Two
Installation
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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.
2.2.2
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.
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.
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.