SATELLINE-EASy / SATELLINE-EASy 869
User Guide, Version 3.0
81
15.3
Antenna installation
15.3.1
Hand-held equipment
o
¼-wave antenna (wavelength at frequency of 450 MHz is approximately 70 cm)
o
Helix-antenna
Antennas are installed directly to the TNC connector at the upper part of the radio modem.
15.3.2
Mobile equipment
o
¼-wave antenna
o
½-wave antenna
The ideal installation position is vertical, and there should be at least 0.5 m of free space
around the antenna. A separate ground plane should be placed under the ¼-wave antenna
(vehicle rooftop or the engine hood or trunk door are usually suitable). In problematic cases the
most suitable type is a ½-wave antenna. It can be installed directly at the top of a pipe with the
added benefit of gaining as much as free space around the antenna as possible. In case the
antenna cannot be directly connected to the radio modem, a coaxial cable with 50 ohm
impedance must be used between the antenna and the antenna connector.
15.3.3
Base stations
o
Omni-directional antennas ( ¼- , ½- or 5/8-wave antenna)
o
Directional antennas (yagi /multi-element antenna or corner antenna)
The antenna should be installed in a vertical position. The exact location of the antenna
depends on several factors, such as the size of the overall system and the coverage area terrain
contours. A rule of thumb is that the base station antenna should be located at the highest point
of the coverage area and as close to the centre of the coverage area as possible. The base
station antenna can also be located inside a building, if the walls of the building do not contain
metal.
15.3.4
General antenna installation instructions
The reliability and the achievable coverage of useful signal strength can be severely affected by
the positioning of the antenna. Antenna and cable connectors should have gold-plated pins and
sockets, as use of low quality connectors can lead to eventual oxidation of the connector
surfaces, which in turn may degrade the contact and cause additional attenuation. Good quality
tools and materials must be used when installing radio modems, antennas and cables. The
weather tolerance of the materials used must also be taken into account. Installed materials
must withstand all foreseeable weather conditions (frost, excess sun, direct UV-radiation,
seawater etc.). Also possible environmental pollution must be considered (acids, ozone etc.).
