User's Manual

SATELLINE-4Pro
User Guide v0.93 DRAFT
62
Vertical polarised antennas (antenna elements are in vertical position) are often used in radio
systems. In a system between a base station and substations vertical polarisation is recommended.
The radio modem antenna cannot be mounted on the same level as the other substation antennas
in the same building. The best way to distinguish from the other antennas situated in the
neighbourhood is to mount the antennas as far as possible from each other on the altitude level.
The best result is generally obtained when all the antennas are in the same mast. With an extra
ground plane between the antennas more distinction can be obtained between the antennas in the
mast.
Horizontal polarisation can be used in data transmission between two points. With the polarisation
attenuation more distinction is obtained to vertical polarised systems. The influence of the
directional patterns of the antennas must, however, be taken into consideration. If a distinction to
another interfering antenna is wanted with the horizontal polarised antennas there must be a good
attenuation of the back lobe. In addition to this the interfering radiator should be situated behind
the antenna.
When a system does not demand the use of an omni-directional antenna it is recommended that
directional antennas are used e.g. two-element yagis in permanent external installations. Please
note that as antenna amplification increases the setting of the direction of the antenna requires
more attention.
Base stations in high places should be supplied with high-Q cavity filters. Please note that the higher
the base station antenna, the larger the coverage area and in turn that the risk of interference is
also increased.
Satel recommends the use of a band-pass filter with a large Q in the antenna cable of the base
station.