User's Manual

SATELLINE-4Pro
User Guide v0.93 DRAFT
61
Antennas must be installed well away from metallic objects. In the case of small antennas this
distance should be at least ½ m. With large antennas the distance should be >5 m and in case of
repeater antenna combinations >10 m.
If the system contains a large number of radio modems, the best location for an antenna is the
highest point of a building and possibly an additional antenna mast. If a separate antenna mast is
used, the antenna can, if necessary, be installed sideways about 2…3 m from the mast itself.
When installing an antenna possible interference sources must be considered. Such interference
sources are, for example:
mobile telephone network base station antennas
public telephone network base station antennas
television broadcast antennas
radio relay antennas
other radio modem systems
PC-related devices (approximately 5 m radius from antenna)
When ordering antennas we request you to note that antennas are always tuned to a specific
frequency range. Simple antennas and antennas, which have been constructed of stacked yagi-
antennas, are typically rather broadband. As the number of yagi-elements increases the frequency
range becomes narrower. Note this specially with 35W.
When designing and installing a system it is advisable to prepare to test the system, and also to
consider serviceability of the system. In particular cabling should be planned to allow easy access
and to allow for maintenance. It is often practical to use long antenna cables, so that the radio
modem can be installed far enough from the antenna itself to a location that is easily accessible
(see section 10).
The type of the antenna cable is dependent on the length of the antenna cable, and the following
table can be used to select a suitable type:
Length Type Attenuation 10m/450MHz
<5m RG58 3.0dB
>20m ECOFLEX10 0.9dB
<20m ECOFLEX15 0.6dB
If there is a line-of-sight path between the antennas a 6 dB power marginal is usually adequate.
However, if the connection is built on the reflection and/or the knife-edge diffraction the path loss
can vary even 20 dB depending on the weather conditions. In this case a short test can give a too
positive result of the quality of the connection. Thus the height of the antennas and topographical
obstacles must be surveyed with great care. From time to time a marginal connection can be used
if the data transmission protocol is well prepared for this and the data transmission that occasionally
slows down does not cause any problems to the system.