Satel SATELLINE-1AS User Manual page 16

The metal-free zone around small antennas should be at least 1/2 m and big antennas
>5 m. The metal-free zone should be > 10 m around a relay antenna combination. This
means that, if a large network of radio modems is to be installed the best place for the
antenna is at the highest point of the building or even the use a radio mast. If a mast is
used, the antenna can be installed using a side-installation up to 2 ...3 m away from the
mast itself.
When mounting the antenna pay also attention to possible sources of interference such as:
mobile phone network base stations
local telephone network base stations
television transmitters
radio links
other radio modem networks
PC equipment (about a radius of 5 m from the antenna)
When ordering antennas please note that the antennas have been tuned to a certain
frequency range. Simple antennas and those made of stacked yagis are relatively wide
band. The frequency range of the antenna becomes narrower the more elements there are
in a yagi.
Keeping in mind the testing and service of the system it is generally useful to use rather a
long antenna cable in order to avoid the installation of radio modems near the antenna
into a place possibly difficult to access.
The antenna cable should be chosen according to the lenght bearing in mind the following
recommendations:
Length Type
< 5 m RG58
5 ... 20 m RG213
> 20 m Nokia RFX 1/2"-50
> 20 m S12272-4
> 20 m AirCom+
*) AirCom+ cable is partly air insulated, thus an absolutely air tight connection
between the cable and the connector is required.
In great distances when the antennas are in optical positions a 6 dB power marginal is
adequate. Since 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 an attenuating 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 process.
SATELLINE-1AS and SATELLINE-2AS
Attenuation
3.0 dB/10 m/450 MHz
1.5 dB/10 m/450 MHz
0.5 dB/10 m/450 MHz
0.5 dB/10 m/450 MHz
0.8 dB/10 m/450 MHz *)
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