SATELLINE-3AS and SATELLINE-3ASd
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SYSTEM DESIGN
SYSTEM DESIGN
8.1
8.1
System Configurations
System Configurations
8.1.1
Factors affecting quality and distance of the radio connection
•
power of radio transmitter
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sensitivity of radio receiver
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tolerance of spurious radiations of the radio modulating signal
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amplification of transmitting and receiving antennas
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antenna cable rejection
•
height
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natural obstacles
•
interferences caused by radio frequencies
The transmitter power of the base model of SATELLINE-3AS is 1 W and sensitivity of receiver
more than -115 dBm. Thus in a flat area and in free space with a 1/4 wave antenna (antenna
amplification 1dBi) and an antenna height of 1 m communications from 3 km to 4 km can be
achieved. Distances may be considerably shorter in situations where there are metallic walls or
other material inhibiting the propagation of radio waves.
Over long distances, problems caused by natural obstacles can often be solved by raising the
height of antennas. A ten fold increase in distance can be achieved with the use of amplifying
antennas. Frequent topographical variations over long distances may require that at least one of
the antennas needs to be raised to a height of 10 to 20 m.
As the placement of the antenna at the base station is more than 10 m from the modem it is
necessary to use a low loss cable (< 0.7 dB /10m ) in order not to waste the antenna
amplification. Problematical connections can also be solved by adding another intermediate
station for repeater. In systems with many base stations an RSSI-signal would assist in choosing
the best receiving base station. A communications network can also be built with a combination
of cables and radio data modems.
The SATELLINE-3AS radio data modem operates in the 450 MHz band, where interference
caused by human beings is insignificant. Long distance interferences need not to be taken into
account even in special weather conditions.
The SATELLINE-3AS eradicates normal levels of interference that occur. However, exceptionally
high levels of interference can break through the safeguards and thus cause errors on
transmssion. In mobile vehicle applications the range of operation can be increased by dividing
the transmitted data into e.g. 50...500 bits blocks and by retransmitting defected blocks.
