User's Manual

SATELLINE-3AS
User Guide, Version 2.2
91
11 DESIGNING SYSTEMS
11.1 Factors affecting the quality and distance of the radio
connection
• power of the radio transmitter
•
sensitivity of the radio receiver
•
tolerance of spurious radiation’s of the radio modulating signal
•
amplification of transmitting and receiving antennas
•
antenna cable attenuation
• antenna height
• natural obstacles
•
interference caused by other electrical equipment
The transmitter power of the base model of SATELLINE-3AS is 1 W (maximum) and the sensitivity
of the receiver better than -115 dBm. Thus in a flat area and in free space with a 1/4 wave
antenna (antenna amplification 1dBi) and antenna height of 1 m communication distances of 3
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, increasing the height of antennas can often solve problems caused by
natural obstacles. 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 be raised to a height of 10 to 20 m.
If the antenna cable is more than 10 meters long it is necessary to use a low loss cable (< 0.7
dB /10 m) in order not to waste the antenna amplification. Adding a repeater station can also
solve problematical radio connections. In systems with many base stations the RSSI-signal can
be used to assist in choosing the base station with the best signal. 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 man made
interference is insignificant. Long distance interference need not to be taken into account even in
special weather conditions.
The SATELLINE-3AS tolerates normal levels of interference that occur. However, exceptionally
high levels of interference can break through the safeguards and thus cause errors in data
transfer. In mobile vehicle applications the range of operation can be increased by dividing the
transmitted data into e.g. 50...500 byte long blocks and by re-transmitting the defected blocks.
A sufficient safety margin can be obtained by testing the communication path using extra 6 dB
attenuation at the antenna connection and with slightly less effective antennas than those to be
used in the final system.