User's Manual

SATELLINE-4Pro
User Guide v0.93 DRAFT
64
12 DESIGNING SYSTEMS
12.1 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 SATELLINE-4Pro is 35 W (maximum) and the sensitivity of the receiver
better than -114 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-4Pro operates in the 450 MHz band, where man made interference is insignificant.
Long distance interference needs not to be taken into account even in special weather conditions.
The SATELLINE-4Pro 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.