CEP AG
Revision 1.2
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the antenna must be designed for the one of the frequency bands in use;
please ask your network provider for more information:
o
GSM 850/900 MHz
o
GSM 1800/1900 MHz;
the impedance of the antenna and antenna cable must be 50 ;
the antenna output-power handling must be a minimum of 2W;
the VSWR value should be less than 3:1 to avoid any damage to the modem.
5.3.3 Antenna placement
The antenna should be placed away from electronic devices or other antennas. The
recommended minimum distance between adjacent antennas, operating in a similar
radio frequency band, is at least 50cm. If signal strength is weak, it is useful to face a
directional antenna at the closest radio base station. This can increase the strength
of the signal received by the modem. The modem’s peak output power can reach 2W.
RF field strength varies with antenna type and distance. At 10cm from the antenna
the field strength may be up to 70V/m and at 1m it will have reduced to 7V/m. In
general, CE-marked products for residential and commercial areas, and light industry
can withstand a minimum of 3V/m.
5.3.4 The antenna cable
Use 50 impedance low-loss cable and high-quality 50 impedance connectors
(frequency range up to 2GHz) to avoid RF losses. Ensure that the antenna cable is
as short as possible. The Voltage Standing-Wave Ratio (VSWR) may depend on the
effectiveness of the antenna, cable and connectors. In addition, if you use an adapter
between the antenna cable and the antenna connector, it is crucial that the antenna
cable is a high-quality, low-loss cable. Minimize the use of extension cables,
connectors and adapters. Each additional cable, connector or adapter causes a loss
of signal power.
5.3.5 Possible communications disturbances
Possible communication disturbances include the following:
Noise
can be caused by electronic devices and radio transmitters.
Path-loss
occurs as the strength of the received signal steadily decreases in
proportion to the distance from the transmitter.
Shadowing
is a form of environmental attenuation of radio signals caused by
hills, buildings, trees or even vehicles. This can be a particular problem inside
buildings, especially if the walls are thick and reinforced.
Multi-path fading
is a sudden decrease or increase in the signal strength.
This is the result of interference caused when direct and reflected signals
reach the antenna simultaneously. Surfaces such as buildings, streets,
vehicles, etc., can reflect signals.
