User's Manual

GM28 INTEGRATOR’S MANUAL
42
LZT 123 7468 P1A
• communication disturbances in the vicinity in which the antenna
operates.
In the sections below, issues concerning antenna type, antenna
placement, antenna cable, and possible communication disturbances are
addressed.
In any event, you should contact your local antenna manufacturer for
additional information concerning antenna type, cables, connectors,
antenna placement, and the surrounding area. You should also
determine whether the antenna needs to be grounded or not. Your local
antenna manufacturer might be able to design a special antenna suitable
for your the application.
4.3.2 Antenna Type
Make sure that you choose the right type of antenna for the modem.
Consider the following requirements:
• the antenna must be designed for the dual frequency bands in use:
GSM850/1900;
• 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 damage to the
modem.
4.3.3 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.
4.3.4 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.