Rainbow Electronics GT864-PY - Manual (Page 14)

GT864-QUAD/PY Hardware User Guide
1vv0300756 Rev.0 08/ 05/07
Reproduction forbidden w ithout Telit Communications S.p.A. w ritten authorization - All Rights Reserved page 14 of 23
5 Antenna
5.1 General
The antenna is the component in your system that maintains the radio link between the network and
the modem. Since the antenna transmits and receives electromagnetic energy, its efficient function will
depend on:
• the type of antenna (for example, circular or directional);
• the placement of the antenna;
• 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 application.
5.1.1 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 one of the frequency bands in use; please ask your
network provider for more information:
• GSM 850/900 MHz
• GSM 1800/1900 MHz;
• the impedance of the antenna and antenna cable must be 50 Ω ;
• 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.
5.1.2 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.