User's Manual

14 M3090 Integrator’s Manual
Doc.no: 198 17 - KRD 102 303 Uen, Rev B
$QWHQQD/HQJWKV
The following lengths are typical for half-wave and quarter-wave antennas in
the frequency range that the M3090 radio modem uses. The lengths given will
vary for a specific realisation, depending on the material that surrounds the core
of the antenna. If in doubt, refer to the documentation included with the antenna.
6KRUWHQHG$QWHQQDV
A shortened antenna is even shorter than a quarter-wave antenna. It can be
designed to have characteristics that are nearly as good as those of a full-length
antenna.
 $QWHQQD&RQFHSW V
The following sections present some fundamental concepts with regard to
antennas.
 $QWHQQD*URXQG3ODQH
An antenna ground plane is an area under the antenna that is connected to
ground and horizontal, flat and sufficiently wide. An antenna with a ground
plane will function more efficiently.
It is especially important that quarter-wave antennas have a ground plane.
 3RODUL]DWLRQ
Radio waves radiate parallel to the antenna. The best reception is achieved when
the receiving antenna is parallel to the transmitting antenna.
The antennas of Mobitex radio base stations are vertical, which means that the
radio waves are vertically polarized.
Frequency range Half-wave antenna length Quarter-wave antenna length
890 to 960 appr. 160 mm appr. 80 mm