SATELLINE-2ASxE
User Guide, Version 2.0
43
12 Equipment
12.1 Connecting antennas to radio modems
Recommended antenna types are as follows:
12.1.1 Hand portable equipment
x
1/4 wave antenna (wave length on 450 MHz is about 70 cm)
x
Helix antenna
The antennas are mounted directly to the antenna connector (TNC) on the top of the radio modem.
12.1.2 Equipment installed in vehicles
x
1/4-wave antenna
x
1/2 wave antenna
Ideally the antenna should be installed vertically and it should have at least 0.5 m of open space
surrounding it. In a small system 1/4 wave antenna is adequate. There should be a ground plane
below the antenna (truck bonnet or roof). In weak conditions a 1/2 wave antenna is the most
suitable. It can be mounted at the top of a pipe, as this provides it with as much open space as
possible. In places where the antenna cannot be connected directly to the TNC connector a 50
ohm coaxial cable must be used to provide the link between the radio modem and the antenna.
12.1.3 Base station
x
omnidirectional (1/4, 1/2 or 5/8 wave antenna)
x
directional (yagi or corner reflector antenna)
The antenna should be installed in an upright position. The exact location of the antenna depends
on a number of factors from system size to physical ground countours. As a general rule, the
antenna for a base station should be located at the highest point in the most central location of the
system.
Alternatively the base station antenna can be situated inside the building, providing that the walls of
the building do not contain metal.
