RTcom Radio Modems - Manual (Page 9)

9
Antenna Installation
The type and location of the antenna used can have a profound effect on your overall system
performance and its legality.
In point to point links it is good practice to make efficient use of the radio spectrum by selecting an
antenna that will project the R.F energy into the direction of desired operation and similarly at the
receiver to collect transmissions only from the location of the transmitter.
(Directional yagi antenna (vertically polarised)) (Directional yagi antenna (vertically polarised)
In polled systems, where there is a central base station, the base station will need an omni-directional
antenna. However, the outstations may still employ a directional antenna pointing back to the base
station.
(Omni-directional antenna (vertically polarised)) (Directional yagi antenna (vertically polarised)
For mobile systems the only practical choice is to use omni-directional antenna at all stations.
It is very important that all antennas in a system share the same polarisation otherwise losses of up to
30dB may be encountered.
Note: Polarisation can be put to good use when it is desirable to reject an unwanted transmission on
the same or a similar frequency.