RFD900ux Data Sheet
www.rfdesign.com.au
13
Last update 12/09/2019
9
Diversity
The RFD900ux has two antenna ports and firmware which supports diversity operation of antennas.
During the receive sequence the modem will check both antennas and select the antenna with the
best receive signal. The antenna selected during receive is then also used for subsequent transmission.
In the case of only one antenna connected, it will automatically select the port with the antenna
connected. Testing by Silicon Labs has shown that link budgets can be improved up to the order of
8dB by employing a diversity scheme.
9.1
Spatial diversity
Spatial diversity is the case where the antennas are separated by some distance from one another. It
is recommended that two antennas connected to the RDF900ux modem be separated by at least
25cm, more if possible.
9.2
Polarisation diversity
Polarisation diversity is the case where the antennas are perpendicular to each other. i.e. one vertical,
and one horizontal. This is effective in reducing multipath effects which affect one or the other
polarisation. T
his scheme also helps to maintain the link between non-static objects such as aircraft
performing acrobatics by increasing the likelihood that one antenna will maintain the same
polarisation as an antenna on the other side of the link.
