User's Manual

14
3 General Considerations
3.1 Frequency Planning
The OS-Gemini is capable of operating in the whole frequency range 5.725 to 5.875 GHz
(defined as the ETSI 5 GHz C band) but for the USA is optimised for the ISM band (5.725-
5.850 GHz), utilising a 10 MHz wide channel. Setting of the operating frequency channel is
automatic and is carried out by the built-in Dynamic Frequency Selection (DFS) functionality.
The user can configure the OS-Gemini to avoid using certain frequencies to prevent interference
to other users of the band and prevent operation in parts of the band containing interference. The
use of this functionality is described in detail in section 6.3.4 “DFS Pages”.
3.2 Distance
The OS-Gemini will operate at ranges from 100m to 40 km. Operation of the system will depend
on obstacles in the path between the units. Operation at 40km will require a Line of Sight
(LoS) path. Operation at 100m could be achieved with one unit totally obscured from the other
unit, but with the penalty of transmitting at higher power in a non-optimal direction, thereby
increasing interference in the band. This subject is covered in more detail in section 4.2 “Path
Loss Considerations”.
3.3 Networking Information
The OS-Gemini operates as a transparent Ethernet bridge. Each unit requires an IP address.
This IP address is for management purposes only; it does not play any part in the operation on
the system. IP addresses are assigned during initial configuration as described in section 5.2
“Installation Procedure”.
3.4 Lightning Protection
The amount of lightning protection is dependant on regulatory requirements and the end user
requirements. The standard OS-Gemini ODU is fitted with surge limiting circuits and other fea-
tures to minimise the risk of damage due to nearby lightning strikes. These standard features
may require some additional equipment to be configured as part of the system installation to be
fully effective. Orthogon Systems recommends the use of screened cable and surge arrestor to
protect connected equipment from nearby strikes.
Note: The OS-Gemini is not design to survive direct lightning strikes. For this reason
the unit should not be installed as the highest point in a localised area, unless
specific precautions are taken. See section 9 “Lightning Protection”.