User's Manual Part 1

16
3 General Considerations
3.1 Frequency Planning
The OS-Gemini operates over the frequency range 5.725 to 5.850 GHz (defined as the USA
ISM band and the ETSI 5 GHz C band), utilising a 11 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 6.3.5 “DFS Pages”.
3.2 Distance
The OS-Gemini will operate at ranges from 100 m to 130 km, this within 3 modes 0-5km, 0-
40km and 0-130km. Operation of the system will depend on obstacles in the path between the
units. Operation at 40 km or above will require a near Line-of-Sight 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  “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 and it plays no part in the operation of 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 dependent on regulatory requirements and the end user
requirements. The standard OS-Gemini ODU is fitted with surge limiting circuits and other
features to minimize 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 designed 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”.