User's Manual

Liberator-V1000 User Manual Rev 04v05
Page 17 of 85 FBN Doc #: FBN-0125_04v05
3.3 Link Distance / Link Availability
The link distance is directly related to the weather conditions. Optimum link range and availability is
influenced by the following environmental conditions:
•
Rainfall - the lower, the better
•
Oxygen absorption – This ranges between about 14 and 16 dB/km, depending on temperature and
atmospheric pressure An accurate estimation of the total link distance (line of sight) is important in
estimating link range and quality. For the rain regions in your country, see appendix A.4.
3.4 Terminal Mounting Options
3.4.1 Wall Mounting
The wall mounting location should be strong enough to secure the terminal to the wall, taking into account all
foreseeable environmental conditions (e.g. wind, rain, ice).
Depending on the material to which the bracket is mounted, differently-sized mounting hardware may be
necessary. To mount the terminals onto the bracket use the enclosed M6 bolts. The bracket allows a tilt angle
of +/- 50° in both axes.
3.4.2 Pole Mounting
The mast mount bracket will be needed to mount the terminal onto poles with diameters from 50 mm to 115
mm (2” to 4.5”).
3.5 Lightning Protection Zones
In order to protect against lightning strikes damaging the equipment, it is important to choose a mounting
position for the radio terminal (ODU), which is located in a “Protected Zone”. In order to determine the zone
of protection against lightning strikes, the rolling sphere method is commonly-used. In this method, an
imaginary sphere is rolled-over the top of the building or mast: regions underneath the lower trajectory of
the sphere are in the protection zone, whilst areas above this are in danger of a lightning strike which can
damage equipment and be hazardous to life. The imaginary rolling sphere can only be elevated by lightning
finials, “air terminations” or adequately-grounded metallic structures, (not simply by the edge of a roof which
has no earth bond). The radio terminal should always be installed in a Protected Zone.
The radius of the rolling sphere depends on the level of lightning protection required, which varies between
geographical areas. See the table below for details. A commonly used value for the sphere radius is 45 metres,
but this will depend on the level of protection needed.
Table 2 - Lightning Protection Levels and Sphere Radius
Lightning Protection Level
Sphere radius (m)
Interception Current (kA)
1
20
2.9
2
30
5.4
3
45
10.1
4
60
15.7