Chapter Three
Operation
Man_805U Rev 1.8
Page
11
Chapter Two
INSTALLATION
2.1
General
The 805U module is housed in an rugged aluminium case, suitable for DIN-rail mounting.
Terminals will accept wires up to 2.5 sqmm in size.
Normal 110-240V mains supply should not be connected to any terminal of the 805U
module.
Refer to Section 2.3
Power Supply
.
Before installing a new system, it is preferable to bench test the complete system.
Configuration problems are easier to recognize when the system units are adjacent.
Following installation, the most common problem is poor communications caused by
incorrectly installed antennas, or radio interference on the same channel, or the radio path
being inadequate. If the radio path is a problem (ie path too long, or obstructions in the way),
then higher performance antennas or a higher mounting point for the antenna may rectify the
problem. Alternately, use an intermediate 805U Module as a repeater.
The foldout sheet 805U
Installation Guide
provides an installation drawing appropriate to
most applications. Further information is detailed below.
Each 805U module should be effectively earthed via the "GND" terminal on the 805U
module - this is to ensure that the surge protection circuits inside the 805U module are
effective.
2.2
Antenna Installation
The 805U module will operate reliably over large distances. The distance which may be
reliably achieved will vary with each application - depending on the type and location of
antennas, the degree of radio interference, and obstructions (such as hills or trees) to the radio
path. The expected range for radio data rates of 19200 bits/sec is 5 km line-of-sight . At
38400 bit/sec, the expected distance will be approx 3 km, and at 76800, the distance will be
1.5 km.
Where it is not possible to achieve reliable communications between two 805U modules, then
a third 805U module may be used to receive the message and re-transmit it. This module is
referred to as a repeater.
An antenna must be connected to each 805U module using the female SMA connector at the
top of the module.
To achieve the maximum transmission distance, the antennas should be raised above
intermediate obstructions such that the radio path is true “line of sight”. Because of the
curvature of the earth, the antennas will need to be elevated at least 5 metres above ground
for paths of 5 km. For short distances, the modules will operate reliably with some
obstruction of the radio path. Obstructions which are close to either antenna will have more
of a blocking effect than obstructions in the middle of the radio path. For example, a group
of trees around the antenna is a large obstruction, and the antenna should be raised above the
trees. However if there is at least 100 metres of clear path before a group of trees, the trees
will have less affect on the radio path.
