905U-G Wireless Gateway
User Manual
Page 27
©September 2004
Chapter 3
INSTALLATION
3.1
General
The 905G module is housed in a rugged aluminum case, suitable for DIN-rail mounting.
Terminals will accept wires up to 12 gauge (2.5 sqmm) in size.
All connections to the module must be low voltage (SELV). Normal 110-240V mains
supply should not be connected to any terminal of the 905G module.
Refer to Section 3.3
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 aerials, or radio interference on the same channel, or the radio path being
inadequate. If the radio path is a problem (i.e. path too long, or obstructions in the way), then
higher performance aerials or a higher mounting point for the aerial may rectify the problem.
Alternately, use an intermediate 905U Module as a repeater.
The foldout sheet 905U-G
Installation Guide
provides an installation drawing appropriate to
most applications. Further information is detailed below.
Each 905G module should be effectively earthed/grounded via the "GND" terminal on the
905U module - this is to ensure that the surge protection circuits inside the module are
effective.
3.2
Antenna Installation
The 905G and 905U modules 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. Typical reliable distances are :
USA/Canada 15 miles
6dB net gain antenna configuration permitted (4W ERP)
Australia/NZ 12 km
unity gain antenna configuration (1W ERP)
Longer distances can be achieved if one antenna is mounted on top of a hill.
To achieve the maximum transmission distance, the antennas should be raised above
intermediate obstructions so the radio path is true “line of sight”. Because of the curvature of
the earth, the antennas will need to be elevated at least 15 feet (5 metres) above ground for
paths greater than 3 miles (5 km). The modules will operate reliably with some obstruction
of the radio path, although the reliable distance will be reduced. Obstructions that 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 larger obstruction than a
group of trees further away from the antenna. The 905G modules provide a test feature that
displays the radio signal strength.
Line-of-sight paths are only necessary to obtain the maximum range. Obstructions will
reduce the range, however may not prevent a reliable path. A larger amount of obstruction
can be tolerated for shorter distances. For very short distances, it is possible to mount the
