User's Manual

455U-D Radio Modem Module User Manual
Page 20 © Jan 2008
Chapter Two INSTALLATION
2.1 General
The 455U-D module is housed in a rugged aluminum case suitable for DIN-rail mounting.
Terminals will accept wires up to 2.5 sqmm (12 gauge) in size.
Normal 110-240V AC supply should not be connected to any terminal of the 455U-D
module. Refer to Section 2.3 Power Supply.
To operate this equipment legally the user must operate on a designated license-free radio
channel and within the operating parameters of the license-free channel, or obtain a radio
operating license from the responsible government agency. This is done so the government
can coordinate radio users in order to minimize interference.
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 455U-D Module as a repeater.
The foldout sheet 455U-D Installation Guide provides an installation drawing appropriate to
most applications. Further information is detailed below.
Each 455U-D module should be effectively earthed via the "GND" terminal on the 455U-D
module - this is to ensure that the surge protection circuits inside the 455U-D module are
effective.
2.2 Antenna Installation
The 455U-D 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 4800 bits/sec is up to 60km (40 miles),
depending on installation, site and path terrain. The expected range at 19200 bits/sec (with
25KHz bandwidth) or 9600 bit/sec (with 12.5KHz), is up to 30 km (20 miles) line-of-sight.
Where it is not possible to achieve reliable communications between two 455U-D modules,
then a third 455U-D 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 455U-D 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 (15 feet) above