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6193-3201
Chapter Two
INSTALLATION
2.1 General
The RM-90 module is 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 SELV. Normal 110-240V mains supply
should not be connected to any terminal of the RM-90 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 RM-90 Module as a repeater.
Each RM-90 module should be effectively earthed via the “GND” terminal on the RM-90
module – this is to ensure that the surge protection circuits inside the RM-90 module
are effective.
2.2 Antenna Installation
The RM-90 module will operate reliably over large distances. The distance which may
be reliably achieved will vary with each application – depending on the transmit power
(user configurable), type and location of antennas, the degree of radio interference, and
obstructions (such as hills or trees) to the radio path. Typical reliable distances for 1W
transmit power 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 cur-
vature 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 which are close to either antenna will have more of a blocking affect 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
RM-90 modules provide a diagnostic feature which displays the radio signal strength of
transmissions.
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 obstruc-
tion can be tolerated for shorter distances. For very short distances, it is possible to
mount the antennas inside buildings. An obstructed path requires testing to determine if
the path will be reliable – refer the section 6 of this manual.
