User manual

905K Radio Telemetry Module User Manual
 ELPRO Technologies Pty Ltd 2010 Page 24
3.1 How to mount the 905K
To mount the 905K, remove the four
screws in the top plate, and carefully
remove the cover. The two mounting
holes should now be visible.
For Class I Div 2 areas in North
America, the 905K must be installed
inside another enclosure.
It is important to effectively earth the
unit to help prevent radio noise and
static electricity damage. The
preferred method is to earth the
module using the mounting screws to
connect to an earthed surface. If this
is not possible, use an earth lug in the
mounting screw connection and
secure the other end of the wire to a good earth.
3.2 Antenna Installation
The 905K 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. 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 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. A 905U module can be used with the 905K to display 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 antennas
inside buildings. An obstructed path requires testing to determine if the path will be reliable.
Where it is not possible to achieve reliable communications between two 905U modules, then a
third 905U module may be used to receive the message and re-transmit it. This module is
905U-K
MOUNTING HOLE