User's Manual

905U-K Radio Telemetry Module User Manual
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ELPRO Technologies Pty Ltd 2001 Page 20
An antenna must be connected to each 905U-K module using the SMA connector that
protrudes though the top of the enclosure.
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, each antenna will need to be elevated at least 5 metres above ground for paths
greater than 5 km (3 miles). The modules will operate reliably with some obstruction of the
radio path, however the reliable radio range is decreased. Obstructions that are close to either
antenna will have more of a blocking effect than obstructions in the middle of the radio path.
Small whip antennas may be connected directly to the 905U-K module. Other antennas may
be connected to the module via 50 ohm coaxial cable (eg RG58 or RG213) terminated with a
male BNC connector. Connections between the antenna and coaxial cable should be carefully
taped to prevent ingress of moisture.
Moisture ingress in the coaxial cable is a common cause for problems with radio systems, as it
greatly increases the radio losses. We recommend that the connection be taped, firstly with a
layer of PVC Tape, then with a vulcanising tape such as “3M 23 tape”, and finally with
another layer of PVC UV Stabilised insulating tape. The first layer of tape allows the joint to
be easily inspected when trouble shooting as the vulcanising seal can be easily removed.
The higher the antenna is mounted, the greater the transmission range will be, however as the
length of coaxial cable increases so do cable losses. There are several types of antennas
suitable for use on unlicensed frequency channels. It is important that the antenna is chosen
carefully to avoid contravening the maximum power limit on the unlicensed channel - if in
doubt refer to an authorised service provider.
Connections between the antenna and coaxial cable should be carefully taped to prevent
ingress of moisture. Moisture in the coaxial cable is a common cause for problems with radio
systems, as it greatly increases the radio losses. We recommend that the connection be taped
with a vulcanising tape such as “3M 23 tape”, with a secondary layer of PVC insulating tape.
Where antennas are mounted on elevated masts, the masts should be effectively earthed to
avoid lightning surges. Surge suppression devices are recommended if lightning surge
problems are likely in the installation area. If the antenna is not already shielded from
lightning strike by an adjacent earthed structure, a lightning rod may be installed above the
antenna to provide shielding.
The available antennas to be used with the 905U-K units are:
CFD890EL 0 dBi Dipole antenna with 15’ of low loss RG-58 and SMA connector
SG900EL 5dBi Colinear omni-directional antenna with N-type connector (use
CC10/900 or CC10/900)
SG900-6 8dBi Colinear omni-directional antenna with N-type connector (use
CC10/900 or CC10/900)
YU6/900 10dBi Yagi directional antenna with N-type connector (use CC20/900
only)
The available accessory cables for use with the 905U-K units are:
CC10/900 33’ low loss RG-58 cable, 3dB loss
CC20/900 66’ low loss RG-58 cable, 6dB loss