User's Manual

105 Radio/Serial Telemetry Module User Manual
Page 54 © March 2000
The following design points should be noted :-
• A test of the radio path between the pump station and the tank station indicated that the radio
path would be reliable provided aerials were installed at 6 m above the ground. At each site,
the coaxial cable would be approx 10 m in length, so it was decided to use 3 element Yagi
aerials with RG58 coaxial cable - the Yagi aerials would compensate for the loss in the cable.
The system was installed in a country which permitted the use of 500mW radio power. If this
had not been the case, then an intermediate repeater station would have been required.
• At the tank station, there was an existing light pole with a mains power supply - the light pole
was 10m high. Permission was obtained to mount the aerial from the pole and to use the power
supply for the radio telemetry module.
As there was no existing electrical panel at this station, a small steel enclosure was installed on
the light pole. A 2 Amp-Hour sealed battery was installed to provide power during any mains
failure. The flow and level transducer were powered from the 24VDC loop supply provided by
the 105 module.
• At the pump station, the aerial was mounted on a 3 m J-bracket installed on the roof of the
pump station building. The final height of the aerial was approx 6 m. Care was taken to align the
Yagi aerials so they pointed at each other. The Yagi aerials were installed with horizontal polarity
- that is, with the elements horizontal. These aerials will not "hear" other radio users on the same
radio channel which generally use vertical polarity.
There was an existing electrical enclosure at the pump station, and the 105U module was
installed inside this enclosure. The module was powered from 220VAC mains with a 2 Amp
Hour sealed battery as backup.
• At the control station, the 105S module was installed inside the existing control panel enclosure.
The module was powered from an existing 24VDC power supply.