The base station provides the interface between the on-reef wireless network and the back-haul data link. The system uses a Campbell Scientific CR1000 logger with an Ethernet module and an appropriate modem to provide the back-haul IP network link and a Campbell Scientific RF411 spread-spectrum radio to provide the on-reef wireless network. The back-haul modem can be a 3G phone system modem to it can hook into other communications links such as a microwave or satellite modem.

The base station is powered off main supply where possible running through a 120 Amp-Hour sealed battery system to give backup power if the main supply fails. The system can also run off solar panels with the additional of a solar regulator and a solar panel. The CR1000 draws only 30 mA, the RF411 radio draws 75 mA when transmitting and a typical 3G modem draws around 800 mA when transmitting giving an overall power budget of less and one Amp at 12 volts or 12 watts and so a 20watt solar panel can power the system although normally 2 x 20 watt panels are used.

The base station is housed in a mid-sized ‘Pelican’ case to aid in weatherproofing; if full water proofing is required then the Pelican case is retained but water proof SeaCon connectors are used for all connections.

The photo below shows the insides of a base station showing the Campbell CR1000 logger (top), RF411 radio (middle) and in this case a Cybertec 1100 series 3G modem (bottom).

The aerials used depend on the deployment but the typical installation uses the RF411 radio for the on-reef network and a 3G CyberTec modem for the back-haul link using the Telstra NextG network. Both systems operate around the same frequency, 850 MHz for the NextG network and 900 MHz for the spread-spectrum radios. Directional ‘Yagi’ aerials are used for the NextG links using RFI Systems YB815-81 aerial. The 900 MHz spread-spectrum link uses either a directional Yagi aerial (RFI systems YB809-94 aerial) or an omni directional whip aerial (RFI MDD-203 aerial or CD1795 aerial). Loos loss coax is used to connect the aerials into the base station.

The distance obtained with the base station is determined by the elevation and type of aerial, it was found through field testing that an elevation of 20m gave a range of around 5 kilometres using the RF411 radios and an elevation of 6-8m gave a range of 2 kilometres.

The photo below shows the aerials located on One Tree Island on a 6M guyed pole (Hills Pty Ltd) with the two aerials, the NextG Yagi and the Spread-spectrum Yagi (smaller aerial).