Government compliance tests clear multi-carrier base station emissions
Tests by the Australian radiation watchdog around a mobile phone tower with multiple antennas transmitting from all three network carriers has found the highest cumulative radiation level at just below two per cent of the Australian safety standard.
The antenna site in the Victorian town of Sunbury, 40km north-west of Melbourne, is the latest to be tested by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) as part of their ongoing base station compliance survey which started in 2007.
ARPANSA took measurements of Radio Frequency Electromagnetic Energy (RF EME) at several locations around the Sunbury phone tower, which carries multiple Optus, Telstra and Vodafone antennas, in an effort to find the highest reading.
“The maximum level of RF EME from this base station (full power) determined from measurements at locations around this site was 1.311% of the ARPANSA Standard limit for public exposure,” the measurements taken in July 2012 found.
The testers calculate the full power value by multiplying their measured values by a factor (usually by 4 to 10 times) to give the maximum possible output of that base station.
“The resulting full power value can be thought of as the maximum level of RF EME present at the location when this base station is handling as many calls as it possibly can,” ARPANSA said.
The ARPANSA researchers also search for the highest measured level of RF EME from all nearby base stations, which for the Sunbury tower was measured at 0.190% of the standard.
MCF Manager Ray McKenzie said the latest survey results showed network carriers took the cumulative signal outputs of all network antennas in an area into consideration when installing new equipment to ensure public exposure remained below the safety standard.
“The results show that base stations still remain compliant with the Australian safety standard even when calculating exposure from multiple base stations in an area at maximum output,” Mr McKenzie said.
Radiation tests of multiple carriers at Sunbury
ARPANSA’s tested maximum was similar to the Environmental EME Report carried out by Telstra in January 2010, which listed the maximum EME level as 0.47% of the ARPANSA Standard limit.
Mr McKenzie said the real life compliance tests confirmed that the carriers own predictions of maximum exposure around every base station gave a worst-case estimate of the likely public exposure levels.
“Under the industry code of practice when new base stations are installed or upgraded the local community are required to be informed about the predicted maximum exposure levels through environmental reports, which are publically available at the RFNSA website, McKenzie said.
“The predicted levels shown in the environmental reports deliberately include many conservative assumptions to ensure they clearly show a worst case level of exposure.
“When independent ground level tests of base stations are conducted, such as those by ARPANSA, the real life exposure levels measured are typically significantly lower than the carriers predicted levels shown in the published environmental reports.”
“In normal operation base stations adapt their power output based on the number of calls they are connecting to and the distance to the connected devices.
“Mobile handsets also reduce their power output in areas of good coverage, that’s why it is important for base stations to be built close to areas where wireless services are required.”
ARPANSA also carried out two base station surveys in 2011 at sites in the metropolitan Sydney suburbs of Ermington and Drummoyne.
Extrapolating the measurements from the rooftop antennas in Drummoyne gave a maximum exposure level of 1.182% while the highest actual measured level near the site was 0.388% of the ARPANSA Standard limit for public exposure.
Tests around antennas mounted on a service station price board in Ermington calculated the maximum exposure from the site to be 0.423% with the highest recorded level from all nearby base stations at 0.124% of the safety limit.
Since their survey program began in 2007, ARPANSA have conducted tests at 25 base stations at sites across every state in Australia.
The radiation agency select a variety of test sites to cover all carriers, technologies, geography and types of installation and will also select sites which may have caused significant community concerns.