SAR Measurements on Mobile Phones With Hands Free Kits
for Australian Consumers’ Association (Choice)
Summary of EMC Technologies Report M000515R 14 July 2000
There have recently been media reports questioning the benefit of hands free kits in reducing the exposure of the head to Electromagnetic Radiation (EMR). The Australian Consumers Association (Choice) commissioned independent testing of mobile phones with and without hands free kits. Specific Absorption Rate (SAR) measurements were performed by EMC Technologies, an independent laboratory accredited for SAR measurements on mobile phones. The tests were performed with the "State-of-the-Art" Dosimetric Assessment System (DASY3) developed by the Swiss Federal Institute of Technology (ETH). The DASY3 is also known as the Kuster System.
Specific Absorption Rate is defined as the rate of absorption of Electromagnetic Energy per unit mass of biological tissue. The measured SAR for each mobile phone quantifies the energy that will be absorbed by the part of the body exposed to the EMR, with and without the hands free kit (microphone and earpiece) in use. A Generic Twin Phantom filled with tissue simulating liquid, was used to simulate the human torso. The methodology used in this testing was generally in accordance with the mandatory human exposure standard specified by the Australian Communications Authority for mobile and cordless phones. SAR requirements are specified only for the head.
Baseline SAR measurements were first performed on three mobile phones (two 900 MHz GSM and one 835 MHz AMPS) transmitting at full power in the standard left and right ear Touch Positions. The second part of the testing evaluated the performance of the hands free adaptors in reducing SAR inside the head. The hands free kits, (microphone and earpiece) were attached and the cable taped along the length of the phone and its antenna to represent worst case coupling of the EMR to the cable. SAR measurements were then performed inside the phantom at the ear position, first with the phone placed 70 cm away from the body (to simulate hand held use), and then with the phone mounted at the flat section of the phantom (to simulate waist or pocket-worn position). The third part of the tests evaluated the SAR performance of the three phones at the waist/pocket position.
Both GSM phones complied with the Australian and New Zealand SAR limits when tested under normal conditions at the ear position. The New Zealand AMPS phone complied with the New Zealand limit but did not comply with the Australian limit.
The hands free kits reduced the SAR inside the head by worst case margins of 92% for the two GSM phones and 92% for the AMPS phone. The SAR reduction at the head was achieved for both hand held and body worn positions for each phone. A further reduction will be achieved when the hands free kit cable is arranged in a manner, consistent with normal use, away from the phone antenna.
The SAR of the New Zealand AMPS phone at the waist position (in hands free mode), exceeded the New Zealand (and Australian) SAR limits. It should be noted that no international standard currently exists for measuring SAR in the hip/waist.
The use of hands free kits with mobile phones greatly reduces exposure to the head, however, wearing the phone on the waist or in the pocket, places it, and the antenna in closer contact to the body and is likely to increase actual exposure. The exposure limits are unlikely to be exceeded when the phone is operated with hands free kit fitted and the phone held in the hand. A copy of the report including detailed procedures, photographs and SAR plots is available from the Choice website at URL <http://www.choice.com.au/articles/a100378p1.htm>
Chris Zombolas <email@example.com>
EMC Technologies Pty Ltd