How far does the RF radiation from your DECT cordless phone reach inside your home and how strong is it. A real-life study performed by us with a DECT cordless phone provides us with some answers. The paper was presented at the EMF Workshop in Rhodes, Greece in 2002.
The use of DECT (Digital Enhanced Cordless Telecommunication) cordless phones has been a major health and environmental concern in Europe and especially in Germany for years. The biological concern arose from studies on HF (high frequency) sources such as GSM cellular phones and towers. Digital cordless phones are also available in the USA – marketed as 2.4 GHz digital technology. A digital cordless phone was placed in a representative private home in California and HF measurements were conducted at different locations inside, using frequency selective spectrum analysis to obtain the cordless phone power densities. The results showed that the radiation patterns and levels emitted by the small cordless phone base station are almost identical to the DECT technology – also digitally pulsed and permanent microwave radiation. The power density values presented for each room inside the home can be compared to average DECT cordless phone radiation exposures found in German homes. The maximum power density was found to be over 500,000 µW/m2 at a normally encountered distance (about 1 – 2 feet) if the base station is placed on an office desk or bedside table. The radiation peak values in the same room are higher than those encountered in proximity to cellular base stations located near residential buildings.
DECT cordless phones usage has been a major health and environmental concern in Europe and especially in Germany for years. Now multiple handsets cordless phones are also available in the USA – extolled as 2.4 GHz digital technology with multiple handsets following the DFHSS (Digital Frequency Hopping Spread Spectrum) standard which is almost identical to DECT. The biological concern arose from studies on high frequency (HF) sources such as cellular phones and cellular phone base stations with GSM technology. The digital pulsed pattern of GSM and DECT radiation has come under suspicion to cause e.g. brain cancer, lymphoma, and changes in the brain blood barrier. The problem with the cordless DECT phones is, that the base station permanently emits full power pulsed microwave radiation, whether the phone is used or not. This creates constant exposure to high levels of the most critical type of HF radiation known throughout the entire home or office. The DECT technology is a European standard for cordless phones in the range of microwave radiation (1.8 to 1.9 Gigahertz, GHz). Identical permanently emitting portable phones with the special option of multiple handsets are available in the US and therefore the exposure issues are relevant for US population. In the US, the cordless phone manufacturers established the 2.4 GHz digital pulsed technology in the range of 2.4 – 2.5 GHz. Cordless phones such as e.g. the GIGASET (same name as a DECT cordless phone series by the same manufacturer in Germany) are available in USA.
A GIGASET cordless phone model was selected as a representative DFHSS 2.4 GHz phone for typical home and office usage. The base station was purchased in the US and placed on a wooden office desk in a representative 3 bedroom residential building in California. In the first test set, the power density in the room was measured prior to the activation of the base station to obtain background levels at the test site. Power density measurements were performed at different distances and directions from the phone (see table 1 and 2) with an Advantest R4131C spectrum analyzer (Rohde & Schwarz) and a calibrated periodic logarithmic log.per. antenna UKLP 9140-A (Schwarzbeck). The power density measurements were conducted under real-life conditions and only peak values (pulse maximum) were measured. All measurements were conducted following VDB guideline (VDB 2002) and the Swiss BUWAL guideline (BUWAL 2002). The power density levels are given in µW/m2 (microwatt per square meter). 1 µW/m2 equals 0.1 nW/cm2 (nanowatt per square centimeter). The background level was <0.3 µW/m2 (-58 dBm) in the range of all wireless, analogue or digital cordless, and cellular phone applications (0.3 to 3.5 GHz). See figure 1.
High frequency measurements were conducted and showed that the radiation patterns and levels emitted by GIGASET 2.4 GHz cordless phone base station are identical to the DECT technology – also digitally pulsed with permanent microwave radiation. For comparison, the radiation levels from the GIGASET located in the same room are even higher than encountered in proximity (50 to 100 feet) to most cellular base station located on pole mount positions or on top of office buildings. However, in this case the source of the radiation is a desktop personal cordless phone.
|Figure 1: Spectrum analysis (no 2.4 GHz)||Figure 2: Spectrum analysis (with 2.4 GHz)|
After the phone was plugged in, the radiation level rose to 673,000 µW/m2 (+0.2 dBm) in a normally encountered distance (about 1 – 2 feet) if the base station is placed on an office desk. See figure 2. The following power density levels were obtained :
Table 1: 2.4 GHz cordless phone base station power density levels in the same room
US GIGASET (2.4 GHz)*
GERMANY GIGASET (DECT)**
DFHSS (Digital Frequency Hopping Spread Spectrum)
digital pulsed 100 Hz
DECT (Digital Enhanced Cordless Telecommunication)
digital pulsed 100 Hz
30 centimeter – 12.5“
50 centimeter – 19.8”
1 meter – 39.4”
2 meter – 78.8“
Power Density (maximum pulse peak value)
Office with phone
Comparison of Standard Threshold Values and Recommendations
Total Power Density
Standards, > 2,000 MHz (e.g.)
FCC/ANSI – USA
Germany, England, Finland and Japan
Switzerland and Italy
Recommendations / References (e.g.)
Ecolog Study, Germany (Ecolog 2000)
Cellular tower radiation – high exposure level, 95. percentile (Haumann 2002)
Salzburg, Austria (Resolution 2000)
EU Parliament (STOA 2001)
Cellular tower radiation – background level, 20. percentile (Haumann 2002)
Low exposure, Oeko-Test (Oeko Test 2001)
Nighttime exposure, Baubiology Standard (SBM 2000)
Natural cosmic microwave radiation (Maes 2000)
< 0.000001 µW/m2