Search This Blog

Thursday, January 31, 2013


Last year I managed to review the reports about WIFI radiation issued by the HPA and INDUSTRY CANADA 
(please use Google translate to read)  .

What they did wrong:
Both Industry Canada and the HPA accept the ICNIRP none biological, extremely high and none protective standard of RF exposure. Both rolled that the RF levels in a class with WIFI routers and laptops is "safe".
In both report none of the measuring took place where a student would relay sit (I assume the user head is 30cm from the laptop's screen, hand on keyboard). 

What they did well:
When locking at the report in a technical eye, both have several problems, but in both you can find good points.
In the HPA report, they tested 12 types of wireless router and 15 types of wireless laptops. They measured the RF radiation from in the 2.4 GHz band and the 5.8GHz band. They measured the radiation levels around the devices and in different distances from the devices (0.5 a meter,1 meter and 1.5 meters). The radiation patterns around the laptops showed "hot-spots" in front of the user and above the laptop keyboard.
In the Industry Canada report the good things they did were the use of spectrum analyzers and the testing of the RF radiation in many testing points in a conference room where laptops and 2 WiFi routers where deployed (the good thing is the number of test points, the bad think is that not even one of them was where a student would sit). The laptops where downloading and uploading.

Picture - the test points and equipment deployment in the Industry Canada report

When reading these reports is it clear that In both reports some of the RF levels measured were higher than what I can suffer, and higher than what I and others considered safe. Both reports refer only to the high, none biological, heat effect causing levels that are known as the ICNIRP standard or "safety code 6". For example in the HPA report the max level that was measured near a laptop was 2.2uW/cm2, and the level near the router was 8.7uW/cm2. In the  INDUSTRY CANADA  report the max level near a laptop was 2.34uW/cm2 and 106-77uW/cm2 next to the router.

How it should be done (to my opinion)
If you want to test WIFI you need to use a fast Spectrum analyzer and a good, fast RF meter that reach up to 8 GHz. 
You need to map the class room using an RF meters and on the stronger hot-spots I suggest to analyze the RF radiation over the frequency span using a spectrum analyzer.
The test points should be where the users sites. If these locations are in the near field then the measurement should be done in V/m (electric field units).
The spectrum analyzer should acquire the signals over about 6 minutes in MAX hold mode.
Then the signals should be analyzed. I think that it would be important to count the number of signals, their span, their levels and to see their modulation (number of time the signals appear in every second) in order to try and assess the danger. 

No comments:

Post a Comment