Blocking Cell Phones in Church

Cell Phone Blocking
The radio jammers used in Mexico sound like the same technology employed by a private school in Italy to defeat text-messagers who were using cell phones to cheat on exams.

There are easier alternatives that won’t create radio licensing problems. DefendAir(TM) Radio Shield Paint contains small whiskers of conducting material (the patent speaks of nanotubes) to create a low density Faraday Cage that reduces radio transmissions in the cell phone frequency range to the point that people can neither send nor receive while inside the painted room. The technology is protected by patent (6,576,336 Electrically Conductive and Electromagnetic Radiation Absorptive Coating Compositions And The Like), so there’s some science involved. The only sales outlet I could easily discover was at
http://www.forcefieldwireless.com/defendair.html.

This is not an endorsement(!). More than a few of us, however, would be interested in learning if it really works. One gallon of paint is claimed to cover 160 square feet.

Re:Cell Phone Blocking
Using the (presumably metal) shelves could work, but not as well. Cecil Adams remains one of the best at translating technobabble into plain language, and I recommend his article on how the glass doors on microwave ovens work (see http://www.straightdope.com/mailbag/mmicromesh.htm l).

The wavelengths that apply to cell phones are about ten times longer, but the key to making any Faraday cage work is making the mesh size smaller than the wavelength. Also, the signal doesn’t need to be blocked completely, just reduced a bit. If you have access to students, turn this into a science fair project. You could generate an interesting backlash effect by having armies of small children wandering through the stacks muttering “can you hear me know?” into Mommy’s cell phone, and recording their findings on a floorplan.