Low-Tech Cell Phone Blocking

nigelc writes: "This BBC story reports on Japanese work to come up with a low-tech solution to cell phones in cinemas! Hey, if it can stop the person next to me from going 'Hey, dude, guess where I am?,' I'm all in favor of it."

Comments

Re:All I want...

[BJH]

They sell them here in Japan - 5000 to 10000 yen ($US40-$US80) for most of them.
A magazine did a study of them, and it looks like most of them don't really work that well, unfortunately - maximum of 1-2 meters radius around you.

Not really...

[Andy Dodd]

There are other ways to block signals.

Metal works pretty well. :)

Or if you need to see through it, there are some forms of glass that have trace amounts of a conductive substance that will give it a mild tint to visible light but make it impassable for RF. Also fine-mesh screen works too.

I'm not sure exactly what they use in the windows, but because the company I work at makes RF power amplifiers, mainly ones for cell phone use, the building is heavily shielded to keep signals INSIDE. (Not for security, but to prevent us from interfering with nearby cellular systems, but security would be an additional benefit if we ran 802.11b) - We do make sure to use dummy loads, but even dummy loads aren't perfect. I've been working with some FM broadcast-band equipment - I'm sure it radiates somewhat, but I can walk out to my car (50 feet away from the lab), turn on my radio, and hear pure static with no sign of a carrier anywhere nearby.

This just happens to be a form of RF shielding for places where they can't afford to shield the room totally with metal/can't design such shielding in as an afterthought.

Conductive paint (perhaps containing graphite, or maybe powdered ferrite) would work well too.