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This topic comprises 2 pages: 1 2
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Author
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Topic: Mobile 'phone blockers
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Jim Bedford
Jedi Master Film Handler
Posts: 597
From: Telluride, CO, USA (733 mi. WNW of Rockwall, TX but it seems much, much longer)
Registered: Jun 99
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posted 01-02-2010 02:47 PM
Now here's a new story about old technology that inadvertently does what so many of us want done in all theatre auditoriums. Maybe just using some traditional building techniques in new theatres would go a long way towards solving this problem before I maim someone. Chicken wire rules! Thank you Mr. Faraday!
WSJ-Old buildings and cell and wifi signals
Culprit in Wi-Fi Failures: Chicken Wire
By GEOFFREY A. FOWLER
Two things beloved by San Francisco resident Galen Pewtherer just couldn't get along: his Edwardian-style house and wireless Internet access.
In 2008, Mr. Pewtherer tried to replace his old-fashioned cable Internet connection with a Wi-Fi network that he could share with other tenants in his building. "It turned out to be impossible," says the 38-year-old program manager at Cisco Systems Inc. "We couldn't get signal in or out of one room."
That is because Mr. Pewtherer's 80-year-old building in the Mission District, like thousands of other old homes in the Bay Area, was built with the technological equivalent of kryptonite in its walls: chicken wire. Metal wiring inside old plaster walls blocks wireless signals, frustrating San Francisco residents as wireless-equipped devices like iPhones and laptops proliferate.
The problem dates to before drywall became a popular building material in the 1950s. Before then, construction crews usually made walls out of plaster applied to lath, a base structure that holds it up. Often, lath in Victorian and Edwardian-era homes was made of wood stapled with chicken wire, a cheap fencing material that also doubles as lightweight support. The problem occurs in other cities too, but San Francisco has an unusually dense collection of old homes and gadget lovers.
"It's the old bumping into the new," says Mike Scott, a technical media manager for network gear maker D-Link Corp., who fields many questions about chicken wire. "How were people 70 years ago supposed to know that we were going to have all of these wireless gadgets?"
Many factors can disrupt wireless networks, including steel girders, air-conditioning vents and water-filled objects -- including humans and pets. But even with its many holes, chicken wire creates a particularly powerful metal shield.
Physicists call it a "Faraday cage" -- a metal structure that impedes electricity and waves -- because the fencing is the perfect size to catch waves generated by 2.4-gigahertz Wi-Fi networks. "It turns out that chicken wire is almost perfectly the right wavelength of a Wi-Fi signal," says Karl Garcia, who sets up Google Inc.'s free Wi-Fi efforts. "It acts just like a solid piece of metal."
Google's plans to bring citywide Wi-Fi to San Francisco died in 2007 for political reasons. But Mr. Garcia says making it work in a city filled with so many hills -- and so much chicken wire -- would have created unique technical challenges.
San Francisco resident Alex Menendez, a partner in boutique Internet service provider MonkeyBrains.net, discovered the difference chicken wire can make when he recently gutted a 130-year-old house in the Mission. He removed one-inch metal mesh behind plaster walls and replaced it with drywall. However, the co-owner of the property left his original walls intact.
The result: Wi-Fi networks flow smoothly through Mr. Menendez's part of the property. But according to their tests, his neighbor's walls lose as much as 75% of the signal and 33% of the throughput.
There are workarounds for the problem beyond knocking out walls, and Mr. Pewtherer in the Mission has tried almost all of them. He bought special equipment to "bridge" signals between the rooms, but it worked only in spots where there was a clean line of sight from a wireless transmitter to the receiver.
He also built a signal-boosting antenna out of an old Pringles can, known as a "cantenna," following some online instructions. Despite cranking the cantenna signal "high enough to cook bacon," it improved his signal only minimally, he says.
In the end, he gave up on wireless entirely and ran Ethernet cable through the walls and floorboards in the building. But the Ethernet network ended up solving only one wireless problem. The same factors that prevented Wi-Fi signals from penetrating Mr. Pewtherer's walls also kept out cellphone signals. "I basically had to stand on the fire escape to get a cell signal," he says.
He has since moved to another building with an open plan -- and no wireless woes.
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