
Wallpaper That Blocks Wi-Fi - nikunjk
http://blogs.wsj.com/ideas-market/2012/05/25/wallpaper-that-blocks-wi-fi/?mod=e2tw
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reginaldo
Before clicking the link I thought it was a malformed computer desktop
wallpaper exploiting some kind flaw in the operating system and using it to
block the computer from connecting via Wi-Fi.

Would have been very much cooler, would it not?

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keeran
I thought along similar lines, but with some special texture that made
monitors emit some kind of wifi-jamming RF :)

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xymostech
"as well as those who, for health reasons, simply want to shield themselves
from as many electromagnetic waves as possible"

Is anyone really still concerned that electromagnetic waves in the cell-phone
range are harmful?

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mukaiji
I'm a scientist (certified for radioactive & x-ray research) so I totally hear
the point to be made regarding something not being a fact until a thorough
investigation has been done on the matter. However, the fact that
electromagnetic wave cause harm or may have secondary effect in some people is
not that far fetched and should not be discarded as "is anyone really still
concerned". We just don't have a sample size of individuals troubled by it
that is sufficiently large enough to prove it. The majority of us may show no
signs of harm; yet I know of at least two people that suffer from
electromagnetic hypersensitivity, probably resulting from having 30 different
wifi signals crossing their walls day & night for the last ten years. Indeed,
I don't believe cell-phone tower signals at long range are really the cause.
It's more likely to be the high concentration of wifi signals inside of
apartment complexes. And even if the exposure intensity is a matter of square
root with respect to distance from source, you can get significant exposure
when you increase the number of source or the relative average distance you
are from them. So no, electromagnetic waves is nothing to sneeze at. If you
think so, why don't you go sleep every night in a tiny room with 15 wifi
routers on and a couple of cell-towers directly above your head?

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bkirwi
I'll see your anecdote and raise you another one:

A friend's downstairs neighbour regularly complained of 'electromagnetic
hypersensitivity'; it got to the point where the building manager asked that
my friend stop using wifi entirely. My friend switched her network to
'hidden'. The symptoms disappeared.

Of course, we shouldn't draw conclusions from anecdotal evidence. Perhaps the
neighbour was only sensitive to broadcast packets containing SSIDs?

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Drbble
Does the neighbor also block out all the harmful EM radiation that floods from
sunrise to sunset? If you want to be cruel, mention that cordless phones and
microwaves emit at similar frequencies as wifi.

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mukaiji
Cordless phones are actually by far the most powerful radiowave emitter inside
a home.

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_delirium
Depending on the size/shape of the apartment, this seems like it could cause
some interference issues. A hallway lined with wifi-blocking wallpaper would
produce some kind of weird multimodal effects, wouldn't it?

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philip1209
In the new houses in my neighborhood, I see that they use some kind of 'home
wrap' on the wood before insulation. I could see them installing this on the
outermost walls of schools, sensitive/government offices, or other places
(e.g. churches, aforementioned concert halls, hostels, etc.) between the outer
walls and insulation.

However, you are correct with your comment. In some cases, though, this could
be desired, e.g. a hotel that wants to provide, track, and bill for WiFi on a
per-room basis.

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diego_moita
Cheap alternative: cover the walls with thin chicken wire.

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malandrew
Unfortunately something like this is not nearly as effective as you may
imagine. I spent more money than I'd like to admit a few years ago trying to
shield my hi-fi stereo from all sorts of interference. I lived on Avenida
Paulista with about a half dozen to a dozen massive radio and tv antennas
within about a mile. No matter what trick I tried the noise was still getting
through in every way imaginable.

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vacri
These kind of filters are attenuators, not blocks. If you're that close to
very powerful transmitters, then even reasonable attenuation is going to allow
some signal through.

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malandrew
Yup. I learned that the hard way. The best I was able to achieve was putting
power cord chokes along the entire length of the interconnects (RCA <-> RCA).

The ideal solution would be balance power amp and balanced pre-amp with XLRs
carrying the audio signal. Unfortunately this would have required completely
new amps.

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lchengify
This might be an effective solution to the "no cellphones in class" rule.

Probably the most important factor is still letting emergency bands through.
Does anyone know if 911 calls go through normal cellphone channels, or if
that's a dedicated channel that can be 'whitelisted' on a device like this?

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gte910h
It's not a device. It's metal in a wall paper.

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huhtenberg
I'd use it at home, just on exterior-facing walls. This would not only block
any interference from neighbors WiFi/microwaves, but also won't let them see
my WiFi traffic. Throw in a cell repeater in the wallpaper package, and it'd
be perfect.

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ljd
Looks a bit like a Faraday cage.

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dudus
It is the same concept of a Faraday Cage.

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gte910h
Wouldn't this be against the law as causing interference, especially with
emergency equipment (in the US)?

Or do those FCC rules only apply to devices?

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Devilboy
Passive blocking is fine, active blocking or interference is not.

