How to shield off wifi/wireless?


I have been searching hi and low for something which may solve my problem of shielding wifi from the outside world!

We (pulz8 Communications) are testing wifi/wireless connections to be used on trains (for instance to provide wifi or CCTV to the passengers) but one of our neighbours is a script kiddie who loves to fill the ether with disassociation frames causing a lot of extra problems for our technicians.

Are there anyone out there who have experience in painting a room with shielding paint? I have found reference to Spyguard and Force Field Wireless (which apparently has gone out of business) and also an ACM article and other pages on the internet which describes how to make a (no it is not a) "Faraday cage" but because of the nature of our hardware we would like to take the paint approach - unfortunately our test room has windows!!! :-)

Any experience?

Andrew Engels Rump

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Andrew Engels Rump
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Civil lawsuit for willful and intentional malicious activity to disrupt a business. May not get you anywhere, but might scare the pants off him.

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Jeff Liebermann

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Yes. Some of my high-rise office building customers, that have glass walls through which they pickup considerable interference, were having problems. I solved most of them by carefully locating the access points and client radios, eliminating un-necessary wireless links, and switching from 2.4 to 5.7GHz wireless.

I've had similar problems with wireless hackers. I personal visitation was usually all that was required to get their attention. They usually think they can get away with anything as long as they are not identified. If you know who they are and what they're doing, the picture changes considerably. However, if they fail to cooperate, calling in the law doesn't do much good. I have other methods of getting their attention, but none of them are legal, so I won't itemize.

If the neighbor is fairly close, just install a large dish antenna on your building pointed directly at him. You don't have to connect anything to it, just make sure he can see it. His imagination will do the rest.

No. Silver doped paint is useful for small areas and is of course rather expensive. The carbon filled stuff (Aquadag) doesnt' really work too well at 2.4GHz. Your best bet is aluminum foil. I've built shield rooms in the distant past out of sheet copper, brass screening, and berillium finger stock. It's not cheap and very difficult to keep microwave frequencies out completely. A small gap is enough to pass some signal. I don't think you need much in the way of attenuation to keep out the neighbors. Some brass screening on the facing doors and walls should be sufficient.

Radio service shops also have similar problems with on channel RF interference. It's very difficult to tune up a receiver when there's a high power transmitter next door on the same frequency. Some rent large metal storage containers and use them as screen rooms. There are also small RF shielded boxes that will do the job.

There are also small test boxes designed for wireless testing that I'm too lazy to dig out the URL.

Lots depends on what manner of testing you're doing. Turning your test lab into an RF echo chamber will not help much. You might want to look into RF absorptive materials instead of RF reflective.

Well, you're not trying to block *ALL* frequencies, just 2.4 and possibly 5.7GHz. You don't need the ultimate in shielding to do that. A metal screen door, metal window screens, some aluminum foil or mesh, and you'll block most of the junk.

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Jeff Liebermann

Virgin trains in the UK have sets with gold film coated windows (to reduce solar gain on our rare sunny warm days).

it plays havoc with GSM phone reception (1.9 GHz?) - so much so that you only get useful reception near a station, or where the lines goes thru the suburbs with heavy cell coverage.

If maybe it will help tame 2.4 G WLAN?

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Well I got a representative from the Danish authorities to come by today but I do not have that high hopes because their "radiocar" has been by in the past.


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