out of curiosity, i have not done this just wondered about it. what are the laws on creating a faraday box out of a classroom? my classroom gets little cell reception anyway, i wondered what would happen if i put copper or even just simple metal screen in the ceiling if it would eliminate it all from my room. that would not affect any other space but my room.
Cell phone jammer on the same freq as wireless mics?
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I do believe Faraday cages are legal as they only disrupt outside signals for people within the cage and do not create interference for the general pubic.
Vreating a Faraday cage out of a public assembly space, while probably not illegal, is at least unethical -- it is one thing to do it in a private electronics lab where everyone who enters knows they are isolated; do it in a large facility open to the public and when the fire department shows up to put a fire out, you had better bet there will be problems if they don't know that parts of the facility are isolated and there's no one coming to help them if they find themselves cornered by a fire, calling on the radio for help.
There are paints out on the market now that, to my understanding, do a reasonable job at blocking the transmission of WiFi signals. This is becoming popular in residential settings where homeowners will paint exterior walls with this so that their neighbors aren't mooching their WiFi or hacking into their home networks. I do not know what sort of effect this has on cellular and radio signals, but I've heard it works pretty well for WiFi.
Vreating a Faraday cage out of a public assembly space, while probably not illegal, is at least unethical -- it is one thing to do it in a private electronics lab where everyone who enters knows they are isolated; do it in a large facility open to the public and when the fire department shows up to put a fire out, you had better bet there will be problems if they don't know that parts of the facility are isolated and there's no one coming to help them if they find themselves cornered by a fire, calling on the radio for help.
There are paints out on the market now that, to my understanding, do a reasonable job at blocking the transmission of WiFi signals. This is becoming popular in residential settings where homeowners will paint exterior walls with this so that their neighbors aren't mooching their WiFi or hacking into their home networks. I do not know what sort of effect this has on cellular and radio signals, but I've heard it works pretty well for WiFi.
As far as I know, there's nothing illegal about creating a cage to keep signals in. I've never tried myself, but I'd imagine the copper mesh you'd need to use would be pretty darn pricey. Keep in mind you'll want continuous coverage around the room (floor and ceiling too) to to make it effective. Never tried the paints, but I have heard of them.
It becomes a question of what frequencies you want to attenuate. Based on that you work out what size apertures become acceptable in the mesh. To build a broadband effective shield may take multiple layers of different sized meshes and possibly sheets. This is the same idea as different forms of shielding being more effective at attenuating different sources of EMR into a coaxial cable...
I've worked on facilities that used passive and active measures for not only EMI/RFI shielding but also to address other forms of potential eavesdropping such as laser interferometry or tapping into communications lines. Most of these were military or government facilities but some were test and research facilities, 'think tanks' and even some corporate spaces (you don't want your competitors learning that you're planning to buy them out or how much you'd accept in a buyout or any of your plans for the next quarter). In comparison to that, I see potential non-technical challenges to any more general application of RFI shielding, especially for any public venues. With all respect, in most cases a classroom or instructional space does not belong to the instructor, it belongs to the public and could have a not only a different user at any point in the future, but unless it is a dedicated use space also a different use.
shiben
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I believe one of the more advanced of these was the US Embassy in Moscow during the cold war. Incidentally, I saw this very pretty building at a government contractor's facility recently, and was wondering why in the middle of an airfield and plant they had a giant glass and steel building... Turns out every inch of the thing was designed to make it into one of the most secure buildings on the planet in terms of resistance to eavesdropping. The link to the other building like it is apparently in a pressurized sleeve so as if anyone bothers to drill a hole to tap the fiber they would know... I thought it was a rather ironic thing... Such a pretty building that used a giant glass sheet (or something...) to keep you from knowing what went on inside. I hope it was something funny/ironic, like planning cooking schedules for the kitchen staff. But lets be honest, they dont let any non-US citizen on the facility without multiple (probably armed) escorts, so it probably was more sinister... Still think the best security measure is building your base in the center of a mountain.
Sayen
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Just one additional point - the rumor mill out here is that it's not just the FCC you need to worry about, but the cell companies and such who paid for those chunks of the spectrum. As Verizon and crew are driving around checking their networks and coverage, they are supposedly also looking into interference. It's probably a slim chance of them happening to cruise by right as you're using a banned wireless mic, but still, does anyone really want that attention as well as the legal ramifications?
FACTplayers
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tdeater
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A jammer is busying the frequencies, not blocking them. Think of it like a crowded room. If you are having a conversation with someone across the room and everyone is quiet, you can hear them fine. Now, if everyone is talking, you can not pick out your conversation from all of the rest of them. RF jamming works the same way, it just generates a lot of RF energy to prevent valid signals from getting trough. it is not selective though, so it will jam your mics, public safety, cell phones, and as mentioned in other posts, is illegal in the United States.
It's interesting that this topic should be revisited today, as I just saw the following comment on another web site:
"The FCC has become concerned about Jamming devices for Cellphones, GPS and WiFi. So much so, they have released Enforcement Advisory No. 2012-02, which specifies fines in excess of $100,000 per incident."
I think that says it all.
"The FCC has become concerned about Jamming devices for Cellphones, GPS and WiFi. So much so, they have released Enforcement Advisory No. 2012-02, which specifies fines in excess of $100,000 per incident."
I think that says it all.
What's the matter Chris? It's only 8 spammers 
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