cell phone shielding
- Thread starter bwyllie
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bluesmoke...oops
Senior Member
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- Tri-Cities, Washington
didn't they come out with some paint that is supposed to do that?
Well using an active blocker or jamming device is illegal, however using passive methods is legal. I do not know of manufactured products to do the job as I have never had a need to look for them, but it can be easily done during a remodel of initial construction by using a wire mesh screen or even chicken wire enclosing the room and bonded to the electrical ground or even the rebar in a concrete pad. The screen material is attached to the wall studs and ceiling joist before the drywall is attached.
The other way I know of works real good, use a steel fabricated building with steel siding and roof.
I havre also heard there is a metallic paint on the market made to do just what you want. Here is a REFERENCE LINK
The other way I know of works real good, use a steel fabricated building with steel siding and roof.
I havre also heard there is a metallic paint on the market made to do just what you want. Here is a REFERENCE LINK
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lakee911
Senior Member
- Location
- Columbus, OH
Did you find that here: http://answers.google.com/answers/threadview/id/413500.html ?
I doubt chicken wire has the proper mesh size to work, but maybe it does...
I doubt chicken wire has the proper mesh size to work, but maybe it does...
K8MHZ
Senior Member
- Occupation
- Electrician
Yes, but is paint enough?
And there is this to consider:
http://www.lessemf.com/paint.html
The shielding you are trying to attain will be tough to do. Since you will not be able to totally isolate the environment you will not be able to assure 100 percent RF shielding. Any wiring coming into the room has the ability to act as a passive radiator. You are dealing with various frequencies, so a method that works well for one band of frequencies may not work for others.
If it were me, I would hire an engineering firm to do the design and be happy with getting the build job. If you have to ask how to do RF shielding on a web site you likely don't know enough about it to do the design work. If you have someone else do the design and it ends up not cutting it down the road, you won't be the one getting sued over the loss of valuable corporate secrets.
EDIT: I would like to add that I know enough about radio to be able to design a room that is 90 percent effective and would NEVER do it for pay. I also know enough about radio to be able to defeat 90 percent of 'cell phone proof' rooms and would still never design such a room for pay.
The liability is too great and there is no way to be able to know for sure your design will work on every cell phone or wireless device there is. Digital comms can get through some amazingly adverse conditions.
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K8MHZ
Senior Member
- Occupation
- Electrician
Metal buildings are only partially effective due to re radiation. I use my cell phone in totally enclosed metal buildings all the time.
No, from experience back in my RF engineering days building RF test cages.
Chicken wire would be more than adequate as it is a function of 1/4 wavelengths. The two frequencies of interest with respect to cell phones is 800 and 1900 Mhz. Since 800 is the lowest frequency and longest wave length is all that has to be dealt with. 800 MHZ 1/4 wave length is .09 meters or 3.6 inches. Chicken wire mesh is considerably smaller and will cut off frequencies 200 Mhz and up.
But as K8 MHZ points out any wiring leaving or entering the room will re-radiate signals inside the space unless measures are taken to divert the energy to ground. I agree with him this should only be done by an engineering firm with experience doing this kind of design.
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- Wisconsin
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- PE (Retired) - Power Systems
Unless it is me that is trying to rely on them.
K8MHZ
Senior Member
- Occupation
- Electrician
NO frequencies will be cut off.
The best you can get is attenuation.
If the signals are strong enough, they will get through anything someone is willing to pay for.
A WWII submarine is an RF cage made of inch thick solidly connected steel. That is one of the few places my cell phone won't work, but our two way radios will work from inside to out as long as they are close. The range is cut from over a mile to a few yards, but even through inch thick solid steel and partially underwater, RF can get into the sub, a museum ship with a ham radio station on board.
So, if inch thick steel isn't 100 percent effective, just what would it take?
Well, they are called Faraday cages. They are used in labs and universities and are extremely costly to build and certify by testing.
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Yes I understand that, brute force will penetrate. Cell towers operate depending on number of calls in place from 1/2 watt to 20 watts per carrier down link. Cell phones max power is 1/4 watt uplink
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Why not? You could just let the client know your concerns, and tell them that's probably the best they can do within their budget, and that there are no guarentees, and it won't be 100% effective.
It sounds to me like they are just tired of having all their meetings interrupted. So I'm not sure there is any liability. If the room cuts out some calls, good. If a few get through, you cover that by telling the client up front that its not a 100% solution.
That said, I could also see the same client asking why their wireless network doesn't work in the conference room anymore:roll:
Steve
You need to build what was once called a TEMPEST room. Currently, the name is EMSEC. I work in such a building and with the TEMPEST doors closed, cell phones, pagers, etc do not work. With the doors open, the phones work if you're within 100' of the door. We have a passive pager "repeater" to allow those to still work.
These are very expensive to build, especially if you need it certified. You pick the level of attenuation you want at given frequency bands and build from there. All metallic conduits and plumbing typically use non-metallic couplings between outside and inside. Fiber is the "wire" of choice. Doors are the biggest problem.
A jammer inside of a mostly shielded room may work and perhaps not be illegal.
Found this link: http://www.eskimo.com/~joelm/complete_unofficial_tempest_page.pdf
These are very expensive to build, especially if you need it certified. You pick the level of attenuation you want at given frequency bands and build from there. All metallic conduits and plumbing typically use non-metallic couplings between outside and inside. Fiber is the "wire" of choice. Doors are the biggest problem.
A jammer inside of a mostly shielded room may work and perhaps not be illegal.
Found this link: http://www.eskimo.com/~joelm/complete_unofficial_tempest_page.pdf
Google "Faraday room".
The ones I have worked with were copper screen, the internal lighting was DC.
They use to be more common at hospitals where ECGs were being performed.
There vendors who will sell you a "Cage" or engineer and construct ( or oversee the construction ). All it takes is mere money.
Some signals from cell phones can radiate out on lighting wires or telephone land lines.
MAby "The Cone of Silence" system would work. It might be cheaper.
The ones I have worked with were copper screen, the internal lighting was DC.
They use to be more common at hospitals where ECGs were being performed.
There vendors who will sell you a "Cage" or engineer and construct ( or oversee the construction ). All it takes is mere money.
Some signals from cell phones can radiate out on lighting wires or telephone land lines.
MAby "The Cone of Silence" system would work. It might be cheaper.
A few other ways to beat cell phones in conference rooms.
Roger
- Have spot lights that will zoom in on the person getting the call so that all the others will get a good look at the offender.
- Stop the meeting or conference and tell the others that the meeting or conference will resume when so and so get's done talking to who ever is more important than the others attendees time
- If the attendees are contractors or sub-contractors charge them $100.00 for each time their phone interupts the meeting or conference.
- Have all parties leave their phones in their vehicles or at the reception desk.
Roger
Good point. You should be able to jam signals in your own space.
I like all those ideas
Some people think their time is more valuable than others. It makes me wonder what happened to good manners. I've even heard doctors say that patients will answer phone calls when the doctor is talking to them. And we've all seen people hold up a line at a check out talking on their phone.Me too.
If I were a doctor performing the right exam I'm sure I give the party on the other end a scream from the patient.. :grin:
Roger
bluesmoke...oops
Senior Member
- Location
- Tri-Cities, Washington
If they manage to be on the phone during that exam I'd be impressed.
Easy Cell Fix
Easy Cell Fix
Once upon a time I was in a "no cell pnone" meeting. One of the more obnoxious people on the job got a call and answered it, he said a few words and put the phone back in his pocket. The project manager said "Can I see that phone"? The guy gave him the phone, he broke it in half and threw both pices back to him. He said something like "I can fix this problem another way but it would be harder on your wife an children."
No more phone problems.
Easy Cell Fix
Once upon a time I was in a "no cell pnone" meeting. One of the more obnoxious people on the job got a call and answered it, he said a few words and put the phone back in his pocket. The project manager said "Can I see that phone"? The guy gave him the phone, he broke it in half and threw both pices back to him. He said something like "I can fix this problem another way but it would be harder on your wife an children."
No more phone problems.
RF shielding is installed around MRI machines in Healthcare projects all the time. I'm sure it's not cheap and they are very specific installation instruction and details that must be followed. Below are some links
http://www.gavenindustries.com/index.htm
http://www.ramayes.com/aluminum_foil_emi_rfi_shielding.htm
http://www.quietrock.com/project-gallery/industry-solutions/scif.html
http://www.gavenindustries.com/index.htm
http://www.ramayes.com/aluminum_foil_emi_rfi_shielding.htm
http://www.quietrock.com/project-gallery/industry-solutions/scif.html
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