Cell Phone Jammers?

[maury]

Just curious: do these things really work?

Anybody had any first hand experience?


Thanks!!

 

[tgiannes]

Yeah they work but i think they might be illegal im not really sure. but i really want one for our restaurant, a$$holes never hang up there phones.

 

[JatMat]

Yeah they work but i think they might be illegal im not really sure. but i really want one for our restaurant, a$$holes never hang up there phones.

I even thought of carrying one to theater, but do I want to accept responsibility for a Dr not getting an emergency call or a Mother being told son was in a wreck and was needed at hospital. More to think about than just the rudeness of jerks that talk loud and often in restaurants and theaters.

 

[Chiro75]

Yes. they're illegal to use.

 

[tgiannes]

Yes. they're illegal to use.

FCC rule right?

 

[ThinkOfTheChildren]

Yes, they work. How well and at what range depends on their size and the amount of power being fed to them. As mentioned, they are illegal (at least in the U.S.)

FCC rule right?

Yep.

There was a lengthy article a few months ago about domestic businesses buying them from overseas (not hard to find online) for installation in their restaurants, etc. Sounded like x% of all orders get snagged by customs and then those businesses that actually try to use them quickly become the targets of FCC investigation. Not sure how much of that was a scare tactic of the article, but I guess these days people notice when their reception drops like a brick and some people will actually complain to authorities when they notice a pattern.

Active jamming is illegal, but there's nothing illegal about using insulation or other building materials that will passively kill reception (if you are a business owner and really that hellbent on stopping cellphone calls). You just basically turn your establishment into a giant Faraday Cage.

I have no idea what is in the walls of my father's house, but it kills signal the second I walk in the door. I can stand outside his house and get perfect reception but once I step foot inside my phone becomes worthless.

That is no help if you are Joe Blow who wants to have a quiet sit in a movie theater, but then you've stepped into a realm of vigilantism that is getting ridiculous. Believe me, I wish I could punch every idiot who has no phone etiquette in the theater (turn the ringer off, don't sit there texting, and step outside if you need to answer), but as mentioned above, you would have no way of knowing what you are blocking. While I firmly believe that 99.99% of cell signals being utilized inside the movie theater are meaningless drivel, I can't in good conscience prevent that 0.01% of people who might have a legitimate need (the aforementioned Doc, for example). After all, if they step outside to answer their silent phone, I have no problem anyway.

... and that's my rant for the evening, ha

 

[orthogonal1]

Chicken wire mesh, if the house is old enough to have used real plaster walls.

BTW - anyone notice that the world seemed to get by just fine without all these people of such import being able to recieve a call 24/7?

 

[Gollnick]

The good ones work perfectly. The military uses them to prevent terrorists from using cell phones to remotely detonate IEDs so, obviously, they are very effective.

But, they are illegal to use in the US.

Furthermore, to use one would expose you to a huge legal liability. If your cellphone jammer prevented an ambulance from being called resulting in a death or injury to someone, expect to be sued for all your worth... and expect to loose.

 

[Gollnick]

Active jamming is illegal, but there's nothing illegal about using insulation or other building materials that will passively kill reception (if you are a business owner and really that hellbent on stopping cellphone calls). You just basically turn your establishment into a giant Faraday Cage.

True, but there's still the legal liability issue. If the way you deliberately constructed your building causes someone an injury or death -- which could result from the inability to make a cell phone call to 911 -- then you could be sued.

But how realistic is it to do this? To be an effective shield, there can be no openings bigger than one-half of the wavelength of the signal intended to be blocked. Cellphones operate in frequencies from about 800MHz to about 2GHz. This means wavelengths between about 1/3 of a meter to about 1/10 of a meter, or about 1 foot to about four inches. So, no opening can be bigger than about 2 inches to assure blocking of most cell phone signals. Doors, windows, ventilation, ultility openings... you'll have a hard time constructing a practical building with no such openings. I sometimes work in rooms that are specifically constructed to block outside radio signals so that they won't interfer with the measurments we're making. The precautions required are elaborate to say the least and certainly expensive. Such rooms cost a good fraction of a million dollars to build. I used to work in a large building built to shield radio signals (as much to keep our emissions from being picked up by people outside of the building as anything else). That building cost just shy of a hundred million dollars to build, it had no windows, and every entrance was like going through two bank vault doors.

 

[ThinkOfTheChildren]

The good ones work perfectly. The military uses them to prevent terrorists from using cell phones to remotely detonate IEDs so, obviously, they are very effective.

Yep. I've heard the new trick amongst the insurgents is to leave a call connected between the remote and the device. When the convoy rolls in with its jammers, the line is cut which then detonates the IED. I'm sure its less effective, because the range is no longer under their control, but there is no end to what they will cook up trying to blow up our military.

[In regards to passive jamming through structures...] True, but there's still the legal liability issue. If the way you deliberately constructed your building causes someone an injury or death -- which could result from the inability to make a cell phone call to 911 -- then you could be sued.

I wasn't actually advocating it, just saying that it was FCC legal.
If I was a business owner, and was so inclined to take such measures, I would either have a good explanation for why I chose said building materials, post signage that warned of signal problems, or both.
Obviously intent would be the issue if it ever went to court because there are plenty of buildings that pretty effectively block signals through the very nature of their construction (like multi-story concrete parking structures).

Again, I'm not advocating anything at all here: I originally just wanted to make the distinction between active and passive jamming.

But how realistic is it to do this? To be an effective shield, there can be no openings bigger than one-half of the wavelength of the signal intended to be blocked. Cellphones operate in frequencies from about 800MHz to about 2GHz. This means wavelengths between about 1/3 of a meter to about 1/10 of a meter, or about 1 foot to about four inches.
[snip]
Such rooms cost a good fraction of a million dollars to build. I used to work in a large building built to shield radio signals (as much to keep our emissions from being picked up by people outside of the building as anything else). That building cost just shy of a hundred million dollars to build, it had no windows, and every entrance was like going through two bank vault doors.

I have no doubt that what you say is true if one is inclined to build a true cage and have 0% signal transmission. But as I have experienced at my father's house, it really doesn't take that much to do the job pretty effectively. No, it can't stack up anywhere close to the places that you are talking about, but despite its various windows and doors, missed calls and text messages are the norm and it seems to apply to any carrier that people bring into the house.

Chicken wire mesh, if the house is old enough to have used real plaster walls.

I'm not sure how old the house would have to be for that to be the case, but it's not a very old house. I believe when he inquired with the previous owner and/or the builder, he was told it was the insulation that the house used. *shrug*

 

[orthogonal1]

True, but there's still the legal liability issue. If the way you deliberately constructed your building causes someone an injury or death -- which could result from the inability to make a cell phone call to 911 -- then you could be sued.

How could you be sued? Is there a legal presumption that one can call via cell-phone at all times? Has there been some law mandating connectivity for cell-phones? Some legal precedent I haven't read.

ADDED - Sound a bit harsh - sorry.

 

[Uk-Fire]

As far as I remember they are extreamly illegal.

 

[sodak]

If they're illegal, how do hospitals get away with it? Every time I go into a particular one, it shows emergency services only.

 

[Gollnick]

I have no doubt that what you say is true if one is inclined to build a true cage and have 0% signal transmission. But as I have experienced at my father's house, it really doesn't take that much to do the job pretty effectively.

We'd have to look at the whole situation to know exactly what the problem is there. So-called "dead spots" certainly do exist. Someday, maybe, a new tower will be built and solve his problem. When I moved into this house, cell service was weak, especially in the basement (T-Mobile at the time). I called T-Mobile and the agent typed my address into their computer to log my complain and said, "Oh, this should change tomorrow. We have a new tower scheduled to come online tomorrow that should solve your problem." And it did.

How could you be sued? Is there a legal presumption that one can call via cell-phone at all times?

Increasingly, yes, there is a reasonable expectation in our society that cellular phone services will be available, especially in urban areas. As Mr. ThinkOfTheChildren points out, the issue is intention, that you deliberately constructed your building in a way that created an obvious hazard. It's no different than building a balcony with a railing that is deliberately build too weak to stop someone from falling. You have deliberately built an obvious hazard.

If they're illegal, how do hospitals get away with it?

Some areas of hospitals are deliberately shielded. I remember when I used to work in a hospital fixing the X-ray machines seeing five or six big guys carrying a single sheet of drywall. "Isn't that just typical of this place," I tought, "six guys to carry a sheet of drywall." But then I found out that the drywall in question was for the new X-ray suite and had an 1/8" layer of lead in the middle. No wonder it took six guys to carry it.

MRI and PET scans require shielded rooms so that radio signals don't interfer with the measurements.

Every time I go into a particular one, it shows emergency services only.

Again, any one specific case would have to be studied to find the cause. Call your cellular carrier and complain. They're very aggressive about unlicensed emitters causing problems in their spectrum space.

 

[Tim-Gabz]

I would imagine advertising a cell phone free environment in social context would be very popular. However even at the risk of huge fines people drive with them attached to their lugghole.

Maybe this will help:

Notice: This Restaurant is a Cellphone free environs. Any calls while seated will attract a noise service charge of $5000.00.

 

[sodak]

Again, any one specific case would have to be studied to find the cause. Call your cellular carrier and complain. They're very aggressive about unlicensed emitters causing problems in their spectrum space.

I'll give it a shot, thanks!