How can I find out if my employer is using a cell phone jamming device?
December 18, 2009 8:39 AM   Subscribe

I suspect my employer has installed a cell phone jamming device . How do I find it if they have?

At the risk of sounding like a paranoid kook - I suspect that my employer may have set up an electronic device to interfere with cell phone usage at my place of work. As of a few days ago, in a very specific area of my building radiating out of one point about 25 feet, all cell phone signals go to one bar or zero out completely. The loss/severe reduction in signal affects both CDMA and GSM phones. If you step beyond the threshold of a separating wall, the signal returns full force.

Is there a feasible way to find out if there is a cell phone jammer being used in this area?
posted by anonymous to Technology (15 answers total)
How about call your cell phone company? It's illegal in the U.S. and I would imagine they wouldn't take too kindly to it and may be inclined to check it out.
posted by jckll at 8:42 AM on December 18, 2009 [1 favorite]

Might just be unintentional interference. Never attribute to malice and all that.
posted by unixrat at 8:47 AM on December 18, 2009

Besides, what's the point of jamming a 25' circle?
posted by unixrat at 8:48 AM on December 18, 2009 [2 favorites]

is there any chance they've done some construction work to your building recently? A few years ago they updated my work building with a new facade and better windows, and now you can't get a signal unless you're right at the windows.
posted by cabingirl at 8:49 AM on December 18, 2009

You could always ask.
posted by Slinga at 8:50 AM on December 18, 2009

i think anon means 25' away from the whole building
posted by Mach5 at 8:53 AM on December 18, 2009

This actually sounds plausible. Yeah, go ahead and ask your boss. If you are embarrassed ask jokingly and gauge his/her reaction from there.
posted by OrangeSoda at 8:57 AM on December 18, 2009

Depending on where you work, it could be the other way around. They may have a malfunctioning antenna inside the building - meaning that in the 25' area, they do not have a functioning booster.

In the age of blackberrys there is little desire for deadzones where someone may be working.
posted by Nanukthedog at 9:01 AM on December 18, 2009

We had the same problem in a building where I worked. If I remember correctly, the company put some coating on the windows which reduced the ability for signals to pass in or out, and then later installed repeaters inside the building to restore the cell signal. There was a period of several months after the coating was applied, but before the repeater was installed, during which we had no signal/1 bar.

I found this link by googling, it's an example of the type of coating I'm talking about.
posted by helios at 10:10 AM on December 18, 2009

If you can repeat this with 100 percent consistency, it would be very easy to raise the subject in a non-threatening way by simply starting a humorous conversation.

"Dude, check this out. Isn't this weird? You got, like, a satellite dish in there? Getting signals from the aliens?"

Dollars to donuts the reaction you get is, "Yeah, that is weird. Maybe it's the (insert innocent answer here) we just had installed?"
posted by Cool Papa Bell at 10:36 AM on December 18, 2009 [1 favorite]

Active cell phone jammers are illegal, but easily available and cheap. You could detect one with a spectrum analyzer, which costs a couple thousand dollars -- but lots of people have them, like professional wireless network installers and cable installers. Maybe you could ask someone like that.

Passive cell-phone-network-blocking materials are expensive and would require construction work, but they're legal. Not sure how you'd detect if they're is being used.
posted by miyabo at 10:54 AM on December 18, 2009

i think anon means 25' away from the whole building

Anon says "from one point"- a building isn't one point.

I'm with the people who say to just ask. It doesn't seem likely that anyone would jam signals if you can just move to the other side of the wall and use your phone there.
posted by oneirodynia at 11:45 AM on December 18, 2009

is it possible there is interferance from something else/ I am a network tech by trade and all our servers block cell phone reception. step right outside the server room and you get full strength.
posted by majortom1981 at 12:18 PM on December 18, 2009

Deliberately jamming the signal is illegal in Europe and, I believe, the USA. It's technically very easy to do, of course, which means that your boss could be doing it but s/he almost certainly wouldn't admit it.

It could work in the way that you describe: if an interfering signal is being broadcast, it wouldn't be a surprise to see it blocked by a particularly opaque wall, e.g. one with lots of metal in it. So when you're the other side of that wall the ordinary phone signal isn't being drowned out by the jamming signal. Of course, it could equally be that the phone signal is simply being blocked by that wall and there's no jamming signal on the other side. It's also worth noting that the bars on your phone are a measure of signal quality not signal strength, so it would make sense that the drop-off in signal would be pretty sharp as you enter the effective range of a jammer.

If you're concerned, you can report your boss to the FCC, whose job it is to regulate frequency use and to license broadcast equipment. They'd have the resources to actually detect and locate an active jamming device as well as the desire to do so.

Given the illegality of such a device, is it possible that your boss is using something passive instead? It's possible to block phone signal with special window and wall coatings that absorb or reflect the radio waves, essentially casting a big shadow. Some of this stuff put up in the building could be casting a shadow in one specific area. I have no idea what the legality of this stuff is; I think doing it deliberately is illegal but I'm not sure.

Finally, there could just be some new equipment. A big, metal case might be casting a shadow (the example of a new/moved server room is a great one), or a new piece of machinery might be throwing out interference. An accidental shadow is definitely not illegal, but a piece of equipment throwing out enough radio noise to block mobile phone signals is probably breaking EM emissions laws.

Find out what's at the centre and edges of the blacked-out circle (or sphere, which would strengthen the possibility that someone's broadcasting a signal, although aren't necessary or sufficient evidence). If it centres on a particular office area (big shared office, or Important Boss' office) maybe that's a motivation for jamming. If it centres on an equipment room, maybe you've just got a faulty piece of equipment? If there's some new machinery at one edge, maybe that's casting a shadow from the local tower?
posted by metaBugs at 1:58 PM on December 18, 2009

By any chance is there a fluorescent light at the center of the radius? Because this one time, I was having horrible cell reception at home. Drove me crazy. Turned out to be a CFL that was failing and putting out horrible interference. As soon as it was replaced, everything went back to normal.

Also, the bars on the cell phone actually reflect (inversely) the amount of signal the phone is having to put out to reach the cell tower, not the signal strength the phone is receiving.
posted by gjc at 4:13 PM on December 18, 2009

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