Sunday, February 26, 2012

Jamming the signals on which we depend


A few weeks ago I rented a car for a few days. It had a GPS navigation system, and although I didn't need it in the areas where I was driving, I began to use it out of curiosity, to get accustomed to its operation. It didn't take long before I began to notice periods - usually on an interstate highway - when the system lost the GPS signal altogether. Observation led to the conclusion that they usually coincided with the passage of a large commercial truck or van.

I asked a friend in the local law enforcement community about this phenomenon. He ascribed the problem to GPS jammers. He said that many companies use GPS systems to track their vehicles' location and movements. However, corporate drivers frequently object to this, and so use GPS jammers to disable such systems. Furthermore, law enforcement agencies have been known to attach GPS tracking devices to vehicles, in order to follow them and/or build up a record of their drivers' movements (although this will be more restricted in future, in the light of a recent Supreme Court decision). Criminals use GPS jamming devices to frustrate such efforts. He believed the 'dead spots' in GPS navigation that I'd encountered were caused by a vehicle carrying a GPS jammer, traveling in close proximity to me for a few miles.

Intrigued, I did a bit more research on the topic. Truckers and other drivers using GPS jammers have been known to interfere with aircraft and airport navigation systems. Military jamming tests have disrupted not only GPS signals, but also cellphone, pager and other important commercial systems. In the UK (and, presumably, in this country as well) organized crime routinely employs GPS jammers when stealing or hijacking vehicles, to frustrate any tracking hardware or software that may be hidden on board. Prisons are faced with huge security risks in the proliferation of cellphones among inmates, who use them to communicate with family members and gang associates, arrange drug deals, plan escapes, and even organize 'hits' on criminal rivals, or potential witnesses against them. There have been proposals for many years to restrict (i.e. jam) or control cellphone transmissions in and around prisons, but so far this has been resisted by cellphone service providers and the FCC (the latter having also increased enforcement against illegal jamming of signals). Schools, too, want to prevent students using cellphones during class, and at least one school has successfully tested a cellphone jamming device.

I was surprised to see that, despite their sale being (at least technically) illegal, jamming devices are freely available online. One company even advertises quite blatantly that you should buy one of their jammers to ensure a cellphone-free evening at the movie theater! Clearly, the law hasn't kept up with the problem - and, given that one can order such products from overseas suppliers, it probably never will succeed in effectively controlling them.

I'd be interested to hear whether readers have encountered problems with jammed GPS or cellphone signals in their daily lives. If you have, please let us know about it in Comments. Also, if you know of ways to get around the problem, please tell us about them. We might all learn something.

Peter

7 comments:

Alex said...
This comment has been removed by a blog administrator.
Peter said...

I'm not going to allow jammer stores and/or salespeople to use my comments as a forum for advertisements. Hence, the deletion of the comment above.

Anonymous said...

I can't say that I noticed direct jamming, but when I was flying full time, I encountered enough dropped signals and RAIM failures (not precise enough for an instrument approach) that I backed everything up with the available ground based navigation aids (VOR, ADF, that AM station that everyone knows about ;), et cetera). I've also never had a battery failure with a paper map. Ever since I learned about GPS jammers I've been leery of the feds' enthusiasm for basing all navigation on GPS.

LittleRed1

Redneck said...

I've never been intentionally jammed as far as I know, but I think if someone jammed my cellphone signal and I found out about it, there'd be little broken bits of jammer all over the floor. My employment requires me to be available at all times.

Shell said...

I could dig having one for trips to the movie theater. Now if I could just buy something with a mute button to use on the audience...

Anonymous said...

I wonder if these Jammers can be used to disrupt smart meters that are made by General Electric?

http://commentarius-ioannis.blogspot.com/2012/02/dictatorship-by-general-electric.html

SewerDweller said...

as a biker, there's not a ride I take where I don't have to dodge someone yammering on the phone. I've been sorely tempted to get a jammer for the bike, just to increase my own survival odds.

Face it, you shouldn't be calling and driving, and if you pull over to take the call...you'll pass out of the range of my jammer in short order, problem solved.