Originally published at: https://boingboing.net/2018/04/20/man-uses-gps-trackers-to-catch.html
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POLICE: So, wait, GPS trackers don’t just work on cars, but other stuff too?
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More like putting a GPS tracker inside a big metal box shouldn’t work. (Faraday Cage) Obviously there was enough opening it could hear GPS satellites and Tx its location. The owner either got lucky or knew what he was doing.
My first thought was “how did that work?” as well.
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Ah yes, that very brief window when police car data terminals had GPS but didn’t have encryption.
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Last year, I had a new AC installed inside the fence. The old unit was outside the fence, and the installers said I was lucky it wasn’t stolen. O mores! O tempores!
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They know it works in my area. Last week I read in the news that a bank robber was caught because the bag of money he got from the teller had a GPS tracker in it.
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My impression was that they pretty much have to be grounded to work.
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The wavelength for GPS frequencies is around 20cm, so a 1/4 wave ground is only ~5cm. Easily included in the device. No external ground needed. Even a full wavelength antenna would fit, although that really isn’t an option since shorter antennas with better gain are what would be used.
A quick search looks like it’s fairly common for these devices to use a cellular data connection to send location info back to you. Obviously that ground plane is small enough it could also be included inside the device. Your phone doesn’t need an external ground.
The only reason they are normally magnetic is for a convenient mounting option. They work just as well riding around in a backpack.
While I’ve never even seen one of these devices other than online, this is 35 years as a communications engineer speaking. Although, I’m the first to admit I certainly could be wrong!
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I was actually referring to the Faraday cage. I thought that had to be grounded to effectively attenuate the signal. But, to be fair, my mathematician brain tends to shut off when it encounters applications.
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That’s pretty cool!
“I have no idea how that large metal box got into the back of my truck, but it is hella windy, maybe it blew in when I wasn’t looking.”
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Given the…very special reputation…of RF propagation in the field, and designs that seek to manipulate it, I’m not wholly convinced that mathematics doesn’t experience some reliability issues when applied too closely to that class of problems.
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Recently wrote a tracking app for my phone using Droidscript. As I don’t have a data plan, I needed an app that used SMS. So it fires up the gps once a minute; if the location has changed by more than 200 meters, it sends a text with a map link to my email. If I want to track where my car has gone, fer example, I just toss my phone in the trunk. Works great. https://groups.google.com/forum/#!topic/androidscript/zSk0r5jEB68
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If they make the story into a movie, it’s going to be shorter than The Bicycle Thieves, unless there’s a B plot or love interest.
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Lots of places bolt a cage around their AC, anchored into the concrete pad it’s on.
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Oh what a genius, hope its easy to install…
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