GPSjamming

[paladin]

Some caution should be used on relying on GPS positioning as your sole method of navigating close to shore. With the advent of modern small tracking devices using an extremely small GPS receiver coupled with a tiny cell transceiver, private detectives, Government agents, spies and other such persons deploy these devices to track peoples movements. The counter to this are small electronic devices used to send a false signal to such devices in close proximity. These items may be smaller than the smallest cell phone, and feed false info to the GPS and also may totally jam the cell communications for several feet/meters around the targeted tracking unit. Such units are being deployed all over the world and are very common. Some units will lie to the GPS and they think they are at a position which may be off by 15-20 miles.

[Mike Field]

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Hh'mmm.... I don't know whether to thank you for this information or not, Chuck. :(
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[paladin]

Mike, it's a cautionary note. When someone builds such a device, the clock is deliberately off by a tiny bit, coupled with a PN generator and since the very weak signal is stronger than that from the GPS satellite, the machine accepts the stronger signal. The information is encoded using a simple PN code generator, but it's a simple task to design one (less than a dollar to build) that is one bit faster or slower, throwing the GPS off.

[JimConlin]

Chuck, aside from not relying solely on GPS, how should I view this uncertainty? What is the approx. range of these devices? Is the probable carrier somebody like my buddy whose soon-to-be-ex-wife's got detectives spooking him and who might just be taking countermeasures? If I ask him to leave all his electronics in the car, can I take him sailing?

[Henning 4148]

Thank you for the information. Wasn't aware that things had gone that far by now. Probably high likelihood of problems especially in the vicinity of military vessels and super yachts.

[paladin]

Jim.....the range of the devices vary but a mile or two might be safe. The ones I designed are effective as adjusted to 2-300 meters. The weird ones coming out of Europe have higher power outputs, I've seen them with 50 milliwatt rf outputs and that can easily mess things up a few miles away. I saw the first European ones 3-4 years ago.

[JimConlin]

Every brothel should have one. :D

[BrianW]

Clearly the next step is the jammer jammer, to prevent such jams.

[paladin]

dunno work that way...just adds to the jamming....

[willmarsh3]

I'm driving around in the country and my Nuvi GPS gets completely confused for some reason and starts saying "Recalculating...recalculating..." or gives directions that don't make sense. There are no tall buildings around or anything else that I could see interfering. And then after I go a bit more it straightens out. Hmm it could be one of these jammers at work. Would there be any way of detecting these?

[paladin]

Yes...there is a way to detect such an item...and I have a test unit for that application when we take our toys to the client for testing...but there is no "commercial" demand for such an item.