you have to actively prevent digital circuits from emitting radio waves. that's what the FCC part 15 subpart B is talking about. "unintentional radiators".
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now spoofing GPS, yes, that is pretty serious. FCC will come and kick your ass too, but meanwhile you're going to seriously affect a lot of infrastructure nearby. this is a growing threat, mostly represented by truck drivers trying to work around fleet surveillance
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Replying to @whitequark
Not sure, but I think it's possible to make a highly spoof-resistant (not jam-resistant of course) GPS receiver using multiple antennas.
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Replying to @RichFelker
you can make a spoof-resistant GPS receiver, and you can even make a jam-resistant GPS receiver (within reason), but the issue is that a) most vendors don't bother doing basic sanity checks b) it's impossible to tell just by looking at the device c) shitty chipsets are everywhere
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Replying to @whitequark
Jam-resistant sounds really really hard due to the low signal strength. With a single point of jamming transmission there may be correlation-based approaches with multiple antennas, but with N independent noise sources...
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Replying to @RichFelker @whitequark
IIUI jam-resistant is possible as long as the malicious interference *) is not sufficiently correlated with any of the existing GPS Gold codes (so signal processing can still separate the real signal out) and *) does not cause the receiver to saturate
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Replying to @rqou_ @whitequark
Obviously a quality jammer would use the PRN codes, something like a random linear combination of the different sequences in different phases.
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Replying to @RichFelker @rqou_
that's why I said "within reason". most jammers are cheap shit that's little more than a PLL and a PA
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Replying to @whitequark @rqou_
These cheap USB VGA things could easily make a good jammer based on the above though.
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Replying to @RichFelker @rqou_
easily accessible? yes. able to confuse most (completely unhardened) GPS receivers on market? yes. good? no
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I was talking about making something that would jam a hardened receiver. Cheap SDR should be able to do that. Off-the-shelf jammer, maybe not.
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Replying to @RichFelker @rqou_
if you're targeting a hardened receiver chances are you can afford a less crappy $50 SDR anyway, so this isn't really changing much
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