Jamming GPS
- Thread starter Kingairer
- Start date
Screaming_Emu
Well-Known Member
It appears GPS jamming is pretty common.
The GPS signal is low power with the L5 signal being two times stronger than the L1-L4 signals and easy to disrupt by just overpowering the gps signal with your own transmitter.
https://gizmodo.com/jamming-gps-signals-is-illegal-dangerous-cheap-and-e-1796778955
But you’re probably not asking about that and are more interested in the large No GPS zones over in New Mexico.
The GPS signal is low power with the L5 signal being two times stronger than the L1-L4 signals and easy to disrupt by just overpowering the gps signal with your own transmitter.
https://gizmodo.com/jamming-gps-signals-is-illegal-dangerous-cheap-and-e-1796778955
But you’re probably not asking about that and are more interested in the large No GPS zones over in New Mexico.
Cptnchia
Dissatisfied Customer
Flyinthrew
Well-Known Member
You're not being targeted. That would be dangerous and imprudent. Most kinds of jamming are kind of an "area weapon". The good news is that the antenna placement on most aircraft is the best technique to defeat most jamming.
HeimerPilot
Well-Known Member
The military controls GPS satellites, and can at their whim degrade the accuracy of GPS receivers in non-military applications. Even to the point of them not working. A safety feature in case some terrorist organization or foreign power was using GPS guided aircraft/missiles/drones/etc. I know nothing of the technical details, something to the effect of the GPS satellites not giving position to receivers without the correct (military) coding. We saw this often in New Mexico (per ATC "they're jamming out of White Sands") Maybe they're keeping nosy drones or civilian aircraft from flying over military exercises, or maybe just testing that their ability to block the signal still works. In either case it seemed to affect everybody. We'd lose GPS in our king airs and hear the airlines all complaining/asking about the loss of GPS signal.
ppragman
FLIPY FLAPS!
Selective availability was turned off by president Clinton.
ppragman
FLIPY FLAPS!
I know you’re up against opsec, but I’m not so this is me regurgitating what I’ve read from open source resources over the years. All of the stuff other than the specifics is open source and in academia anyway.
I doubt the Y code (which is just the P code plus another super secret squirrel code called the W code IMS) protects you much from jamming if it’s crazy loud. If you jam the hell out of that freq such that the unit can’t hear the Y code to decrypt you’re not gonna get a signal.
The Y code will (ideally if the bad guys don’t know how the code is generated) prevent you from being spoofed though, so that’s cool, but straight up jamming is still a risk. I’m still curious about how Iran snagged that RQ-170 though. I suspect they were able to exploit some hardware or software issue but I’ll probably never get to know.
There are probably ways to use the Y code to get a position through all but the noisiest jamming, since ostensibly no one knows how the W code is generated, but I’m not sure. I think Null-Steering Antennas can help with jamming too - but I don’t know enough about the physics to intuitively know why. That said, ITAR restricts null-steering antennas along with GPS that works faster than 1,000kts or ones that can decrypt Y codes so I would suspect this is the case. Wild speculation follows.
Speaking of Y codes, if you wanted to degrade the signal for everyone else but still be able to use GPS in a location, I’d jam on the frequency of the P code with a public key then transmit a private key as a Y code. It would take the GPS a little while to boot up if it was a good encryption, but it’d be super secure and you could degrade the effectiveness of every hiking GPS being used by the Aloha Snackbar guys in an area (or just straight up deny the frequency to them). If you then went on to constantly change Y codes in some randomish fashion it’d be practically impossible to use our own GPS against us.
This is exactly how I suspect that this works (but this is wild speculation on my part) when they are doing GPS jamming practice in a region. Whatever code box or software in the GPS has a spot where you can put the Y code for the exercise into the unit. The people in the exercise then put this special code into the unit (or even better would be a series of codes over the duration of the exercise) and they practice hunting the jamming antenna while another group of people practice operating while being jammed.
Cptnchia
Dissatisfied Customer
ppragman
FLIPY FLAPS!
The GPS signal stuff is really interesting if you’re up for it - there’s badass OCW presentations on how it was designed. GPS is one of the most important technologies of the last 500 years.
ppragman
FLIPY FLAPS!
If you’re bored and interested there used to be a badass collection of PDFs here which detail how GPS works in great detail. Basically all the theory you need to understand a GPS is there. If you’re interested in space stuff like me a lot of this stuff is really insanely interesting. Everything from the orbit wobble to how the system processes ionospheric interference is in there.
And then there’s this guy. Who built his own receiver in his living room. I wish I had the chops to just sit down and do this - it’s pretty freaking nuts.