3 ms·

I was reading the specs for the GPS satellites vs. the GLONASS ones a while back, and it seemed like they transmit on a similar frequency but with a different m

• londons_explore 3y ago
  To jam something, you ideally jam the same frequency, PRN code, and direction. If you don't know frequency, you need to jam a wide range of frequencies. Defences like frequency hopping make use of this. Bluetooth uses this for example, to prevent inadvertent jamming. In GPS, frequencies aren't secret. If you don't know the code, you need to jam with as much power as the benefit of the code. For GPS, thats a 10x 1024 bit code, which provides 43 dB of processing gain. This can be increased almost without limit, as long as you don't plan to move much during the code period. There are clever methods to make encryption keys double-up as PRN codes that the enemy doesn't know. For direction, it depends on the receiver. Your phone has an omnidirectional receiver, so the attacker is 'on par with' the real signal. A military directional phased array system might have 200 elements, and therefore 30db of gain. Add that up, and the enemy needs to use far far more signal power than the real signal to 'outshine' it. Turns out that's pretty much impossible - and if they get near to doing that, your biggest problem is probably being cooked by their jammer.