But how do these jammers work? They can't point at the sky to blind the satellite because there's no receiver; they broadcast from above ground, so in theory putting your receiver in a metal box with the top removed solves the problem?
No. Radio can turn around corners. It can also bounce off things. Radio is light, but at a much longer wavelength. It is less like blocking a laser and more akin to blocking out sound waves. Blocking line-of-sight to the transmitter would block the laser but would do little to block sound waves.
The other really annoying thing about radio waves is that even relatively long wavelengths can leak through really narrow cracks (<1mm) if they are long enough (eg a wavelength) in the right polarization.
Isn't that above the critical frequency you'd get ionosphere reflection at? (Which makes sense, since the signals are coming from outside it at LEO)
Pretend you're having a conversation. Now pretend you're having a conversation at a concert/club/any loud place. So like this[0]
> so in theory putting your receiver in a metal box with the top removed solves the problem?
You'd think so, but not actually. Think about it this way: you're trying to toss a ball into a cup (or box).
Is it easier or harder if that cup has a wide mouth or a narrow one? Make it V shaped for easier visualization and we'd be talking about the angle of that cone. Obviously the wider one right? The extreme other end of this is like a carnival ball tossing game where the cup is just as big (or they cheat and its smaller) than the ball you're trying to throw in. Now pretend you're trying to make that shot from a moving car. You come from far away and drive right past it and you get more points in this game the more shots you score.
That's analogous to what then satellite is doing. Remember it comes from over the horizon and then passes to the other horizon. You want to maximize your viewing angle because that gives the satellites more chances to make contact. This is more complicated because you need to kinda do this in parallel as you're handing off data collection to the next satellite coming through so the better viewing angle the more chances you have to smoothly negotiate that pass over.
Then there's the whole issue that we're talking about waves instead of particles but I'll let someone else handle that. You can actually find some cool visualizations on the internet about these. See knife edge diffraction.
Also, the more directional you get, the more it may be possible to determine where you are.
The real "hack" answer is to bypass the GPS system and just feed the starlink terminal its true/known ground position/timing.
Wrong. Utterly wrong.
what you did wasn't that -- but I would just like to point out that simple concise explanations helps the community as a whole; it's not just the ignorant that lose out.
Yes, I know it's likely not your job to educate, and maybe it's a bother that someone acts expert on something that they're clearly not -- but those that care to educate serve everyone in the context of an online forum, not just the naive or ignorant.
I'm no GPS expert, I've read some of the theory had enough of a working understanding to deal with tactical navigation systems, but that was in my past. I remember using El-Rabbany's "Introduction to GPS" text.
No, GPS positioning uses the precise time information encoded in the data from the satellites.
With signals from 4 satellites one can triangulate oneself in 3D space, with 5 signals, in 4D! (3D + time). I once did the math and astounded myself that it worked.
It will get another signal from another satellite, which could have the timestamp before X, because it left earlier and took longer to get to your receiver.
As I said, if you do the math, with 5 signals you can then determine your location in 3D space, and time!
GPS doesn't use the strength of the signal at all. Instead, each signal contains precise information about the current time at the highly-accurate atomic clocks onboard the corresponding satellite (plus some important metadata about each satellite, including things like their orbit parameters). If the receiver already knew the precise time, it could calculate the distance to each satellite from the difference between the true time and the received time (and the speed of the light), and 3 satellites would be enough to triangulate its position. Since the receiver usually doesn't know the precise time, it needs an extra satellite because there are now 4 unknowns (3 for its position plus 1 for the current time).
(Obviously, that's a very simplified explanation, there are plenty of other things which complicate the calculations.)