I'm calling shenanigans. I used to work in a lab where we had GPS repeaters to test consumer equipment. That alone costs big bucks. And, we had the FAA come down on us big time, because our GPS repeater broadcast outside the building too far and we got into some hot water.

If you were spoofing GPS campus wide over 1.544 GHz and had all your GPS sentences correct, with simple radios and antennas... and you hadn't got in trouble with Uncle Charlie or the FAA....

Just for clarification, it was not campus wide, only a small part between some institutes. Also, the hardware was not consumer grade thanks to the electrical engineering, geodesy and geoinformatics labs.

Still, it was illegal and could get everyone expelled, so I wouldn't do it again.

Spoofing GPS is trivial. Getting caught or not is a toss of the coin

Cheating the location on my phone is gravy.

Broadcasting an RF signal to spoof GPS (and especially across a campus), that my friend, is not trivial or cheap.

> not trivial or cheap

From your previous comment, it sounds like your experience may have been from a while ago? In 2022, it is fairly trivial and cheap: https://github.com/osqzss/gps-sdr-sim

I can not ;^) personally confirm that this works with a HackRF, which is like $300, but probably also with any other reasonable tx-capable sdr.

Trying to set up an alternate 3d volume of GPS space sounds very difficult.

But broadcasting a loud signal that tells everyone in range that they are at the same exact point doesn't seem too hard to me. Couldn't that even be as simple as replaying a single-antenna recording taken somewhere else?

Yes exactly.

Doesn't work well with some receivers that cache data from the real network and stay locked onto the much weaker real signal. But works with most receivers.