[Merad]

> Shouldn't it have better protections against a $25 internet purchased jammer? Are such protections possible?

I don't think so. GPS is a purely passive system. If someone is broadcasting a signal in your immediately area that overpowers the GPS satellites, there isn't much you can do.

[contingencies]

Along the same lines, I'm surprised there aren't well publicized amateur UAV combat competitions with directional GPS jammers and EMP weapons yet.

[knodi123]

> If someone is broadcasting a signal in your immediately area that overpowers the GPS satellites, there isn't much you can do.

directional receivers?

[sathackr]

It would be pretty difficult to track 3-12 satellites at a time with a directional antenna, particularly with both the satellites and the plane in motion.

You could employ something like a directional antenna who's radiation pattern will basically look like a half-circle, with the flat part facing down, but, radiation patterns are not black and white, even if 90% of the energy is received from the main side, there is always some signal still received from unwanted directions. With as weak as GPS signals are, it wouldn't take much to drown them out, even on the back side of a directional antenna.

[grkvlt]

Yes, that's pretty much how military anti-jamming works. You have a steerable (via phase switching, not physically moving) antenna that can form a beam with nulls pointing at the sources of interference/jammers. See https://en.wikipedia.org/wiki/Zero-forcing_precoding for more info.