It's extremely easy to locate the jamming device!

The device is transmitting at high power, it's like beacon, and very easy to see.

If you do it in war the jamming station is likely to be visited by a http://en.wikipedia.org/wiki/Anti-radiation_missile such as the http://en.wikipedia.org/wiki/HARM_missile

I can't say for sure how "they" do it, but there are a number of options available. Radio in general is very leaky - even rather low power and directional beams can be detected off axis if they travel enough distance and you have sensitive enough equipment. In general you just need a few antennas (or even one, if your're a masochist) and an ability to point them at things. Check for when the signal is the strongest, and check for timing between the receivers and you can get a very good idea of where the transmission comes from. In practice you could do this with multiple antennas (an array) on a single satellite, multiple other satellites or spacecraft, or simply an aircraft or trucks if you control the ground space. I'm willing to bet it's usually done on the targeted bird itself, they aren't completely cut off from communication, have multiple antennas and can even adjust their attitude if it was necessary.

This is broadly how the SETI program works for example.

If you'd like a good demonstration of how a jamming device could be found, simply buy a high-power 10 meter radio transciever and set it up to constantly transmit music at 28.400 MHz. You'll effectively monopolize the frequency over a large distance, and within a very short period of time the FCC will arrive to demonstrate their RF tracking techniques.

And to levy a huge fine. Do not do this.

Think of it this way: radio is light. There's a light sensor on a satellite that the BBC shines at. Someone else is shining a really-bright light at the satellite so it can't "see" the BBC's light through the glare of the other bright light.

Kind of like trying to see a flashlight when someone's shining headlights at you.

But ... if you're shining a really bright light then everyone who cares to look can see where it's coming from.

Very possible. In fact, some aircraft and ship navigation systems (prior to GPS) at a very basic level determine position through triangulation based on direction to known RF emitters. (See Loran, NDB, etc).

Its also a popular sub-activity of HAM radio, in which its called "Foxhunting."

Yes, location is possible, narrow directional signal makes it more difficult to locate than omnidirectional broadcast signal.