"But no one has been able to triangulate exactly where the broadcast is coming from." - How difficult and expensive would it be to build a system to exactly triangulate these stations? It seems if you had three receivers many miles apart and precisely synchronized, and you timed the signals at nanosecond resolution, then you could correlate and find the location within a foot. I'm sure it's much harder than that, but it seems with SDR you should be able to do much better than primitive triangulation based on approximate direction. Does anyone know how to do high-accuracy triangulation.

On a different topic... "If you drop a rock in this hole, it will take about a second to reach the bottom—whatever is down there is at least 32 feet below ground." - I've been thinking about high-school physics a lot lately so I feel obligated to point out that 1/2 A T^2 would be 16 feet.