I think you'd be very surprised what a lot of power and a shit antenna can do. Obviously won't last when someone comes along with DF equipment, but it really wouldn't be hard to conceal visually.
Visually is the key word here. RF-wise, you may as well put a beacon on the moon and scream "LOOK AT ME" for all the good it'll do when the very, very angry FAA/FCC vans show up.
