Hey James, I fly at Birmingham RC field in Morris on Hwy I-65. We have the freq. pin board up that you clip your AMA card to go along with the proper channel that you on. No impound though. We have posted on a sign: If someone turns on their radio while the person who has the proper pin is flying and it causes a crash, that person is responsible and liable for any damage.
thanks
John McGowan, Birmingham, Al