It'll work about as far as you can shoot.... /ubbthreads/images/graemlins/smile.gif
But, It is kinda line-of-sight. Don't put the caller over the hill...(You want to watch the caller anyway)
If I had to put a yardage on it, I think it'll turn on the caller at 4-500 yards plus.
Your milage may vary.. /ubbthreads/images/graemlins/grinning-smiley-003.gif