This is a project that never quite got finished. The goal was to make a dog door for my dogs that would unlock only for them and not other dogs, skunks, coyotes, etc. So I built an RFID reader that could detect a tiny tag on the dogs' collars as they approach and unlock the door for them. Problem is, I could never get enough range out of it to be practical. I got about eight inches and I want 2-3 feet. The RFID chip is very sensitive to the resistance and impedance of the antenna (wrong values can even damage it), so changing the antenna myself without knowing a lot more about RF engineering than I do is impractical.