I'm trying to test my 3 month old AT-PRO that I just got. I put a bottle cap on a piece of clean ground to try and get the low high low tone and all I get is a garbled mess. I have swept the area with my Ace 350 and the AT-PRO and it's clean. I have also tried air testing the bottle cap with the same results. I have the machine in Pro,Zero with 35 disc and Iron Audio on and can't get that clean crisp tone that I've seen on the Garrett tutorial vid. Does anyone know what I'm doing wrong? I have a area at a old school that is totally infested with bottle caps and I'm not sure if there is a problem or not.I want to be sure I have it right before I hunt it.I haven't dug any coins deeper than 2" so far, but I'm not sure if I've put the coil over a deep coin yet or not. I'm just worried why I can't get the crisp tones like on the vid. Any Idea's?