I apologize if this has been asked, i did a search couldn't find exactly what i was looking for-I have a new AT Pro with both the stock 8.5X11 and the 5X8 DD coils. What kind of depth are you all getting with these coils? I laid a 1961 Franklin half dollar in the ground at 6", and barely get a reading with the large coil, no reading with the smaller coil........running pro-zero, sensitivity maxed, ground balanced. The signal on the large coil is "choppy" at best like there is iron in the hole with coin, but I checked the area thoroughly before I planted the coin. I also changed batteries, re-wrapped the coil cable correctly and removed then re-inserted the coil connector.........at 6" I would think the large coil would "chirp", and the small coil would produce something............again, its a new unit from a sponsor on this site.........suggestions?