why am i finding all this iron stuff when i am in coin mode on my ace 250. it bounces between dime and dollar. indicating a coin. doing a bench test things are alright except penny, it always comes up as dime. so does a dime. nothing comes up as a penny. as you can probably tell i am a newbi at this. actually i'm .25 in the hole now. to do a test i buried a quater about 8-10 deep and cant locate it now. not a signal at all. i have found iron that deep. so why not my .25? the batts. are at half chg. i rasied sen. up to where it was making erratic noises so i backed it back down to 8 any ideas what im doing wrong??still learning. lee thanks