Using a 50 cent size piece of Hematite the F70 will stay on 99 in both Disc and AT modes, will not balance out, why?. I can ground balance outside with no problem but another question, in the same piece of ground, if I ground balance in the disc mode the number will be 42, in the AT mode the number will be 27, why the difference and will this cause the F70 to ID the target differently? I have noticed that when I GB in AT it is so much smoother and easier than in the disc mode. Thanks, John