I did a test with one of the rocks that are in my ground and a dime. I balanced out the rock (4 with the stock coil and 11 with the 10.5" DD MF coil) and then I passed the dime under the rock over the coil. If I pass just the rock I get nothing.. so the rock is balanced out...but if I pass the rock with the dime under it.. the dime comes up as -8 (Iron). Do you guys know of anyway I can mitigate this TID problem? This is the same thing that is happening in my soil with coins that are down 3"+. Here's a video of it: http://www.vimeo.com/12124994