A couple of days ago I experienced a strange phenomen, I was teachinga new e-trac owner his machine and located a weak signal and called him over to check it out. To mark the spot I put a small piece og brick over it but he couldnt for his bare mind get anything. We checked settings and tried more but no. I took my own machine to check ,but the signal was gone, couldnt understand why and kicked away the small piece of brick and then bang, the signal appeard again on both machines. Didnt know that brick had masking abilities. Have anyone experienced the same?