Ok, I think I get it... you essentially put the front 1/3 or 1/4 of your DD coil over the suspected target, then sweep side to side and pull back off the target, looking for a drop in numbers and tone. A drop in tone and numbers indicates the target is probably trash.
A neat trick, if I understand it correctly. I'll have to give it a shot. Many thanks!
A neat trick, if I understand it correctly. I'll have to give it a shot. Many thanks!