My Golden with 8x9 coil will go from low tone to high tone 5" max on a dime in air tests and a quarter 6" max. Beyond that the tone remains low. I used a nail to return to low tone each time before sweeping over the coins again. Example, a dime at 6" would remain low tone and not change. Anybody getting more depth in air going from low tone to high tone? If you do the test be sure to use the nail to bring it back to low tone each time. Thanks, Jabbo