hi, I have a question regarding the older whites units. I recall a local dealer that had a 5000D (which for most of us was a waste of time). His unit could detect quarter size coins at 12" depth. During that time period that was amazing (and thought not possible). He wouldn't tell us how except to tell us it was modified. Some people suggested that there was a resistor in the coil or somewhere in the unit itself that was limiting the transmit and receive signals. Any truth to that? thanks!!