Another coil question.  Given that a mono coils sends a signal that is cone shaped into the ground what would the field of detection be on say a 12 in mono at say 10 inches vs a DD coil that has a blade shaped signal.  Say this is in mild ground.  Just how much depth is actually lost using a DD coil in the same soil conditions.  Would a broader signal at that same 10 inches of depth have an advantage with coverage at that depth?