if you keep digging an never seem to find it,I can almost bet your pin point is off.Being that you are new at this pin pointing can be tricky, sometimes even throws the best of us off.Most coins will be less then 6" an if you have a coin reading an your past the 6" I bet you missed your pin point.One other thing that can make it hard on a new pesron is a large target buried deep, a aluminum can for instance, at 10" + deep will have a coin reading. A test garden will help you alot, but make sure you put in it an area with no signals.I would plant objects less than 5" for now, then you can always go back an plant a little deeper if you feel the need.A more expensive machine will not help you alot , you will still have to learn that machine also, but after you master this machine going to a diffrent machine will be much easier.It took me months before I got to were I can pin point dead on (95%) of the time.