hi, I was emailed this by Mike Hills hope this helps you out !
when u set for a site you want to run the detector as hot as u can, and still tell good signals from the false ones.
You can start by seeing how high the local electrical interference will let u turn up the sensitivity.
set your threshold to - 10 and start raising your sensitivity until your display goes erratic. Then turn it down until the display stabilizes .now ground ballance. Once you've ground ballanced see how much falsing u get, if the chirps and falsing are so bad you carnt tell the difference between them and good targets, even deep good targets, then you need to start adjusting downwards. Start by lowering your threshold - 5 at a time. If you get to - 35 and don't really see a difference then return to a - 10 setting and decrease your sensitivity by one and start over. You do this until you get to a point where the falsing doesn't interfeare with recognizing the good signals.
turn tracking on it will eliminate the tiny chirps from the ground minerals if you find that they bother you too much.