I got in on this post late, but they are right. Cell phones , loose cables , and ( I wear western boots most of the time and figured out there is metal pegs in the soles on the arches which set mine off ), if I use my left hand which has the ring on it in some cases the ring sets it off going wild. Certain rocks and soil set it off wildly because of the mineralization. Power lines , some network cable dishes have set mine off if I am too close. Sensitivity too high usually as they say about 3 bars or 4 max. Then too if your in a very trashy area like my yard where previous owners pitched pop tops like crazy, (I have found over 300 pennies in the front yard alone. must have had a thing for pennies ). It all takes practice and patience and getting to know your machine. My wife uses a BH Lone Star and I use an Ace 250 so far we havent had clashes yet. Sometimes she is so close our coils colide and havent had an issue yet with them setting each other off . Might think of that too.