welcome Bill,
I too am a newbie to the explorer, and are having many problems with the detecter finding coins that I have buried. Did you do a air test on the machine? I have no broblems with the machine when I do an air test, but when I put the coil to my yard I cant get nothing, I dont know all that much yet, but I do have a suggestion, I know it is extremely inportant to make sure there is nothing in the area you are buriing your coins, the trash in the ground will cause alot of interference. try this, when turning on the unit hold on button to get into factory settings, press iron mask button once, set iron mask to-16,press iron mask button again to enter detect mode, set sensitivity to 30, leave in semi auto, now using this setting check the area you want to use for your test garden, and remove any target you find, once the area is cleaned out, you can convert back to the factory pre-sets, and put some coins back in the cleaned area, and try again, keep the coins shallow at first, dont know if this will help, but I know my yard is so trashy I cant get no good signals. good luck