renantagum 30 ...Am guessing u mean they don't work due to there great depth in the ground or mountainside ..my dad told me that most metal detectors are only good at 3 feet max to many iron rocks give false signals ....By the way i hope to search in Valencia for yam treasure the site will soon have a cement road nearby ...wish i had a xrf to detect with its probably 25-30 feet deep near a waterfalls ..to all members good luck in the Philippines