I found out what to do with the large coil on the fisher f75. put it in your bag,and grab the small coil . works for me in the hi iron ,and the minerial soils too. the same goes for my whites v3. several times i have gone behind the large piles of dirt that everyone gave up on. try the piles of dirt with the small coils,and behold out comes the beep that we are looking for. you have to be persistance,go slow,and cover the hole pile of dirt. try it. happy hunting
ps let me know what you find. also i have a nice tejon for sale.