Re: Day 1 with the F70 3/16/09
After dozens of hours of air testing, I've discovered a few things not in the manual. What sensitivity can be used & have stable detection & no falsing, at least in the presence of household electrical noise-which is also present in our back yard-depends on the threshold setting, mode, & to some degree, the disc setting. It isn't very intuitive, IMO.
Some of the better settings: DE all metal threshold -9 may be best. At sens 40, it correctly IDed a quarter at 9 inches (all tests are air tests-the ground is just starting to unfreeze here).
DE disc: threshold -1, sens 60-99; thresh 0, sens 30-50; thresh +1, sens 15, may or may not be occasional falsing, but can ID quarter at 9 1/2".
SL all metal: sens 30-45 with thresh -9 to -6, 11" on quarter with correct ID. Fairly soft beep.
SL disc: threshold -3, sens 60-90, 10" correct ID on quarter, even when I slowed to a moderate speed. Quarter was very loud!
IDs jump even in moderately mineralized soil on the deeper coins. Around here a 5" deep copper penny or dime may read zinc, dime, or quarter (#s 55-85), in DE disc mode.
People write about how much deeper the all metal mode is. Probably significant difference when sweeping slow. The disc likes a fairly fast to very fast sweep for best depth.
The manual mentions the detector may be more stable on the ground than in the air, so if above settings are stable, then you might try turning up sens or thresh & see what happens.
I haven't had a chance to try the + threshold settings away from electrical interference, but they are supposed to be good for tiny items as in gold prospecting. HH, George (MN)