Fisher F75 Iowa said:
Air tests are good for learning what objects sound like
Its also good for testing equipment,
if a quarter is hitting low like a Zinc penny (you have a problem)
or a Nickel is actually in the iron range, (you have a problem)
or you can't get out past three inches from the coil with a US quarter no matter what the settings are, (you have a problem)
or your detector doesn't hit on a silver dollar AT ALL in discrimination mode (you have a problem)
you should get good air test depth and expect in most cases to get less in the ground (except iron halo)
And yes! I've seen all the above at one time or another, the no hit silver dollar is actually a pretty common problem.
A detector should ID best in air test, nothing in the ground is going to make it ID better.
This is just to say that your stuff should work correctly doing air test, if it don't then you need to figure out the problem before you go out on a hunt!
But's his distance on the coin with "0" sensitivity is pretty impressive!
Mark