Convo,
On the smaller chains, the F5 hits on the clasps, not the links. So when you air tests objects like those, focus on the clasps.
The best way to learn your F5 is to go somewhere where you can easily recover every target. Somewhere like a sand or woodchip playground where it doesn't matter that you can't pinpoint very well, and it doesn't matter if you can't dig a decent plug. Put it in disc mode, with the disc setting around 8 or 9 and recover every target that sounds off. Change the audio modes over a few of them. It won't take you long to match tone and target id (TID) to objects and you'll soon learn what audio and TID have a higher chance of being a good target, verse a trash target. Practice your pinpointing, learn where the sweet spot on the coil is. Learn how to get the best response, both audio and visual, for targets by experimenting with sweep speeds, and heights. Teach yourself how to read the visual information of the display so you get the whole picture. Put some time into it early and you'll be ahead of the game.
When you move into the turf, it can get very noisy. Lots of iron and aluminum trash in the turf. If the audio gets to much, there is nothing wrong with raising your disc and limiting the audio to something simpler and more tolerable for your ears. Sure, you might miss something good that go around, but you'll never recover it anyway if you can't process the audio. You'll get to go back later with more experience and pick through it all over again.
I hope you have fun and enjoy the F5.
HH
Mike