Well, there's nothing "wrong" with the detector itself. It's the settings. (By the way, which coil do you swing with ?)
Notching out everything below dime will bring some problems to daylight.
You should notch NOTHING, when and where it's possible, and as long as your patience and your ears can stand it.
First, dimes (clad & silver) in the vicinity of a rejected target (be it iron or aluminum or whatever...), will not give a dime signal. It will give a rather jumpy one, but if zincolns are disced out, you will miss a good amount of dimes. Yes, silver ones too, their mass is feeble, so anything in the vicinity will distort the signal, causing you to miss it.
Then, the rusty iron targets respond because they have some conductive contents, or become conductive due to their shape, it's a well known phenomenon. If you DON'T disc out iron, they wil either register as iron only, or jump between iron grunt and high tone, letting you know youre swinging above some rusty target.
If you want to upgrade later, look then at detectors like the G2 or the Eurotek pro (the latter being a demon in iron -read the manual available on line !). With my ETP, I seldom have rusty bottlecaps/pieces of iron problems. Things go forward. I like detectors with notches, but newer FTP roducts (ETP, G2, Goldbug) offer much better discrimination features.
At last, notching that much results in loss of depth. Significant loss of depth, and certainly with a detector offering preset GB. Next time you dig a rusty targets with your usual notching below dime, notch everything back in, and sweep the target. It should ring as iron, or jump. The better you will become in the hobby, the LESS you will discriminate.
Happy Hunting !
Grumpy
