Authorman, it's partly you and partly the machine!
Seriously, all metal detectors have big problems with trash - but once you get used to it, you can ID trash pretty easily. Here's a couple of things with the silver umax.
You will always dig pulltabs if you site is newer than say 1920. I have used $1000 TID machines that do it all, and they ALL dig pulltabs sometimes.
You can eliminate digging the crushed cans easily.
Remember almost all signals will not be coins. Most sounds you hear will be trash. You absolutely must focus on the makeup of the sound you hear. Forget the discrimination dial for now. Since you want to dig coins, you need to
trust that they will almost always give "small" smooth signals.(especially on the silver umax) Sweep back and forth from many angles centering the target and you will just know it when you hear it. You will be able to visualize a tiny round object, I know it sounds strange but it's true! A larger crushed can or chunk of aluminum will almost always give a "large mis-shaped" overwhelming signal. The coin and can will both register like a coin on the dial, but you
must concentrate on the
size of the signal and the duration as you swing the coil over it. Doing this will eliminate 95% of the large aluminum.
Also, once you get that "smooth, round, small" target sound you are not done yet. You need to get a rough estimate of depth by sweeping the coil back and forth from the ground and slowly raising it up. If you life about 3-5" up, and the signal disappears - then you have a target a few inches deep. If you can only lift it 2" - then it's a little deeper. This can also help ID large trash b/c with it, you will be able to lift the coil about a foot off the ground before the signal disappears - it's a can - don't even dig it. Some people say, wah! That could be something good. Yes it could, but the chance of a buried treasure chest in the middle of a park is slim, so I usually just skip it.
Now, for pulltabs. This is tricky but you can do a few things to help avoid most of them with the silver umax. First realize that different pulltabs read differently and based upon how old they are if they are broken/bent. Some you will never ever be able to avoid - the old circular ones and old large square tabs. But for the new ones, this trick works for me.
When you dig one, wave it in front of the coil and very slowly dial the discriminate up while swinging it over the tab until it just starts to break up or crackle. Make sure it gives a broken signal. Make a note of
exactly where the dial was when the signal "broke up". Now with every good small smooth signal you detect, slowly scroll up the discriminate dial while swinging it back and forth. If it breaks up on the line, there you go - likely a pull tab-skip it. If it continues to sound strong - probably a coin - if you keep going up past tab - probably a copper coin or silver coin.
As for bottlecaps and screw caps - I got no help for you, they always fool me.
When I hunt in a modern park I always try to remember to ONLY dig the signal after I have used everything possible to identify it. There are so many GOOD signals to dig in most parks, that one should not necessarily get caught up on that broken signal that you have a "hunch" is a coin - it probably isn't. Of course when all the good signals are gone, dig the broken ones. However, you must maximize your chances of success by digging mostly high probability targets. The more trash you leave in the ground, the more coins you will dig.
Don't give up. You will get it. It just takes a little more practice. PM me anytime for specific questions.
ian
