John a little confused.
If gold falls in to the range of iron and junk why would you want to discriminate it out or have I misunderstood you?
You can't discriminate it out, but what you can do is, if you are only searching for gold, dig ONLY the high-low signals. That can eliminate a lot of digging. If you are searching for old coins...ie silver/copper, dig only low-high signals. Now, that is a pretty generalized statement. Add other learned features, such as the unique sound the Garrett PI detectors make on nails and bobby pins, the audio duration the machines make on a large target compared to a small one, the iron check, the smoothness of a target, the intensity of the audio over a target and location of the hunt, you now are getting more unique forms of discrimination. A new PI user has to relearn how to use this type of detector. It takes a lot of time. I have often times said that if you are new to metal detecting, don't buy a PI detector, as it can be a severe lesson with frustration. There are no knobs to discriminate iron, foil, pull tabs. There are no knobs to show depth. There are no graphs on the screen giving lots of useful information. It's just you, your ears, brain and a metal detector, which goes deep, and is capable of punching deep in a salt water and or highly mineralized environment. The more expensive PI detectors can be manually ground balanced, eliminate interfering EMI and even utilize automatic ground tracking, which can overall squeeze yet some more precious depth, another reason PI's do so well.
I have been using my PI detectors since 2006, and have done exceptionally well. I have learned when and where to use one, learned discrimination features and had some of my best ever years digging deep gold rings from hunted out areas. I have also had some success using them on land coin shooting (digging only low-high signals) and digging the softer sounding deep coin sized targets. Using a PI detector is not for everybody. You do end up digging up a lot of junk targets you probably would not have using your VLF detector and using a PI in well used parks is not recommended, as it will beep on every target underneath the coil, often times sounding like a classical piece of music. But......in the hands of a seasoned user in the right location, a PI detector will do very well.
