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Notes On The Axiom Iron Check Feature

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6 hours ago, Beeper Bob said:

Wonder how well the discrimination works on the axiom.

As well as any PI discrimination - anyone expecting VLF type discrimination will be disappointed. PI discrimination no matter how you do it is pretty poor with lots of good judgement necessary by the user. When in doubt, dig it out. But light years better than the 6000 in that regard. I get it. Minelab is saying that PI disc sucks, so forcing the issue by not offering the option at all. There is no doubt we should dig all targets. But I think there is also no doubt many of us still cherry pick when faced with too many targets, most being nails. We simply dig what sounds good. If that is indeed our reality, and I think it is for most of us, then having all the disc ability possible for use is a good thing, and so I welcome the Garrett Iron Check feature as just that. Another way of double checking targets in trashy areas. But do not fall into a bad habit of leaning on it a lot all the time. The more naturally occurring iron ground mineral you have, the more risk the system gets fooled, to the point where in heavy magnetite I'd say it's more likely to be fooled than not.

The disc is better for coin and relic hunters in one way. If the system tricks me in bad ground and I miss a nice gold nugget, that is a pretty big deal. If I am relic hunting, and it makes me miss a bullet or two, but gets rid of most ferrous, well, that seems more acceptable deal to me at least. Though the relics hunters may beg to differ! :laugh:

If you want to be conservative and use the Iron Check in the safest way, consider using it as a reverse disc system.

In other words, many of us get pretty good at picking and choosing targets with a pulse induction detector. Most gold tends to give sweeter high/low tones. Most low/high tones are larger junk (or larger gold nuggets). So people like myself will sometimes focus more on high/low tones and ignore the low/high as nails. But the low/high can be the largest nuggets!

So think about this. You are in a nail pit and decide at some point to skip the low/high as being trash targets. OK, so far, that's normal. But now, go ahead and use the Iron Check to verify this. If it gives a consistent iron grunt on a low/high target, it is almost sure to actually be ferrous. If it does not give the grunt or seems unsure, maybe you better dig that one after all.

The Iron Check has limitations, first being it does not work at all on the deepest targets. The tones do, but Iron Check only works at 2/3 or half of the full depth. The deepest nails are not going to Iron Grunt. However, a lot of nails are shallower, so this offers a middle ground. Instead of ignoring low/high signals, only ignore low/high signals that also have a solid Iron Grunt. This double check verification is a much less risky strategy. Yes, it does mean you will dig the deeper nails. Sorry, but you can also with good accuracy eliminate all those much more common nails that are just below the surface. Consider also that a deep low/high is not going to be a small nugget; if it's gold, it might just be the biggest nugget you ever dig in your life. You are looking for a trophy nugget in a nail pit, this might help you better your odds.

What I am saying here is to use the iron check to make you dig targets you might have otherwise passed on - reverse discrimination.

Now what about the small nuggets, the high/low tones, that by nature will be shallower targets? And small ferrous trash, that sounds the same? The ferrous check is also great for small ferrous in milder soils. But again, if in heavy magnetite, be less trustful. Look for reasons to dig, not reasons to skip targets. If the iron grunt is indecisive at all, dig it! When in doubt, dig it out!! A good super magnet on your pick head is a more accurate and very efficient way of dealing with the shallower smaller stuff.

A reminder - the Iron Check only works with the Garrett DD coils. Another reason to consider the 11" DD over the 11" mono for hunting the trashy sites.


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So people might ask why, if it is a PI detector, does the iron mineralization have such an adverse affect on the accuracy of the Iron Check?

My answer is people are complacent in their faith in VLF detectors in bad ground. In iron mineralized soil, as you bury any target, large or small, deeper, the signal gets weaker. As the target signal gets weaker, the ground signal is getting larger by proportion. Every detector with discrimination I have ever used, if you bury the target deep enough, the signal flips from non-ferrous to ferrous.

People tend to think this only happens with small gold nuggets. No, it will happen just as much with silver coins and one ounce gold nuggets. The size does not matter, because if buried deep enough all targets sound the same - small and weak. Anyone using a VLF in bad soil is constantly missing targets at depth that are called ferrous, but actually are not. It can happen at ridiculously shallow depths in bad ground. I have seen very good detectors call a non-ferrous target sitting on the ground, in plain sight, a ferrous target!

Frankly, people who only hunt turf and mild ground are completely clueless as to how severe this issue is. It makes those of us who work in the worst ground laugh when we see depth testing in YouTube videos showing things like a VLF hitting a dime at 14". Yeah, in some other world, or my dreams, because it sure won't happen where I hunt! :laugh:

Anyway, the Axiom as a PI sees even more dirt than a VLF, so the iron mineralization to good target signal is horrible, and there is far less info for a PI to work with in the first place, since phase is not involved. Mostly it’s all time delay and eddy current retention, so when it comes to targets, PI is only really halfway good at separating large or strong conductive targets, from small or weak conductive targets. Not ferrous from non-ferrous.

I don't use YouTube for much besides learning how to fix my washing machine or truck. This video though I have posted quite a few times because it is a great illustration of something you do have to see to believe. Long story short PI discrimination is pretty unreliable in bad ground, where nugget hunters tend to work, but VLF has little to brag about either. It's why, at the end of the day, I always end up going back to my PI detectors. I have tried and tried and tried to be happy with a VLF as a nugget hunting device in bad ground, and it is not happening. Milder ground, sure. But in bad ground, it quickly gets down to digging everything, and if I am doing that most of the time, may as well have a PI.

This video is inches on a button. Keep in mind a good VLF can pull targets like these up at over a foot in the worst ground with no problem. Just a note though. At the very end, when he makes it look like the Deus is doing better than the other detectors, he stops waving the coil over the adjacent nail that was masking the other detectors, and just hovers over the target. :wink: But the lesson is still there. Bad ground really impedes ferrous vs non-ferrous discrimination, and put some ferrous trash in the mix, it's basically game over.


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