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Steve Herschbach

Metal Detector Discrimination Really Sucks

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Very good and important write up Steve. Looking forward to your results with the Deus.

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Hi Steve.  I'm slowly making my way through the links you put up to my other question.  They have all been interesting and I am learning!! 

So, your thoughts above were disheartening for you. Has that ALL changed with the Equinox or is it just a decent step in the right direction?  

Thanks :wink:

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All VLF detectors suffer the same problem when trying to employ discrimination. In simple terms it is a target signal to ground signal ratio thing. You want to find a tiny item in the middle of a large volume of ground the detector is seeing. The ground reads ferrous and the desired target non-ferrous. In bad ground, it is easy for the ground signal to overwhelm the target signal causing it to be detected but to read ferrous.

All Equinox does is improve on that situation, but it only does so by pushing the depth at which these changes occur back a little further. But if the target is deep enough, or the ground bad enough, Equinox can still make a wrong call. This is the number one reason I prefer to hunt with tones identifying ferrous items instead of blocking out ferrous items entirely.

An old tip from my White's MXT page (edited)...

"There are four things to know. 1. Target ID numbers increase as the nugget size increases. So a 1/4 oz nugget may read around 25 whereas a 1 oz nugget may read around 40 and a 2 oz nugget may read around 50 on the meter. 2. The larger a nugget, the deeper you can detect it. 3. Certain steel items can give positive target ID numbers and 4. Target id numbers are pulled down the deeper the nugget is buried. A 1/4 oz nugget near the surface will read 25, but at depth might read 10, and at max depth may finally read at 0 or lower and actually be identified as iron.

This last point is very important, for if you run a Fisher Gold Bug 2, or Tesoro Lobo, or Troy X5 in disc mode to tune out iron, as is common, deep nuggets may read as iron. If they are, the machines will reject them; you will get no signal, and walk past the nugget. You will never know it is there. Or at best you have to search in all metal mode, then constantly switch to the discriminate mode to check the target. With the MXT employing tones to separate ferrous from non-ferrous, there is no switching and you hunt completely by ear.

With the MXT I like to run the detector in relic mode, with the disc set precisely at 2. Non-ferrous items will give a high tone, and ferrous junk a low tone. If you get a faint low tone, the first thing you do is kick and inch or two off the surface until you get a honk or a chirp. Now dig a little deeper. If the VDI number rises, keep digging. Targets that read iron initially and rise will often turn into non-ferrous readings, hopefully gold. If the VDI number stays the same or goes even lower, you have an iron target."

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I started using 0 discrimination with the XTERRA 705 while living in Ohio I always felt when in 0 discrimination and prospecting mode I gained quite a bit of depth with the 705 I also would run with 4 tones or 2 tone when I would run in coin mode I always had a feeling that when you ran in the 99 tones the 705 also lost depth but I don't know if that is true or just my own thoughts and the 99 tones always drove me nuts so I would always end up switching back to 2 or 4 tones,one thing that convinced me to run with 0 discrim was while in my back yard in Ohio I had went over an area next to a big oak tree with discrim and 99 tones set and was getting no signals what so ever so I stopped and set discrim to zero and went to 4 tones re scanned the same area again around the tree and ended up getting a signal which ended up being a 1941 merc down about 10 inches so since then I always run with zero discrim and 2 or 4 tones set    

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Thanks Steve, I needed to read this, it clears a lot of my questions up being new to it all and I most definitely won't be relying on discrimination like I once was, it seems silly now but if it said ferrous at all, I just kept walking thinking well my detector must be right or they wouldn't put that "feature" on there plus I did some very basic air tests, my gold ring.... good, a nail... bad, so that confirmed my belief the discrimination was working well.

Without all the information this forum has provided I could of been a detecting casualty, giving up on it all by now as detectors aren't like TV's, you can't press the change channel button knowing your channel will change and then it changes, everything has so many variables, difficult for a beginner without the wealth of information provided here.

So thanks everyone for contributing, you may not know it but all the little bits of information you talk about really help someone new.

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Thanks phrunt, I am glad the information is helping people.

On 1/3/2018 at 3:45 AM, Northeast said:

So, your thoughts above were disheartening for you. Has that ALL changed with the Equinox or is it just a decent step in the right direction?  

Thanks :wink:

Sorry, I missed this bit earlier. No, Equinox changes nothing. The issues appear to be inherent in the basic technology itself. There are clearly good targets, clearly bad targets... and then the mess in the middle where everything overlaps. No matter how you slice it, discrimination is unreliable at best, and robs machines of significant depth.

Yet I use discrimination quite often! :smile: The trick is understanding the trades that are made when doing so.

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