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I've been comparing numerous detectors as of late.

I wonder about iron audio.

I've been thinking about this,,based on what I see with some of my detectors,,,and am wondering if there would be some benefits.

Iron volume as far as it being ON,,,does give distinct audio when the coil passes over detected ferrous material,,,but the being able to hear the iron volume tone(s) seems is tied to disc setting(s).  Meaning run too high a disc setting,,,no iron tone whatsoever (with it selected).

Could this be changed,,,where iron audio would be provided no matter the disc setting if a user wanted??

I could see at least some application,,where it might come in handy.

For example hunting in a site with gobs of maybe lower conductive materials,,,just turn up the disc and hunt,,,,but operator might want to know if any areas seemed to be maybe moreso afflicted with iron and nails,,,,to maybe want to hunt this particualr area,,,using different strategy, detector settings,,,or even another coil or detector.

I may be off base here,,,but would like to hear some folks thoughts on this.

BTW,I do realize maybe notch could be used along with lower disc and do maybe the same thing.

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I guess I don't understand the question. Iron audio to me just means the ability to set the volume of the iron response.

First we had accept items or reject items, like with a good old single knob discrimination control. Items accepted go beep, items rejected are ignored and silent.

Then tones became the thing, so instead of outright rejecting ferrous, a low tone became common in identifying ferrous targets.

But in dense trash, like a nail bed, the sheer number of ferrous responses were tiring. Along came the ability to vary the volume of the ferrous response to make it easier to listen to for hours on end.

If you are talking about wanting to reject/silence higher level items, like a pull tab for instance, while still retaining iron tones, then yes, notching would be the answer.

Something Like a White's V3i you can independently pick accept or reject for every VDI number or alternatively pick a custom tone for each VDI, even reversing the tone scheme if you wish. For my ears just picking an exceptionally low tone is about the same as a choosing a lower volume with a higher tone.

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I guess what I am saying(asking),,,can a detector be made that already has capability to turn iron audio off and on,,and vary volume of this audio,,,,,does the iron audio have to be tied to disc setting???

Like give the user an option,,to run any disc they desire,,,and if they choose can have iron audio on or off,,,and be user adjustable for volume.

A good example here,,,let's say we have a detector,,,that is capable of distinguishing bottle caps using iron audio,,,I've heard At Pro can do this.

But bottle caps can come in at various VDIs,,,,so trying to notch them would not be very useful.  And let's assume a user is in a site,,with varying junk targets of lower conductivy.

And the user would like to run disc,,,and vary this depending on a site.  But setting up notch depending on detector does take more time generally than moving disc setting.

Now all this in conjunction with what I said about bottle caps above,,,,,if iron audio wasn't tied to disc setting,,,,a user could quickly move their disc setting around,,,and at the same time,,have a better shot at IDing a bottlecap,,,using provided iron audio.

Some of this comes from the fact how running higher disc,,,doesn't seem to affect depth as much as some of the older detectors.

True,,though running higher disc can pose some separation problems.



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Today I was using my AT PRO, Zero Disc. with Iron audio on, a Musket ball would give a good tone like a nickel but I would still get a iron grunt. After I dug it the grunt would disappear. This is a 1830s Indian village and i have been hunting it for 3 years, 5 musket balls 2 1832 Dragoon cuff buttons and some parts to flintlock guns and a lot of small targets. I usually use my Tejon  But today used my Garrett AT PRO it will find some awful small targets

I hopes this will help answer your question and I have  followed your posts on the other Forum you just left. Thanks for your insight  and info.


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Yes KS Stick,,,very familiar with what you were hearing on your targets iron tone wise.

Deus on lead will do this a lot.  Almost like the ground minerals is trying to drive the signal into the iron range,,,but Deus withstands.

Nokta Relic detector will pound smaller lead and medium lead,,,with a great signal,,,same target Deus will tone in but overall more dodgy sounding.

A beginner with Deus,,might pass on many of these,,,until they get the hang of.

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1 hour ago, Tnsharpshooter said:

Deus on lead will do this a lot.  Almost like the ground minerals is trying to drive the signal into the iron range,,,but Deus withstands.

That is exactly what is going on. That type of behavior is very common when nugget detecting since prospectors frequent some real bad ground. Nuggets will almost always flip to a ferrous signal once a certain depth is reached. The places I coin detect here around Reno a dime will flip to ferrous at 5-6 inches. Fe3O4 meters typically run one bar short of max. Very heavy magnetite content.

I saw in a spot in Alaska that gold nuggets sitting directly on the ground would read iron on an F75 and Gold Bug Pro! That is a freak out moment, believe me, and a real lesson in why any discrimination at all in bad ground is going to leave some good finds behind.

You are certainly welcome here David. I had to create this forum just to get myself away from the behavior on other forums!

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On 2/12/2017 at 8:56 PM, Steve Herschbach said:

I saw in a spot in Alaska that gold nuggets sitting directly on the ground would read iron on an F75 and Gold Bug Pro! That is a freak out moment, believe me, and a real lesson in why any discrimination at all in bad ground is going to leave some good finds behind.


Ok, so please take this only as a challenge for you to elaborate more, not disbelief in the least.  If I was standing next to you with my F75, seeing those conditions...I can assume at that point you are saying AM is the only mode to use, but what about the signal would tell you to dig anything?  Just that you assume the objects are not iron, and you are digging everything?  Or some other clues that the object is nonferrous even though the reading is otherwise?  Or are you saying put the F75 away in those areas?

 My ground is very mild compared to anything out your way, so I am just trying to understand how these things behave.  


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Hi Rod,

All metal detectors using a discrimination circuit have a possibility of mis-identifying weak signals as ferrous in bad ground. Bad ground basically means the ground itself has a high ferrous content. The coil sees everything under the coil, both target and ground. The key is weak target, either small items, or large items at the edge of detection depth. If the target is weak and the ground ferrous content high, the detector blends the signal and the predominating ferrous content can cause the detector to identify the target as ferrous.

So yes, nearly all prospectors will tell you to dig all targets. Many, like myself, use detectors that have no discrimination at all. It is simply common knowledge among prospectors that discrimination results in lost depth and some good targets being called bad. Target masking can also be an issue.

That is not the end of the world or anything, just a base line fact. From there you do what you have to do. Any detectorist runs into situations where digging all targets is not acceptable for many reasons. Park detecting is one reason obviously. For a prospector it may be an old camp littered with ferrous trash.

So you use a good discriminating detector. On most decent targets they will sort the good items from the bad with a high degree of accuracy. Nothing wrong with that. Just don't kid yourself that you are not missing targets.

Specifically when nugget detecting the idea is not to just accept what the detector is telling you. If you get a weak ferrous reading, simply scraping the surface with your boot and removing an inch of material can make a ferrous reading flip to non-ferrous. Dig everything if you can, and if not, be skeptical of weak signals in bad ground. Remove enough soil to get a better signal if possible.

If you look at many detectors you will see that the ferrous and non-ferrous range overlaps - this is exactly why.

You also have to know your detector well. I have observed that European machines focus on simply digging non-ferrous targets, and proper identification is considered to be a bit of a waste of time. Too many possible targets over thousands of years. They excel at pulling non-ferrous out of ferrous but are generally poor at identifying this coin from that coin or that pull tab from a coin.

U.S. detectors cater to the fact people hate to dig junk, and they like to tell a nickel from a pull tab from a dime. They are more conservative, and biased to calling borderline targets as ferrous.

It boils down to knowing your detector. The F75 for instance. I will never forget a guy in the U.K. I met who was freaking out that a buried gold coin was reading ferrous on his F75 - totally blew his confidence in the machine.

The F75 has a two tone ferrous / non-ferrous mode, the 2F mode. Ferrous goes low tone, non-ferrous high tone. Check your F75 manual and you will see it considers VDI 1 - 15 as ferrous. 2F mode gives a low tone on VDI 15 and lower, and higher tone on 16 and higher. Use 2F and you will dig very little ferrous stuff.

The problem is that 2F is set at the high end of the overlap. It has been found that the F75 will actually read borderline non-ferrous targets all the way down to about VDI 6, and so the VDI 6 - 15 area is the overlap range. You have to avoid 2F and use single tone mode and manually set your disc to about 5 or 6. Or the way I hunt when nugget detecting is run in boost all metal and just investigate any target that pops 6 or higher on the screen on any pass of the coil. In other words, even a single pass of the coil can't be trusted, since the numbers jump around. I work the target and if it even jumps up once above my desired cutoff point it is worth checking out. Look for a reason to dig, instead of a reason to not dig. Running in 2F will cause many borderline targets, like that gold coin in the U.K., to be missed.

If mineralization is very bad, as in the western U.S. or Australia, depth and target id accuracy of any VLF is severely impacted, and that is why so many prospectors use PI detectors or the GPZ 7000 and dig all targets. For coin hunters in the west, max depths of 5-6 inches are not unusual on coins, and I always chuckle when I see guys back east talking 10 inch dimes. Not going to happen here with a VLF. Air tests get little attention on this forum because for all intents and purposes they are worthless for predicting in ground performance in a gold prospecting scenario. All that matters is how a detector handles the ground and air tests ignore that all important factor. In fact, machines that air test the best often make poor prospecting detectors from a max depth perspective, though they are often hot on shallow targets.

Big coils on a VLF make it worse (they see more ground relative to the target), so I lean to smaller coils. I also use a PI for coin detecting but that is a whole different subject. Bottom line is there are lots of old coins out there still waiting to be found due to over reliance on discrimination and not understanding exactly how it works. The real key is knowing exactly what the ferrous / non-ferrous overlap range is on your detector, and be wise to the fact that target id of weak targets is very unreliable. The worse the ground, the more unreliable the id.

The video below features a T2 as part of the test, which is basically a F75. Be sure and watch the whole thing - there is a pause at one point that makes you think it is over. The guy is running in 2F and simply going to single tone mode and lowering the disc would probably change the entire nature of this video. It still is a good illustration however of the effects of mineralization.

You can sum this whole thing up by something you hear a lot of coin hunters say - "Dig iffy targets". Too many people look for reasons not to dig instead of reasons to dig. Sure, you will dig more trash. But unless you have a rare virgin area these days you have to pull out the stops to make good finds.

More on the subject - Tune Out Nails - You Will Miss Gold!

Metal Detector Discrimination Really Sucks

Metal Detectors With Reliable Target ID Numbers

Discriminate, Discriminate, Discriminate!

Adjustable Tone Break

Garrett AT Pro Overlap Range - Note that although 40 is considered the normal start of the non-ferrous range, non-ferrous items can read down to 30 or lower. Detector manufacturers imply this is only tiny foil or gold, but it can also be any larger items at borderline depths. It is not so much what the size or composition of the target is, but the signal strength that the detector has to work with. Weak targets plus highly mineralized ground means any item can be identified as ferrous at borderline depths.

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On 2/12/2017 at 2:31 PM, Tnsharpshooter said:

I guess what I am saying(asking),,,can a detector be made that already has capability to turn iron audio off and on,,and vary volume of this audio,,,,,does the iron audio have to be tied to disc setting???

The MX Sport does this. The rejected range of VDI's can be audible by enabling REJECT VOLUME at a user-specified setting. So you get the lower tone at a lower volume.

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Steve, Thanks.  I enjoyed the Western lesson.

 I have been running in AM the last few hunts exclusively in two areas I have been getting old buttons, mostly from the point of view that the iron shank is as likely to get picked up as the brass, tombac, or pewter front, especially the teeny cuff buttons.

I started a notebook of airtest results since getting the F75, but mostly to understand the differences between how a huge range of items like buckels and silver jewelry, coins and buttons show an ID when close, then at max range, then at max range with various junk items very close, reasonably close, and even a foot between the target and junk.  ID skews well down into Iron range for some, but I would have to recheck the book to say what is the lowest ID I have of a legitimate target.  No raw gold here, but I do have US gold coins for testing from 1$ to 10$.  I know none of this can take dirt into account, but it does keep me from discounting targets too easily.



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