Beer Caps

[Steve Herschbach]

Separating ferrous from non-ferrous is not the same thing as differtiating non-ferrous targets. A detector cannot tell the difference between gold, aluminum, and lead and these targets will always overlap.

[GB_Amateur]

16 minutes ago, Steve Herschbach said:

A detector cannot tell the difference between gold, aluminum, and lead and these targets will always overlap.

I've been wondering about doing the following experiment, which I think is in line with or related to the above quote:

1) Choose the common US coins, let's just go with clad coins -- dime, quarter, half dollar, Susan B. Anthony dollar, Eisenhower dollar.

2) From a roll of aluminum foil, craft coin-shaped (that is, round disks with reasonable thickness) 'globs' which produce the same response to the detector as each of the coins in the list.

I arrived at this idea after digging many different aluminum foil globs that ID'ed on or very close to coins.  If this works then I don't see aluminum as anything special.  Couldn't you cut steel disks (or maybe just find the right size steel washers) to mimic the coins, too?  Also, would the set of fakes work on every detector+coil combo or do you need to craft a unique set for each different detector?  In particular, does the frequency of the detector matter?  If that is the case then does mult-frequency help distinguish the fakes from the authentics?  (Heck, maybe someone in the past 40 years has already done this experiment.  Saves me the trouble. )

[Steve Herschbach]

Separating coins from aluminum is not a serious issue in most cases. It is the overlap between gold that you want, and lead and aluminum that you don’t want, that people would love to fix. Won’t happen with current technology. If you go for gold, you had better be digging lead and aluminum also. If not, you are passing on gold.

[GB_Amateur]

4 minutes ago, Steve Herschbach said:

Separating coins from aluminum is not a serious issue in most cases. (cut out a couple sentences)  If you go for gold, you had better be digging lead and aluminum also. If not, you are passing on gold.

I understand this good advice.  My point was more on how detectors work.  Let me emphasize with a real-world example (from the coin hunting zone):

Some people get so annoyed with pulltabs that they give up digging US nickels just so they don't have to dig pulltabs.  (And it's even worse, as you and every jewelry hunter knows, to give up the nickel&pulltab ranges when hunting gold jewelry.)  Of course nickels aren't gold nuggets so what the pulltab hating coin hunters are sacrificing isn't that great.  And not all pulltabs mimic nickels, but in my experience some do it perfectly.  It seems to me that I'm referring to the same principle:  with today's technology, if you want all the goodies you're going to have to put up with some baddies.

While writing this I do see something that makes my example an imperfect match:  coins tend to cover a tight region of ID space with a discriminating detector.  Native gold can be all over the map.  Trash can be all over the map, too.  (And then there's the fact that you don't hunt native gold with discrimination, although everyone would like to!)  So you can eliminate much of the trash while coin hunting, assuming you know your ID's, and you can't do that when searching for native gold.  Even then, you don't want to be too picky in a 19th century site because of all the (today) uncommon denominations and compositions, like half-dimes, nickel 3-cent, silver 3-cent, and especially the myriad of gold coinages.  Another example:  Indian Head pennies can ID close to Zincolns.  Where are the cupro-nickel Indian Heads and Flying Eagles?  Where are the silver-alloy nickels from World War II?  (I don't know, but I'm digging it all.)

I dig chunks of iron that hit right where silver dimes and quarters ID.  I suspect there are tricks (spatial extent of target, for example) that can be used to distinguish between the two most of the time.  But is it true or not that the right size, shape, condition (that is, not rusted so badly that it's basically all iron oxide) piece of iron/steel will perfectly mimic a coin?  I'm pretty sure that's true with my single frequency detectors (but as always I could be wrong).  Do multiple frequency detectors split the ambiguity?

 

[Steve Herschbach]

Multiple frequency comparison gives the machine more information that helps get better target id numbers. What it can’t do is eliminate situations where two different items really do read the same. Target id mostly boils down to a combination of conductivity and mass. Only items that are the same every time, like a dime, can be assigned a place on the target id scale. Aluminum trash, lead fragments, and gold nuggets/jewelry come in every size and shape. For every gold signal, I can find an aluminum item and lead item that will overlap and read the same. Since these items tend to inhabit the lower 3/4 of the target id scale and U.S. coins the upper 1/4 there is little overlap with coins except nickels.

Ferrous items are different because they have both conductive and magnetic properties. Many ferrous items are tossing off a complex mix of ferrous and non-ferrous signals. Many detectorists discriminate out the ferrous portion of the signal, leaving only the high non-ferrous spikes. The solution very often is to hunt with full tones and no targets rejected. This reveals the true audio profile of the target as being a mix of ferrous and non-ferrous tones. Some meters like the White’s SignaGraph and SpectraGraph plus the Minelab 2D display (especially as enhanced in the CTX with target tract) can reveal these same multiple target id “smearing” effects from ferrous targets.

I will try and explain this better in a longer article when I have time. Illustrations are needed to make it clearer.

[GB_Amateur]

3 minutes ago, Steve Herschbach said:

Ferrous items are different because they have both conductive and magnetic properties. Many ferrous items are tossing off a complex mix of ferrous and non-ferrous signals. Many detectorists discriminate out the ferrous portion of the signal, leaving only the high non-ferrous spikes. The solution very often is to hunt with full tones and no targets rejected. This reveals the true audio profile of the target as being a mix of ferrous and non-ferrous tones.

Ok, now I see my problem.  I almost always run wide open (no discrimination threshold) but apparently my brain is doing the discrimination of the iron tones.  I need to pay attention to that.  I've tried full tones on both the X-Terra and the F75, but couldn't handle it.  Maybe I just haven't been patient enough.  Thanks for the explanation and I look forward to your 'longer article' when you get the time to post that.  In the meantime I have some more things to work on.

[canslawhero]

great information Steve! also looking forward to the 'dissertations'. Hopefully you'll have them pretty much ready to go on EQ release, lol.

Have you considered some trips to other locales, say California, for EQ testing in some different/better dirt?

Also, are the silver/copper coins you're finding 50's/60's era?

[Jackpine]

On 11/25/2017 at 12:19 PM, Steve Herschbach said:

The big thing the CTX has that the Equinox lacks is the dual target id system combined with a 2D display that can “paint” information on multiple target id numbers onscreen in real time. Similar to the White’s SignaGraph and SpectraGraph displays, this can produce target id “smears” that help identify ferrous targets.

I have several of my long dissertations in mind as regards how the more basic linear target id system on the Equinox compares to this more visual type system. Soon. For now I can say that I have been making copper/silver signals (copper penny, dimes, quarters, etc) a particular focus. Two things ARE NOT happening.

First, I am not digging bottle caps when going after this target id range though the rare aluminum screw cap appears.

I have done less work in the nickel range because I am time limited and would rather focus on silver than nickel responses. There are some bottle caps that appear close to the nickel response.

The other thing that is not happening is aluminum is not “upscaling” to a high coin signal. This has actually been my number one problem with single frequency detectors, especially the “Euro” models. They like turning rolled up beaver tails and other smallish aluminum items into coin signals. This is a known issue with single frequency detectors in magnetite laden soils.

That’s not happening with Equinox.

Basically when I target copper/silver I only dig copper/silver unless I get very aggressive going after “iffy” targets. Just a few oddball aluminum screw caps, oddball jewelry items, etc. hit the in the same target zone.

One thing I appreciate about the 705 is its ability to tell most nickels from beaver tails and pieces by the audio and TID stability.  At 18.75 kHz and equipped with elliptical coils in the 6x10" size range it's fast enough to give a varied response on aluminum shapes while nickels are more solid. 

Here's hoping the fast response of the Equinox will also let one profile Beaver tails in the same manner.

Which brings up the question.  Steve are you lobbying ML for for a 10" elliptical? I hope so.

Tom

 

[DDancer]

I did not feel there would be any marked improvement in non-ferrous information between lead and gold I was curious as to whether the multiQ system would provide improved target data for areas that one caliber of bullet is more common than other sizes of targets.  Yes one will be walking away from gold I'm sure but as a patch finding feature~ *shrugs*  just a thought.

[Cabin Fever]

Unlike most FBS users I started with the CTX and then later moved to the E-Track.  I thought I would miss the target trace moving to the E-Trac I but can’t think of a single time I’ve missed it.  If the target trace would give good indication of a target it also showed up in the audio. The problem was that the target trace also got fooled a lot with iron falsing.  If the Equinox has good audio I’m not worried about not having a target screen.  Because of its superior audio and better coil selection I feel I have done better with the E-Trac then I did with the CTX.  I do miss the nice clear depth numbers of the CTX though. 

Bryan