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Target ID More About Target Size, Than Type Of Metal


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Nice post Steve. US classic coinage provides an excellent example. We have 4 coins (dime, quarter, half, dollar) that are all the exact same alloy: 90% silver, 10% copper. Yet have different responses due to size & thickness. And a nickel that is larger and thicker than a dime yet has a much lower phase response, showing that metal type can also play a strong role. But, yeah, any alloy can end up just about anywhere. I'm reminded of the big aluminum token I once found that had the exact same TID as a silver dollar.

 

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Steve you bring up some interesting points with the size vs conductivity discussion. 

Although I started park hunting, I mainly relic hunt these days.  I run my EQX in F2 not because it's supposed to be hotter on a certain type of metal, but because it's more sensitive to smaller targets.  This opens up a lot of types of targets as well as targets on the fringe/edge/etc.  But if it's more about target size vs conductivity, in theory using the Gold modes on the EQX vs Park or Relic modes for relic sites should work better eh 🤔

The college of hard knocks taught me that the only test that really matters on a detector is that detector in your hands at your sites. There's no such thing as inert soil in California or Nevada where I enjoy detecting.  Inert Florida soil doesn't tell us much out here about how a detector will operate in the field.  It's a bit akin to the nail board test, it's one metric we like to see our detectors pass, but it's only one of an endless variety of variables we're up against.

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This is a fantastic topic. Since I usually use an Equinox in my area, I get lots of questions from fellow detector users about which mode to use.....

This is just from my experience so it could be totally wrong. The frequency used in my detecting area which like KOB and Cal Cobra has soil that is definitely not inert, really matters in terms of what frequency can actually penetrate far enough to hit deeper targets. SMF tech like Multi IQ really helps but single frequency detectors in certain ranges work too. The rule of thumb would say a lower frequency would penetrate farther on say, coin sized US targets. That is just not the case here. Frequencies in the vicinity of 20 kHz or a bit higher seem to be able to get through the magnetic ground fog created by all of the magnetite and volcanics in the soil in my area. Detectors running below 12 kHz get absolutely no depth here. Even some approximately 13 kHz VLFs (MXT/MX7, T2 F75 are great examples) that ordinarily are incredibly deep don't do well at all here.

So it seems to me that the amount and type of iron and volcanic content of the soil mineralization also determines what the best frequency/SMF frequencies may be for a certain area which may be determined by the size of the frequency wavelength. Using Multi IQ tech which seems to make the ground more invisible using the Equinox certainly helps here too.

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Geotech:  I've been away from the forum for a while and just dropped in on this very interesting conversation.  I have a question about conductivity and apologize in advanced if I missed the answer elsewhere.  When you talk about conductivity of metals, do you refer to electrical conductivity or magnetic conductivity as in magnetic susceptibility?  Thanks

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Steven : It's electrical conductivity ... how good would it work if you made an electric cable out of it ?

Copper, silver = great choices

bronze = not that good

lead, tin = going to need pretty thick wire

cupro-nickel, stainless steel = they will be glowing red all the time

Here's a decent reference table for many 'industrial' metals/alloys:

http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/

 

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18 hours ago, Steve Herschbach said:

You have to know enough to read between the lines when it come to marketing, and in this case it is really telling you lower frequency for larger stuff, higher frequency for smaller stuff. Again, does not matter if it is silver, copper, or gold. It's all about size.

What you're saying here applies to Equinox update 3.0.. According to Minelab adding 4 kHz to the single frequencies "enhances the detection of large deep targets, particularly those found in parts of Asia".. I'm not sure why Minelab focuses on Asia, but it does reinforce their message that lower frequencies are for larger stuff.. Like you said: "It's all about size".. 

This does have me thinking about update 4.0.. if we ever get one.. maybe they'll go for a higher frequency next time? say 45 kHz for small shallow targets to bring the Equinox inline with the Gold Monster.. now that would be good.. I'd definitely get that update.. 

Thanks Steve for always explaining this stuff so well.. 

 

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  • Steve Herschbach changed the title to Target ID More About Target Size, Than Type Of Metal

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