Prepping: Metal Detecting 101

In Saturday’s column I hinted that I would wade a little deeper into the idea of “hobbies that can make money” for you…and by the title, you ought to know where this one is going.

For the gold!

Bit of personal background:  When I lived in the PNW – and even when I was on my sailboat – I often carries a small 10-12″ plastic pan to do a “little sniping” for gold.

Problem up there is that most of the good places to pan are either a) already someone’s claim, b) owned by people who want nothing to do with miners, and even if you get through all that there is still c) environmental regulations.

A few times up into Canada I tried some “sniping” on the mainland side, but honestly, the best I ever saw were a few flecks of ‘color.’

Surely, there has to be a better way?

Then about five years ago when we were out looking for this & that, I happened to spy a used metal detector.  Put it into the storage shed – where I have a nearly unlimited supply of incomplete projects lined up – and didn’t think any more about it until a month or so back.

Then the “gold bug” bit – and bit hard.

I figure I could use a new hobby about now:  After living on a sailboat for more than 10-years, rebuilding a homestead in the wilds of East Texas, flying our own plane on transcons…oh, and marrying the most wonderful mate in the world…perfect ham radio collection, antenna farm, ideal (for my needs, anyway) shop…..anyway, what more can a fellow do?

To find the 40-pounds of gold stolen by outlaws back in 1852…yeah, that’d be the peach, huh?

In keeping with “economic reality” – which hobbies should conform to – my choices can down to a) building a “rat rod” or b) hauling out the metal detector.  It was a harder choice than you might think:  eBay is full of pricey rat-rods and I’m pretty sure I could build a tricked-out ride that would fetch a decent price and profit.

Except for one thing:  Suppose the market continues its nose-dive.  Do I want to be stuck with a 2-ton whale that eats gas and insurance?  Nope.

I didn’t know anything about detectors when  I picked up this one.  It’s an old Treasure Tracker, model DX-5000.  Set me back about $30-bucks.

After looking into detectors a bit, I figured there were three main types.

First are units like this one – which is a VLF (very low frequency) oscillator type.

The second class is more spendy – and use a process called “pulse induction” to detect metal and minerals.

The last class – and possibly the best – is the high-end multi-frequency detectors.

Theory or Operation

I’ll keep this simple.  They eat batteries and (sometimes) find useful bits of metal.  I’ve gotten exactly one penny with it so far…

Once I get the battery cover replacement cobbled-up…

The VFL models use an oscillator which uses (as part of its circuitry) an inductance  – a coil – that is swept over the ground.  The ground has a certain electrical property so when you “ground balance” the unit, and adjust the discriminator just right, any change in the field under the loop changes the electrical properties of the  circuit and the unit makes noice.  The general frequencies of most retail machines nowadays is in the 15-20 kilohertz range, but my old one looks like it’s down in the 6.5 kHz range.

VLF machines are inexpensive to make – only a few dollars worth of electronics… but the physical parts still cost money.

Pulse-Induction (Pi) machines are more graceful.  They generate pulses which drop into the ground and offer a change in the return which is also picked up by the search loop.    Think of this as a “baby EMP” and listening for a return…not quite, but a useful visualization of pulse induction systems.  These are your second level up in the pricing food chain.

Multi-Frequency machines are the top of the food chain units – and from here about all the further you could go would be a ground-penetrating radar – which I’m also noodling!

The MF machines are essentally two VLF machines, operating on different frequencies.  Maybe you have one operating down around 6 kHz and a second loop (hence, four-wire loops) may be using 18 kHz.  Using a comparator chip, and some not terribly complicated logic, the builders of such machines figure:

If the lower frequency circuit goes up in frequency, but the higher frequency unit only goes up by this proportion, not something else, then it’s likely (fill in the material; gold, copper, or another damn pull-tab!).

Now you’re talking real money.

ROI Considerations

So far, my “investment” in this hobby is the $30-bucks at a sale long ago.  Toss in some Gaffer tape, and a case of Amazon Best 9-volt batteries, and that could be it.

Except (you know me) is is nver enough!

So I picked up a unit from England called a Surf PI 1.2 and in a further epistle, I run you through radical design and re-forming the terrible form factor of most units.

This should get me into the area of super performance as there are a couple of sites on the new which do a fine job of walking people through how to build a Surf PI, but they aren’t as good when it comes to making something “Old Man Friendly.”  (Biting my tongue not to get deeper into the design part, but seriously, another morning for that…)

What’s the return on investment?  On $35 bucks who cares?  If you get a $5,000 machine, then you damn-sure better be retied AND be living in an area where there are lots of places people drop thing!  (Under bleachers after Little League games, I hear, works out sometimes….

The Historical Information Quest

My son has also taken an interest in treasure hunting.  Like me, he’s had a lot of serious adventures.  How can one base jump and not be an adrenaline junkie?

What has him fascinated is – because he does things like hike the Pacific Crest Trail (PCT) in modest slices, as time permits – ghost towns.

“That’s what I’m talking about.  I fet out in some of the most wild country but you’ll find places that humans have been before.  That’s why i’m interested…plus if I could fine a place where there was some loot stashed from a bank robbery in distant history, well, that’d be fine too…”

Elaine and I have been slowly “circling” a couple of areas that our research into “America’s Lost Treasure” books have gotten us interested in.  One is a supposed stash of gold to the southeast of us an hour’s drive, or so.  The other is a hundred miles west/northwest of us.

The point is there are two ways to look at this hobby:

Approach 1:  Get a modest detector and then spend endless hours our in public parks, ball fields, playgrounds, beaches…anywhere there are people because people are always dropping things.

Your odds of getting “rich” this way are thin…but there are enough coins to be found that in an urban area, you might be able to keep up with battery consumption.  Then, it’s only a matter of time (though the Law of Large Numbers is at work) before you luck into something of real value.  it doesn’t take too many $400 rings to pay for the hobby…

Approach 2:  Use half your time in the hobby to get out and do some real detecting.  But, be more selective and careful about where you go.

Take the other 50-percent of your available time to study the hell out of local history.  Old battlefield and ghost towns are first-rate prospects and the odds are fair…if you dig deeply-enough into history books…that there will be a site, or several, that have never had a thorough detection plan applied.

Here, we can see how the results from the hobby “sort out.”  You may have the “fair weather amateur” OR you can go off the rails in the other direction, buried in topo maps, Google Earth shots zoomed in, and books from the dustty “State History” stacks of the regional library.  Many of these will never be digitized…because Librarians (like my older sister) have a very good sense of what the public wants and libraries all operate on a budget.

Between Google Books, SribD, some state-by-state Kindle books, and yes, even the old Louis L’ Amour books are useful because he actually went out and walked almost every inch covered in his books.

One last point:  If you’re fortunate, as we are, and have some old foundations or piles of rock around property that just “shouldn’t be there” then old foundation remnants like this one out in our South 16 become great afternoon projects to test your skills…

A special note to Santa and Mrs. Klaus:

Three units to think about in a variety of price ranges:

Under $140 try the Bounty Hunter Discovery 3300 Metal Detector.

If you’re in the $230 class maybe a Garrett ACE 250 Metal Detector with Submersible Search Coil Plus Headphones.

Up the food chain (and just down the block from the poor house)? Try the $18,365  Zxh 3D Imaging Detector Underground Metal Imager.  Small enough to fit in the boot of the Rolls….

Time to warm up the soldering iron, I have a Surf PI to complete…

Write when you get rich (or the buzzing sounds increase, lol)

george@ure.net