Eureka Moment?

John Howland offers up a little food for thought and it’s from a few years ago. Give it a read and see what you think? I found it interesting and it reminded me of ‘reverse discrimination’, another creative user designed aid. Thanks John.

Eureka! Maybe not….

John Howland

How deep your metal detector penetrates is a direct correlation between coil diameter and the amount of electrical power pumped through it. Therefore, maximum depths were achieved with ‘standard’ coils over thirty years ago thanks to the laws of physics; approximately 9” depth for an 8-inch diameter coil and 11” for a 10-inch diameter coil.

Equally, larger after-market coils absorb the finite electrical power output ‘diluting’ it, making it less sensitive to smaller targets. Conversely, small diameter coils such as the 5-inch diameter ‘Sniper’ types, concentrate the electro-magnetic output into a dense beam from which nothing metallic escapes. I have recovered tiny, solid silver spacers from Pandora charm bracelets using these coils, which would otherwise have been missed by a standard coil.

1980 ad for the White’s 6000D

Way back, the Whites 6000D was touted (rightly) as being able to locate an English penny at 10” irrespective of its angle to the searchcoil; end-on; flat; 45-degrees and every angle in between. I also owned a Garrett ADS ‘Groundhog’ with a 8” diameter standard coil and its performance was generally about the same as the 6000D.

Significantly, I found back then as much as I do now, though back then I dug targets based on tone, sharpness, and was rarely wrong. Nowadays, my ATPro International gives me more target information, depth, metallic composition, and sounds off a warning if the target is ferrous. It is never wrong! In a perverse way, these modern-day detectors could be rightly considered ‘beginners’ machines being much easier to operate and learn than ye olde 6000D’s, Groundhogs, et al.

Many, many, moons ago while talking discrimination with my late friend and hunting partner, Ron Scearce, over a Rebel Yell or three, there was something of a ‘Eureka!’ moment; how to find rings and coins while rejecting ring-pulls.

Talking detectors with Ron Scearce

It works like this. Suppose you own a machine with a single discrimination dial, and for our purposes here, is numbered ‘1’ to ‘10’ with ‘10’ being maximum discrimination.

Let’s also assume that ‘1’ to ‘3’ on the dial eliminates foil and iron. Set the dial to ‘3’, then pass a ring-pull over the coil and turn up the Discrim until you reach a point where it JUST rejects the ring-pull. Mark this position which will be about ‘5’. Turn the dial back to ‘3’.

Then pass a thin-section ring over the coil and again turn up the Discrim until that too JUST starts to be rejected, typically at ‘4’. Mark this position. Turn the dial back to ‘3’.

Then finally, pass a coin, say a £1-coin across the coil and turn up the Discrim until this too is JUST rejected, typically about ‘8’. Mark this position. Turn the dial back to ‘3’.

Begin hunting with the Discrim set at ‘3’. Then you get a signal. Turn the Discrim dial to position ‘4’. If the signal disappears then the target is a thin-section ring. If not, and the signal persists, turn up to position ‘5’. If it disappears you have a ring-pull. If it does’nt turn up to position ‘8’. If the signal vanishes you have a pound coin. If the signal persists beyond ‘8’ also indicates a good target.

I explained this technique to a manufacturer who shall remain nameless. I asked them if what I could do manually, they could replicate electronically; their engineers simply couldn’t grasp the concept. They saw it as a type of notch Discrim, which of course it isn’t. Why? Maybe the engineers were too close to the design action, and couldn’t think like treasure hunters.

Any takers? Gimme a call and I’ll explain further….


Unintentional Oversight?

As I recall, this little nugget of archaeological embezzlement somehow failed to make it onto the pages of the Warsaw Clown’s semi-educated scrawl (that which poses as an educated blog but is hugely popular with archaeology’s DE social classes and the dimwit end of the heritage circus).

Cambridge Don Made Up Bogus Archaeological Projects to Steal £220,000



“Whoever is careless with the truth in small matters cannot be entrusted with important matters”...Albert Einstein



Filed under Metal Detecting

6 responses to “Eureka Moment?

  1. DougF

    hey, John, what is the purpose of the yellow wrapping on those coils? I haven’t seen that before.

  2. Bob Sickler

    My guess would be better underwater recognition of the searchcoil in murky conditions.

  3. Doug & Bob:
    As Garrett don’t make coil covers for their PI coils, I applied layers of tape for a modicum of protection. And yes, ideal when searching murky water.

    Oh, Ricardo, I don’t do ‘tipsy’…..rat-arsed, yes!

  4. John is correct, this type of a maneuver in using the discriminate control to ID the target is a manual analog way of doing things humans are so good at that computers have a terrible time with even nowadays.. Computers and electronic circuits are number crunchers, using hard and fast data and values during calculations and calibrations and are incapable of independent reasoning or thought, despite what a lot of engineers and scientists trying to personify and make the public believe. Brilliant piece there John…a look into the old ways and techniques…I love it! And WHAT??? A dishonest, funds-seeking archaeologist? There are always a few bad apples in any group, and this one was worm-eaten to his core!

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