Wednesday, July 6, 2016

7/6/16 Report - How To Conduct More Meaningful Ground And Air Tests With Your Metal Detector. Summer FUN Convention.

Written by the TreasureGuide for the exclusive use of

Florida United Numismatists, Inc., is hosting the 10th Annual Summer FUN Convention in Orlando Florida, July 7 - 9 2016. The convention will be held at the Orange County Convention Center, 9800 International Drive.


I was looking for something the other day - don't remember what - and ran into a video showing some fellows testing and comparing metal detectors on a small piece of buried gold.  They did what most people do.  They buried their target and tried the different detectors to see which did the best. Only one detector gave a good strong signal on the target.  Although I saw a few problems with their method of testing, I wanted to focus on one problem that is not usually seen as a problem.  Almost everybody makes the same mistake.

As you know, there are several things that will affect a detector's signal.  The nature of the target is one thing.  Its composition, size, shape and how it is laying will all affect the detector's signal.

Of course the ground will affect the detector's signal.

And the environment, including such things as electrical interference, will affect the signal.

So will the detector's settings.

But one thing that is not often taken into account is the behavior of the detectorists.  If you watch either an air test or a ground test, you'll always see the same behavior.  The target, relative to the coil, is moved rapidly, in very short sweeps, and right over the sweet spot of the coil.  That is not how the coil is moved in actual field use.  As bad as that is, there is yet another problem.  The exact position of the target is known, which is not the case when you are hunting.  That is a more serious problem than you might think.

When scanning ground during a hunt, the coil would usually be move more slowly, and the target would usually not be directly under the sweet spot of the coil.

When conducting either an air test or ground test, if you want to get results that are similar to actual field performance, the exact position of the target should not be visible to the operator.  I've conducted psychology experiments and know something about how the sensory systems work.

There is always some level of noise, and a signal can be interpreted as noise, and noise can be interpreted as a good signal.  When the location of the target is known, any noise that occurs when the coil is over the target will be interpreted as noise, and the threshold for detecting a good signal in noise will be much lower when the operator knows when there should be a signal.

I've done this myself when I was testing a new detector in a noisy environment with a lot of static. Noise when the coil is over the target will often be interpreted as a good signal when it is actually noise.

People do not realize how much the tendency is to interpret noise or a marginal signal as a good signal when you know that the coil is centered over the target and a signal is expected..  You know when there should be a signal and therefore interpret almost anything as a good signal when you are expecting a signal.  Noise created by hitting the ground or grass or any random noise will be interpreted as a good signal when you know that the coil is over the target. That tendency is multiplied by a coil that is being moved in short bursts over the spot.

The stereotypical very short and rapid movement that is inevitably seen during air tests and ground tests when the location of the target is known and centered under the coil, is unlike anything that would normally happen in the field, except after a target has been located and is being pinpointed.

To get more significant and realistic air and ground test results, move the coil relative to the target like it would be moved during a hunt.  Remember, most of the time in the field the target will not be under the sweet spot of the coil.

In addition to moving the coil more realistically, during ground tests the operator should not be able to visually identify the location of the target.  He can close his eyes and start a few steps away, proceeding the same way he would in the field.  You might be surprised by how often the target is missed altogether when that is done.


Gold and silver prices have been going up for the last few days.


It looks like we'll be having another week or two of smooth surf on the Treasure Coast.  There is no tropical weather to watch.

Happy hunting,