Saturday, September 19, 2015

9/19/15 Report - Surprising Results of Detector Test With Three Small Cobs. Tropical Storm Ida And Other Weather.

Written by the TreasureGuide for the exclusive use of

Three Small Under Weight Cobs.
In the past I've talked a good bit about specific target training and tuning.  By that I mean learning the optimal detector settings for finding particular targets, and also tuning in the field for those specific targets.

If you are interested in finding small silver items like those shown above, you need to experiment with different detector settings to find the settings that are best.

These particular cobs are way under weight.  They were found on a beach near a 1715 wreck site. They lost much of the original material.  The one on the left is only about .015 ounces, and the other two around .02 ounces.  The second is actually a touch lighter than the third.  My scale isn't highly accurate for small weights like that.

When selecting test targets, I will often select those that are on the smaller side, assuming that if I can find the smaller ones I will have no trouble with the larger ones.

Size is much like depth in relation to signal strength.  Small items sound much, not exactly, like larger but deeper targets.

One thing I try to keep the same is the material.  If you want to find silver, test with silver.  You generally want test targets that are as similar to the desired targets as possible.  One possible exception, as I said, is size.  Again, I tend towards smaller test targets.

If you are going to hunt for a particular type of item, you want to know if your detector will detect it and what settings are required.  It is best to test your detector before going on a hunt so you have confidence that your detector will detect whatever you are hunting.  What a waste it is to spend hours hunting with a detector set up in a way that would not detect what you want to find if you were right on top of it.

I hadn't tested one my newest detector on small cobs and wanted to find out how it would do with those types of targets, and secondly, what settings would be best.  I had tested these test targets with a couple other detectors, and knew how they would perform, but I wanted to know how this detector would perform with the same test targets.

I took these items out to a space that I have cleaned out and often use as a test area.  I kept changing the settings and modes to see which worked best on these test targets.

My test area is not the easiest even though there is no ground mineralization.  There is a lot of ambient electrical interference to deal with that causes a lot of detector noise.  In this area, there are some inexpensive detectors that actually do better than some of the more expensive and powerful detectors because of the electrical interference.

Which of the above three test targets do you think gave the strongest signal?  You might well guess the first, which is both lightest and presents the smallest surface area.

Charles Garrett in his book Successful Coin Shooting, said that generally detectors are surface area detectors, and that mass makes little difference.  He suggested a way to prove that for yourself.  Take a coin and run your coil over it.  Then take a stack of the same coins and run your detector over it.  You should get about the same signal because the surface area that is presented to the coil is the same.

He threw that word "generally" in there, and that is a good thing, because I have found exceptions.  I haven't done a real precise experiment on that, but I have observed enough to feel confident about that.  There are times when thickness, or mass, seems to make a difference, though not a large one.

To answer the question, the first and third targets (as shown in the photo above) cause much stronger detector signals that the second one.  That is very consistent.  And it proves out with different detectors.

The first item, has a small surface area.  You can see that.  The photo accurately shows that.  It is however thicker than both the second and third items.

The second and third items are nearly the same weight, and one might be a bit thinner than the other, but it is not enough to be obvious from look or feel.

So what is it about the second item that produces a weaker signal?   I can't say for sure, but it does seem to be something other than surface area.  Perhaps it is the material, although the three cobs should not be very different.  They should have similar silver content.  Maybe they are a touch different though.

I've shown in the past that shape makes a big difference.  Detect a coin laying flat, and then turn it on edge and you'll probably notice a big difference in the signal.  On some detectors the difference will be greater than on others.

The second item does not appear to be shaped hugely different from the third item, but it is a little less round.  The first item is much less round than the second, but still produces a better signal even though it also presents a smaller surface area.

I've done experiments that show that angles and irregular surfaces make a difference.  A slanted surface may not produce a signal that is as strong as if the surface was flat and parallel to the surface of the coil.

The top surface of the small item is a little convex.  I don't know if that produces a better signal.

It is pretty complex.  I'd have to do a lot more experimenting before I could say exactly why the second items produces a much weaker signal than the other two.  At this point I just have some ideas.

The main thing I want to say today is that you should experiment with detectors and their various settings and relevant test targets before you go for a hunt.  Get to know what your detector will and will not do, and get to know the best settings.


We now have a named tropical storm, Ida.  Also a tropical depression, Nine.  And another disturbance up by Georgia.

I doubt we get much of anything from any of these, however there is a chance.  Both tropical depression nine and Ida will probably live and die out there in the Atlantic.

The disturbance up by Georgia might turn into something, but North Carolina has a better chance of getting something out of it than we do.

Right now the surf predications are for a slightly increase surf for mid week.  If you look out a week from Monday, they are predicting something like 4 - 7 feet.  That might be nice - if it actually happens.  I guess there is some chance, but I'm not betting on it.

Happy hunting,