Saturday, August 30, 2014

8/30/14 Report - Silver Cobs Metal Detector Test Continued With Results. Quartz Crystal Pendant.

Written by the TreasureGuide for the exclusive use of

Silver Quartz Crystal Pendant

Here is a beach find.  Oxidized silver and quartz with a tigers eye.

Notice the phantom in the quartz. 

I don't know how old it might be.

Now I'm going to pick up today where I left off yesterday.  I'm going to show you something new that might surprise you.  It also shows how specific you have to be about detector tests, particularly the types of targets you are interested in and the environments they are used in.  A number of factors have to be considered when selecting a detector for a particular job.

A lot of people seem to accept what they hear or accept the results of simple tests on clad coins that actually leave out a lot of important factors.  They think if detector A is a good detector or has a good reputation it is the detector to use.  The fact is, as I'll show today, it is much more complicated.  And as I showed yesterday, there are situations when an inexpensive detector will actually do a better job than a highly regarded more expensive detector.  The basic questions are, what do you want to find and where are you going to hunt.  I say those are basic questions, but to answer them well involves more factors than you might think.

If you haven't read yesterday's post yet, I recommend that you do that before continuing.

Here are the same small beach cobs that I used for the tests that I reported on yesterday.  The one on the left weighs about 0.4 grams, the next 0.5 grams, the next 0.6 grams, and the next 2.0 grams.  I will refer to these cobs going left to right as 1 - 4.

Four Treasure Coast 1715 Fleet Beach Cobs.  Three Half-Reales and One 1-Reale.

Yesterday I tested these in a high EMI environment using the Ace 250.  Today I'll report on my results using an Excalibur.

I used both discrimination mode and pinpoint mode for all my Excalibur tests.

Which cob do you think consistently produced the best (loudest and clearest) signal?  It was cob 3.  You might expect it to be cob 4.  I did.   But cob three consistently produced a signal that was a loud and distinct, and a slight bit better than cob 4.  That was true on many attempts varying the sweep speed, and sweeping at different directions.

Tests were done with the coil at the approximate same height over the cobs, and also at different heights to give a rough measure of depth.  By varying the height of the coil I essentially did a type of air test but with a sugar sand background and relatively high EMI environment.

In case you wondered, signal loudness and distinctness correlated with air-test depth.  In other words, cobs that produced a fainter signal when the coil was at the same height for all cobs, were detected only at smaller distances from the coil.  Those cobs that produced louder more distinct signals were detected at greater heights when the coil was raised.  So relative signal strength, as you might have suspected, is a decent (not perfect) measure of how deep a target would be detected.  That makes sense, but the test results did strongly support that conclusion.

Now the question is why did cob three, even though smaller by weight and presenting less surface area produce a louder signal.   I do not yet know.   Yesterday I suggested that one possibility could be different alloys or composition of the silver.  We know that the composition of cobs was regulated,  but we also know that there were some differences.

Surprisingly, cob 1 consistently produced a more distinct signal than cob 2 despite its smaller surface area.  It is thicker.  All other cobs produced better signals than cob 2 without exception.

Another reason could possibly be the ground under the cobs, but I changed where I did the tests and the results were the same.

The results did not change when I switched from discrimination to pin point mode. 

I often hunt in pin point or all metals mode.

Ordered by signal strength, it was cob 3, 4, 1 and last, 2.

Being in a high EMI environment, I varied my sensitivity.  I actually got slightly better signals with reduced sensitivity. 

Some people are afraid to reduce sensitivity.  I seldom reduce sensitivity and am accustomed to identifying signals in noise, but there are times to do it.

I always recommend testing your detector and settings with the type of target that you want to find and in the environment that you will be hunting before beginning to hunt.  I think these tests support that recommendation.  Things are not always simple, and if you want to optimize your detector and settings, do it in the environment and with the most desired targets.

When selecting a test target, Id select a smaller test target.  Generally if you are set for the smalls, you will find the larger targets too, whereas the other way around is not necessarily true.

A lot of people are running around with detector settings that would not detect the smaller cobs shown above if the cobs were laying on the surface with the detector coil right over them.  I know I have met people on the beach who were discriminating out anything that small.

As I showed yesterday using the Ace 250, these test cobs generally were identified as nickels.  That's not bad.

The best way to learn how to better understand and use your detector is to experiment.  What you read may or may not be true, and your detector and your environment might not be the same as those you read about. 

On the Treasure Coast we're back to a one-foot surf again.  Nothing much in the Atlantic either.  Just one disturbance down by Central America.

Get to know your detector better.

Happy hunting,