Why on Earth Would You Need to Perform an Air Test or Build a Test Garden?
The UPS truck had not even left the driveway before Jim was tearing open the shipping box containing his brand new metal detector. After watching episode upon episode of the many treasure-hunting reality shows as well as spending hours surfing the myriad of Internet sites that cater to today's treasure hunters, Jim had convinced his wife that he needed a new hobby and a new metal detector was ordered. He was like a little kid at Christmas and just knew that the areas around his house contained all sorts of treasure just waiting for him to come by and recover it. He was glad that the detector came with batteries as that meant he could get out and start digging up those old coins and gold jewelry as soon as he pulled on his jacket. Waving to his wife, Jim grabbed his detector, jumped in his truck and drove over to the nearby park to begin what he knew would be an exciting and profitable hobby. Turning it on, he started searching near the picnic tables figuring that would be an area loaded with coins but was confused by all of the beeps-&-chirps that his detector was producing. The display was jumping from one end of the scale to the other as he swept the coil across the ground and Jim was not sure what it was trying to tell him lay beneath the surface of the ground. Thinking the area was cause, he moved to the grass surrounding the basketball courts and had the same experience. After more than an hour, Jim gave up in frustration and headed back to the truck . . . the only coin he had to show for his efforts was one he saw laying on the pavement in the parking lot just before he reached the truck! Totally dejected, Jim wondered how he was going to break the news to his wife that treasure hunting was a bust and he would be looking for some other hobby to fill his time.
I hate to say it but Jim's initial experience is not unique and there have been many people that became interested in the hobby, bought equipment and just as quickly became disillusioned and sold what they had just acquired at a loss based on their initial experiences. Does anyone want to take a guess as to why Jim became so discouraged on his first trip into the field? If you said it was his lack of understanding of what the detector was telling him as he searched the park, you are 100% correct. All too often, people unpack their new equipment and head out in search of instant success only to find that frustration is about all that usually turns up. And before you think that this is limited to complete novices, it happens to those with years of experience under their belt almost as frequently. Treasure hunters that have been hunting for some time with a particular model and opt to switch brands based on new features or wanting to try searching for a different type of treasure can find themselves just as frustrated on their first few times out without the proper preparation.
Over the years I have often quoted Greg, a good friend and seasoned treasure hunter, on this subject. He frequently conducts training sessions for beginners and sums up the need to learn your detector this way. "How can you hope to be successful when you start detecting without knowing how to set your detector or what type of response to expect from the types of targets you are looking for or hoping to avoid? Going out searching for unknown targets with a detector you do not fully understand is a guaranteed recipe for frustration and failure. There are simply too many variables for you to be successful!" This is excellent advice for any brand of detector and for any type of treasure hunting you might be interested in trying your hand at.
Well where is this guide taking us? Well let's start with what Jim did once his new metal detector arrived. He unpacked it and since they tend to go together only one way, he quickly assembled it and headed out the door leaving what might have been the most important item laying in the bottom of the box . . . the instruction manual. I know many of us subscribe to the philosophy of "When all else fails read the manual"; however, when it comes to equipment like metal detectors, that can often be the difference between success and frustration. Even if you have experience with metal detectors, different manufacturers tend to use different terminology to describe features. Some models may have unique controls that if not adjusted properly, will produce erratic operation and as a result, frustration. All of this combines to leave one with the nagging question as to the soundness of the decision to purchase a particular piece of equipment. I can't tell you how many times I have received a new detector and thought I knew everything there was to know about it only to find that the performance failed to meet my expectations . . . and then after looking through the manual and / or talking to someone that knew the unit, found that a slight adjustment made it perform at an entirely different level.
OK, you've done your homework and narrowed down your choices for a new detector - what's next? Place an order and hope for the best? Actually, unless you are basing your selection on input from a fellow treasure hunter in your area that is searching for the same types of targets you will be looking for (coins, relics, jewelry, etc.), you need to realize that every detector on the market will not perform equally under all conditions, in all areas and for all types of targets. Depending on what you are looking for and where you live, you may find that a detector that costs half of what you were planning on spending will actually perform better than your original choice for your application(s). The staff at Kellyco is well versed in the capabilities of everything they sell and combining that knowledge with talking with customers from across the country on a daily basis, know what works and what doesn't in your area. A call to one of these factory trained and certified experts can help you avoid making an expensive mistake by ordering the wrong detector for your specific needs.
So you've made your selection and the big day as arrived . . . your new detector has just been left at the front door. Fight the urge to unpack it and head out to see what you can uncover! Once you have it assembled, set it aside and pull out the instruction manual. Skim through the pages on how to assemble it if that activity went well and focus on the section that covers each of the controls and what function they perform. Often there will be paragraphs that are highlighted, bolded, outlined or annotated with asterisks to let you know that they provide information the manufacturer feels is crucial to your success and these are typically marked that way based on repeat questions received from previous customers. Take the time to read through the information that has been provided as it will have a direct bearing on your overall success once you head out into the field.
With a basic understanding of the controls and how to adjust them, you are ready to move on to the next stage which is to conduct an air test. This is simply a way to get familiar with the response various targets will produce as the search coil sweeps across them. You will find that real world conditions such as target depth, ground conditions and having multiple targets in close proximity to one another can and often will impact the response received; however, an air test will help you see the response produced by targets you are hoping to find (or avoid) as well as what effect changes to the individual controls will have on these responses.
Start by collecting an assortment of the types of targets you expect to come across in your searches and remember, the items will vary depending on what type of hunting you plan to focus on. Coin hunters will have a different set of test targets than a Civil War relic hunter or beach hunter will so be specific for what you plan on searching for. Don't forget to include examples of the trash you can expect to come across so you can start to learn what not to dig and what settings will help you do that.
Lay the detector on a table with the coil away from any metal including heating ducts, braces in the table, nearby appliances or even items in your pockets or a belt. Remember that metal is detected both beneath and above the coil. Turn your detector on and start passing various targets across the top of the coil at a normal sweep speed with the discrimination control set at "0". Pass each target across the coil keeping them at least 4 inches away from the coil to ensure you are not overloading the circuitry and are receiving a consistent signal. The point of the air test is to listen the audio response and see how even subtle changes in settings affect the response which will prove to be invaluable when you head out in search of actual targets. Experiment with various adjustments and repeat the air tests to see how these changes alter the responses received. Change the Discrimination and Sensitivity controls among others that your specific model may have on it and make note of where the optimal signals are produced.
Once you've done some air testing to see how slight changes can impact the response to specific targets, it's time to move on to the test garden phase. As we discussed earlier, changes in ground mineralization, moisture contact, depth and proximity to other targets (good or bad) can alter the response from specific targets and the only way to find out what that change will be is to check the response on known targets IN THE GROUND.
The basis for setting up a test garden is to provide you with an area where you can see how your detector responds to various targets buried at various depths in the type of ground that you will be searching in. You can also revisit the test garden throughout the year to see how changes in moisture content can affect the response each target produces. A good example of how moisture content can dictate what sites to focus on is tied to silver coins. Without going into a drawn-out technical discussion of detector circuitry, silver coins will produce a stronger signal when the ground is damp than when it is bone dry. Copper coins on the other hand are less affected by the moisture content making them easy to detect under a wide range of conditions. So if you have seen this phenomena in your test garden (you are getting less depth on silver coins when the ground is dry), start keeping track of sites that you have searched where Wheat cents and Indian Head pennies have turned up so that you can rehunt them after periods of rain and pick up some of the deep silver that might have been missed previously due to the low moisture content.
You don't need a large area to setup a test garden - even a 4 foot square plot can provide you with a wealth of information that will improve your success rate in the field. Start out by scanning the area with the detector set at "0" discrimination to ensure there is no metal present which will produce more frustration and confusion than anything else. Now assemble the items you want to use for testing and again, what you use will depend on the type of treasure hunting you plan on doing. Remove a plug of dirt and carefully place the test item(s) into the hole. If you want to see how two targets close together react, put them in the same hole. Put the targets at different depths to see how deeper targets tend to react differently than those just under the surface. Shallow targets are easy to detect but the older, more valuable targets tend to produce mere whispers and are easily missed. This is the main reason there are still so many valuables waiting to be found despite countless people having searched sites for decades. Once you have placed each target in the hole and refilled it, mark the exact location with something such as a golf tee with a number written on the top with a permanent marker. Make sure you press them down so that they are not pulled out the first time a lawnmower comes through the area . . . and let me say that this is advice based on personal experience! After each tee is placed, make a list showing the number, what the target is and its depth so you know what you are checking whenever you use the test garden.
A comment I've heard from detectorists that live in apartments is that they are not able to make a test garden and I always remind them that very little "real estate" is required. If you are careful in removing the plug, there will typically be no sign of targets having been buried. All that will be visible - and that is only if someone is actually looking - will be the tops of 10 or so golf tees with numbers written on them.
If you stay in the area and can keep your test garden undisturbed, you will see that the longer the targets are buried, the stronger the response will be that they produce. This will be especially noticeable on the deeper targets which many have only produced a faint signal when first buried. Over time the signal will improve as a result of what is known as the "Halo Effect" which makes the target seem bigger to the detector as the metal "leaches" into the surrounding soil. Some targets have a more pronounced halo than others due to their composition with items made of gold or silver leaching very little which tends to make them harder to detect. Check the responses after a period of rain to see how moisture content affects the signals. Conversely, if you have a drought, see what no moisture will do to signals in terms of limiting overall detection depth.
It is advisable to take a spin through your test garden if you get a new search coil, have not hunted in a while or if ground conditions have changed since you were last in the field. You may find that slight changes are required to get the desired level of performance. I always take any new detector, search coil or set of headphones through my test garden so that I am familiar with the response from known targets and as a result, tend to do better in less time when I am searching for actual targets under a wide range of conditions.
I almost hate to share this story but it demonstrates the point I am trying to make with this guide. I started metal detecting in the 1960's and had nearly a decade of experience under my belt by the time the first detectors capable of ignoring mineralization made their appearance. My father and I were intrigued by the ads that were popping up in the treasure magazines and drove to a local dealer to see one of these new "wonder machines" in operation. A short demonstration was all it took to know we needed to get one of these and a week later, we returned and picked one up. The first site we visited was an old school near our house that we had hunted for years and had recovered literally 1,000's of coins and other items during that time. My father was running one of our old detectors and I was using the new one hoping to start recovering the real old coins we knew had to be there. Well, my father's detector had limited detection depth but did have rudimentary discrimination while my detector got amazing depth but lacked any discrimination. So while my father has digging coins at 4" and ignoring most of the trash, I was digging targets at 10" of which most were rusted nails and other trash. After an hour we compared targets and my 3 coins and a pile of trash could not hold a candle to my father's pile of coins and a small gold ring. Frustration continued to build over the next hour or two and when he yelled over that he had just recovered a silver half dollar, I literally wrapped the new detector around a tree and snapped the shaft in two. My father laughed and suggested we head home but it took a few days for me to cool off enough to head back out AFTER I took the time to test the detector on known targets and that preparation allowed me to ignore most of the trash the next time out with far different results . . . a handful of coins that dated back to the mid-1800's! By the way, I still have that old detector in my collection and when I look at the welded spot on the shaft where my father repaired the damage caused by my frustration, I have to smile and remember that no matter how experienced I am, spending time with a new detector performing air tests and taking a spin through a test garden is essential if I want to unlock the true capabilities any detector has to offer.
Good luck in your searches and hopefully some of the techniques contained in this guide will help you find more and enjoy your time in the field in less time than simply heading out the door would have produced.
An old 14KT gold wedding band that turned up from more than 9 inches deep in mineralized soil. Learning what small, deep targets sounded like in a test garden played a key role in being able to detect and recover this exceptional artifact from the early 1900's. (Item was recovered by the author on private property with permission from the landowner)